UPTAKE OF NITROGEN BY COTTON (GOSSYPIUM HIRSUTUM L.) UNDER SALT STRESS

Nitrogen (ammonium-('15)N) absorption studies were made on cotton (Gossypium hirsutum L. var. Deltapine 61) grown in complete Hoagland nutrient solution in pots with various concentrations of NaCl (0, 4, 8, and 12 bars osmotic pressure). Two different stages of growth, vegetative and reproductive, were investigated. Plants were grown in a controlled environment growth chamber.;The absorption rate of water substantially decreased by increasing salinity levels. This reduction was proportional to plant growth and total dry matter production. Water uptake rate and plant growth and development were affected to a greater extent than ('15)N absorption rate.;The effect of salinity was more pronounced for a longer uptake time and the vegetative stage than for a shorter uptake time and the reproductive stage of growth.;Low and medium levels of salinity (4 and 8 bars osmotic pressure of the nutrient solution) did not exhibit a significant effect on ('15)N absorption rate by cotton plants. The high level of salinity (12 bars osmotic pressure of the culture solution) resulted in substantial reduction in ('15)N absorption rate. The concentration of ('15)N in plant shoots was higher under salinity stress than it was in the control.