Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2010
Publication Date: 6/1/2011
Citation: Snider, J.L., Oosterhuis, D.M., Kawakami, E.M. 2011. Mechanisms of reproductive thermotolerance in Gossypium hirsutum: The effect of genotype and exogenous calcium application. Crop Science. 197(3):228-236. Interpretive Summary: It is important to understand the biochemical role of the pistil in promoting fertilization under high temperature because fertilization is a prerequisite for seed and yield development in cotton. To evaluate the effect of temperature, genotype, and calcium application (for stress amelioration) on fertilization and pistil biochemistry in cotton, heat-sensitive and heat tolerant plants were grown under control (30/20 degrees C) or high temperature (38/20 degrees C) conditions during flowering, and CaCl2 was applied to floral buds one day prior to flowering. On the day of flowering, pistil measurements included fertilization efficiency, proteins and antioxidants, pistil energetics (ATP), and calcium. Exogenous calcium application had no effect on reproduction under high temperature due to poor calcium uptake by the floral bud. High temperature decreased fertilization efficiency for the sensitive cultivar but did not change fertilization efficiency for the tolerant cultivar relative to optimal temperature conditions. Pre-stress antioxidant enzymes, pistil calcium, and pistil ATP content were significantly higher in the tolerant cultivar. It is concluded that pre-stress antioxidant enzyme activity, calcium content, and ATP content of the cotton pistil may be important indicators of genetic tolerance to high temperature extremes. Utilization of these parameters for cultivar screening purposes may help mitigate the detrimental effects on crop productivity projected to result from global climate change.
Technical Abstract: Although genotypic mechanisms of photosynthetic thermotolerance have been investigated previously in cotton leaves, reports on the biochemical influence of the pistil in promoting genotypic fertilization thermostability are non-existent for cotton. To evaluate the effect of temperature, genotype, and exogenous calcium application on fertilization and pistil biochemistry in cotton, thermosensitive (cv. ST4554 B2RF) and thermotolerant (cv. VH260) plants were grown under control (30/20 degrees C) or high temperature (38/20 degrees C) conditions during flowering, and exogenous CaCl2 was applied to flowers one day prior to anthesis. Measured pistil parameters included fertilization efficiency, protein and antioxidant enzymes, NADPH oxidase, carbohydrates, adenosine triphosphate (ATP), and calcium. Exogenous calcium application had no effect on reproductive thermostability due to poor calcium uptake under high temperature. High temperature resulted in a 19.2% decline in fertilization efficiency for ST4554 but no change in fertilization efficiency for VH260 relative to optimal temperature conditions. Pre-stress glutathione reductase and superoxide dismutase activity were significantly higher in VH260 than ST4554 pistils, and calcium and ATP content were significantly higher in VH260 than ST4554 pistils regardless of temperature regime. It is concluded that pre-stress antioxidant enzyme activity, ATP content, and calcium content of the cotton pistil may be important determinants of innate reproductive thermotolerance in cotton.