Adaptability Comparison between the Seedlings of Eucalyptus grandis and Alnus cremastogyne under the Condition of Continuous Drought Stress

A pot experiment was carried out to study the growth and physiology responses of Eucalyptus grandis and Alnus cremastogyne seedlings subjected to continuous drought stress. The results were as follows (1) In the case of short treatment time (0~6 d), the leaf water status of both species were good, but comparatively higher stomatal conductance(Gs) and transpiration rate(Tr) values of E. grandis leaves might lead to higher water consumption. (2) In the more severe drought conditions(9~18 d), both species could avoid drought threat by decreasing Gs and Tr. However, A. cremastogyne also took the strategy of defoliation so that the remaining leaves could get adequate water, resulting in its better leaf water status and slighter responses of osmoregulation substances and antioxidant enzymes during 18 d treatment. (3) A. cremastogyne was more sensitive to drought than E. grandis because of the earlier significant rises but unstable changes of the activity of superoxide dismutase(SOD) and the contents of H2O2, soluble protein(SP) and proline(Pro) in leaves. (4) In face of drought stress, A. cremastogyne might mainly focus on the drought-avoid strategy to save water and reduce oxidative damage at the cost of growth, however, E. grandis consumed more water for assimilation and production, probably evolved out of a relatively stronger mechanism to face the drought threat such as oxidation damage.