Sex-specific Heterogeneity in Stomatal Distribution and Gas Exchange of Male and Female Populus cathayana Leaves

Abstract

In this experiment, we investigated sex-related heterogeneity in stomatal distribution and gas exchange on leaves of male and female trees of Populus cathayana using grids measurement and 2-D contour maps. There were significant differences in stomatal length (SL), stomatal width (SW) and stomatal ratio (SR) between leaves of female and male and the significant variations were P=0.000, P=0.000 and P=0.002, respectively. Compared with leaves of male trees, SL and SW in leaves of female trees increased 51.86% and 67.06%, respectively, while SR in which decreased 11.46%. Moreover, the patterns for stomatal density (SD) as "middle zonesapical zonesbasal zones" and for SL as "apical zonesmiddle zonesbasal zones" were found in both male and female leaves. The patterns for SW were observed as "middle zonesapical zonesbasal zones" in female leaf and "apical zonesmiddle zonesbasal zones" in male leaf. It was also detected that the patterns for SR in female leaf as "basal zonesapical zonesmiddle zones" was opposite to that in male leaf. Significant difference was found in distribution pattern of net photosynthetic rate (Pn) between female and male leaves. Pn of female leaf was lower in base regions (2.00-3.00 μmol m-2 s-1) while higher in front regions (8.00-9.00 μmol m-2 s-1), and increased gradually from basal to apical zones. However, Pn of male leaf didn′t show certein pattern. The transpiration (Tr) and stomatal conductance (Gs) showed significant lower value in basal zones on male leaf comparing with famale leaf. Furthermore, CO2 concentration (Ci) showed pattern as "basal zonesmiddle zonesapical zones", which was opposite to stomatal limiting value (Ls), were observed on female leaf. Only Ls was found increased gradually from apical to basal zones although Ci and Ls varied obviously in each zones. To summarize, our result showed that there were significant differences in heterogeneity of stomatal distribution and gas exchange on male and female Populus cathayana leaves.