荷木叶片生理特性在树冠空间层次上的差异

Foliar physiological characteristics of Schima superba along a vertical canopy gradient

通过对荷木(Schima superba)树冠空间层次上叶片形态、光合日变化和叶绿素含量的分析,揭示荷木树冠在空间层次(顶层、中层、底层)上叶片生理的变化规律。结果表明:顶层叶片的比叶面积显著低于中层和底层,叶长和最大叶宽表现为顶层<中层<底层的趋势(P<0.01);顶层光合有效辐射显著高于中层和底层,并且顶层叶片具有更高的净光合速率(P_n)、气孔导度(g_s)、蒸腾速率(T_r)和羧化效率(V_c),底层叶片的胞间二氧化碳(C_i)则显著高于顶层;各层次的光合有效辐射与叶片的P_n、g_s、V_c、T_r和L_s有显著地正相关,与Ci呈显著负相关;顶层叶片的叶绿素a+b(Chl-a+b)和类胡萝卜素(Car)含量显著低于中层和底层,而叶绿素a/b(Chl-a/b)的均值则高于中层和底层。研究表明,光照是导致荷木叶片生理特性在树冠垂直空间层次上出现差异的主要因素。

We investigated leaf morphology,diurnal variation of photosynthesis,and chlorophyll content of Schima superba along different positions of canopy（top,middle and bottom layers） to determine its eco-physiological response to spatial variation.The results showed that specific leaf area of S.superba from the top layer was significantly lower than that from the middle and bottom layers.Leaf length and maximum width were significantly different among the three layers（P〈0.01）,being bottom layer 〉middle layer 〉top layer.Compared with the middle and bottom layers,photosynthetically active radiation was the highest at the top canopy.Leaves from the top layer had significantly higher net photosynthesis rate（Pn）,stomatal conductance（gs）,carboxylation efficiency（Vc）,transpiration rate（Tr） and stomatal limitation（Ls） than that from either the middle or bottom layer.Conversely,leaves from the bottom layer had the highest intercellular CO2 concentration（Ci）.Photosynthetically active radiation from each layer had a significant positive correlation with Pn,gs,Vc,Trand Ls,and was negatively correlated with Ci.The highest contents of chlorophyll a＋b（Chl-a＋b） and carotenoid（Car） of leaves were found from the middle and bottom layers,while the top layers had much higher chlorophyll a/b（Chl-a/b）.The results indicated that illumination was the primary driver of variation in leaf morphological and physiological characteristics of S.superba along the vertical space of canopy.