We analyzed the alternative in functional phenotypic plasticity responding to variational entironments , consequently , we interpreted the difference between endangerment and wide - distribution of these closely related species , and the results showed : 1 all of the daily changes of photosynthetic rate responding to different water status show " double apices " except m . d , the daily changes of photosynthetic rate in m . d shows " simple apices " responding to arid soil water content , while " double apices " responding to the other soil water content . emerging time of daily maxim of pn is difference between species and between treatments . daily course of transpiration and stomatal conductance of these for species all show " double apices " , but the emerging time of daily maxim of transpiration rate and stomatal conductance rate are all different between species 结果表明： 1 、除小鱼仙草外，四物种的光合速率日变化在不同水分梯度下均表现出“双峰型” ，小鱼仙草的光合速率日变化在于旱时表现出“单峰型” ，其余水分梯度下表现出“双峰型” ，种间和梯度间日最大光合速率出现时间有一定的差异；四物种蒸腾速率和气孔传导力日进程也表现出“双峰型” ，但种间日最大气孔传导力和蒸腾速率出现的时间也存在一定的差异。
