香樟冠层光环境对叶片功能性状和光合特性的影响

doi:10.13287/j.1001-9332.202308.027

摘要/Abstract

摘要： 为了解香樟冠层不同光环境叶片光合能力的适应机制,提升冠层碳汇功能,本文选取香樟单株冠层南向外侧(100%全光)、南向内侧(34%全光)和北向(21%全光)3个方位的叶片,研究光环境对叶片形态结构、营养和生理性状以及光合特性的影响,分析弱光环境下导致光合能力下调的主要限制因子。结果表明:随着冠层光强减弱,叶片的比叶重、表皮角质层厚度、下表皮厚度、栅栏组织厚度、栅栏组织细胞数和细胞宽度、栅栏组织与海绵组织的厚度比、细胞结构紧密度均显著降低,而海绵组织厚度、栅栏组织细胞长宽比、细胞结构疏松度均显著升高。与全光环境相比,2个弱光环境下叶片的碳含量、可溶性糖、淀粉和可溶性蛋白含量均显著降低,而氮含量在北向显著升高。弱光导致净光合速率(P_n)、暗呼吸速率、CO₂气孔导度(g_sc)、叶肉导度(g_m)、CO₂总导度(g_tot)、胞间CO₂浓度(C_i)、叶绿体CO₂浓度(C_c)等气体交换参数显著下降,且P_n与g_sc、g_m、g_tot、C_c呈显著正相关。尽管最大光化学量子效率、实际光化学量子效率、光化学猝灭系数、最大羧化效率(V_{c max})和最大电子传递速率(J_max)在不同光环境间均无显著差异,但V_{c max}和J_max与P_n呈显著正相关。g_m是弱光下光合速率降低的主要限制因子,且随着光照的进一步减弱,g_sc限制逐渐增强,而生化限制对净光合速率的影响相对较小。综上,全光照可以提升香樟冠层叶片的光合潜力,降低g_m和g_sc对光合性能的限制,增强碳同化能力。

关键词: 香樟冠层, 光环境, 功能性状, 光合特性, 光合限制

Abstract: To explore the adaptive mechanism of leaf photosynthetic capacity in different light environments within Cinnamomum camphora canopy and enhance carbon sequestration, we investigated morphological structures, nutritional and physiological traits and photosynthetic characteristics of leaves in different orientations of C. camphora canopy, southern side in the outer layer (100% full light), southern side in the inner layer (34% full light) and northern side (21% full light). We analyzed the main limitation resulting in down-regulation of photosynthetic capacity in low light environments. Results showed that specific leaf weight, the thickness of lower and upper epidermal cuticle, lower epidermis, palisade tissue as well as cell number and width of palisade tissue, the thickness ratio of palisade to spongy tissue, cell structure closely degree significantly decreased with decreasing light intensity within canopy, opposite to the responses of spongy tissue thickness, cell length-width ratio of palisade tissue, and cell structure loose degree. The contents of leaf carbon, soluble protein, soluble sugar and starch were significantly lower in two low light environments compared with full light, whereas nitrogen content was markedly higher in north side. Low light prominently reduced gas exchange parameters, i.e., net photosynthetic rate (P_n), dark respiration rate, stomatal conductance to CO₂(g_sc), mesophyll conductance to CO₂(g_m), total conductance to CO₂(g_tot), intercellular CO₂ concentration (C_i), CO₂ concentration at the chloroplast (C_c). P_n was positively correlated with g_sc, g_m, g_tot and C_c. There were no differences in maximum quantum photochemical efficiency, actual quantum photochemical efficiency, photochemical quenching coefficient, maximum rate of Rubisco carboxylation (V_{c max}) and maximum rate of electron transport (J_max) among light environments. V_{c max} and J_max were positively correlated to P_n. Of the shading-induced limitations to photosynthesis, g_m limitation was the most important, and g_sc limitation was enhanced with further weakened light intensity while biochemical limitation was rather limited. In summary, the results suggested that full light could improve leaf photosynthetic potential in C. camphora canopy leaves, reduce the effects of g_m and g_sc limitation on photosynthesis, and consequently enhance carbon assimilation capacity.

Key words: Cinnamomum camphora canopy, light environment, functional trait, photosynthetic characteristics, photosynthetic limitation.

冷寒冰, 万宁海, 刘群录. 香樟冠层光环境对叶片功能性状和光合特性的影响[J]. 应用生态学报, 2023, 34(8): 2113-2122.

LENG Hanbing, WAN Ninghai, LIU Qunlu. Effects of light environments within Cinnamomum camphora canopy on leaf functional traits and photosynthetic characteristics[J]. Chinese Journal of Applied Ecology, 2023, 34(8): 2113-2122.

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