| Comparative studies on the physioecological traits of photosynthesis, transpiration and stomatal conductance in four congeneric species, Mosla hangchowensis (M.h), Mosla scabra (M.s\ Mosla chimnsis (Me) and Mosla dianthera (M.d) were investigated under controlled soil water status in this paper. We analyzed the alternative in functional phenotypic plasticity responding to variationalentironments, 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.2 Photosynthetic rate, transpiration rate and stomatal conductance in four species are higher in forenoon than in afternoon, it is mainly due to daily decreasing soil water.3 Environment factors have some effects on photosynthetic rate, transpiration rate and stomatal conductance, and the effects show difference with changing species and treatments.4 The optimal water niche of M. h and M c are wetter than middle soil water content, belongs to mesophytes; The optimal water niche of Mosla scabra, on photosynthesis is more wetter than that of M.h and Me, the optimal water niche between mesophytes and hygrophytes, and leaning to hygrophytes; The photosynthetic water condition of M.d is arid environments, and its ecotype exits between mesophytes and xerophytes, and leaning to xerophytes.5 M.h and M.s are locating between shade plants and sun plants, while M.c and M.d obviously belong to sun plants. Chlorophyll content of all the species expect Me show the same rule as the plants locating from sun leaves to shade leaves with the changing soil water content.6 Rewatered after extreme drought, the photosynthetic rate of M.h, M.c and M.s increase evidently, showing "compensation effect" , but there have differences between these three species. Contrarily, when rewatered after extreme drought, the photosynthetic rate of M.d. decreases obviously, making out that this species are adaptive to existing in arid environments.7 The transpiration rate and stomatal conductance of these four species show increase first and then decrease with the leaves locating from lower to upper, and the causes for this change due to the changing environment and the different physiological traits of the leaves. |
PDF Full Text Request