Comparative Studies On Shade Tolerance Among Four Shrub Species

Shade tolerance of plant refers to the ability of plants to develop and grow in relatively low light conditions. To adapt to different photon flux density, plants can change their metabolic systems to maintain growth balance. The correct selection and application of shade-tolerance plants is of significance to establish comprehensive plantation structure and increase unit efficiency of green environment, which is critical step to civic forest planning.This study analyzed and measured different physical and photosynthetic index of four different shrub species: Deutzia grandiflora, Vitex negundo var. heterophylla, Myripnois dioica and Jatropha curcas under four different light conditions for more than 60 days: 4.8%, 14.9%, 46.0% and 100%, by employing black velaria.By comprehensively analyzing the shade tolerance on these four shrubs, our study suggested that shade has different effects on these four shrubs in terms of physical and photosynthetic index. Under the shade, the density of stomata for leaves decreases, the relative specific leaf weight decreases, the respiratory rate of leaves increase, the ratio of content of chlorophyll a to chlorophyll b decreases, the compensation points of leaves decrease slightly, the apparent quantum efficiencies increase and the biggest true photosynthetic rates decrease. Moderate shade increases the relative water content of leaves, but excessive shade decreases the relative water content of leaves. The order of shade tolerance from strong to weak is Myripnois dioica>Deutzia grandiflora>Jatropha curcas>Vitex negundo var. heterophylla.