Effect of High Night Temperatures During the Vegetative Stage of Cotton

Global temperature is expected to increase by 1.4 to 5.8 oC by the end of the 21st century due to increases in greenhouse gases concentrations (IPCC, 2007). High temperatures are considered to be a major environmental stress contributing to yield loss; however, night temperatures are anticipated to increase faster than day temperatures due to increased cloudiness that will result in decreased radiant heat loss (Alward et al., 1999). Previous research has reported that higher than optimum night temperatures during cotton’s vegetative stage of growth resulted in significant increases in respiration rates (Loka and Oosterhuis, 2010). Consequently, depletion in leaf carbohydrates content and significant reductions in leaf adenosine triphosphate levels were observed (Loka and Oosterhuis, 2010), ultimately resulting in yield reduction (Arevalo et al., 2008). The reproductive stage appears to be more susceptible to heat stress compared to the vegetative stage (Hall, 1992). Research in other crops has indicated that high night temperatures during the reproductive phase have detrimental effects on yield due to increased male sterility and floral abscission (Warrag and Hall, 1984; Guinn, 1974), floral bud suppression, decreased pollen viability, spikelet fertility and poor grain filling (Mohammed and Tarpley, 2009). However, little or no attention has been given to the effects of increasing night temperatures on the reproductive forms of cotton. The objective of our study was to evaluate the effect of high night temperatures on carbohydrate content of cotton’s squares and their subtending leaves.