Growth, ionic absorption and ionic distribution responses to soil drought and drought-salt stresses in two Robinia pseudoacacia clones

Key words: 
• plant physiology /
• Robinia pseudoacacia clones /
• drought stress /
• drought-salt stress /
• growth /
• ionic absorption and distribution

Abstract: Growth, ionic distribution and selective ionic absorption(transportation) responses to soil drought stress alone and drought-salt stress two Robinia pseudoacacia(black locust) clones(W1and L78) were determined. The salt and drought stresseswere set by controlling the amount of NaCl and water in potted plants.Results showed that both stresses inhibited growth of the two clones with drought-salt stress inhibiting growth more than drought stress alone. In addition, drought stress alone inhibited growth more on W1than on L78, whereas drought-salt stress inhibited growth more on L78than on W1. Also, under drought stress, total Na+, K+, Ca2+ and Mg2+ contentin W1 roots had a greaterdecline than L78. With both stresses the growth of L78was inhibited due to low RK,Na(relatively selective ratio), RCa,Na, and RMg,Na rates of L78roots and large rates for leaves causing a severe decreasing of K+,Ca2+, andMg2+ in the roots. Contributing to lowion levelswas root inability to control both Na+ absorption and Na+ transportation to shoots. W1had higher drought-salt resistance because itmaintained a relatively stable mineral nutrient level, especially with K+ and Ca2+, and because under drought-salt stress its rootswere able to control Na+ absorption and Na+ transportation to the shoots. The lowerNa+, K+, Ca2+, and Mg2+, in W1roots compared to L78under drought stress alone was due to a decrease in the proportion of inorganic oins in osmotic adjustment and an increase in organic ions. This, then, increased consumption of own substances and energy leading to greater inhibition on W1growth.[Ch, 5 tab. 15 ref.]