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Effects of light and water availability on the morphology and allelopathy of the native outbreak species Merremia boisiana (Gagnep.) Oostr.

HUANG Qiao-qiao1, SHEN Yi-de1, LI Xiao-xia1, ZHANG Guo-liang2, HUANG Dong-dong1, FAN Zhi-wei1**   

  1. (1Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou 571101, China;  2 Institute of Environmental and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China)
  • Online:2015-02-07 Published:2015-02-07

Abstract: Merremia boisiana is a native species in Hainan Province of China, and its population quantity has been rapidly increasing in recent two decades, which poses a heavy threat to many secondary forests, planted forests and shrublands. There are different light and water quantity conditions in habitats where populations of M. boisiana have broken out, and outbreak species usually adapt to diverse environmental conditions through high phenotypic plasticity. To reveal the ecophysiological mechanisms underlying the adaptation of the outbreak species M. boisiana to diverse environmental conditions, this study assessed the effects of different light and water availability on the growth, morphological traits and their plasticity, and allelopathy of M. boisiana through a greenhouse pot experiment. Biomass of M. boisiana decreased under high light intensity and drought. Low light increased total stem length, specific stem length, and specific leaf area, and decreased the root/shoot ratio of M. boisiana. The mean phenotypic plasticity index of these morphological traits was 0.36. Under high light and drought, aqueous leachates from dry leaves of M. boisiana were least inhibitory to seed germination and seedling shoot growth of Lactuca sativa var. ramosa, possibly because M. boisiana decreased its resource allocation to competition (allelopathy) under stress conditions. Plasticity in morphology might facilitate M. boisiana to better capture light as well as grow to the canopy at a faster rate under low light availability in the forest understory, while plasticity in allelopathy indicates that M. boisiana might adjust its resource allocation to competition (allelopathy) to adapt to various water conditions. We conclude that plasticity of M. boisiana in morphological traits and allelopathy might be one of the ecophysiological mechanisms of M. boisiana adapting to various environmental conditions and causing outbreak.

Key words: life table, effective accumulated temperature, population trend index, developmental threshold temperature, temperature