Boll Retention in Relation to Leaf and Boll Development in Cotton ( Gossypium hirsutum L.) 1

The effect of leaf area and gibberellic acid (GA) boll retention was studied on cotton plants growing in nutrient culture. Leaf area was reduced to approximately half the control by two methods of leaf clipping, and two concentrations of GA were applied to all flowers. In control plants, the ratio of leaves to retained bolls was initially high. It declined to approximately three at midseason, and thereafter remained constant to the end of the fruiting period. After adjustments for differences in leaf size, ratios for partially defoliated plants were similar to those of the control. Percent boll retention paralleled leaf‐boll ratios. Seed cotton yield and percent retention were significantly reduced in the partially defoliated treatments; however, no differences were found when seed cotton yield was expressed as a function of maximumle af area developed. There were no differences between the GA treatments and control for any of the characters measured. That retention was not increased by treating all the flowers contrasts with results obtained when only a few flowers or young bolls were treated. The number of seeds per retained boll for all treatments was low initially, increasing to a maximum at the time of greatest shedding. This may indicate that a high seed complement is required for a boll to be retained when competition for assimilate occurs. The results are interpreted as supporting the view that boll retention depends on the presence of a sufficient number of developing seeds to mobilize the assimilates required for contiuued growth, and upon the availability of assimilates as governed by the vegetative‐reproductive status of the plant.