Osmotic Adjustment of Cotton to Moderate Potassium-Chloride Stress and Subsequent Water Stress During Early Stages of Development
- A. Bar-Tsur and
- J. Rudich
High KCl fertilization of drip irrigated cotton (Gossypium hirsutum L.) under intensive growth conditions, mainly in wheat- (Triticum aestivum L.) cotton double cropping when the soil profile is dried out and the cotton has a restricted root volume, may cause moderate osmotic stress. Therefore, the response of cotton to KCl stress and successive water stress was evaluated by measurements of leaf water potential (ΨL), osmotic potential (Ψs turgor pressure (P), and mineral composition of leaves and flower buds. Young cotton plants (var. Acala SJ2) grown in 10-L plastic pots filled with a peat/ tuff mixture (1:l) in a field environment were exposed to prolonged osmotic stress for 35 days by application of KCI. Electrical conductivity of the nutrient solutions was 1.5,3.6,6.7,9.8, and 13 dS m−1, and the final Ψs of the growth medium at the time of measurement 65 days after planting was 0.05, 0.16, 0.27, 0.38, and 0.47 MPa, respectively. The prolonged 35-day-long KCl stress caused stunting of vegetative growth and reduced ΨL, which was accompanied by reduction in Ψs and maintenance of positive P. Osmotic adjustment was also observed in developing flower buds, but their Ψs, was higher than leaf Ψs. The main contribution to osmotic adjustment was from the accumulation of inorganic minerals such as K+ and Cl− in leaves and flower buds. Exposure of the control and KCl-treated plants to successive water stress by withholding irrigation reduced ΨL in both treatments. Plants from the KCl treatment responded by a concomitant decrease in Ψs, which enabled maintenance of positive P, whereas the control plants that were exposed to water stress did not show osmotic adjustment. The results indicate that prolonged KCl stress enabled the cotton plant to exist and withstand successive water stress, but the cotton plant could not overcome growth inhibition.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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