Effects of Alternate Fresh and Brackish Water Irrigation on the Diurnal Variation of Photosynthesis of Summer Maize

MIN Yong; ZHU Chengli; SHU Muchen; ZHAI Yaming; HUANG Mingyi; MU Hui

doi:10.13522/j.cnki.ggps.2017.0473

Abstract：[Objective]Investigate the effects of alternate irrigation with fresh and brackish water on diurnal vari-ation of photosynthesis of summer maize (Zea mays L.) in different growth periods.[Method]A pot experiment was carried out with three alternate fresh and brackish water irrigation methods. The various levels brackish wa-ters were irrigated respectively at the seedling stage (i.e. BFF1:1 g/L NaCl, BFF3:3 g/L NaCl and BFF5:5 g/L NaCl), the jointing and tasseling stage (i.e. FBF1: 1 g/L NaCl, FBF3: 3 g/L NaCl and FBF5: 5 g/L NaCl), and the filling stage (i.e. FFB1:1 g/L NaCl, FFB3:3 g/L NaCl and FFB5:5 g/L NaCl). The control treatment (CK) was set with fresh water (0.08 g/L NaCl) irrigation throughout the whole growth period.[Result]The net photo-synthetic rate (Pn) under BFF1, BFF3, BFF5 and CK treatments charged with double peak curves ,and the majori-ty of peaks appeared at 12:00 and 16:00. The similar trends were found in FFB1, FFB3 and FFB5 treatments while the majority of peaks appeared at 10:00 and 12:00 in advance. Diurnal variation of Pn was expressed as a single peak at 10:00 in FBF1, FBF3 and FBF5 treatments. The Pn, transpiration rate (Tr) and water use efficiency (WUE) of maize with brackish water treatments were reduced in different degree compared with the control treat-ment which resulting in decrease of photosynthesis. Moreover, these reductions were found in stomatal conduc-tance (Gs) and intercellular CO2 concentration (Ci) (increase in BFF3, BFF5, FBF1, FBF3 and FBF5 treatments) which causing decrease of photosynthesis by stomatal and non-stomatal factors.[Conclusion]The effect of brackish water irrigation on diurnal variation of photosynthetic of maize is the most significant in the jointing and tasseling stage, followed by the seedling stage, while the effect is the minimum in the filling stage. So, sum-mer maize is seriously sensitive to brackish water irrigation in the jointing and tasseling stage. Fresh water should be applied in the jointing and tasseling stage and brackish water can be irrigated in the filling stage.