66-11 Genotypic Differences in Thermotolerance Depend On Pre-Stress Capacity for Antioxidant Protection of the Photosynthetic Apparatus in Cotton.

Poster Number 147

See more from this Division: C02 Crop Physiology and Metabolism
See more from this Session: C02 Graduate Student Poster Competition
Monday, November 1, 2010
Long Beach Convention Center, Exhibit Hall BC, Lower Level
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John Snider, Derrick Oosterhuis and Eduardo Kawakami, University of Arkansas, Fayetteville, AR

Numerous studies have illustrated the need for antioxidant enzymes in acquired photosynthetic thermotolerance, but information on their possible role in promoting innate thermotolerance is lacking. We investigated the hypothesis that genotypic differences in source leaf photosynthetic thermostability would be dependent upon prestress capacity for antioxidant protection of the photosynthetic apparatus in Gossypium hirsutum. To test this hypothesis, thermosensitive (cv. ST4554) and reportedly thermotolerant (cv. VH260) G. hirsutum plants were exposed to control (30/20°C) or high-day temperature (38/20°C) conditions during flowering and source leaf gas exchange, chlorophyll content and maximum photochemical efficiency (Fv/Fm) were measured for each treatment. The relationship between source leaf thermostability and prestress antioxidant capacity was quantified by monitoring the actual quantum yield response of photosystem II (PSII) (ΦPSII) to a range of temperatures for both cultivars grown under the control temperature regime and measuring antioxidant enzyme activity for those same leaves. VH260 was more thermotolerant than ST4554 as evidenced by photosynthesis and Fv/Fm being significantly lower under high temperature for ST4554 but not VH260. Under identical growth conditions, VH260 had significantly higher optimal and threshold temperatures for ΦPSII and glutathione reductase (GR) activity than ST4554, and innate threshold temperature was dependent upon endogenous GR and superoxide dismutase (SOD) activity. It was concluded that maintaining a sufficient antioxidant enzyme pool prior to heat stress is an innate mechanism for coping with rapid leaf temperature increases that commonly occur under field conditions.

 

See more from this Division: C02 Crop Physiology and Metabolism
See more from this Session: C02 Graduate Student Poster Competition