Abstract:

Planting of salt-tolerant plants is vital for the development of available coastal land resources. We studied the effects of different concentrations of seawater (diluted in 1/2 Hoagland’s solution) on the biomass and chlorophyll, ion, soluble sugar and soluble protein contents of Lactuca indica seedlings by sand culture in the greenhouse. The dry weight of L. indica shoots was more susceptible to seawater stress than that of roots. Compared with dry weight of controls, that of roots of L. indica seedlings was unchanged with seawater concentrations from 10% to 30%. With increasing seawater stress, the ratio of roots to shoots and Na⁺, Cl^– and soluble sugar contents were increased significantly. With 10% and 20% seawater treatments, chlorophyll content did not differ from that of controls but was significantly decreased with further increased seawater stress. At a seawater concentration of 10%, K⁺ content in the shoots and roots of L. indica seedlings did not differ from that of controls, but with increased seawater stress, the K⁺ content was markedly dose-dependently decreased. However, as gradually increasing soluble sugar content significantly, soluble protein content first increased then decreased with increasing seawater concentration. Adaptation to seawater in L. indica was mainly caused by strong K⁺ selective absorption and transport. Furthermore, accumulating soluble sugar and protein were important osmotica in L. indica seedlings and could be an indicator of salt tolerance.

Key words: ionic absorption, ionic transport