Variation in the Thermal Sensitivity of Electron Transport and Proton Uptake in Wheat Thylakoids under High Temperature Stress
Ranjani R., Kumar Prasanna, Babu G. Nagendra, Murthy S.D.S.
Department of Biochemistry, S.V. University, Tirupati-517502 (A.P.).
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%.