Effects of Water Stress/Rewatering on Leaf Photosynthetic Characteristics and Grain Yield of Foxtail Millet

Abstract

Foxtail millet behaves strong drought resistance, but its photosynthesis process and grain yield are restricted by drought. The effects of water stress/rewatering on photosynthetic characteristics and yield of foxtail millet are studied through field water control experiment at booting and flowering stage and grain filling stage. The restraint factor on photosynthesis rate and the follow-up impact on grain yield are expounded, which may provide guidance for foxtail millet grain yield assessment and field water management under drought condition. The results are as follows: Water stress can lead to the decrease of photosynthetic rate and grain yield of characterized by larger decrease amplitude with the increase of stress intensity and duration, and increasing water use efficiency is the main survival strategy. The effect of water stress/rewatering on foxtail millet yield at grain filling stage is more obvious than that at booting and flowering stage, characterized by 22.1% production loss under 14-day mild water stress and 47.1% for FH-21 treatment group. After rewatering, photosynthesis performs compensation effect, and the photosynthetic capacity is recovered to some extent. The recovery of photosynthesis ability is lower when the the water stress intensity is stronger and the water stress duration is longer, and the recovery of photosynthetic capacity at grain filling stage is weaker than that at booting and flowering stage. Under mild and short duration water stress, the decrease of photosynthetic rate is mainly determined by stomatal factors, and the non-stomatal restriction gradually becomes the main cause for the decrease of photosynthetic rate with the increase of water stress intensity and the extension of duration. Mild negative effects of water stress on grain yield for 7 and 14 days, and severe effects for 7 days can be partially offset by the compensating effect after rewatering to some extent at booting and flowering stage, so the final effect on grain yield is not significant. In comparison, the effect of water stress on photosynthetic rate is larger, and the recovery of photosynthetic is not as good after rewatering at the grain filling stage. The formation of grain yield is more sensitive to water stress at the grain filling stage, for the closer synergistic relationship between photosynthetic rate and ultimate grain yield. The results reveal that a mild or short-term water deficit can be made up by rewatering, when the water use efficiency and photosynthesis rate will rise, and stable foxtail millet grain yield can be obtained. This can improve sustainable development by allowing deficit irrigation and water-saving agricultural practices. These critical information for optimizing water management practices is beneficial for foxtail millet sustainable development, particularly under warmer and drier climate in the future in the northern China.