Abstract

Two experiments were conducted to evaluate the endogenous hormones content of cotton plants grown hydroponically, and supplied with varying levels of phosphorus (P) and potassium (K) mineral nutrients in the first cropping. In the second cropping, varying levels of exogenous indole-3-acetic acid (IAA), gibberellic acid (GA₃) and zeatin (Z) and their combinations were applied to high level of PK in the hydroponic. In the first experiment, low K and low P treated plants had higher content of gibberellic acid (GA₃) in the leaves than high PK treated plants, and low K treated plants also produced more Zeatin (Z) in the leaves than either low P or high PK treated plants. Furthermore, low K treated plants had higher Zeatin (Z) content in the root than either low P or high PK treated plants. However, the two cotton varieties expressed different hormones content in the leaves, stem and root. In the second experiment, GA₃ concentration was highest in the cotton stem treated to IAA x GA₃ x Z. Moreover, Zeatin content in the leaves, stem and root was highest in the cotton treated to IAA x GA₃ x Z and 2IAA x 2GA₃ x 2Z for leaves, IAA x GA₃ x Z for stem and Z, IAA x 2GA₃ x Z for root. Nevertheless, two cotton varieties possessed different hormones content in the leaves, stem and root. In general, there was no relationship between the first cropping and second cropping. The results demonstrated influence of exogenous hormones application in altering the endogenous hormones content of cotton plants.

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