FAST GROWTH-KINETICS OF PLANTS UNDER SALT STRESS

A sensitive and rapid recording technique is applied to the studies of fast kinetics of root and aerial organ growth in plants under salt-induced stress. For five species differing in salt tolerance (sunflower > barley > maize > pea = bean), it is demonstrated that both high (100 - 200 mM) and low (10 - 20 mM) NaCl concentrations induce retardation or arrest of growth of the plant ograns. Growth retardation is preceeded by a r apid significant reduction in organ size. Removal of the stress factor leads to an increase in organ size and to restoration of the initial (or even higher) growth rate. The concentration dependence of growth response exhibited by maize and bean roots correlated with the salt tolerance of these plants. The effects of isotonic NaCl and KCl at low concentrations (20 mM) were similar. The growth response of roots was nondelayed, whereas aerial organs showed a lag period of up to 30 - 60 min. Rapid development of the response, its reversibility and reproducibility, as well as salt nonselectivity indicate die osmotic nature of plant growth response to salt stress. A direct and strong dependence of growth on the osmotic pressure of the medium is evident. Growth by elongation, being a complex physiological process, appears to include an osmotic component.