Variation in the Thermal Sensitivity of Electron Transport and Proton Uptake in Wheat Thylakoids under High Temperature Stress

The whole chain electron transport and the photosystem 2 electron transport activities were declined sharply in thylakoids treated at temperatures above 40°C while photosystem 1 mediated electron transport showed no decline in activity. Photosystem 1 assays with 2, 6-Dichlorophenol indophenol was not inhibited even at a preheated temperature of 50°C while N, N, N’, N’-tetramethyl-1,4phenylenediamine (TMPDH) and 3,6-diaminodurol(DADH) were reduced to about 60%. PS 2 lost its sensitivity to uncoupler NHCl at 30°C while PS 1 retained sensitivity to the uncoupler up to 45°C. At 35°C, the extent of noncyclic methyl viologen mediated electron transport supported proton uptake was inhibited by 80% while pyocyanin mediated cyclic proton uptake was reduced by less than 15%.