Response of gas exchange and chlorophyll fluorescence of maize to alternate irrigation with fresh- and brackish water

Abstract

The scarcity of good-quality water is forcing the use of brackish water for irrigation in many areas around the world. Alternate fresh- and brackish water irrigation is a feasible irrigation method (IM). A pot experiment was carried out with three brackish water IMs and at three levels (1, 3 and 5 g NaCl L−1). The various levels of brackish waters were irrigated at the seedling stage, the jointing and tasseling stage and the after tasseling stage, respectively. The responses of maize (Zea mays L.) to alternate irrigation were investigated through gas exchange and chlorophyll fluorescence. The results showed that the alternate use of fresh- and brackish water reduced the increasing soil salinity caused by brackish water irrigation. The changes in net photosynthesis rate (Pn), stomatal conduction (gs), intercellular CO2 concentration (Ci) and chlorophyll content (SPAD) values revealed that maize was more resistant to brackish water at the after tasseling stage. Moreover, significant reductions in maximum quantum yield (Φpo), effective quantum yield of photochemical energy conversion (Φ2), photochemical quenching (qp), non-photochemical quenching of variable chlorophyll fluorescence (qN) and non-photochemical chlorophyll fluorescence quenching (NPQ) of photosystem II, grain yield and biomass weight of maize subjected to high NaCl level brackish water at the jointing and tasseling stage were observed. This implied that maize plants were extremely sensitive to brackish water irrigation during the jointing and tasseling stage, and freshwater should be applied at this growth period. Our results would be helpful for sustainable maize production using alternate irrigation with fresh- and brackish water in arid and semi-arid areas.

Keywords

• alternate irrigation
• brackish water
• maize
• gas exchange
• chlorophyll fluorescence