Characterization of photosynthetic performance during reproductive stage in high-yield hybrid rice LYPJ exposed to drought stress probed by chlorophyll a fluorescence transient

Abstract

In the condition of prolonged drought stress during the reproductive stage, we addressed the photosynthetic performance in flag leaves of the high-yield hybrid rice (Oryza sativa L.) LYPJ. The chlorophyll a fluorescence transient dynamics analysis indicated a timely and constant responsive pattern involving in both PSI and PSII. For PSII functionality, uncoupling of oxygen evolving complex at the donor side and inhibition of electron transport from QA to QB at the accepter side were both accounted for the decrease of quantum yield of primary photochemistry at early stage (before 21 days after the onset of drought stress). Likewise, increased size of functional antenna may be primarily responsible for early reaction centers inactivation in drought stressed plants, but transformation to non-QA-reducing centers for the later. The consequent redundant excitation energy was predominantly eliminated by the increasing thermal dissipation. Advanced accumulation of drought stress (from 21 to 35 days) showed preferential impact on the donor side of PSII and significant loss of RC/CS0 was induced during this period. In brief, up-regulation of thermal dissipation and possible cyclic electron transport, as well as down-regulation of activated reaction centers and linear electron transport was crucial for rebalance the energy distribution between the two photosystems from deviant stoichiometry resulting from the uncoupling of oxygen evolving complex.