Exogenously Supplied Trehalose Accelerates Photosynthetic Electron Transport in Heat-Stressed Maize

Plants are constantly threatened by adverse environments including heat stress which can significantly decrease crop yield. Trehalose involvement in plant resistance to heat stress has been reported, but the mechanisms of trehalose-induced plant resistance are unclear. In this study, the role of trehalose in enhancing heat—stressed maize (Zea mays L.) light reaction of photosynthesis was investigated. We observed that exogenously supplied trehalose accelerated photosynthetic electron transport in heat-stressed leaves. We further found that exogenously supplied trehalose under heat stress conditions greatly improved the values of actual photosystem II (PSII) efficiency [Y(II)] and the photochemical quenching coefficient (qP) and accelerated the rate of photosynthetic electron transport from pheophytin (Pheo) to QA to QB in PSII. In addition, exogenously supplied trehalose elevated the rate of cyclic electron flow (CEF), the xanthophyll cycle, ATPase activities, the osmotic component of the trans-thylakoid proton motive force and size of the plastoquinone (PQ) pool and reduced photosystem I (PSI)donor-side limitation. We conclude that exogenously supplied trehalose improves electron transport from Pheo to QA and QA to QB by protecting the oxygen-evolving complex and the PSII reaction center, thereby improving the values of Y(II) and qP during heat stress. Our study reveals a good technological method to improve photosynthetic electron transport in maize under changing climatic conditions like heat.