Exogenous Application of Putrescine Ameliorates the Effect of High Temperature in Gossypium hirsutum L. Flowers and Fruit Development

Polyamines have been shown to stimulate fruit set and the initial phase of fruit development in several crops. The effect of exogenous application of putrescine on ovary development and seed set of cotton under high temperature stress was investigated under controlled environmental conditions. Putrescine was applied to floral buds of cotton, 24 h prior to anthesis, and caused a significant increase in putrescine content of cotton ovaries collected at anthesis compared with the control treatment. However, there was no increase in spermidine and spermine. High temperature (38 degrees C) significantly decreased the spermidine content of cotton ovaries in both years of the study compared with the untreated control (30 degrees C). Spermine was significantly decreased in the high temperature treatment the first year of the study; however, this result was not consistent for the second year. Ovarian putrescine concentration was not affected by the high temperature treatment. Increased temperatures in this study decreased seed set in cotton flowers; however, exogenous application of putrescine ameliorated the negative effect of high temperature on seed set, as expressed by the number of seeds per cotton boll. This was evident in both years of the study. Exogenous application of Putrescine increased the level of putrescine in cotton flowers, which was associated with increased seed set despite the negative effect of increased temperature.