Salinity-alkalinity tolerance in wheat: Seed germination, early seedling growth, ion relations and solute accumulation

Abstract

Germination and early seedling growth are the most critical stages for plant establishment in saline-alkaline soil. To gain a better understanding of relations between germination and seedling establishment, and the physiological adaptive mechanisms of the two stages under salt and alkali environments, wheat was tested by mixing two neutral salts (NaCl:Na2SO4) and two alkaline salts (NaHCO3:Na2CO3). Results showed that reductions of germination percentage and seedling growth were greater under alkali stress. Nongerminated seeds germinated well after being transferred from higher salinity and lower alkalinity to distilled water. The Na+ concentration and Na+/K+ ratio increased much greater under alkali stress, especially in root. The K+ concentrations in both shoot and root were not affected under salt stress, but decreased under alkali stress. Proline and soluble sugars were the primary organic osmolytes under the two stresses. Our results suggest that the deleterious effects of alkali stress are more severe than salt stress. Higher Na+ concentration in root is an important feature of wheat tolerance of salinity-alkalinity at early seedling stage. The different saline-alkaline tolerant abilities between germination and early seedling stage indicate that for wheat, successful germination does not ensure seedlings can survive in saline-alkaline soil of Northeast China. Key words: Alkali stress, germination recovery, osmotic adjustment, physiological change, salt stress.