Plant Stress ©2008 Global Science Books Physiological Responses of Brassica napus Genotypes to Combined Drought and Salt Stress

Physiological responses of Brassica napus genotypes were studied when drought and salinity stress were applied together. Irrigation of plants, which first started with 150 mM NaCl solution, was stopped when soil EC (electrical conductivity), NaCl EC and water fraction volume (WFV) values reached 0.04 dSm-1, 0.64 dSm-1 and 15%, respectively. Growth, osmotic potential, ion concentration and stomatal conductance were determined. Fresh weight and dry weights were significantly affected by the combined stress. Fresh weight was abridged more than dry weight. The dry weights and leaf area per unit dry weights of treated plants were considerably reduced compared to unstressed, control plants. The osmotic potential of each genotype decreased in the combined-stressed plants compared to unstressed plants showing a variable trend regarding osmotic adjustment. Na+ ions of each genotype increased significantly in the combined-stressed plants compared to unstressed plants. There were less K+ and Ca++ ions in the stress-treated plants than in the control, unstressed plants. Stomatal conductance of each genotype was retarded by the stress combination. Variable physiological responses were found among the genotypes showing slow- and fast-growing ecotypes