Effect of Drought Stress on Photosynthetic Pigment and Photosynthesis of Sapium sebiferum Seedlings

Effect of drought stress on photosynthetic pigment and photosynthesis of Sapium sebiferum Seedlings was studied by water control experiment.The results showed that the changes in chlorophyll a,chlorophyll 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(p0.05)during the drought period.Meanwhile the carotenoid increased significantly(p0.05),this illuminated that drought stress accelerated the synthesis of the carotenoid.The contents of both chlorophyll,and carotenoid from HZ2 provenances droped rapidly under drought stress,but reversed afterwatering.Net photosynthetic rate(Pn) and the stomatal conductance(Gs)of seedings showed the tendency of decreasing under drought stress.Correlation analysis showed that Pn was significantly positively correlated to Gs and Tr(p0.01),the correlation coefficients(R) were 0.642,0.728,respectively.Correlation was not significant between Pn and photosynthetic pigment(p0.05),so the decline of Pn could be due to the stomatal restriction and the decrease of intercellular CO2 concentration(Ci),and did not result from the decline of photosynthetic pigment content.