ALLEVIATION OF SALINITY AND BORON STRESS BY POTASSIUM APPLICATION IN COTTON (Gossypium hirsutum L.)

Among abiotic environmental stresses, high salinity in association with boron has more adverse effects retarding crop production in arid to semiarid area throughout the world including Pakistan. Cotton is one of the major cash crops and called as a white gold of the Pakistan which is critically affected by higher levels of salinity and boron stress. Potassium helps the plant to maintain its life under salinity and boron stress conditions. Keeping in view the stated facts, different sets of studies/ experiments were conducted in the wire house of Saline Agriculture Research Center, Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad, Pakistan, for screening of tolerant and sensitive cotton varieties against salinity and boron stress. In first study salinity levels i.e (Control, 70 mM and 140 mM) and boron levels (5 mM, 10 mM ) alone and in combination were developed by using NaCl and H3BO3. Six varieties of cotton (NIAB-777, IUB-222, FH-114, FH-113, NIAB-846 and SG1AA) were allowed to grow in half strength Hoagland's Solution. After 30 days plants were harvested and on the basis of growth and ionic parameters ranking of varieties were done to identify salinity and boron stress tolerance. The variety FH-114 was found tolerant to salinity and boron stress and NIAB-846 was found very sensitive to salinity and boron stress. Second study was a pot study which was conducted to alleviate the adverse effect of salinity and boron toxicity in cotton (Gossypium hirsutum L.) by exogenous application of potassium. In this study two varieties were used which were selected from the first study. Potassium was applied in the form of K2SO4. Results depicted that by the application of potassium growth as well as ionic parameters were improved. The exogenous application of potassium improved the growth of both varieties. So it was concluded that potassium alleviate the adverse effect of both salinity and boron stress. Third study was a lysimeter experiment which was conducted to evaluate the effect of potassium on biochemical attributes of selected cotton varieties under combined stress of salinity and boron in lysimeter. When potassium was applied in the form of K2 SO4 the antioxidant enzyme activity was enhanced which give ability to the plant to survive under stress conditions. More over the percent decrease in salt load was more in case of FH-114 than NIAB-846