See more from this Session: C02 Graduate Student Oral Presentation Competition
Growth chamber experiments were conducted in 2009-2010 at Altheimer Laboratory in Fayetteville, University of Arkansas. Cotton (Gossypium hirsutum L.) cultivar ST5288B2F was planted into 2L pots with Sun-Gro horticulture mix and growth chambers were set for normal conditions of 30/20°C (day/night), ±60% relative humidity, and 12h 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, (2) Water-deficit stress during squaring and, (3) Water-deficit stress during flowering. Measurements of stomatal conductance, fluorescence, and respiration were taken from the fourth main-stem leaf and flowers for carbohydrate and antioxidant content were sampled whenever they were available. The results showed that both early (during squaring) and late (during flowering) water-deficit stresses had a detrimental impact on carbohydrate metabolism of cotton flower pistils. Late-stress caused glucose, fructose and sucrose levels to significantly decrease, which resulted in a reduction in respiration rates. The early stress caused a similar reduction to glucose levels which was not accompanied by a corresponding reduction in respiration rates. Additionally fructose and sucrose levels of early-stressed flowers were significantly higher than those of the late-stressed flowers indicating a perturbation in the breakdown and interconversion of carbohydrates in the flower. These responses would most likely result in a compromise of fertilization efficiency and seed set.