Abstract

Several environmental factors adversely affect plant growth and development and final yield performance of a crop. Drought, salinity, nutrient imbalances and extremes of temperature are among the major environmental constraints to crop productivity worldwide. Gibberellic acid (GA₃)treatment has alleviated the drastic effect of salinity in growth parameters (leaf area, dry weight of grains and photosynthetic pigments) and chemical constituents (carbohydrates, proteins, amino acids and proline content in two wheat cultivars (Sohag 3 and Giza 168). The effect of GA₃ on alleviation of damaging effects of different levels of salinity was studied in view of, wheat grains (Triticum aestivum L. Sohag 3 and Giza 168) were screened for germination and growthresponses to different NaCl concentrations (50, 100, 150 and 200 mM). After four weeks, two groups; each of pots were sprayed with GA₃ (100 mg L^-1 synthetic plant growth regulators). The result in this report reveals that the wheat cv. Sohag 3 was the most sensitive to salinity, while cv. Giza 168 was the most tolerant. Thus salinity stress had no effect on leaf area, photosynthetic pigment and consequently crop yield at mild salinity (100 mM), while in cv. Sohag 3, there was a marked and progressive reduction in these parameters by increasing the salinity stress even at the lowest salinity (50 mM) level used. Carbohydrate and proline content increased significantly by salinity stress in the different organs of the two wheat cultivars except for Giza 168 stem where carbohydrates were significant declined by salinity stress. Soluble protein content varied not only between the two wheat cultivars but also between the different organs. While salinity stress induced a significant increase in the soluble protein content in root and leaf, on the other hand itdeclined the soluble protein in stem of Giza 168. In cv. Sohag 3, the soluble protein content in root and stem decreased slightly by increasing salinity in the soil, this reduction was obvious only at higher salinization. While in leaves the soluble protein content increased markedly by salinity stress. Proline concentration in root, stem and leaf of both cultivars significantly increased with increasing salinity in soil. The accumulation was greater in the salt sensitive cv. Sohag 3 compared to the salt tolerant cv. Giza 168 especially at higher salinity concentration. GA₃treatments (100 ppm) improved the growth criteria, photosynthetic pigments and consequently the crop yield of two wheats cultivars. This was injudged with the observable increase in protein content in the different organs of the two wheat cultivars.

Key word: Leaf area, carbohydrate, protein, proline, salinity, wheat cultivars, GA_3.