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ARS Home » Southeast Area » Booneville, Arkansas » Dale Bumpers Small Farms Research Center » Research » Publications at this Location » Publication #262742
Title: GENOTYPIC THERMOTOLERANCE IS ASSOCIATED WITH ELEVATED PRE-STRESS ANTIOXIDANT ENZYME ACTIVITY IN COTTON LEAVES AND PISTILS

Author
item Snider, John
item OOSTERHUIS, DERRICK - University Of Arkansas
item KAWAKAMI, EDUARDO - University Of Arkansas

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 12/7/2010
Publication Date: N/A
Citation: N/A

Interpretive Summary: Although antioxidant enzymes are considered important in the acclimation response of plants to high temperature, information on their possible role in promoting genotypic tolerance to high temperature in either leaves or reproductive tissues is limited for cotton. We investigated the hypothesis that genotypic differences in leaf photosynthetic thermostability and fertilization thermostability would depend on pre-stress antioxidant enzyme activity. To test this hypothesis, heat sensitive (ST4554) and reportedly heat tolerant (VH260) cotton plants were exposed to control (30/20°C) or high-day temperature (38/20°C) conditions during flowering. Source leaf photosynthesis was measured for each treatment, and the relationship between photosynthetic heat tolerance and pre-stress antioxidant capacity was measured Under both temperature regimes, measured pistil parameters included fertilization efficiency and antioxidant enzyme activity. VH260 was more heat tolerant than ST4554 as evidenced by photosynthesis and fertilization efficiency being significantly lower under high temperature for ST4554 but unchanged for VH260. Under identical growth conditions, VH260 had significantly higher optimal and threshold temperatures for photosynthesis than ST4554, and both photosynthetic and reproductive high temperature tolerance were associated with elevated pre-stress antioxidant enzyme activity. It was concluded that elevated pre-stress antioxidant enzyme activity may be an important criterion for identifying heat tolerant cultivars.

Technical Abstract: Numerous studies have illustrated the need for antioxidant enzymes in acquired photosynthetic thermotolerance, but information on their possible role in promoting innate thermotolerance in either leaves or reproductive tissues is limited for cotton. We investigated the hypothesis that genotypic differences in subtending leaf photosynthetic thermostability and fertilization thermostability of the subtended flower would be dependent upon pre-stress antioxidant enzyme activity. To test this hypothesis, thermosensitive (cv. ST4554) and reportedly thermotolerant (cv. VH260) cotton plants were exposed to control (30/20°C) or high-day temperature (38/20°C) conditions during flowering. Source leaf photosynthesis was measured for each treatment, and the relationship between source leaf thermostability and pre-stress antioxidant capacity was quantified by monitoring the actual quantum yield response of photosystem II (PSII) (FPSII) to a range of temperatures for both cultivars grown under the control temperature regime and measuring antioxidant enzyme activity for those same leaves. Under both temperature regimes, measured pistil parameters included fertilization efficiency, glutathione reductase (GR), and superoxide dismutase (SOD). VH260 was more thermotolerant than ST4554 as evidenced by photosynthesis and fertilization efficiency being significantly lower under high temperature for ST4554 but unchanged for VH260. Under identical growth conditions, VH260 had significantly higher optimal and threshold temperatures for FPSII than ST4554, and both photosynthetic and reproductive thermotolerance were associated with elevated pre-stress GR and SOD activity. It was concluded that maintaining a sufficient antioxidant enzyme pool prior to heat stress may be an important determinant of innate photosynthetic and reproductive thermotolerance in cotton.