Effect of Foliar Application of Some Growth Regulators on Endogenous Growth Hormone Levels of Cotton Plant

Abstract

Endogenous auxins and gibberellins of leaf extracts of untreated plants, gained high significant levels at the pre-bloom stage (80 days after sowing), then gradually decreased with advancing age and disappeared completely at harvesting stage (240 days from planting). On the contrary, auxin and gibberellin-inhibitors were significantly much less at pre and full bloom stages, than at fruiting and harvesting stages. Pre-bloom foliar application of IAA at 25 or 50 ppm, GA, and promalıin either at 100 or 200 ppm led to significant increase for auxin and gibberellin activities, comparing with control plants specially at full bloom and fruiting stages, as well as at the harvesting stage only, with promalin at high concentration for endogenous gibberellins. Whereas, all growth -promotors under investigation induced significant levels of endogenous auxin comparing with control. The same plants were free, from any significant levels of auxin and gibberellin inhibitors along flowering to fruiting stages, except at harvest stage. On the other hand, ABA applied at 2.5 & 5 ppm, CCC at 40 & 80 ppm, and Alar at 400 & 800 ppm on cotton plants, resulted in significant levels of auxin and gibberellin-like substances at full-bloom and at fruiting stages, comparing with control plants, except gibberellin content at full bloom which showed lower level than control plants. The same treatments achieved significant levels of auxin and gibberellin-inhibitors along life of plants, specially with high concentration of growth regulators used above control plants.