臭氧与干旱胁迫对海南蒲桃和盆架子幼苗光合生理的影响

以海南蒲桃（Syzygium hainanense）和盆架子（Alstonia scholaris）幼苗为材料，置于开顶气室进行人工臭氧熏气和干旱处理。通过测定0 d、15 d、30 d时2种树木幼苗叶片的净光合速率、气孔导度、胞间CO₂浓度及蒸腾速率，计算气孔限制值，分析这些指标在臭氧胁迫和干旱胁迫下的变化情况。结果显示：⑴受臭氧和干旱胁迫的影响，2种幼苗叶片的净光合速率、气孔导度、蒸腾速率随处理时间的延长呈现下降，胞间CO₂浓度和气孔限制值上升或下降，臭氧与干旱交叉胁迫的影响大于臭氧或干旱单一胁迫。在臭氧胁迫下，海南蒲桃幼苗的净光合速率下降以气孔限制为主，干旱胁迫下以非气孔限制为主。（2）盆架子幼苗在臭氧胁迫和干旱胁迫下从气孔限制转为非气孔限制，说明海南蒲桃的抗臭氧能力强于盆架子，抗旱能力不如盆架子；臭氧和干旱交叉胁迫下，2种幼苗的净光合速率下降均以非气孔限制为主，说明他们抗臭氧与干旱交叉胁迫的能力相近。

Effects of ozone stress and drought stress on photosynthesis characteristics of Syzygium hainanense and Alstonia scholaris seedlings

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 (P_n), stomatal conductance (G_s), transpiration rate (T_r), intercellular CO₂ concentration (C_i) and stomatal limits (L_s) of the two tree species were evaluated. The results showed that under ozonic stress and drought stress, P_n, G_s and T_r of S. hainanense and A. scholaris seedlings declined, while their C_i and L_s increased or decreased. The combined effect of ozone and drought stresses was greater than ozonic stress or drought stress alone. The decrease of P_n 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 P_n was mainly from non-stomatal limitation for the two species under ozone-drought intercross stress.