Abstract:

Three twoyearold woody saltbushes (Atriplex gardneri, A. tridentata, A. canescens) and Hippophae rhamnoides were used to study effects of drought stress on physiological characteristics of woody saltbush. Three levels of soil moisture were used as the following: control (CK), moderate water stress (T₁), and severe water stress (T₂), and the soil moisture was controlled by weighing the pots. The results showed that: 1) the water holding capacity of three kinds of woody saltbush was far higher than H. rhamnoides, because of maintenance high bound water content; 2) under drought stress conditions, the cell membrane oxidation of A. gardneri and A. tridentata was low. MDA, resulted from cell membrane oxidation, of A. canescens under T₂ treatment was increased 19.3% than that of CK. The membrane permeability of three saltbushed did not significantly increased, suggesting good cell membrane structure and function. Under T₁ and T₂ drought level, a significant variation for MDA content of H. rhamnoides was found, increased 20.68% and 24.34% respectively in comparison with the control. There was severe cell membranes oxidation, which caused permeability of cell increased 37.38% and 41.58% respectively. 3) drought stress had no obviously impact on the synthesis of photosynthetic pigment of saltbushes. Under T2 treatment the Chl a and Chl b of H. rhamnoides was decreased 27.76% (P<0.05) and 44.18% (P<0.05) respectively. 4) according to the viewpoint of stomatal restriction value presented by Farquhar, under moderate drought stress, the decrease of P_n was caused by closure of stomata except A. tridentata whose low P_n was caused by nonstomatal factors. 5) Subordinate function value was used to evaluate the drought tolerant ability for the four species. The order was: H. rhamnoides>A. tridentata>A. gardneri>A. canescens.

Key words: drought stress, woody saltbush(Atriplex), water holding capacity, MDA, P_n