Indian Journal of Plant Physiology

Changes in endogenous levels of IAA, GA₃ and ABA during in vivo fibre growth of Gossypium arboreum L. cv. LD 327 showed an over riding influence of ABA in limiting the rate of fibre elongation. The fiber growth of unfertilized cotton ovules cultured in vitro was elevated by the application of fluridone. Fluridone markedly decreased the ABA level concomitant with an increase in the levels of promoter (IAA, GA₃) in cultured ovules. The enzymic hydrolysis of the β-glucopyranosyl ester of ABA by β-glucosidases and esterase were studied in fibres at 15 and 35 days after anthesis. Since, the activity levels of two hydrolase did not correlate with the ABA contents at two stages of fibre growth, it is suggested that the high content of free ABA at 15 DAA was not a consequence of the increased activity of the ABA-Glc splitting enzymes. Our data suggest that ABA conjugate is final product of the ABA metabolism under different stages of fibre growth.