Plants only interact with neighbors over restricted distances,so local conditions are of great significance for plants.In this study,a spatially-explicit,individual-based model was constructed to explore the effects of size variation and spatial structure on adaptive plasticity of plant height in response to light competition.In the model a plant maintains its height at an optimal value in order to maximize its growth rate,and this optimal height increases with the increase of the intensity of light competition experienced by the individual plant.When the spatial pattern of the population is non-uniform or there is size variation among individual plants,the height growth curves of individuals different from each other vary due to the differences in the local light environment,and there is also variation in the allocation of photosynthate to height growth among the individual plants.There is no ESS height or height growth strategy on which all plants will converge.Our results indicate that the plasticity of plants' height growth reactions to the light competition should be considered at the individual level and they argue strongly for the importance of the spatial pattern and neighborhood effects in generating the diversity of heights and height growth strategies in plant population.
CHEN ShuYan ZHANG JiaLin JIA Peng XU Jin WANG Gang XIAO Sa
Various cadmium （Cd） concentrations （0, 50, 100, 200 and 300 μmol L-1） affected Elymus dahuricus seed germination, seed- ling growth, antioxidative enzymes activities （AEA）, and amounts of malondialdehyde （MDA） and proline present. These in- fluences were determined for separate E. dahuricus cohorts known to be either infected （E＋） or non-infected （E-） by a Neo- typhodium endophyte. Under high Cd concentrations （100, 200 and 300 lamol L-l）, E＋ specimens showed a significantly （P〈0.05） higher germination rate and index, as well as higher values for shoot length, root length and dry biomass. However, the germination rate and index, root length and dry weight did not show a significant （P〈0.05） difference under the low Cd concentrations （0 and 50 μmol L^-1）. AEA and proline content increased, as did MDA content, in the E＋ （vs. E-） specimens under high Cd concentrations. There was no significant （P〉0.05） difference under low Cd concentrations. Endophyte infection was concluded to be of benefit to E. dahuricus exposed to high Cd concentrations.
