Growth, utilization and salt tolerance of Atriplex species

Atriplex species are highly salt tolerant since substantial reductions in growth occur at 400-600 mol m(-3) external NaCl. Leaves of Atriplex species contain a very high salt concentration. However, much of the Na+ in young leaves is located in salt bladders. Leaf tissues (i.e. leaves excluding salt bladders) have a low Na+ when young, but a high [Na+] when old. In contrast to Na+, [K+] shows much less change with leaf age. However, the very young leaves have higher [K+] than old leaves. Similarly apical segments of roots have a higher [K+] and much lower [Na+] than the bulk roots. High [Na+] in old leaves was accompanied by high succulence in old leaves. Estimations on cytoplasmic concentration for K+ and Na+ show that even at 600 mol m(-3) (K++Na+) does not exceed 200 mol m(-3) and K+/Na+ remains higher than one. Consequently, sufficient metabolic activity is maintained in various plant parts even at high salt concentrations.