Comparative effects of NACL and PEG stress on leaf and root growth and proline content in seedlings of three rice cultivars

Abstract

ABSTRACT             The effects of salinity and water stresses on the growth and proline content of seedlings of three rice cultivars were determined. Three cultivars of rice were used: Pokkali, a salt-tolerant cultivar; IR64, which was moderately salt-tolerant; and Khao Dawk Mali 105 (KDM105), which is salt-sensitive cultivar. Rice seedlings were grown in nutrient solution for 21 days, and subsequently in nutrient solution containing NaCl at the electrical con-ductivity (EC) of six desisiemens per meter (dS/m), 10%, and 20% of PEC for nine days. The relative water contents in leaves and roots were determined from their fresh and dried weights, and the proline content by a spectrophotometric assay. The dry weights of leaves and roots of rice seedlings decreased in response to stress induced by NaCl and PEG. Under most stress treatments, the relative water content of leaves and roots decreased until day 5, then slightly increased on day 9. However, the relative water content of leaves of IR64 grown in NaCl (12 dS/m) decreased more sharply than with other treatments until day 9. The relative water content of leaves of KDML105 grown on NaCl (12 dS/m) decreased continuously until day 9. The proline content of all three cultivars increased in response to both NaCl and PEG-induced stresses. Leaves and roots of KDML105 accumulated the highest amount of proline, followed by IR64 and Pokkali