Effect of salt stress on physiological response and leaf polyamine content in NERICA rice seedlings

NERICA is a new African rice variety, developed by the West African Rice Development Association (WARDA) in 1990s. NERICA rice shows both vigorous growth and tolerance of stressors such as drought and disease. The purpose of this study was to clarify the physiological and biochemical responses to salt stress of NERICA rice seedlings. The degree of growth inhibition caused by salt stress was small in NERICA rice varieties as compared with japonica Nipponbare. Na accumulation in leaf blades was high in salt-sensitive varieties. Accumulation of proline, a known compatible solute, was also induced by salt stress, especially in salt-sensitive varieties; it was thought that this accumulation was brought on salt-stress injury. The contents of polyamines, especially spermidine, were high in the pre-stressed leaf blades of NERICA rice seedlings. After the salt-stress treatment, the polyamine content of leaf blades differed with the degree of salt tolerance of the NERICA rice seedlings. These results suggested that the salt tolerance of NERICA rice seedlings might be associated not only with the regulation of Na absorption and translocation but also with their ability to maintain leaf polyamine levels under salt-stress conditions.