EFFECT OF PRE-BLOOM SPRAYS OF SOME GROWTH REGULATORS ON GROWTH. FLOWER & FRUIT SHEDDING AND YIELD OF COTTON PLANTS

Abstract

Two fleld experiments were carried out during the seasons of 1988 & 1989, to investigate the effect of pre-bloom sprays with number of some plant growth regulators S growth, flower & fruit shedding and yield of "Giza 75"cotton cultivar. AI growth regulators were sprayed at pre-bloom stage 80 days from sowing" with two concentrations each during the two seasons. Gensrally, all growtt promoters IAA, GA, and promalin resulted in a significant increase in plant height and leaf area and nsignificant increase in internode length and number of nodes/plant. However, the latter character showed significant increase with high concentration of IAA and significant decrease with high concentration of GA, comparing with the control. On the other hand, ABA at low concentration of 2.5 opm and Aar at 400 & 800 ppm followed almost nearly the same trend as that of growth promotors On the contrary. ABA at high concentration of 5 ppm and CCC at 40 and 80 ppm followed a different manner. AJl growth regulators under investigation showed significant decrease in the number of leaves/plant and consequently significant increase in leaf abscission percentage in most cases except IAA at high concentration which led to significant increase in the number of leaves/plant and significant decrease in leaf abscission percentage comparing with the control. In most cases all growtr regulators under investigation achieved significant increase in number of flowers, number of bolls as well as seed cotton yield, except promalin at both concentrations and ABA at high concentration. GA, promalin, ABA; and IAA at 200; 100 and 200; 5; and 25 & 50 ppm respectively, resulted in significant decrease in flower and fruit shedding comparing with control. On the contrary, CCO gave significant increase in flower and fruit shedding percentage, when compared with the control.