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Title: HEAT-STRESS-INDUCED INHIBITION OF THE ACTIVATION STATE OF COTTON RIBULOSE- 1,5-BISPHOSPHATE CARBOXYLASE/OXYGENASE (RUBISCO) IS MEDIATED BY RUBISCO ACTIVASE

Author
item Law, Robert
item Crafts-Brandner, Steven

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 6/1/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Glandless upland cotton plants were subjected to heat stress in a growth cabinet. Carbon exchange rate (CER), ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (rubisco) activation state, and RuBP and 3- phosphoglycerate (3-PGA) content were monitored. Air temperature increases from control (28 Deg C) values were in 2.5-to 5 Deg-steps to 45 Deg C, with ha 1-h equilibration at each step with high ambient humidity to allow leaf temperature to approach that of the air. Samples taken from young, fully- expanded leaves indicated that rubisco activation state began decreasing when leaf temperature was raised above 35 Deg C and decreased to 25% of control values at 45 Deg C. This was mirrored by decreases in net photosynthetic rate (CER) to 61% of control values at 42.5 Deg C, and by a 50% decrease in the rubisco product 3-PGA, starting at 40 Deg C and reaching a maximum at 45 Deg C. Additionally, these changes in rubisco activity, activation state and 3-PGA content were reversible by subsequently lowering the temperature of the heat-stressed leaves. Fluorescence measurements indicated that increasing leaf temperature adversely affected flux through the photosynthetic electron transport chain. Cumulatively, these results complement a previous study (Feller et al. (1998) Plant Physiol 116, in press) demonstrating the importance of rubisco activase in the maintenance of maximal rubisco activity at relatively high temperatures.