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 in Leaves of Melastoma candidum Grown in Hilly and Swampy Habitats

对在坡地和沼泽地生长的野牡丹叶的解剖特征与气孔气体交换特性的研究表明:两者在形态结构方面存在着一定的差异,坡地野牡丹叶较窄,上表皮细胞小而排列紧密,气孔密度较大,上表皮厚,沼泽地野牡丹整个叶片和海绵组织比较厚,最大导管直径和栅栏细胞长度/宽度比值大,但栅栏组织厚/海绵组织厚比值较小。坡地野牡丹与沼泽地野牡丹的叶绿素a、叶绿素b的含量和类胡萝卜素的含量以及叶绿素a/b比值的差异都很小。沼泽地野牡丹净光合速率、蒸腾速率及气孔导度较高,常用的水分利用效率(Pn/Tr)接近,沼泽地野牡丹的内在水分利用效率(Pn/Gs)略高于坡地,但差异不显著。综合分析其生境条件,土壤与野牡丹叶片解剖结构和生理生态特性相关性密切。但实验结果不足以确定两种生境下生长的野牡丹为不同的生态型。

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.