Analysis of high temperature stress on the dynamics of antenna size and reducing side heterogeneity of Photosystem II in wheat leaves (Triticum aestivum)

This study demonstrates the effect of high temperature stress on the heterogeneous behavior of PSII in Wheat (Triticum aestivum) leaves. Photosystem II in green plant chloroplasts displays heterogeneity both in the composition of its light harvesting antenna i.e. on the basis of antenna size (alpha, beta and gamma centers) and in the ability to reduce the plastoquinone pool i.e. the reducing side of the reaction centers (Q(B)-reducing centers and Q(B)-non-reducing centers). Detached wheat leaves were subjected to high temperature stress of 35 degrees C, 40 degrees C and 45 degrees C. The chlorophyll a (Chl a) fluorescence transient were recorded in vivo with high time resolution and analyzed according to JIP test which can quantify PS II behavior using Plant efficiency analyzer (PEA). Other than PEA, Biolyzer HP-3 software was used to evaluate different types of heterogeneity in wheat leaves. The results revealed that at high temperature, there was a change in the relative amounts of PSII alpha, beta and gamma centers. As judged from the complementary area growth curve, it seemed that with increasing temperature the PSII beta and PSII gamma centers increased at the expense of PSII alpha centers. The reducing side heterogeneity was also affected as shown by an increase in the number of Q(B)-non-reducing centers at high temperatures. The reversibility of high temperature induced damage on PSII heterogeneity was also studied. Antenna size heterogeneity was recovered fully up to 40 degrees C while reducing side heterogeneity showed partial recovery at 40 degrees C. An irreversible damage to both the types of heterogeneity was observed at 45 degrees C. The work is a significant contribution to understand the basic mechanism involved in the adaptation of crop plants to stress conditions. (C) 2010 Elsevier B.V. All rights reserved.