应用控水试验研究干旱胁迫对乌桕1年生幼苗光合色素及光合性能的影响.结果表明,种源GC2、SC4、HS1、XN1叶绿素含量变化基本一致,在整个干旱期尽管存在一定起伏,但差异不显著(P＞0.05),说明干旱对4种源幼苗叶绿素含量的影响不明显；种源GC2、SC4、HSt、XN1类胡萝卜素含量在干旱后期均有一定程度升高,且含量变化达显著水平(P＜0.05),说明干旱对幼苗类胡萝卜素的合成具有促进作用；HZ2断水后叶绿素与类胡萝卜素含量迅速下降,复水含量回升.干旱胁迫下,乌桕幼苗净光合速率(Pn)普遍下降,气孔导度(G(s))也呈下降趋势.相关分析表明,Pn与G(s)、Tr呈极显著正相关(P＜0.01),相关系数(R)分别为0.642、0.728,与光合色素指标的相关性不显著(P＞0.05).在干旱胁迫下,乌桕幼苗光合作用强度下降可能源于叶片气孔的关闭以及细胞间隙CO2浓度降低,而与光合色素的含量变化无直接相关.%Effect of drought stress on photosynthetic pigment and photosynthesis of Sapium sebiferum Seed lings was studied by water control experiment. The results showed that the changes in chlorophyll a, chloro phyll b,and chlorophyll ( a + b) contents of S. Sebiferum seedings from GC2,SC4,HS1 and XN1 provenances were consistent with drought time extended, and the changes were not significant(p >0.05)during the drought period. Meanwhile the carotenoid increased significantly (p 0.05) ,so the decline of Pn could be due to the stomatal restriction and the decrease of intercellular CO2 con centration (Ci) , and did not result from the decline of photosynthetic pigment content.
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