Abstract:
A pot culture experiment was conducted to study the effects of four different levels of salinity having osmotic potential of 0.00, -4.67, -9.35, and -14.03 bars on the uptake of macronutrients (N, P, K+, Ca²+, and Mg²+) by 2 hybrids of sunflower (Helianthus annuus L.). Salinity levels were achieved by dissolving calculated amount of NaCl, Na₂SO₄, CaCl₂, and MgCl₂ (4:10:5:1) in half strength Hoagland culture solution. Results suggested that salinity significantly (P<0.05) and linearly increased the uptake of macronutrients (except K+) both by roots and shoots. A significantly maximum amount of N, P, Ca²+ and Mg²+ for roots (16.80, 4.13, 40.03 and 10.28 g kg⁻¹) as well as for shoots (26.70, 3.95, 37.52, and 15.62 g kg⁻¹), respectively, were recorded in highest dose of salinity (-14.03 bars). This might be due to excess use of S₄-⁻²over Cl- ions in the culture media. Results further suggested that K+ uptake both by roots and shoots were significantly reduced by applied doses of salinity. A maximum reduction in both root (19.82 g kg⁻¹), and shoot (10.52 g kg⁻¹) were observed where highest level of salinity (-14.03 bars) was applied. This inhibitory effect on K+ uptake could be attributed to excess use of Na+ salts in the growth media. Results also showed that, sunflower hybrid DO-728 accumulated more P & K+ by their roots and shoots when compared with hybrid DO-730. Therefore, hybrid DO-728 could be rated as salt tolerant followed by hybrid DO-730 as salt sensitive. Results further suggested that based on grand mean values of all mentioned species of nutrients (including K+), shoot exhibited 1.027 % increased uptake over their roots.
