[Effects of different irrigation treatments during heading and flowering stage on cold resis-tance, yield and physiological characteristics of late rice].

Taking super hybrid rice variety 'Wufengyou T025' as test material, the effects of different irrigation methods and water layer depth on physiological characteristics and yield in double-season late rice under low temperature conditions during heading and flowering stage were investigated. Three treatments were set, i.e., draining during day and containing 4-5 cm water layer during night (H ₁ ), draining during day and containing 8-10 cm water layer during night (H ₂ ), and containing 8-10 cm water layer day and night (H ₃ ), with the 0-1 cm water layer day and night was as the control (CK). The results showed that rice leaf temperature, soil layer temperature and canopy temperature under the different irrigation treatments were higher than that of CK, and the warming effect of treatment H ₂ was the best during the low temperature period. Leaf chlorophyll content, net photosynthetic rate, transpiration rate, leaf stomatal conductance and intercellular CO ₂ concentration of rice plants decreased gradually under the low temperature, while the smallest reduction occurred in H ₂ . The increase ranges of malondialdehyde and proline content in H ₂ were lower, while its soluble protein content was the highest compared with other irrigation treatments. The increase ranges for the activities of superoxide dismutase and peroxidase in H ₂ were lower, while its decrease range for the activity of catalase was the lowest. Irrigation for heat preservation could increase the yield, and H ₂ performed best. Yield of H ₂ at the second sowing date in 2014 and 2015 encountering low temperature increased by 12.9% and 13.5% respectively compared to CK. The yield components including the effective panicle numbers per plant, panicle length, seed setting rate and 1000-grain mass were improved in all irrigation treatments compared to CK. Draining during day and containing 8-10 cm water layer during night (H ₂ ) was the most effective agronomic measure to enhance the tolerance to low temperature during heading and flowering stage for double-season hybrid late rice.