Alleviation of adverse effects of salt stress on sunflower (<em>Helianthus annuus</em> L.) by exogenous application of potassium nitrate

Abstract

To assess whether the adverse effects of salt stress on sunftower could be mitigated by exogenously applied potassium nitrate, a greenhouse experiment was conducted. There were two salt treatments (0 or 150 mmol/! NaCl) and different concentrations of KNO₃ [NS (No spray), WS (spray of water + 0.1 % Tween 20 solution), 0.5% K^{+ + 0.8% NO₃-, 1.0% K+ + 1.6% NO₃-, 1.5% K+ + 2.4% NO₃-, and 2.0% K+ + 3.2% NO₃- in 0.1 % Tween 20 solution] which were applied foliarly two times i.e., one week after the commencement of salt stress and the second, one week after the first application to nonstressed and salt stressed plants. Varying levels of KNO₃ improved the growth, achene yield, chlorophyll contents, net CO₂ assimilation rate, F₁/F_m, leaf turgor, and leaf K and N contents in the salt-stressed plants of sunftower. Of the various KNO₃ levels applied foliarly, 1 % K+ and 1.6% NO₃- from KNO₃ were found to be the most effective in up-regulating different growth and physiological processes under saline conditions. In conclusion, exogenous application of KNO₃ increased the photosynthetic rate and leaf turgor which in turn resulted in enhanced growth and yield in sunflower plants subjected to salt stress.}