Water-Deficit Stress and Reproductive Development in Cotton

Water deficit is a major abiotic factor limiting crop productivity around the world. Even though cotton is considered to be relatively tolerant to drought, plant growth and yield reduction still occur when water supply is limited or interrupted. However, little is known about metabolic responses to water deficit in the cotton flower. Research is needed to elucidate the metabolic responses of cotton reproductive units under conditions of water stress in order to facilitate methods of amelioration. The objectives were to document the physiological and biochemical changes that take place in cotton flowers and their subtending leaves when subjected to limited water supply. It was hypothesized that water-deficit stress would severely impair gas exchange functions which consequently would result in perturbation of carbohydrates of cotton reproductive units.

Field studies were conducted in 2011 in four locations in Fayetteville and Marianna, AR, Corpus Christi, TX, and Lubbock TX. Cotton cultivar ST5288B2F was planted in all locations and treatments consisted of: (1) Untreated control and, (2) Water-deficit stress during flowering. The experimental design was a split-block and measurements of stomatal conductance were taken weekly. White flowers for carbohydrate, antioxidant and polyamine content were collected weekly, along with their subtending leaves. Seed set efficiency was estimated as seed number per boll.

In general, water-deficit stress during flowering significantly decreased leaf physiological functions, while pistils appeared to be more tolerant. However, biochemical functions of the pistils appeared to be more sensitive compared to the leaf with significant compromises in carbohydrate, antioxidant and polyamine metabolism. Those compromises resulted in a significant decrease of seed set efficiency at one location.