Physiological aspect of Nacl-salt stress tolerant among cucurbitaceous cultivars

Abstract

Experiment was conducted in the experimental farm of Agricultural Botany Department, Faculty of Agriculture, Ain Shams Univ. during the two successive seasons of 2008 and 2009 to study the responses of four cucurbitaceous cultivars on salinity effects: Shintosa Supreme pumpkin (Cucurbita maxima x C. moschata) 'Major', Bottle gourd (Lagenaria siceraria), Gourd Black Seed (Cucurbita maxima) and pumpkin (Cucurbita moschata). Four salinity levels were applied through irrigation water containing 0, 2500, 3500 and 4500 PPM NaCl. Samples were taken at six weeks after planting to determine plant growth, leaf electrolyte leakage percentage (Membrane Permeability) and salt injury index (SII). As well as, the distribution of chloride, sodium and potassium ions in all plant parts. The dry and fresh weights of stems and roots, plant height, leaf area and root length in the 4 cultivars decreased gradually with increasing NaCl concentration comparing with control plants. Shintosa Supreme pumpkin showed the best salt tolerance at 3500 ppm as indicated by plant height, leaf area and root length, fresh and dry weights of stems and roots. With increasing NaCl concentrations, the salt injury index of all cultivars increased significantly. There was insignificant difference in the salt injury index between pumpkin and Bottle gourd cultivars under different levels of salinity. Gourd Black Seed showed significant increase in salt injury index comparing with other cultivars at the 3500 and 4500 ppm NaCl. Salt injury index of Shintosa Supreme pumpkin was lower than that of other cultivars. The membrane permeability of the four cultivars increased significantly with increasing concentrations of NaCl; the membrane permeability of Shintosa Supreme pumpkin was lower than that of other cultivars. However, a difference between the cultivars in response to the salinity was apparent. In addition, the contents of Na+ in the root and stem of Shintosa Supreme pumpkin cultivars increased significantly but in the leaf decreased, whereas the contents of K+ versa decreased significantly, resulting in an increase in the Na+/K+ ratio when NaCl concentrations increased.