采用人工气候室控制环境条件,研究了高温(30 ℃和40 ℃) 对印楝(Azadirachta indica A. Juss.)、木豆[Cajanus cajan(Linn.) Huth]、赤桉(Eucalyptus camaldulensis Dehn.)、蓝桉(E. globulus Labillardière)、柠檬桉(E.citriodora Hook.)、大叶相思(Acacia auriculiformis A. Cunn.)和麻风树(Jatropha curcas Linn.) 7 个干热河谷植被恢复树种幼苗叶片光合参数的影响,以及低湿条件对麻风树幼苗叶片光合参数的影响,并对高温及低湿条件下各树种叶片光合参数与叶片含水量的关系进行了探讨。结果表明:在高温条件下,供试树种叶片的净光合速率(Pn)和Fv/ Fm 值均随叶片含水量的提高逐渐增加,但在40 ℃条件下各树种的Pn 以及Fv/ Fm 值均明显降低,表明叶片含水量高有利于各树种叶片Pn 和Fv/ Fm 的提高,而40 ℃高温则对其Pn 和Fv/ Fm 有明显抑制作用。在非干旱条件下,高温对各树种幼苗的Pn、气孔导度(Gs)、胞间CO₂ 浓度(Ci)和蒸腾速率(Tr)均有不同程度影响。在40 ℃条件下,供试树种中印楝和赤桉幼苗的Pn 降幅最小;大叶相思、蓝桉和木豆幼苗的Gs 明显增加;各树种幼苗的Ci 均明显提高;除印楝外,其他6 个树种幼苗的Tr 明显加剧且叶片水分利用效率降低。在叶片含水量较高的状况下,供试7 个树种中印楝和赤桉幼苗的Fv/ Fm 值受高温的影响较小。在空气相对湿度20% 的条件下,麻风树幼苗的Pn、Gs、Ci 及Tr 均明显降低,且均随叶片含水量的提高而增加,表明叶片含水量下降是麻风树幼苗光合作用减弱的重要影响因素。研究结果表明:干热河谷地区的高温引起的植物光合限制以非气孔因素为主导;在供试的7 个树种中,印楝和赤桉对干热河谷高温干旱生境的适应或忍耐能力较强。

Under controlling environmental condition of phytotron, effect of high temperature (30 ℃and 40 ℃) on photosynthetic parameters of leaf of seedlings of seven tree species including Azadirachta indica A. Juss., Cajanus cajan(Linn.)Huth, Eucalyptus camaldulensis Dehn., E. globulus Labillardière, E. citriodora Hook., Acacia auriculiformis A. Cunn. and Jatropha curcas Linn. used for vegetation restoration in dry-hot valley and effect of low humidity on photosynthetic parameters of leaf of J. curcas seedling were studied, and also, relationship between photosynthetic parameters and water content of leaf of tree species tested under high temperature and low humidity conditions was discussed. The results show that under high temperature condition, net photosynthesis rate (Pn) and Fv/ Fm value of leaf of tree species tested gradually increase with enhancing of water content of leaf, but those all obviously decrease under 40 ℃condition, meaning that higher water content of leaf is beneficial to increasing of Pn and Fv/ Fm, while high temperature of 40 ℃has an obvious inhibition to their Pn and Fv/ Fm. Under non-drought condition, high temperature has the influence on Pn, stomatal conductance(Gs), intercellular CO₂ concentration (Ci) and transpiration rate (Tr) of seedling at different degrees. And under 40 ℃ condition, Pn decreasing range of seedlings of A. indica and E. camaldulensis is the lowest, Gs of seedlings of A. auriculiformis, E. globulus and C. cajan obviously increases; Ci of seedlings of all tree species tested obviously increases; and except A. indica, Tr of seedlings of other six tree species markedly enhances and water using efficiency decreases. Under state of higher water content of leaf, Fv/ Fm value of A. indica and E. camaldulensis seedlings in seven tree species tested is less influenced by high temperature. Under relative air humidity of 20%, Pn, Gs, Ci and Tr of J. curcas seedling all markedly decrease and all increase with increasing of water content of leaf, meaning that decreasing of water content of leaf is an important influence factor on photosynthesis reduction of J. curcas seedling. It is suggested that photosynthesis restriction induced by high temperature in dry-hot valley is mainly due to non-stomatal factor. And A. indica and E. camaldulensis in seven tree species tested have relatively stronger adaptation or resistant abilities to high temperature and drought habitat of dry-hot valley.