Effects of ozone stress and drought stress on photosynthesis characteristics of Syzygium hainanense and Alstonia scholaris seedlings
Abstract
Photosynthesis characteristics of Syzygium hainanense and Alstonia scholaris seedlings were studied under ozonic stress and drought stress in open-top chambers(OTC). Net photosynthetic rate(Pn), stomatal conductance(Gs), transpiration rate(Tr), intercellular CO2 concentration(Ci) and stomatal limits(Ls) of the two tree species were evaluated. The results showed that under ozonic stress and drought stress, Pn, Gs and Tr of S. hainanense and A. scholaris seedlings declined, while their Ci and Ls increased or decreased. The combined effect of ozone and drought stresses was greater than ozonic stress or drought stress alone. The decrease of Pn was mainly from stomatal limitation under ozone stress, and from non-stomatal limitation under drought stress for S. hainanense seedlings, whereas it was changed from stomatal limitation to non-stomatal limitation under the both stresses for A. scholaris seedlings. The decrease of Pn was mainly from non-stomatal limitation for the two species under ozone-drought intercross stress.