High Night Temperature Effects During Flowering in Cotton.

The effects of high night temperatures on the physiology and biochemistry of cotton’s first day flowers and their subtending leaves during reproductive development were evaluated in growth chamber experiments conducted at Altheimer Laboratory of the University of Arkansas. Plants were exposed to higher than optimum temperatures (30ºC compared to 24ºC) from 18:00-24:00 for a total period of two weeks after plants had reached flowering stage (approximately 8 weeks after planting). Measurements of  photosynthesis and respiration  were taken, while white flowers and their subtending leaves were collected and analyzed for their carbohydrate and antioxidant content at the end of each week. The results showed that high night temperatures significantly increased respiration rates while photosynthesis rates remained unaffected. Leaf sucrose concentrations also remained unaltered, while leaf starch content was significantly decreased. Leaf glucose levels were significantly increased and a similar pattern was observed in pistil glucose, sucrose and starch concentrations. Leaf glutathione reductase content was increased under conditions of elevated night temperatures, while pistil glutathione reductase content was decreased, however not significantly compared to the control.