Water stress and stress recovery of Portuguese maize cultivars

Abstract

Water stress is the most important limitation to plant productivity. The development of drought resistant cultivars has become extremely important as we face the dramatic climate changes over the last years. Maize is one of the world’s most cultivated crops, but its production is limited to warm regions, where water limitation is often common. In six Portuguese maize cultivars (AD3R, PB64, PB260, PB269, PB304, PB369), from different regions of Portugal, drought was imposed, over one week, withholding water supply. Supply of water was restored afterwards and the plants studied for another week. Gas exchange and chlorophyll fluorescence measurements were made. Relative water content (RWC) was assessed as a measure of plant water status. In control plants, RWC was superior to 90% in all cultivars but stressed plants showed a strong decrease, especially in PB260. Photosynthesis reached values close to zero after a week of stress and all cultivars recovered, with the exception of PB369. The same pattern was observed in transpiration and stomatal conductance. AD3R showed the highest water use efficiency (WUE) and PB64 the lowest. The maximum potential photochemical efficiency of photosystem II and the photochemical quenching showed a small decrease in the last day of stress in all cultivars. The non-photochemical quenching remained constant. The electron transport rate decreased but recovered in all cultivars. PB269 seems to be the cultivar most tolerant to drought, showing the highest rates of photosynthesis and an intermediate WUE. On the contrary, PB369 seems to be the most susceptible cultivar to water stress.