A HYDROPONIC APPROACH TO EVALUATE RESPONSES TO NUTRIENTS AND PHYTOHORMONES IN COTTON PLANTS (Gossypium hirsutum L.) GROWTH AND DEVELOPMENT
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Cotton plant growth and development, as well as monitoring nutrient use efficiency were evaluated using hydroponic approach. Two set of experiments were conducted to determine the influence of phosphorus (P), potassium (K) and PK and exogenous application of Indole-3-acetic acid (IAA), gibberellic acid (GA3), zeatin (Z) and their combinations on growth and development of cotton plants (Gossypium hirsutum) grown hydroponically. In the nutrient solution experiment, cotton vegetative growth was positively influenced by low P (half strength Hoagland standard solution), low K (one-sixth strength Hoagland standard solution) and high PK treatments (Hoagland standard solution). Phytohormone experiment negatively supported vegetative growth except root length at 43 days after transplanting (DAT). The nutrients levels applied significantly favoured NPK uptake by cotton plants while exogenous phytohormones application did not affect NPK uptake by cotton plants, except N uptake by stem. Low P and low K treatments estimated to have high nutrient use efficiency (NUE). For chlorophyll formation, low K and high PK significantly increased formation of chlorophyll a, b and total ab while the application of GA3, IAA, Z and IAA x GA3 x 2Z treatments significantly increased chlorophyll a, b and total ab at 80 DAT only. Low K and low P treatments stimulated endogenous phytohormone contents in the cotton plants. In the phytohormone experiment, cotton plants treated to IAA x GA3 x Z increased endogenous phytohormone contents in the cotton plants. Low P, low K, high PK treatments and phytohormones treatments significantly increased root area, root volume and root activity. Low P, low K and high PK treatments applied significantly influenced residual level of P and K in the hydroponics while phytohormone treatments did not affect residual level of P and K except at 43 DAT. Evapotranspiration rate was high at early and reproductive stages of plant growth. This report shows the response of mineral nutrients and phytohormones to support growth and development of cotton plants grown hydroponically.