Anatomical Features and Stomatal Gas Exchange in Leaves of Melastoma candidum Grown in Hilly and Swampy Habitats
坡地和沼泽地野牡丹(Melastoma candidum)叶片的解剖特征与气孔气体交换特性

Anatomical features and stomatal gas exchange of the leaves of Melastoma candidum grown in hilly and swampy habitats were compared. The cells of upper epidermis was thicker with smaller cells which were closely arranged, and the stomatal density being higher in hilly melastoma compared to those in swampy one. Thicker sponge tissues, larger maximum vessel diameter, and higher ratio of palisade cell height to cell width were observed in swampy melastoma. However, the ratio of palisade thickness to sponge thickness was lower in swampy melastoma than that in hilly one. There were little differences in the contents of chlorophyll a and chlorophyll b, carotenoid and chlorophyll a/b between hilly and swampy melastoma.The hilly melastoma had lower net photosynthesis rate, transpiration rate and stomatal conductance than those of swampy melastoma. The diurnal courses of average water use efficiency(net photosynthetic rate/transpiration rate, WUE) were similar between plants grown in two habitats. Intrinsic water use efficiency (net photosynthetic rate/stomatal conductance, Intrinsic WUE) was lightly higher in swampy melastoma than that in hilly one, but no significant difference was found. It is proposed that these differences between two populations of melastoma might be mainly due to the different soil conditions. However, the above results could not confirm that the hilly and swampy melastoma are different ecotypes.