Water-Deficit Stress Effects On Polyamine Metabolism During Cotton Reproductive Development.

Water deficit is a major abiotic factor limiting plant growth and 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 polayamine metabolic responses to water deficit in the 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 of this study were to document and quantify the changes in polyamine metabolism 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 and polyamine metabolism of cotton reproductive units.

Growth chamber experiments were conducted in 2010-2011 at Altheimer Laboratory in Fayetteville, University of Arkansas. Cotton (Gossypium hirsutum L.) cultivars ST5288B2F and Siokra  were planted into 1L pots with Sun-Gro horticulture mix and growth chambers were set for normal conditions of 32/24°C (day/night), ±60% relative humidity, and 14h photoperiods.  Plants were arranged in a completely randomized block design with 20 replications and half-strength Hoagland’s nutrient solution was applied daily in order to maintain adequate nutrients and water. The water-deficit treatments consisted of: (1) Untreated control, and (2) Water-deficit stress during flowering. Measurements of stomatal conductance, and photosynthesis were taken from the fourth main-stem leaf. White flowers and their subtending leaves were sampled whenever they were available and were analyzed for polyamine concentrations. Results from these experiments are not available since the data are still being processed.