[Effects of water-controlled irrigation on maize yield and photosynthetic characteristics of ear leaf in Xinjiang Province, China.].

In order to explore the suitable water management patterns for high yield of spring maize under drip irrigation in oasis regions of North Xinjiang, two maize cultivars (Zhengdan 958 and Kenyu 02) were used to study the effect of water-controlled irrigation on the leaf SPAD value at V12-R5 stage, and chlorophyll content, photosyntheticcharacteristics and chlorophyll fluorescence parameters of ear leaf at filling stage in the field. Results showed that the leaf SPAD values peaked under moderate soil moisture treatments during V12-R3 stage. The field capacity of soil moisture above 65% was suitable for the development of corn at R5 stage. The chlorophyll a, b and total chlorophyll contents, carotene, chlorophyll a/b were significantly decreased when soil moisture was less than 75%, however the above parameters had no significant difference when soil moisture was more than 85%. The net photosynthetic rate (P), transpiration rate (T) and stomata conductance (g) of ear leaf were significantly decreased in filling stages when soil moisture was less than 75%, but the intercellular CO concentration (C) was significantly increased. The reduction of g was not observed when the soil moisture was more than 85% of field capacities. Meanwhile, the variable fluorescence to maximal fluorescence (F/F), potential activities of PSII (F/F), PS2 actual photochemical efficiency (Φ), photochemical quenching (q) and electron transport rate (rETR) decreased significantly under both higher and lower soil moisture treatments. However, the F/F and non-photochemical quenching (NPQ) significantly increased at the same time. The path analysis showed that the decrease of P resulted from the decrease of F/F and rETR, which finally resulted in decreased production of spring maize. Therefore, the optimal field moistures for these two spring maize cultivars were >60%, >70%, >75%, >80% and >65% for the growing stages V6, V12, R1, R3 and R5, respectively, to obtain a high yield in the oasis region.