Foliar Application of Potassium Nitrate Affects the Growth and Nitrate Reductase Activity in Sunflower and Safflower Leaves under Salinity

Abstract

Effect of foliar application of KNO3 on growth and the activity of nitrate reductase were studied in the leaves of sunflower (Helianthus annuus L.) and safflower (Carthamus tinctorius L.) plants growing under different levels of salinity. The seeds were sown in pots under non saline condition and saline water irrigation was started at three leaf stage after germination. Different concentration of saline water (i.e. 0.3% and 0.6%, equivalent to an EC of 4.8 and 8.6 dS/m respectively) were made by dissolving sea salt per litre of tap water. Nutrient solution of KNO3 was sprayed at the rate of 250 ppm. The concentration of Na+ and Cl- rapidly increased in the leaves of both the plants under salinity stress. In contrast the nitrate (NO3-) and soluble protein concentration were decreased with the increasing salinity. Salinity reduced leaf area, its fresh and dry weight per plant and also inhibited the activity of Nitrate reductase (NRA) enzyme. The application of KNO3 significantly reduced the increasing tendency of Na+ and Cl- and increased leaf area, its fresh and dry weight per plant, NO3- and soluble protein concentration and NR activity in leaves irrespective to the growth of plant under non saline or saline conditions.