PHOTOPHOSPHORYLATION, PROTON PUMPING, AND GAS EXCHANGE IN TWO WHEAT CULTIVARS UNDER DROUGHT

Abstract

The aim of the this study was to evaluate photochemical and stomatic differences between two contrasting cultivars drought tolerance cv. Ciano T-79 (sensible) and Temporalera M-87 (tolerant) wheat cultivars (Triticum aestivum L.). Plants were grown in a greenhouse at Colegio de Postgraduados, during 1994, water deficit was induced by withholding irrigation during the vegetative stage, plants were under drought during seven days, thereafter they were rewatered. At the end of the drought period and after rewatering photophosphorylation and proton pumping in isolated chloroplasts were evaluated as well as intact leaves stomatic traits. Water deficit increased the ATP synthesis in 183 %, proton pump in 197 %, and temperature leaf in 3°C, and decreased 50 % the stomatal conductance as compared with the irrigated control; differences in intercellular CO₂ concentration and transpiratory rate were similar in both cultivars. Stomatic traits were regenerated after rewatering of two cultivars, Temporalera M-87 recovered its photochemical activities, and Ciano T-79 increased three times these activities. All these results confirm the hypothesis that Temporalera M-87 cultivar seems to have photosynthetic metabolic adjustment that confers its tolerance to drought.