Table of Content

15 July 2020, Volume 31 Issue 7

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Special Features of Plant Allelopathy

Inter-specific and intra-specific chemical interactions among plants

KONG Chui-hua

2020, 31(7):  2141-2150.  doi:10.13287/j.1001-9332.202007.019

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Plant-plant interactions is a fundamental issue in ecology. Plants are able to detect and perceive inter-specific and intra-specific neighbors and then adjust their growth, reproduction and defense strategies. Such inter-specific and intra-specific recognition and perception are mostly media-ted by secondary metabolites. Those chemical communications can initiate and activate the corresponding mechanism in allelopathy. In recent years, several novel plant-plant chemical interactions have been observed, such as kin recognition, and flowering and reproduction mediated by root communication. Till now, the inter-specific and intra-specific chemical interactions among plants mediated by volatiles have been substantially clarified. However, the mechanisms and soil-borne signaling chemicals involved in plant-plant chemical interactions mediated by root exudates remain poorly understood. Belowground chemical interactions not only determine the behavior of root invasion (approaching) and avoidance (repelling), but also regulate the flowering time and florescence. Accordingly, the chemical interactions involve the coordination between belowground and aboveground parts. On the basis of allelopathy and chemical recognition as well as corresponding allelochemicals and signaling chemicals, this review outlined recent research advances regarding plant-plant chemical interactions from kin recognition, root communication and behavior patterns, belowground chemical interactions to regulate flowering and reproduction. The efforts represented a mechanistically exhaustive view of plant-plant interactions.

Research progress in chemical interactions between plants and phytophagous insects

ZHANG Yue-bai, LOU Yong-gen

2020, 31(7):  2151-2160.  doi:10.13287/j.1001-9332.202007.017

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There are complex chemical interactions between plants and phytophagous insects. On the one hand, when infested by phytophagous insects, plants can recognize herbivore-associated molecular patterns and trigger early signaling events and phytohormone-mediated signaling pathways. The activated signaling pathways thus result in the reconfiguration of transcriptomes and metabolomes as well as the increases in direct and indirect defensive compounds in plants, which in turn enhance the resistance of plants to phytophagous insects. On the other hand, phytophagous insects can recognize defense responses in plants and then inhibit or adapt to plant chemical defenses by secreting effector, sequestrating and detoxifying defensive compounds, and/or reducing sensitivity to defensive compounds. The deep analysis of chemical interactions between plant and phytophagous insects could improve the understanding of the relationship between insects and plants in theory and also provide important theoretical and technical guidance for the development of new technologies for crop pest control in practice.

The “chemical defense” of plants against pathogenic microbes: Phytoalexins biosynthesis and molecular regulations

WU Jinsong

2020, 31(7):  2161-2167.  doi:10.13287/j.1001-9332.202007.018

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Plants can produce diverse groups of secondary metabolites to adapt to environment. Many secondary metabolites are involved in the defense responses against pathogenic microbes, including phytoanticipins which are low molecular weight anti-microbial compounds presented in plants before infection, and phytoalexins produced by plants de novo in response to pathogen attack. Phytoalexins are an important part of plant defense repertoire to pathogenic microbes, especially to necrotrophs. Since the concept of phytoalexin was proposed 80 years ago, many kinds of phytoalexins were identified. In contrast, the biosynthesis of most phytoalexins and their regulatory networks are largely unknown. In this review, I summarized recent research progress of phytoalexins in Arabidopsis and Nicotiana species, with special focus on molecular regulations of their biosynthesis. The problems and future directions in phytoalexin research were also discussed.

Effects of alleolchemicals on morphological traits of roots: A meta-analysis

YAN Shao-bin, WANG Peng

2020, 31(7):  2168-2174.  doi:10.13287/j.1001-9332.202007.001

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Allelopathy is a plant-plant interaction mediated by the allelochemicals, which directly or indirectly influence plant growth. As the major part in response to allelochemicals, root morphological traits play an important role in allelopathy research. The global pattern of effects of exogenous allelochemicals on root morphology is not well known. We carried out a meta-analysis based on 61 studies to assess the effects of allelochemicals, including phenols, terpenoids, nitrogen-containing allelochemicals, on root morphology, especially on root length. We found that the allelochemicals significantly inhibited root length, but had little effect on root biomass, root surface area, and root volume. Phenols exhibited the most inhibitory effects on root length, while the allelochemicals had more inhibitory effect on root length of herbs than woody species as well as crops and other species. There was a linear relationship between phenols concentrations and their effect size. We quantified the dose-effect relationship of four phenolic acids, ferulic acid, p-hydroxybenzoic acid, vanillic acid and cinnamic acid. The inhibitory effect of flavonoids on root length was significantly higher than that of phenolic acids. Together, these findings suggested that the responses of target plant root traits to allelochemicals depended on allelochemicals type and dose, species identity, and culture conditions. Future studies need to decipher the mechanism underlying the allelochemicals on root traits of morphology, physiology and architecture under soil environment.

Understory plant species diversity and allelochemicals in rhizosphere soils of Eucalyptus grandis plantations with different densities

LI Jin-jin, ZHANG Jian, ZHANG A-juan, WU Jiao, ZHANG Dan-ju

2020, 31(7):  2175-2184.  doi:10.13287/j.1001-9332.202007.003

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To explore the influencing factors of understory plant species diversity of Eucalyptus grandis, we examined understory plant species diversity and phenolic allelochemicals in the rhizosphere soils of four-year-old and eight-year-old E. grandis plantations with different densities (1200, 1600, 2000 ind·hm^-2) in Danling County of Sichuan Province. The results showed that a total of 45 plant species were recorded, belonging to 33 families and 44 genera. With the increases of stand age and decreases of stand density, plant species richness increased and their importance values were evenly distributed. Phanerophytes was the dominant life form across all stands. Shannon index and Margalef index of shrub in the four-year-old E. grandis plantations increased significantly at the density of 1600 ind·hm^-2. All herbage plant diversity index except for Margalef index in four-year-old ones and Pielou index in eight-year-old plantations increased significantly with the decreases of density. Shannon index and Margalef index of shrub in 1200 ind·hm^-2 were significantly higher in eight-year-old E. grandis stands than those in four-year-old ones. Five phenolic allelochemicals in the rhizosphere soils of E. grandis plantations were identified. In four-year-old stands, salicylic acid concentrations decreased significantly at the density of 1600 ind·hm^-2. The concentrations of chrysin in four-year-old stands reduced significantly with the decreases of density. The concentrations of salicylic acid in eight-year-old stands increased significantly with the decreases of tree density. Salicylic acid concentrations in 2000 ind·hm^-2 were significantly higher in four-year-old stands than that in eight-year-old ones, but the result was opposite in stands with density of 1600 ind·hm^-2. The concentrations of chrysin in stand with density of 1200 ind·hm^-2 were significantly higher in eight-year-old stands than that in four-year-old ones. Rundancy analysis (RDA) result showed that soil pH, bulk density, and the concentrations of soil organic matter, total nitrogen, total phospho-rus, and allelochemicals were the main environmental factors influencing understory plant species diversity. Therefore, prolonging rotation period and reducing stand density would improve micro-environmental condition of forests and buffer the allelopathy of E. grandis, which could facilitate the development of understory vegetation.

Diversity of bacteria and allelopathic potential of their metabolites in differently aged Casuarina equisetifolia litter

ZHANG Ya-qian, HUANG Rui, ZUO Lin-zhi, CHEN Pan, LI Lei

2020, 31(7):  2185-2194.  doi:10.13287/j.1001-9332.202007.037

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Litter plays an important role in ecosystems. To compare the diversity and community structure of microorganisms inside and outside litter, Casuarina equisetifolia were selected from three forests in Guilin coastal area of Haikou City, Hainan Province. Illumina Miseq high-throughput sequencing was used to analyze the diversity and composition of epiphytic and endophytic bacteria of litter. The results showed that the diversity of epiphytic bacteria was higher than that of endophytic bacteria. Moreover, the diversity and richness of bacteria inside and outside C. equisetifolia litter in the intermediate-aged forest were the highest, followed by young forest and mature forest. Proteobacteria and Actinobacteria were the most abundant at the phylum level, accounting for about 80% of the total. At the genus level, Curtobacterium, Jatrophihabitans, Mycobacterium, Actinomycetospora, Mucilaginibacter and Pseudomonas showed significant variation among different forest ages. PCoA results showed that the endophytic bacteria of litter were greatly affected by forest age, while the epiphytic bacteria were greatly affected by environmental factors. The fermentation broth of Bacillus amyloliquefaciens had the strongest allelopathic potential to C. equisetifolia seeds and 2,2′-methylenebis (6-tert-butyl-4-methyl-phenol) was found in it, indicating that B. amyloliquefaciens was involved in the synthesis of allelochemicals. The diversity of litter microbial community affected the allelopathy of C. equisetifolia, which laid a foundation for studying the role of microorganisms in the degradation process of C. equisetifolia litter.

Chemical composition analysis of Eucalyptus essential oil and allelopathic effects of α-terpineol

LI Ao-xin, HOU Xin-cun, ZENG Jia-jia, WEI Yun

2020, 31(7):  2195-2201.  doi:10.13287/j.1001-9332.202007.002

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We extracted Eucalyptus essential oil by steam distillation and analyzed its chemical components by GC-MS. The inhibitory effects of α-terpineol, a component in Eucalyptus essential oil, were tested in Petri dishes on the germination and growth of Amaranthus retroflexus. The allelopathic effects of α-terpineol on A. retroflexus were examined with a pot experiment by measuring germination rate and biomass. The yield of essential oil was 0.04%. Ninety-two chemical components were detected from the essential oil. In Petri dish experiment, the germination inhibitory effect under 5 μL and 7.5 μL of α-terpineol per dish reached 100%. In pot experiment, germination, aboveground fresh and dry weights of A. retroflexus were significantly affected by α-terpineol. At the concentration of 1.6 μL·cm^-3, the inhibition effect was strongest, with the allelopathic response index being -0.51 for germination, -0.62 for aboveground fresh weight, and -0.44 for aboveground dry weight, and the inhibition ratio being 51%, 62% and 44%, respectively.

Allelopathic effects of water extracts from sweet potato on the growth of invasive alien species Alternanthera philoxeroides

DENG Li-li, LYU Pei, HUANG Xue-qi, ZHANG Zhen, WANG Li-chao, LIU Yao

2020, 31(7):  2202-2210.  doi:10.13287/j.1001-9332.202007.020

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It is an effective approach to control invasive plants based on the allelopathic effect of native plants with higher economic values, from the perspective of allelopathy. The aim of this study was to test the allelopathic effect of a local crop, sweet potato (Ipomoea batatas), on the invasive plant Alternanthera philoxeroides. Water extracts from different organs of sweet potato (roots, stems, leaves) with three concentrations (0.025, 0.05, 0.1 g·mL^-1) were used in the study. To test the effect of sweet potato on rhizome growth of A. philoxeroides, the morphological index (ramet number, node number, leaf number, leaf area, plant height, total dry weight and root number of new ramets), allelopathic response index, trait values (succulent degree, root-shoot ratio, specific leaf area, leaf mass ratio, stem mass ratio, root mass ratio), CAT, POD, MDA and SOD in young leaves were measured. The results showed that 1) Water extracts from different organs of sweet potato with different concentrations differed in their effects on the growth of A. philoxeroides. Water extract from root with 0.1 g·mL^-1 significantly inhibited all morphological indices. Except total dry weight and root number, other morphological indices decreased significantly with increasing concentration of water extract from all organs. 2) The synthetic allelopathic response index (RI) was negative under all treatments, indicating that water extract of sweet potato had negative effects on all indices of A. philoxeroides and thus inhibited their growth. Among all the treatments, water extract from root with a concentration of 0.1 g·mL^-1 had the strongest allelopathic inhibition (RI=-0.73), followed by that from stem with a concentration of 0.1 g·mL^-1(RI=-0.44) and from root with a concentration of 0.05 g·mL^-1(RI=-0.44). 3) Water extract of sweet potato had significant inhibitory effects on the degree of succulence, root-shoot ratio, specific leaf area, and leaf mass ratio, but did not affect stem mass ratio and root mass ratio. 4) Water extract of sweet potato significantly increased the contents of MDA and SOD in the fresh leaves of A. philoxeroides, while had no effect on the contents of CAT and POD. All these results indicates that water extract of sweet potato significantly suppress the ramet growth of A. philoxeroides.

Allelopathic interactions between Borreria latifolia and two common Asteraceae species

ZHANG Tai-jie, TIAN Xing-shan, ZHANG Chun, WU Dan-dan

2020, 31(7):  2211-2218.  doi:10.13287/j.1001-9332.202007.004

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Borrelia latifolia is an annual herb suitable to be used as cover crop for weed control in orchards in southern China. To understand the competition between B. latifolia and common weeds in orchards, we investigated the allelopathic interactions between B. latifolia and two Asteraceae species, Ageratum conyzoides and Bidens alba. The results showed that the aqueous extracts of B. latifolia at 10-50 mg·mL^-1 significantly inhibited seed germination and seedling growth of A. conyzoides and B. alba, with the radicle length of A. conyzoides and B. alba being reduced by 57.4%-90.2% and 57.3%-62.3%, respectively. The aqueous extracts of A. conyzoides and B. alba also had strong allelopathic effects on seed germination of B. latifolia. Under the treatment of 50 mg·mL^-1 aqueous extracts, the two Asteraceae species almost entirely inhibited the germination of B. latifolia. After treated with 10 mg·mL^-1 aqueous extract of B. latifolia for 30 d, net photosynthesis, plant height and biomass of A. conyzoide were reduced by 15.2%, 20.6% and 41.5%, respectively, compared with the control, while the biomass of B. alba also showed a decreasing trend. Instead, the growth of B. latifolia was not affected. Under mixed culture, biomass of B. latifolia was comparable to that under monoculture, whereas those of A. conyzoides and B. alba were reduced by 86.0% and 27.1%, respectively. Compared with A. conyzoides and B. alba, the allelopathic advantage of B. latifolia is that it can inhibit growth of the two Asteraceae species as well as inhibit seed germination.

Allelopathic effects of Miscanthus floridulus on seed germination and seedling growth of three crops

LI Jin-xin, YE Jun-wei, LIU Da-hui

2020, 31(7):  2219-2226.  doi:10.13287/j.1001-9332.202007.006

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Allelopathic effects of Miscanthus floridulus at different growth stages on Brassica peki-nensis, Lactuca sativa, and Oryza sativa were examined using six parameters of seed germination and seedling growth, including germination rate, germination speed index, germination index, root length, stem length, and biomass. The results showed that the allelopathic effects of M. floridulus leaf extract were stronger than that of stem extract, with the germination index and biomass of reci-pient plants treated by leaf extract being significantly lower than those treated by stem extract. The allelopathic effect of M. floridulus in the withering stage was stronger than that in the vigorous growth stage. There was a significant dose-effect relationship between the concentrations of leaf extract and the allelopathic effects on three different receptor plants. The higher the extract concentration was, the stronger the allelopathic inhibition was. Leaf extract of M. floridulus could completely inhibit all the germination indices of B. pekinensis and L. sativa at the concentrations of 0.075 and 0.10 g·mL^-1, respectively. The inhibition rates of 0.10 g·mL^-1 leaf extract on germination rate, germination speed index, and germination index of O. sativa were 13.8%, 27.2% and 19.3%, respectively. Leaf extract of M. floridulus could completely inhibit all the growth indices of B. pekinensis and L. sativa at the concentrations of 0.05 and 0.10 g·mL^-1, respectively. However, the inhibition rates of 0.10 g·mL^-1 leaf extract on root length, stem length, and biomass of O. sativa were 64.6%, 92.9% and 21.8%, respectively. In summary, according to the comprehensive allelopathy response index (SE) of seed germination and seedling growth, the susceptibility of the three tested species to the extracts of M. floridulus was B. pekinensis (Cruciferae) > L. sativa (Compositae) > O. sativa (Gramineae).

Allelopathic effect of extracts from Panax notoginseng mono-cropped soil on its root rot pathogens

YAO Chun-zhi, JIANG Yu-ting, YANG Yu-ting, MA Yan-yu, PAN Lei-lyu, LI Yun-long, SUN Yong-quan, CHEN Ji, ZHAO Jun

2020, 31(7):  2227-2235.  doi:10.13287/j.1001-9332.202007.016

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Methanol, ethyl acetate, and water were used to extract the continuous cropping soils of Panax notoginseng, with the solution/soil ratios of 3:1, 6:1, and 9:1. We investigated the effects of those soil extracts on the growth and population of root-rot pathogens of P. notoginseng. Results showed that the methanol, ethyl acetate and water extracts all promoted mycelial growth of Fusarium oxysporum and Fusarium solani after 72 h of plate culture. The response indices of methanol and ethyl acetate extracts on the growth of F. oxysporum were 14.0%-19.8% and 16.2%-20.2%, being higher than that of water extract (8.9%-14.2%), but without significant difference between diffe-rent extraction ratios. However, methanol extract inhibited the mycelial growth of Alternaria spp. The inhibitory effect was highest at the extraction ratio of 3:1, reaching -33.2% to -38.5%. Ethyl acetate and water extracts did not affect the mycelial growth of Alternaria spp. After four weeks of soil culture, methanol, ethyl acetate and water extracts all increased the F. oxysporum populations. The positive effect of water extract was higher than that of methanol (1.68×10⁴-6.73×10⁴ copies·g^-1 dry soil) and ethyl acetate (1.77×10⁴-3.72×10⁴ copies·g^-1 dry soil) extracts, being 3.49×10⁶-9.56×10⁶ copies·g^-1 dry soil. This increment was weakened along with the increase of extraction ratio. Both water extract and methanol extract with low extraction ratio could increase the F. solani populations, while there were no significant effects of methanol, ethyl acetate and water extracts on the population of Alternaria spp. Therefore, the extracts from continuous P. notoginseng cropping soil showed allopathically promoting effects on the growth and population of root-rot pathogens, F. oxysporum and F. solani, which may be one of the reasons for the occurrence of root rot and other soil-borne diseases in replanted P. notoginseng gardens.

Safety evaluation of allelochemical derivative pyrone on different millet varieties

YANG Xue-fang, SUN Peng, SUN Da-sheng, SONG Xi-e, DONG Shu-qi, YUAN Xiang-yang, GUO Ping-yi

2020, 31(7):  2236-2242.  doi:10.13287/j.1001-9332.202007.005

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The development of new herbicides based on allelochemicals is a potential strategy of weed control in arable field. Pyrone, a novel derivative of tricin, has significant inhibitory effects on weeds. Its safety for crops, especially for millet that are sensitive to commercial herbicides, is still poorly understood. In this study, germination test and pot experiments were conducted to evaluate the safety of pyrone on 20 millet varieties, compared with 2,4-D. The results showed that, except that Jinfen109 was sensitive to high concentration 2,4-D, both pyrone and 2,4-D had no effect on the germination rates of other varieties. Results of the pot experiment showed that pyrone treatment significantly increased the chlorophyll content of millet by 9.0%-67.9%, which was the greatest for Jigu 42. Pyrone treatment did not affect maximal photochemical efficiency, potential photochemical activity, actual photochemical efficiency, and non-photochemical quenching coefficient. On the contrary, 2,4-D significantly inhibited the fluorescence parameters of millet varieties. Pyrone treatment increased the activities of superoxide dismutase, peroxidase and catalase in leaves of Dunza16, Jigu 39, Jigu 41 and Jingu 28, with the magnitude of enhancement being higher than 2,4-D. The results indicated that the allelochemical derivative pyrone is highly safe to the growth of millet seedlings and has the potential to be a new herbicide to millet field.

Allelopathic effects of water extracts from different parts of foxtail millet straw on three kinds of weeds

DONG Shu-qi, CAO Peng, HU Chun-yan, SHER Alam, YUAN Xiang-yang, YANG Xue-fang, GUO Ping-yi

2020, 31(7):  2243-2250.  doi:10.13287/j.1001-9332.202007.009

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We examined the allelopathic effect of extracts from different parts of foxtail millet straw with different concentrations (undiluted water extracts, 10-fold, 50-fold, and 100-fold dilution) on three different kinds of malignant weeds (Amaranthus retroflexus, Chenopodium album, and Setaria viridis) by water extract. In this experiment, we measured biological indicators for seed germination period and potted seedling physiological parameters. The results showed that water extract of foxtail millet leaves and stems had significant allelopathic effects on the three species of weeds, with the effects of different concentrations being different. Undiluted water extract inhibited the growth, while dilution (10-fold, 50-fold, 100-fold dilution) promoted the growth. Under the treatment of undiluted water extract of leaf and stem, the germination rate of three weeds decreased 63.9%, 37.3% and 41.7%, respectively, while root length was only 27.8%, 37.8% and 18.4% of the control. The bud length was only 34.5%, 27.7% and 17.6% of the control. The net photosynthetic rate accounted for 66.6%, 89.9% and 88.2% of the control. The transpiration rate accounted for 69.0%, 87.5% and 56.1% of the control, while the synthesis allelopathic index of the three weeds were -0.699, -0.716 and -0.795 by undiluted water extract, respectively. Results implied strong allelopathic inhibition. The allelopathy promoting effect of dilution increased first and then decreased with the increases of dilution folds. Among which, 50-fold dilution had the strongest promoting effect with the germination rate, root length and bud length of the three weeds being significantly different from those of the control, with the synthesis allelopathic index being 0.261, 0.217, and 0.165, respectively. A large number of associated weeds grow in foxtail millet field which is related to the leaching of allelopathic substances in straw.

Allelopathic effects of velvetleaf volatile oil on germination and seedling growth of wheat, maize, and soybean

LI Chun-ying, TIAN Yao, YU Mei-ting, ZHAO Chun-jian

2020, 31(7):  2251-2256.  doi:10.13287/j.1001-9332.202007.030

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Velvetleaf (Abutilon theophrasti) is a common weed in dryland, which can reduce crop yield. Allelopathy is one of the possible reasons resulting in crop yield reduction. In this study, we analyzed the allelopathic effect of velvetleaf volatile oil components on germination and seedling growth of three dryland crops, wheat (Triticum aestivum), maize (Zea mays), and soybean (Glycine max). A total of 26 compounds in velvetleaf volatile oil were identified by GC-MS, accounting for 98.1% of the total chromatographic peak areas. The terpenes with lower molecular weight in the volatile oil were α-pinene, eucalyptol, α-terpinolene, β-terpinene, trans-α-ionone, and trans-β-ionone. The saturated aqueous solution of velvetleaf volatile oil could inhibit seed germination of three crops by filter paper and soil. Velvetleaf volatile oil could inhibit the seedling growth of three crops through air, filter paper, and soil. Wheat was the most susceptible to volatile oil, followed by maize and soybean. The inhibitory effect of volatile oil on the growth of wheat was the strongest in air medium, followed by filter paper and soil medium. The lower molecular weight of terpene components from volatile oil might be the important allelochemicals.

Chemical composition and allelopathic potential of essential oil isolated from Origanum vulgare

ZHAO Yun, YANG Yun-hai, WANG Kai-bo, FAN Li-ming, SU Fa-wu, YE Min

2020, 31(7):  2257-2263.  doi:10.13287/j.1001-9332.202007.032

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This study aimed to explore the chemical composition of essential oil isolated from Origanum vulgare and investigated its allelopathic potential. The essential oil isolated by hydro-distillation from the whole plant of O. vulgare was analyzed by GC and GC-MS. Fourteen different components were identified, constituting 93.56% of the total area of peaks. The major components were methyleugenol (16.5%), myristicin (15.6%), carvacrol (15.0%), thymol (9.8%), and apioline (9.4%). We examined the inhibitory effects of essential oil on seed germination and seedling growth of wheat (Triticum aestivum), mung bean (Vigna radiata), and radish (Raphanus sativus). The results showed that essential oil of O. vulgare inhibited seed germination of all tested crops, with wheat being the most susceptible, followed by radish and mung bean. The inhibitory effects of essential oil on growth of the aboveground part of tested crops were greater than that of underground part. The inhibitory effects of essential oil on the seedling length of all tested crops increased in a dose-dependent manner, with the same pattern for radicle length of wheat and radish as well. Meanwhile, essential oil could stimulate radicle growth of V. radiata at low concentration, but inhibit the growth at high concentration. Our results confirmed the existence of allelochemicals in the essential oil of O. vulgare. However, what the compounds will be and how about their allelopathic mechanism needs further investigation.

Effects of root extract of host plants on seed germination and haustorium formation of Cistanche deserticola

HE Xiu-li, LI Dai-qing, FENG Ru, QIAO Hai-li, LIU Sai, XU Rong, XU Chang-qing, CHEN Jun

2020, 31(7):  2264-2270.  doi:10.13287/j.1001-9332.202007.008

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We examined the effects of root extracts of Haloxylon ammodendron and Beta vulgaris in Chenopodiaceae extracted by water and ethanol on seed germination and haustorium formation of Cistanche deserticola by filter paper culture dish method. The results showed that only adding root extract had no effect on seed germination and haustorium formation of C. deserticola. The germination rate of C. deserticola seeds treated by adding 10 mg·kg^-1 gibberellin to the root extracted by ethanol was not significantly different from that of the control (GA₃), whereas those treated by adding gibberellin to the ethanol extract of two kinds of host root was increased by more than 10 times. The germination rate of C. deserticola seeds in the treatment with adding 1 mg·kg^-1 fluridone (FL) to root extract was not significantly different from that in the control with only fluridone, while those in the treatment with B. vulgaris root water extraction was the highest (39.4%). Compared to the treatment of adding gibberellin to the root extract, the germination rate of C. deserticola seeds was only increased. When FL was added to the host root extract, the haustorium was formed on the germination tube, with the formation rate of the ethanol extraction group being the highest (16.2%). Seed germination rate of C. deserticola increased to 52.3% when GA₃ and FL were added to the ethanol extract of H. ammodendron, but the formation rate of haustorium was not different from that of FL treatment. Only 6.7% of the seed formation haustorium in the control was significantly lower than that in FL treatment. There were differences in the position and shape of the haustorium of C. deserticola seeds under different treatments. The haustorium produced by adding the extract of the host root mostly appeared at the top of the bud tube, and many papillae raised into claws. The haustorium of FL treatment without adding the extract of the host root mostly appeared at the bottom or the top of the bud tube splitting. The results indicated that ethanol extraction and water extraction could extract the substances that could promote the formation of C. deserticola seeds haustorium from the host root, but did not affect seed germination. GA₃ and FL could significantly improve the germination rate of C. deserticola seeds, but the formation of the haustorium was affected by some substances in the host root extract.

Effects of Brachythecium plumosum and Plagiomnium venustum on seed germination and seedling growth of invasive plants

HANG Wei, GE Yu-ying, LIU Hao-yu, JIANG Hao-ran, ZHANG Shi-hang, TAO Ye

2020, 31(7):  2271-2278.  doi:10.13287/j.1001-9332.202007.010

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Invasive plants can inhibit the survival and reproduction of native species through alle-lopathy. It is not clear whether the native plants, especially the mosses in the ground layer, inf-luence the invasive plants. In this study, we examined the effects of two native moss species, Brachythecium plumosum and Plagiomnium venustum, on two malignant invasive plants, Echinochloa crusgalli and Daucus carota. The effects of mosses on seed germination and seedling growth of both invasive species were determined based on the clump structure and allelopathy of the mosses. The germination rate, germination potential and germination index of the two invasive species were significantly inhibited when seeds fallen on or into the moss clump, with an order of inhibition effect: above moss clump>below moss clump>no moss. Radicle length and radicle/plumule of D. Carota were significantly affected when seeds fallen into the moss clump. Moss water extracts significantly reduced germination rate, germination potential, and germination index of the two invasive plants, with these effects being concentration-dependent. To some extent, moss water extracts increased the plumule length, radicle length and radicle/plumule of D. Carota seedlings, but without effect on E. crusgalli. Both mosses showed inhibitory effects on seed germination and seedling growth of two invasive plants, with higher sensitivity of E. crusgalli than D. Carota. Along with the increases in concentration of water extract, stronger inhibitory effects were found. Therefore, mosses could partially inhibit seed germination and seedling growth of invasive plants.

Biological effects of root exudates from resistant and susceptible banana varieties on Fusaiurm oxysporum f. sp. cubense and Bacillus subtilis

GAN Lin, DAI Yu-li, YANG Xiu-juan, DU Yi-xin, SHI Niu-niu, RUAN Hong-chun, CHEN Fu-ru

2020, 31(7):  2279-2286.  doi:10.13287/j.1001-9332.202007.039

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Root exudates of banana resistant variety (‘Nantianhuang') and susceptible variety (‘Guijiao No. 6') to Fusarium wilt were collected in vitro by bathing root system to examine the biological effects of root exudates from banana varieties on Fusaiurm oxysporum f. sp. cubense and Bacillus subtilis. We explored the effects of root exudates of different banana varieties on the abundance of soil microorganisms and the growth of F. oxysporum f. sp. cubense and B. subtilis. The results showed that root exudates from resistant variety could significantly reduce the abundance of soil fungi and inhibit the spore germination of F. oxysporum f. sp. cubense. Root exudates from susceptible variety could significantly stimulate mycelia growth and spores germination, whereas root exudates from the tested banana varieties could significantly increase the growth and biofilm formation of B. subtilis. By dealing with the root exudates of resistant and susceptible varieties, the growth rate of mycelia were 11.28 and 12.28 mm·d^-1, and the germination rate of spores were 34.6% and 79.5%, respectively. After culturing for 12 h, the growth rates of B. subtilis (OD₆₀₀) were 1.27 and 1.14, and the biofilm formation (OD₅₇₀) were 1.11 and 1.30 after static culturing 72 h, respectively. There were significant differences between the values of resistant and susceptible varieties. The colonization amount of B. subtilis in the rhizosphere of susceptible variety was significantly higher than that of resistant variety. The contents of free amino acids and organic acid in root exudates of the resistant variety were higher than that of susceptible variety. The content ratio of acetic acid and proline in the root exudates of resistant variety were 3.7 times and 2.4 times of that of susceptible variety. In conclusion, root exudates of banana resistant variety could inhibit the growth of F. oxysporum f. sp. cubense. Root exudates from susceptible variety could promote the growth of F. oxysporum f. sp. cubense,while that from the tested banana varieties could all significantly enhance growth, biofilm formation and colonization ability of B. subtilis.

Optimization of the fermentation conditions of Bacillus nematodes and screening of macroporous adsorption resin

LIU Hao-yue, JIN Hui, ZENG Li-ming, YANG Xiao-yan, XIN Ai-yi, QIN Bo

2020, 31(7):  2287-2292.  doi:10.13287/j.1001-9332.202007.036

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Bacillus sp. SMrs28, metabolites from which had significant nematicidal activity, was isolated from the rhizosphere soil of Stellera chamaejasme. To determine the optimal fermentation conditions of the strain and the resin type of preliminary purified active ingredient, fermentation conditions were optimized by single factor experiment, while the macroporous resin types were screened in a static adsorption experiment. The results showed that the optimal fermentation conditions of SMrs28 strain were as follows: glucose and yeast powder were the best carbon source and nitrogen source, fermentation for 48 h, inoculum volume of 10%, temperature at 28 ℃,a rotation speed of 180 r·min^-1, liquid volume of 30 mL in 150 mL triangular flask, and with an initial pH of 7.2. The static adsorption experiments showed that the adsorption and desorption of active ingre-dients in the fermentation broth by the macroporous adsorption resin D101 was significantly better than that of XAD-4, HP20 and AB-8, with the nematicidal activity of the desorption liquid being significantly improved. The nematicidal activity of fermentation broth was significantly improved by the optimization of fermentation conditions and the screening of optimal macroporous adsorption resins. These results laid a foundation for the further isolation and purification of active ingredients from SMrs28 strain, and provided theoretical basis for the development and utilization of microbial nematicides.

Differences in exogenous methyl jasmonate-induced quinclorac resistance between resistant and sensitive barnyardgrass and the underlying mechanism

CAO Jing-jing, PENG Qiong, YANG Xia, YANG Qian, BAI Lian-yang, LI Yong-feng, ZHANG Zi-chang, GU Tao

2020, 31(7):  2293-2298.  doi:10.13287/j.1001-9332.202007.038

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The effects of exogenous methyl jasmonate (MeJA) on the resistance levels to quinclorac and endogenous hormone levels were examined using the resistant and sensitive biotypes of barnyardgrass with the same genetic background. The results showed that exogenous MeJA could significantly increase the resistance of resistant plants to quinclorac, but did not affect the resistance of sensitive plants. There were significant differences in the contents of indole-3-acetic acid (IAA), abscisic acid (ABA), salicylic acid (SA), and jasmonic acid (JA) among the tested materials. Quinclorac treatment could significantly increase the contents of ABA, SA, and JA in barnyardgrass, with stronger increase of ABA and JA contents in the sensitive plants. Exogenous MeJA could significantly enhance the induction of ABA and JA contents by quinclorac, especially in the sensitive biotypes. These results showed that rapid hormone variations in sensitive plants inhibited their response to herbicide, while gentle hormone variations endowed resistant plants with a strong adapta-bility to herbicide, which closely related to the enhanced resistance by MeJA. ABA and JA hormone signals might play an important role in the resistance of barnyardgrass to quinclorac stress.

Electrophysiological and behavioral responses of gall midge, Jaapiella sp. to volatiles of host plant Lycium barbarum

ZHANG Fan, XU Chang-qing, CHEN Jun, MA Mei, LU Peng-fei, LIU Sai, LI Jian-ling, QIAO Hai-li

2020, 31(7):  2299-2306.  doi:10.13287/j.1001-9332.202007.040

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Plant-derived volatiles are important for guiding herbivorous insects to their host plants. Jaapiella sp. (Diptera: Cecidomyiidae) is the most serious pest of Lycium barbarum. The young flower buds of L. barbarum are attractive to females of Jaapiella sp. for oviposition in the field. In this study, we compared response of Jaapiella sp. to volatiles from flower buds of L. barbarum at different stages, and clarified the crucial semiochemicals attracting Jaapiella sp. to lay eggs. Volatiles from young and mature flower buds were collected using SPME, and then identified and quantified by gas chromatography-mass spectrometry (GC-MS). Both electrophysiological and behavior experiments were conducted to measure the attraction of eight synthetic compounds to females and screen the crucial components based on gas chromatography-electroantennogram detection (GC-EAD) and Y-tube bioassays, respectively. Results showed that qualitative and quantitative diffe-rences between two odor profiles. Consistent electroantennographic response was observed for eight compounds from headspace collections, of which five synthetic compounds (3-carene, camphene, terpinolene, d-limonene, and (+)-pinene) were essential for significant preference or avoidance. Our results indicated that these compounds from L. barbarum flower buds could be effective candidates as oviposition attractant or repellents of Jaapiella sp., which would be helpful in the exploitation of new control agent to Jaapiella sp. in the field.

Hormone response of Lycium barbarum to gall mite Aceria pallida and effects of exogenous salicylic acid on the infestation and development of gall mite

YANG Meng-ke, LI Jian-ling, LIU Sai, QIAO Hai-li, GUO Kun, XU Rong, CHEN Jun, XU Chang-qing

2020, 31(7):  2307-2313.  doi:10.13287/j.1001-9332.202006.039

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To investigate the hormone responses of Lycium barbarum to Aceria pallida infestation and the effects of exogenous salicylic acid on the infestation and development of gall mite, four phytohormones (salicylic acid (SA), jasmonic acid (JA), Auxin, and abscisic acid (ABA)) of L. barbarum leaves infested with A. pallida were determined by LC-MS/MS. Moreover, the effects of exogenous SA on the growth of gall and mite population were investigated. The results showed that contents of SA and JA in leaves infested with A. pallida were significantly higher (4.0 and 13.0 folds, respectively) than that in control, but that of Auxin and ABA did not change. The growth of gall was inhibited significantly by exogenous SA, with the inhibition increasing with the prolongation of treatment time. Meanwhile, mite population in galls treated with SA was significantly lower than that in control. Our results suggested that A. pallida could induce SA and JA resistance of L. barbarum, and that the exogenous SA could inhibit the growth of gall and mite population. Exogenous SA could be potentially used in A. pallida prevention.

Original Articles

Effects of water and nitrogen coupling under furrow irrigation on tree growth, absorption and utilization of water and nitrogen of Populus tomentosa

YU Jing-lin, LIU Feng, HE Yue-lin, ZHU Wei, XI Ben-ye, JIA Li-ming

2020, 31(7):  2314-2322.  doi:10.13287/j.1001-9332.202007.007

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We explored the coupling effects of water and nitrogen in furrow irrigation on the growth and absorption and utilization of water and nitrogen in young poplar trees (triploid Populus tomentosa), under three irrigation levels (W₂₀, W₃₃, W₄₅; when the soil water potential of 40 cm under the ditch reaches -20, -33 and -45 kPa respectively, irrigate), four N application levels (N₁₂₀, N₁₉₀, N₂₆₀ and N₀; the fertilization amount was 120, 190, 260 and 0 kg·hm^-2·a^-1), and natural conditions (CK). Based on the growth status of trees, the optimal combination of irrigation level and nitrogen application rate under furrow irrigation conditions was determined. The results showed that W₂₀N₁₂₀ (high water and low fertilizer; soil water potential threshold for initiating irrigation was -20 kPa and N application rate was 120 kg·hm^-2·a^-1) had the strongest effect on the stand productivity, with a value of 33.37 m³·hm^-2·a^-1. The significant coupling effect of water and N was detected only for tree height and total individual biomass. The increase of both irrigation amount and N application rate could increase the amount of N uptake, being mainly affected by the latter. The total amount of N uptake was the highest in the W₂₀N₂₆₀ treatment and reached 112.17 kg·hm^-2·a^-1, being 74.0% higher than that in CK. Among all the treatments, N uptake efficiency and N fertilizer partial productivity of W₂₀N₁₂₀ were the highest and significantly higher than those of the other treatments. The N uptake efficiency of the whole plant, aboveground part, and belowground part reached 36.8%, 28.5% and 6.4% in the W₂₀N₁₂₀ treatment, and its total N partial productivity reached 221.4 kg·kg^-1. The effect of irrigation amount under different water-nitrogen coupling treatments on the irrigation water use efficiency was significant. Among them, irrigation water use efficiency in W₄₅N₂₆₀ was the highest and reached 13.66 g·kg^-1. W₂₀N₁₂₀ had the highest water uptake amount and efficiency, which were 13268.28 t·hm^-2 and 129.4%, respectively. To achieve great benefits, adequate irrigation (-20 kPa) and relatively low N application rate (120 kg·hm^-2·a^-1) should be selected during the young growth of the triploid P. tomentosa.

Value evaluation and ecological compensation of endangered species from the perspective of stakeholders: A cases study with Elaeagnus mollise

ZHANG Yin-bo, NIU Yang-yang, WANG Wen-zhi, QIN Hao, LIU Ying-li, LI Jun-sheng

2020, 31(7):  2323-2331.  doi:10.13287/j.1001-9332.202007.011

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The value evaluation of endangered species can provide important supports for policy-making in biodiversity conservation. We evaluated the stakeholders' preference and willingness to pay (WTP) from the perspective of stakeholders by the choice experiment method (CEM) and discussed the ecological compensation mechanism, with Elaeagnus mollis, a national secondary key protected plant as an example. Based on the interest demands analysis of three stakeholders, the management departments, enterprises and farmers, we measured five species attributes of E. mollis, including planting area, product classification, seedling varieties, protection investment, and far-mers' income. Furthermore, the preference of stakeholders and WTP for different attribute variables were analyzed using random parameter model (RPL). The results showed that the preference of respondents for the variable of “increase investment in protection” was the strongest and WTP was the highest (331.00 yuan·a^-1·household^-1). The stakeholders had stronger preference for the variables of “simultaneous development of high and low-end products” and “development of high-end products”, with WTP being 242.71 and 227.57 yuan·a^-1·household^-1, respectively. For the variables of “farmers' income”, “unchanged investment in protection”, “seedling varieties” and “planting area”, stakeholders showed certain preference and WTP from strong to weak. The prefe-rence for “no investment in protection” and “development of low-end products” was weaker and the WTP was negative. Through direct and indirect approaches of compensation, ecological compensation could be implemented for the objects of ecological compensation (E. mollis and associated habitat). The value of compensating surplus (CS) calculated was 285.62 yuan·a^-1·household^-1.

Identification of the priority conservation areas of national park: A case study of Lishui City, Zhejiang Province, China

HOU Meng, TANG Xiao-ping, HUANG Gui-lin, LI Ren-qiang

2020, 31(7):  2332-2340.  doi:10.13287/j.1001-9332.202007.015

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It is the goal of protected area management to make full use of limited resources to better protect biodiversity. Currently, the main tasks of developing national park system in China are to combine conservation features, optimize the spatial network of protected areas, and identify the prio-rity conservation areas of national parks effectively. In this study, we assessed the spatial distribution of key ecosystem services (carbon sequestration, oxygen release, hydrological regulation, water resources, and soil retention) using ecological model, and simulated the distribution of suitable habitats for 37 endangered species by MaxEnt in Lishui City, Zhejiang Province. The irreplaceability index of each planning unit in Lishui was calculated on the 0.4 km×0.4 km grid using the systema-tic conservation planning model (MARXAN), setting key ecosystem services and endangered species as the conservation objects. Combined with the local management needs, the priority protection areas of national parks were identified comprehensively. The results showed that during 2005 to 2015, the annual carbon storage, oxygen release, hydrological regulation, water resource, and soil retention in the study area was 0.05 kg C·m^-2·a^-1, 0.13 kg O₂·m^-2·a^-1, 83.25×10⁸ m³·a^-1, 803 mm·a^-1, and 95.53 t·hm^-2·a^-1, respectively. The irreplaceability index of different land use types was significantly different. The irreplaceability index of forest, river and reservoir, garden, cultivated land, residential land was 50-100, 60-100, 30-50, 15-35, 0-25, respectively. The priority conservation areas accounted for 11.8% of the study area. This study put forward a systematic conservation planning idea combining biodiversity and ecosystem services, which could provide a useful framework and technical support for optimizing the network layout of protected areas and priority conservation areas of national parks, and help to enhance the overall effectiveness of the establishment of the protected areas system with national parks as its main type in China.

Comparison of spatial-temporal evolution of habitat quality between Xinjiang Corps and Non-corps Region based on land use

LIU Fang-tian, XU Er-qi

2020, 31(7):  2341-2351.  doi:10.13287/j.1001-9332.202007.014

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Regional habitat quality is an important indicator of ecosystem health. Understanding land use change and habitat quality will help protect biodiversity and build an ecological security pattern. We used the InVEST model to quantitatively evaluate the habitat quality of the Xinjiang Corps and Non-corps Region based on land use data of 1990, 2000, 2010 and 2018, and further analyzed the similarities and differences of the spatiotemporal distribution. The results showed that from 1990 to 2018, Xinjiang's land use types were generally stable, characterized mainly by the expansion of cultivated land and construction land, and the decrease of grassland and unused land. The main changes were shown as the mutual conversion of grassland and cultivated land, and the conversion of cultivated land to construction land. The cultivated land and construction land of the Corps increased by 8.3% and 0.7%, while the grassland and forest land decreased by 6.7% and 0.3%, respectively. The change in the Non-corps region was relatively small, with a 1.5% reduction of grassland, a 1.2 % increases of cultivated land, and a 0.2% increase of construction land. From 1990 to 2018, the degree of habitat degradation in Xinjiang first decreased and then increased, with the quality of habitats decreasing gradually. The low-quality habitat areas were distributed in cities and towns, which gradually expand. The high-value areas of the Corps were distributed on the edge of the basin, and the patches tend to be fragmented. The high-value areas of the Non-corps Region were located in the mountains, with little change. The habitat quality level of Corps was higher than that of the Non-corps Region, with fast decline. Higher or lower habitat quality grades were easily transferred to medium ones. Compared with the Non-corps region, the transfer rate of the Corps was higher and the habitat damage was more severe. Economic development resulted in rapid expansion of low-level regions, which seriously threatened the quality of regional habitats. The prediction of land use showed that the area of cultivated and construction land in the Crops and the Non-corps Region would gradually increase in 2018-2035, and forest land and grassland would gradually decrease, which may lead to a gradual decline in habitat quality.

Characteristics of agricultural climate resource changes during the growth stages of tobacco during 1961-2017 in Panxi Region, China

ZHANG Yu-fang, YANG Liu, LIU Yan-yan, ZHANG Xiu-qiong, CHEN Chao, XIE Shi-juan, FENG Wen-shuai

2020, 31(7):  2352-2362.  doi:10.13287/j.1001-9332.202007.012

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It is of great significance for the sustainable development of regional agriculture to understand the changes of agricultural climate resources during the growth period of local main crops. Based on data from 15 meteorological stations in tobacco planting area of Panxi region, Sichuan, from 1961 to 2017, the average temperature, diurnal temperature range, water deficit, and radiation were used to analyze the temporal and spatial distribution of agricultural climate resources such as light, temperature, and water in the whole growth period and each growth stages respectively. From 1961 to 2017, the average temperature of tobacco during the whole growth period gradually decreased from south to north in Panxi, while temperature showed an increasing trend in most areas. The area with significantly increased temperature accounted for 54.5% of the total planting area. The diurnal temperature range in most area of the eastern Panxi and some of the central Panxi showed an upward trend, and these areas accounted for 76.4% of the whole Panxi region. Water deficit gradually decreased from south to north, with an increasing trend in the whole region. The radiation during the growth stage of tobacco was high in the southwest and low in the northeast, and the climatic tendency was positive values in the southwest. During the study period, average temperature was the highest in the period from vigorous growth to the beginning of maturity, with an overall upward trend. The diurnal temperature rage and water deficit were the highest in transplanting squatting seedling stage. Radiation was the highest at the beginning of maturity, which increased slightly at the beginning of seedling growth.

Effects of annual distribution difference of precipitation on evapotranspiration characteristics of dry orchard in Loess Plateau, China

ZHANG Li-na, ZHANG Yu-bin, WANG Jun-de

2020, 31(7):  2363-2372.  doi:10.13287/j.1001-9332.202007.013

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Precipitation is the main driving factor for hydrological cycle in rain-fed agricultural areas, which determines the water-related ecological environment and affects the evapotranspiration characteristics of crops. By analyzing the annual distribution characteristics of precipitation across different years, this study clarified the concentrated trend of precipitation in Jingning County. Based on a field experiment in 2018 and 2019, the changes of soil moisture with precipitation and the response process of orchard evapotranspiration characteristics to the annual distribution differences of precipitation were explored. The results showed that the concentration degree of precipitation was high in the study area over the years. The concentration period was mainly distributed in July and August, with the proportion of August being up to 75%. Moreover, the time of precipitation concentration period varied greatly among years. The response of soil moisture to precipitation was mainly concentrated in the 0-40 cm layer, while moisture in deep soil layer would change significantly only in response to heavy and continuous rain. Both 2018 and 2019 were water-rich years. The precipitation concentration degree in 2018 was high, and the concentration period was earlier and shorter, with the diurnal water consumption of apple trees showing a single peak with large amplitude. In 2019, the distribution of precipitation was uniform, the concentration period was late, and the diurnal water consumption showed double-peak with a small amplitude and a lagged large peak. The maximum water demand period of apple trees lasted a long time. The concentrated distribution of heavy rain in 2018 could not meet the physiological water demands of apple trees in the later period, which damaged the yield, and the utilization efficiency of precipitation decreased by 30.2% compared with 2019. In the Loess Plateau region, there is often a brief drought during the young fruit growth period, which would affect fruit quality. Therefore, water management during this period should be strengthened.

Effects of different organic amendments on soil organic carbon and its labile fractions in the paddy soil of a double rice cropping system

WEI Xia-xin, XIONG Jun-fen, LI Tao, WEN Jiong, ZENG Xi-bai, YU De-hai

2020, 31(7):  2373-2380.  doi:10.13287/j.1001-9332.202007.021

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Application of organic amendments is an effective approach for improving soil organic carbon and soil fertility. To investigate the effects of different organic amendments on soil organic carbon and its labile fraction content, a batch of incubation experiments was conducted on the fluvo-aquic soil in Dongting Lake region, Hunan Province. There were six treatments, including soil amended with rice straw, soil amended with Chinese milk vetch, soil amended with bio-organic fertilizer, soil amended with pig manure, and soil amended with rice straw-derived biochar, with unamended soil as control. Each treatment had the same amount of carbon input. After 180 days of incubation, application of organic amendments increased soil labile organic carbon content. Application of bio-organic fertilizer, pig manure and rice straw-derived biochar significantly increased soil organic carbon content by 26.1%, 9.7% and 30.7%, respectively. There was no significant change in soil organic carbon content in rice straw and Chinese milk vetch treatments which were more favourable to the accumulation of soil dissolved organic carbon and microbial biomass carbon. Pig manure was more favourable to the accumulation of soil dissolved organic carbon. Bio-organic fertili-zer could benefit the accumulation of soil microbial biomass carbon and readily oxidizable organic carbon. Rice straw-derived biochar could promote the accumulation of soil microbial biomass carbon and light fraction organic carbon. Compared with rice straw, soil carbon pool management index was increased by 31.8%, 111.6%, 62.2% and 50.7% in Chinese milk vetch, bio-organic fertilizer, pig manure and rice straw-derived biochar treatments, respectively. The performance of bio-organic fertilizer, pig manure, and rice straw biochar was better than rice straw and Chinese milk vetch from the perspective of soil carbon sequestration and soil carbon pool management index.

Effects of nitrogen fertilizer reduction and biochar application on paddy soil nutrient and nitrogen uptake of rice

LIU Rui, HAFEEZ Abdul, LI En-lin, MENG Jia-lin, TIAN Ji-hui, CAI Kun-zheng

2020, 31(7):  2381-2389.  doi:10.13287/j.1001-9332.202007.025

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We explored the impacts of nitrogen (N) reduction and biochar application on soil fertility and nutrient uptake of rice in early and late seasons of 2018 with a field experiment. There were six treatments, including control (no N application, CK), conventional N application (N₁₀₀), 20% N reduction (N₈₀), 20% N reduction plus biochar application (N₈₀+BC), 40% N reduction (N₆₀), 40% N reduction plus biochar application (N₆₀+BC). Our results showed that 20% and 40% N reduction and/or with biochar application did not affect soil pH, organic matter, total N, total phosphorous (P), total potassium (K), ammonium N, available P and K in comparison with N₁₀₀ treatment. N₈₀+BC and N₆₀+BC substantially increased soil cation exchange capacity (CEC) at tillering stage and electrical conductivity (EC) at heading stage in late season, respectively. Compared with the treatment with single N reduction, N₈₀+BC significantly increased soil available K in early and late seasons and soil pH and total N in late season, while N₆₀+BC increased soil total K at mature stage in early season. Soil nitrate content was decreased along with the growth stages for all treatments in early season. Compared with tillering stage, soil nitrate N content in conventional N application at heading stage and mature stage was decreased by 50.0% and 71.6%, respectively. Soil nitrate content in biochar treatment only was decreased by 6.3%-45.5%. N application along with biochar application had no significant effects on plant N uptake and utilization in early season. However, N reduction with biochar application significantly increased plant N uptake and N utilization rate by 34.8%-52.4% in late season, compared to conventional N application and single N reduction. Our findings suggest that adequate N reduction along with biochar application could maintain soil health and improve plant N uptake and utilization efficiency.

Effects of high efficiency and stability ammonium sulfate fertilizer applied in black soil

CUI Lei, LI Dong-po, WU Zhi-jie, LI Xue-hong, LI Yong-hua, YAN Zeng-hui, ZHENG Ye, ZHANG Jin-ming

2020, 31(7):  2390-2398.  doi:10.13287/j.1001-9332.202007.022

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To develop high efficiency stabilized N fertilizer, a pot experiment was conducted to examine the effects of stabilized ammonium sulfate with different nitrification inhibitors on soil avai-lable nitrogen (N) contents, nitrification inhibition rate, apparent nitrification rate, yield, some agronomic parameters and N fertilizer utilization rate of corn in black soil of Jilin Provinve. In this study, blank (CK) and (NH₄)₂SO₄ (N) were set as controls, and nitrification inhibitor 3,4-dimethyl-pyrazolate phosphate (DMPP), 2-chloro-6-trimethyl-pyridine (CP), ammonia protectant N-GD and nitrogen fertilizer synergist HFJ and their combination applied to ammonium sulfate to form nine treatments. The results showed that compared with the treatment of N, application of DMPP and its combinations in black soil significantly affected soil available N contents and the apparent nitrification rate. The contents of ammonium increased by 1.4-2.0 times, while the contents of nitrate and the apparent nitrification rate of soil decreased by 13.6%-17.9% and 55.3%-59.8%, respectively. DMPP, DMPP+HFJ, DMPP+N-GD had the highest nitrification inhibition rate, which reached higher than 16.5%. DMPP+HFJ+N-GD and HFJ increased the chlorophyll content in maize leaves by 4.5-5.3 times. The addition of nitrification inhibitors and fertilizer synergist to ammonium sulfate did not affect plant height. Compared with the treatment of N, HFJ increased corn biomass, grain yield, economic coefficient, harvest index, agronomic utilization rate of fertilizer, N uptake utilization rate, fertilizer contribution rate and N partial productivity of corn by 1.2, 2.5, 0.7, 0.6, 2.7, 2.1, 1.3 and 2.5 times, respectively. In general, HFJ, DMPP, DMPP+HFJ, DMPP+N-GD performed best in black soil. By considering both the cost and N utilization rate, N fertilizer synergist HFJ is the first choice for stable ammonium sulfate N fertilizer biochemical inhibitor, followed by DMPP+HFJ or DMPP+N-GD.

Remote sensing inversion of surface soil organic matter at jointing stage of winter wheat based on unmanned aerial vehicle multispectral

WANG Xi, LI Yu-huan, WANG Rui-yan, SHI Feng-zhi, XU Shao-tang

2020, 31(7):  2399-2406.  doi:10.13287/j.1001-9332.202007.023

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The rapid monitoring of soil organic matter (SOM) content in large-scale salinized wheat fields can provide data for promoting research in saline soils and carbon cycle. Based on field sampling and remote sensing images of unmanned aerial vehicle, we established remote sensing prediction models of regional SOM using three methods, i.e., multiple linear regression (MLR), partial least squares (PLSR), and support vector machine regression (SVR) for bare land and wheat field, respectively. The models were validated and compared to identify the optimal inversion model of SOM. Moreover, the SOM in the area was inverted using the optimal model, with the inversion results being compared with the data by interpolation. The results showed that the spectrum after the filtering of 5×5 median was best related to surface SOM. Among the three models, the SVR model had the highest prediction accuracy, followed by the PLSR, while the MLR lowest. The SVR model was the best one for estimating wheat field, with coefficient of determination (R²) and root mean square error (RMSE) of 0.89 and 0.20, respectively, and the validated R² and RMSE were 0.82 and 0.24, respectively. The bare land SOM was also best fitted by the SVR model, with R² and RMSE were 0.63, 0.26, respectively, and the verified R² and RMSE were 0.61, 0.25, respectively, but without statistical significance. The inversion of the optimal model revealed that SOM content in this region ranged from 17.51 to 22.53 g·kg^-1, with an average of 19.51 g·kg^-1, which was generally consistent with the field measurement. Compared with the inversion results, the interpolation data were limited in accuracy. Overall, our study suggested that the unmanned aerial vehicle-based multi-spectral analysis could be applied to quick and accurate estimation of SOM content in saline soil at the jointing stage of winter wheat.

Effects of high CO₂ concentration, drought, and their interaction on different stay-green wheat seedlings

NIU Yin-quan, SHI Yu-gang, TANG Xiao-sha, JIN Xiu-juan, CAO Ya-ping, YANG Jin-wen, WANG Shu-guang, SUN Dai-zhen

2020, 31(7):  2407-2414.  doi:10.13287/j.1001-9332.202007.024

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In this study, a pot experiment was carried out to examine the effects of high CO₂ concentration, drought and interaction on seedling growth traits, biomass accumulation and physiological characteristics of different stay-green wheat seedlings, with a stay-green wheat variety Yannong 19 and a non stay-green wheat variety Hanxuan 3 as test materials. There were four treatments in the Open Top Chamber with factorial of CO₂ concentration (370 μmol·mol^-1 vs 550 μmol·mol^-1) and drought (45%-55% vs. 75%-85% of field water-holding capacity). Drought significantly inhibited the growth and development of wheat seedlings, while CO₂ concentration significantly increased the number of tillers and promoted the growth and development of wheat seedlings. Under drought condition, high CO₂ concentration increased the number of tillers of Hanxuan 3 and Yannong 19 by 61.0% and 42.3%, respectively. Under both water conditions, high CO₂ concentration significantly increased the biomass of wheat seedlings, and decreased the content of peroxidase and proline in leaves. Under drought condition, high CO₂ concentration showed stronger “fertilizer effect”. Furthermore, different varieties had different responses to high CO₂ concentration, with higher sensitivity of Hanxuan 3 to enhancement of CO₂ concentration. Under the scenario of increasing CO₂ concentration, the amount of irrigation water applied to a field can be appropriately reduced for efficient use of water resources. Meanwhile, it is necessary to pay attention to the selection of suitable wheat varieties.

Control effects of different herbicides on weeds as well as their effects on growth and deve-lopment of broomcorn millet

ZHAO Ying-nan, ZI Xue-jing, WANG Wan, FENG Yu, YANG Pu, GAO Jin-feng, WANG Peng-ke, GAO Xiao-li

2020, 31(7):  2415-2421.  doi:10.13287/j.1001-9332.202007.027

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Selecting a herbicide suitable for broomcorn millet is a key issue in high efficiency and safe production of broomcorn millet and ecological environment improvement. We compared the control effects of 22 different herbicides on weeds as wells as their effects on growth and development of glutinous millet (Yumi 2) in the field. The results showed that, 1) soil applied Goyou, Butachlor, atrazine, and Benzipram, and stem- and leaf-applied WP mixture of tribenuron-methyl·carfentrazone-ethyl·MCPA-Na, Sigma Broad, Tengjing, Taoshi·Youxian and Kuofei had little phytotoxi-city, with broomcorn millet seedlings growing normally, and the other herbicides had phytotoxicities on broomcorn millet. 2) All the herbicides controlled weeds in the field to some extent, with better performance of soil applied herbicides than the stem- and leaf-applied ones, and affected plant height, functional leaf SPAD and spike weight per plant of broomcorn millet. 3) Compared with manual weeding, all herbicides reduced yields of glutinous millet. Compared with no herbicides application, some herbicides had yield-increasing effects. Among the soil applied herbicides, Go-you, Butachlor, atrazine, and Benzipram performed better in weeding control, increasing the yield of broomcorn millet by more than 60% compared with no herbicide control. Among the stem- and leaf-applied herbicides, Sigma Broad and WP mixture of tribenuron-methyl·carfentrazone-ethyl·MCPA-Na performed better in weeding control, increasing the yield of glutinous millet by more than 50% compared with no herbicide control. Therefore, applying 38% atrazine or 44% Monosulfuron to soil before the emergence of broomcorn millet, or stem- and leaf-applied 3.6% mesosulfuron-methyl or 55% WP mixture of tribenuron-methyl·carfentrazone-ethyl·MCPA-Na after the emergence of broomcorn millet, performed better in weeding control and with limited effects on the growth and development of broomcorn millet.

Effects of different slow/controlled release fertilizers on yield, quality of fresh maize and ammonia emissions

AN Wen-bo, SUN Yan-xin, LI Zhan-tai, WANG Ji-qing, ZOU Guo-yuan, YANG Jun-gang

2020, 31(7):  2422-2430.  doi:10.13287/j.1001-9332.202007.028

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A field experiment with five treatments, control (CK, no fertilizer), conventional fertilization (U), double-effect inhibitor synergistic urea (DU), coated urea (CU) and slow/controlled release urea mixture (CDU), was conducted to investigate the effects of conventional fertilization (240 kg N·hm^-2) and one-off application of different slow/controlled release fertilizers (180 kg N·hm^-2) on the yield and quality of fresh maize, soil inorganic nitrogen (N), and ammonia (NH₃) emissions. The results showed that the total amount of ammonia volatilization was the highest in treatment of conventional fertilization (U), with N topdressing being an important source of NH₃ emission. Compared with U treatment, the NH₃ volatilization in the DU, CU, and CDU treatments was reduced by 78%-81%. At harvest stage, the soil layer of 80-100 cm in the U treatment had the highest nitrate concentration (51.6 mg·kg^-1), resulting in a high risk of N leaching. In contrast, the nitrate concentrations in the same soil layer in the slow/controlled release fertilizer treatments were much lower, reducing the risk of leaching. In comparison with U, three slow/controlled release fertilizer treatments with 25% lower N application did not decrease yield but increased seed Vc, soluble sugar and protein contents. The agronomic efficiency and economic benefit of DU treatment were the highest among three slow/controlled release fertilizers treatments. In conclusion, the application of new type of slow/controlled release fertilizer could improve the yield and quality of fresh maize, and significantly reduce the risk of ammonia loss and N leaching. Considering the higher cost of the polymer coated urea, the double-effect inhibitor urea has lower cost and is more convenient to make. It is therefore a better choice to fresh maize planting.

Characteristics of soil saturated hydraulic conductivity on different positions and their controlling factors of granite collapsing gullies

HUANG Wan-xia, DENG Yu-song, XIE Fu-qian, YANG Gai-ren, JIANG Dai-hua, HUANG Zhi-gang

2020, 31(7):  2431-2440.  doi:10.13287/j.1001-9332.202007.029

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Collapsing gully is a common phenomenon of hydraulic-gravity combined soil erosion in granite hilly area of south China. The study aimed to explore the relationship between soil hydraulics pro-perties and erosion mechanism and the intrinsic controlling factors. The active, semi-stable, and stable types of granite collapsing gullies in southeastern Guangxi were selected to examine the spatial variation of soil saturated hydraulic conductivity and identify the influencing factors. Main results were as follows: 1) Soil saturated hydraulic conductivity of collapsing gullies fluctuated on different positions, with the bottom of collapsing wall showing the minimum value, the top of colluvial deposit showing the maximum, and followed by the top of alluvial fan. 2) All the models being selected to model the soil saturated hydraulic conductivity, including Cosby, Compbell, Julià, and Hypre, performed poor. 3) Results of correlation analysis showed that soil saturated hydraulic conductivity was negatively correlated with capillary porosity and clay content, and positively correlated with non-capillary porosity and sand content. 4) Results of path analysis showed that sand content was the most influencing factor in controlling soil saturated hydraulic conductivity of collapsing gullies, followed by non-capillary porosity and soil bulk density, where sand content and non-capillary porosity exerted a positive effect and bulk density exerted a negative one. Our findings will provide theoretical basis for the mechanistic understanding and prevention of collapsing gullies erosion.

Mechanism of thymol inhibiting Botrytis cinerea: PAO-H₂O₂ system

YANG Kang, CHEN Jian, XIN Ai-jing, CAI Jin-xia, SHI Zhi-qi, YANG Li-fei

2020, 31(7):  2441-2448.  doi:10.13287/j.1001-9332.202007.031

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Gray mold disease caused by Botrytis cinerea infection is one of the major crop diseases. The application of environmental-friendly fungicides to control gray mold disease has been drawing great attention. Thymol, a natural compound, showed strong antifungal activity against Botrytis cinerea. We investigated the role of polyamine oxidase (PAO)-dependent hydrogen peroxide (H₂O₂) production in thymol-inhibited B. cinerea growth by using physiological and biochemical approaches. The results showed that: 1) Thymol significantly inhibited the growth of B. cinerea, with remarkable increases in H₂O₂ content, malondialdehyde (MDA) content, and PAO activity in mycelium. 2) Inhibition of PAO activity (addition of specific inhibitor MDL, N,N'-butanedienyl butanediamine) resulted in significant decreases in the contents of H₂O₂ and MDA as well as the partial recovery of mycelial growth under thymol treatment, suggesting that thymol might trigger PAO-dependent H₂O₂ accumulation resulting in oxidative injury and thus inhibit the growth of mycelium. 3) A PAO homologue gene BcPAO was cloned from B. cinerea. Multi-alignment combined with phylogenetic analysis showed that BcPAO protein had typical conserved domain of PAO family members. 4) Thymol at low concentrations did not affect the transcriptional level of BcPAO. However, the transcription of BcPAO was up-regulated remarkably by thymol at high concentration. This suggested that thymol-stimulated PAO activity may be resulted from the regulation of BcPAO. We conclude that oxidative injury caused by PAO-dependent H₂O₂ production is one of the possible antifungal modes of thymol against B. cinerea. The antifungal mode of thymol found in this study may provide basis for the application of environmental-friendly fungicides.

Effects of microbial agents on bacterial community composition during swine manure composting

WANG Jian-cai, ZHU Rong-sheng, LIU Xing-hua, SUN Shou-li, WANG Huai-zhong, TANG Qian, QI Bo, HUANG Bao-hua

2020, 31(7):  2449-2456.  doi:10.13287/j.1001-9332.202007.033

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The process of swine manure and wheat straw aerobic composting was examined, with exogenous microbial agents being added in treatment group. The physicochemical properties were measured by conventional methods, and bacterial community characteristics were investigated by high throughput sequencing analysis. Exogenous microbial agents increased high-temperature duration, reduced pH value at the end of fermentation stage, augmented total nitrogen content, reduced C/N ratio. Results from principal component analysis showed that microbial agents affected the stability of bacterial community during composting. At the phylum level, the relative abundance of Firmicutes, Proteobacteria, and Chloroflexi was higher in the treatment group. At the class level, the relative abundance of Clostridia, Alphaproteobacteria, and Gammaproteobacteria in the treatment group were higher at the mesophilic and thermophilic phases. At the family level, Peptostreptococcaceae, Clostridiaceae_1, and Halanaerobiaceae of the Clostridia and Micromonosporaceae in the treatment group were higher at the mesophilic and thermophilic phases. Halocella was significantly positively correlated with exogenous microbial agents, while Ammoniibacillus was significantly negatively correlated with it. It suggested that microbial agents significantly changed the physicochemical properties and bacterial community structure during swine composting.

Changes of chilling and heat accumulation of apple and their effects on the first flowering date in the main planting areas of northern China

LIU Lu, GUO Liang, LI Man-hua, FU Wei-dong, LUAN Qing

2020, 31(7):  2457-2463.  doi:10.13287/j.1001-9332.202007.026

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Studies on variations in chilling and heat accumulation in apple trees and their effects on first flowering date under climate change are important for guiding apple planting and productions. In this study, we carried out experiments in representative stations of apple planting areas in the northern China, including Fushan of Shandong, Wanrong of Shanxi, Xifeng of Gansu and Akesu of Xinjiang. The first flowering data and hourly temperature data during 1996-2018 were used to calculate the daily chilling and heat accumulation units by applying the dynamic model and growing degree hour model. Partial least squares regression (PLS) correlated daily chilling and heat units with the first flowering dates was used to identify the chilling and heat accumulation periods for apple flowering. We evaluated the impacts of temperatures during these periods on apples' flowering. Our results showed that the chilling accumulation period of apple trees in the examined sites started at October 1, ended in late February or mid-March, with chilling accumulations of 74.1-89.3 CP (chill portion). The heat accumulation periods were from late January to the first flowering dates with the heat accumulation of 4010-5770 GDH (growing degree hour). The chilling accumulation at Xifeng and Akesu was correlated positively with mean temperature during the respective accumulation period, with 3.8 and 5.0 CP enhancement following 1 ℃ increase during the accumulation period. Heat accumulation at all stations correlated positively with mean temperature during the respective accumulation period, with 725-967 GDH enhancement following a 1 ℃ increase during the accumulation period. Compared to the effects of chilling accumulation on tree flowering, the first flowering data of apples in the main planting areas were mainly affected by mean temperature during the heat accumulation period. Climate warming is beneficial for apple blossom and production in the areas with low mean temperature during the chilling accumulation period.

Reviews

Responses of forest soil microbial communities to drought and nitrogen deposition: A review

ZHENG Yong, HE Ji-zheng

2020, 31(7):  2464-2472.  doi:10.13287/j.1001-9332.202007.035

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Drought and nitrogen input are profoundly influencing most life on Earth and the substance cycling in forest ecosystems in the Anthropocene, with consequences on global carbon balance and feedback on climate changes. Soil microorganisms drive biogeochemical cycling and key ecological processes, with central role and global importance in climate change biology. Here, we reviewed the research in the area of the effects of drought and nitrogen deposition on soil bacteria and mycorrhizal fungi in forest ecosystems. We proposed that future studies should focus on how microbial diversity, activity, and ecological functioning respond to multiple global change factors and their interactions; how subtropical forest ecosystems respond to global changes on the basis of establishment of the long-term field experimental station; the interaction of different soil biological guilds; utilizing microbial big data to construct the relevant mechanistic models. Taken together, based on improved understanding of the responses of soil microbial diversity and community composition to global changes, further research may subsequently focus on manipulating the microbial communities to enhance forest management, ecological resources protection, and environmental sustainability. This review would provide some critical theoretical basis for the microbial strategy in mitigating climate change in future.

Research progress on the effects of biochar application on soil fauna community

TANG Jing, YUAN Fang, SONG Li-hong

2020, 31(7):  2473-2480.  doi:10.13287/j.1001-9332.202007.034

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Soil fauna is an indispensable component of soil biotic communities and an important biological driver controlling soil ecological processes. Exploring the effect of biochar on soil fauna community and their relationship, is of great significance to understand the ecological process and services of soil ecosystem. We reviewed the changes and possible mechanisms of soil fauna community to biochar application. The effect of biochar application on soil fauna was caused directly by the difference of raw material, carbonization temperature, and application amount, and indirectly by the changes of biotic factor, including changes of plant physiological characters and microbe biomass, and changes of abiotic parameters (e.g. soil physiochemical characters). The growth, reproduction and behavior of soil fauna could be promoted under low amount of biochar application (mass ratio <5%). In contrast, toxicity effect occurred with a heavy application (>10%). Meanwhile, activities of soil fauna would affect the stability of biochar, and its ecological and environmental role. A road map for future researches about biochar and soil fauna interaction must focus on long-term field studies, spatial and temporal variation, merge of multi-discipline, and comprehensive analysis and prediction.