Effects Of Chemical Control Agents On Growth And Yield Formation Of Spring Maize Under Chilling Injury

Under the background of climate change,the risk of chilling injury increased in northern corn growing areas.The inhibition of chilling injury on maize growth is mainly related to the low content of chlorophyll in leaves.However,the mechanism of chilling injury on Maize chlorophyll inhibition is not clear,and the effective chemical control way to alleviate chilling injury on Maize chlorophyll inhibition has not been studied.In this study,the effects of chilling injury on maize root and shoot growth,nutrient accumulation,chlorophyll content and their relationship were systematically studied under the field production conditions of early sowing and simulating delayed chilling injury.The regulation mechanism of four chemical control measures（Spd,Ami,Dtb and Sf）on maize growth was studied.The main conclusions are as follows:（1）The content of chlorophyll decreased under low temperature stress,mainly because of the blocked nitrogen accumulation and then inhibited chlorophyll synthesis,among which chlorophyll a was most affected by low temperature stress.The maize varieties with strong cold tolerance have strong root plasticity,promote the root absorption of nitrogen,accumulate more nitrogen for chlorophyll synthesis,and improve the content of them to promote plant growth.（2）Under low temperature stress,chemical control regulators can increase nitrogen accumulation by 16.8%,which is beneficial to provide raw materials for chlorophyll synthesis in leaves.Among them,chlorophyll a is the key factor to improve photosynthetic rate and the formation of photosynthetic products.The strong growth ability in the early stage provided favorable conditions for biomass and grain formation in the later stage,thus reducing the abortion rate,increasing the number of grains per spike and increasing the yield.（3）Spermidine had the best control effect on Maize under chilling injury,and the yield increased by 10.11%compared with the control.Further study showed that exogenous spermidine could increase the accumulation of endogenous polyamines,enhance the protective effect of antioxidant enzyme system at low temperature,and increase the activities of antioxidant enzymes SOD,POD,CAT and GR in leaves,which was beneficial to remove harmful substances H₂O₂ and prevent cell membrane peroxidation damage.