江西阳际峰73种阔叶植物叶片光截获和水分排除策略对树冠位置的响应研究

Trade-off relationship between light interception and leaf water shedding at different canopy positions of 73 broad-leaved trees of Yangji Mountain in Jiangxi Province,China

为研究常绿阔叶林林木树冠位置是否会对叶片与光截获和水分排除相关的性状间的权衡关系产生影响,本研究采用标准化主轴回归(standardized major axis,SMA)的方法,对江西阳际峰73种阔叶树上、下树冠位置(冠层二分法)的叶形态性状(叶片厚度和叶长宽比)、构型性状(倾角和滴水尖长度)以及生理性状(光合-光饱和点和光合-光补偿点)进行分析,以期阐明亚热带阔叶树叶片在应对资源变化时的策略.结果显示,(ⅰ)不同树冠位置的叶片厚度和长宽比无显著差异(P>0.05);上冠层叶片的倾角(34.92°±1.15°)、光饱和点((954.89±27.86)μmol/(m^(2)·s))和光补偿点((29.45±1.02)μmol/(m^(2)·s))均显著高于下冠层叶片(倾角:16.66°±0.50°;光饱和点:(520.74±15.47)μmol/(m^(2)·s);光补偿点:(12.54±0.38)μmol/(m^(2)·s);P<0.05),但上冠层叶片的滴水尖长度((4.26±0.15)mm)显著低于下冠层叶片((7.18±0.22)mm;P<0.05).(ⅱ)不同树冠位置叶片的叶倾角、滴水尖长度与光饱和点及光补偿点均存在显著相关关系(P<0.05),但其滴水尖长度与叶片长宽比仅在上冠层叶片中呈显著弱相关(P<0.05).(ⅲ)不同树冠位置叶倾角、滴水尖长度、光饱和点和光补偿点均存在共同的异速指数(P>0.05),并呈现出等速生长关系,但异速常数存在显著差异(P<0.05).研究结果表明,树冠位置不会改变叶片光截获和水分排除性状间的权衡策略,叶滴水尖长度和叶倾角主要受与叶片光资源利用能力相关的生理性状的影响.

As light interception and leaf water shedding may require different leaf traits,trade-offs may exist between the leaves’abilities in light interception and leaf water shedding.Moreover,such trade-offs may vary with the vertical canopy position as leaf traits vary with tree height.We studied the variations in leaf traits at different canopy positions to study how canopy positions would affect the trade-off between the traits related to light interception and leaf water shedding in subtropical broad-leaved trees.We used the standardized major axis regression method to analyze the relationships among leaf morphological traits(leaf thickness and leaf length/width ratio),configuration traits(leaf angle and leaf drip tip length),and physiological traits(photosynthesis-light saturation point and photosynthesis-light compensation point)between sun and shade leaves.The results are as follows:(i)There was no significant difference in the leaf thickness and leaf length/width ratio at different canopy positions(P>0.05).The leaf angle(34.92°±1.15°),light saturation point((954.89±27.86)μmol/(m^(2)·s)),and light compensation point((29.45±1.02)μmol/(m^(2)·s))at the upper canopy were significantly higher than those at the lower canopy(leaf angle:16.66°±0.50°,light saturation point:(520.74±15.47)μmol/(m^(2)·s),and light compensation point:(12.54±0.38)μmol/(m^(2)·s);P<0.05).However,the leaf drip tip length was significantly shorter at the upper canopy position((4.26±0.15)mm)than at the lower canopy position((7.18±0.22)mm;P<0.05).(ii)There were significant correlations among leaf angle,leaf drip tip length,light saturation point,and light compensation point at different canopy positions(P<0.05),but the leaf drip tip length and leaf length/width ratio were only weakly correlated at the upper canopy leaves(P<0.05).(iii)Common slope(P>0.05)and isometric scaling existed among the leaf angle,light saturation point,and light compensation point at different canopy positions,but there was no common constant(P<0.05).These results indicated that the canopy position does not alter the trade-off strategy between light interception and leaf water shedding.The leaf drip tip length and inclination were mainly affected by the light saturation point and light compensation point.