The Study Of Influencing Mechanism Of Drought Stress On Winter Wheat Growth And Its Model Simulation

Under the background of global warming and extreme weather events increasing,the fluctuations of regional precipitation and river runoff in China have increased significantly.The frequency and severity of drought events have also become increasingly serious.The predecessors were mainly based on drought experiments to maintain a stable intensity of drought,which restricted the understanding of mechanism of crop growth under the processing of developing drought.In order to investigate the influencing mechanism of winter wheat under drought stress and realize the application of WOFOST model on drought impact simulation,four drought treatment were set during jointing-flowering stage,using winter wheat variety“Jimai 22”as the test material.This experiment carried out one-time irrigation of water according to 80%?W1?,50%?W2?,25%?W3?and 0%?W4?of normal water replenishment?75mm?.Winter wheat with normal water replenishment in the field was as control?CK?.Based on the winter wheat data of Taian agricultural meteorological station and drought data,WOFOST model was used to revise the production of winter wheat and drought simulation.The quantitative evaluation of the influence in different drought degrees on the growth and yield formation of winter wheat was established,in order to provide theoretical reference for regional drought impact assessment.The main conclusions were as follows:?1?Drought stress reduced the net photosynthetic rate,transpiration rate,stomatal conductance,intercellular CO₂concentration and chlorophyll content of winter wheat leaves.The more severe the stress,the more significant the decline.Drought stress increased the activity of SOD,POD,CAT,MDA content and carotenoid content of winter wheat leaves.The more severe the stress level,the more obvious the increase.With the extension of drought time and the intensification of stress,extreme drought?W4?resulted in the decrease of activity of SOD,CAT and carotenoid content as well as the increase of intercellular CO₂concentration.After rewatering during flowering stage,the gas exchange parameters,antioxidant enzyme activities,and MDA content of winter wheat leaves under moderate?W1?and severe?W2,W3?drought treatments gradually recovered to CK,while photosynthetic capacity and antioxidant capacity of extreme drought?W4?treatment could not be restored.The chlorophyll content of severe and extreme drought?W4?treatments were still significantly lower than CK,while the carotenoid content decreased significantly.?2?Drought stress reduced the leaf area,total dry weight and ear dry weight of winter wheat.The more severe the stress,the more obvious the impact.Drought stress made the development of winter wheat earlier,so the total dry weight and ear dry weight in water control prophase were higher than CK and then decreased significantly in the later stage.The leaf growth after rewatering during flowering stage was stimulated.The leaf area under moderate?W1?and severe?W2,W3?drought treatments recovered to CK,while the leaf area under extreme drought?W4?treatment was significantly lower than CK.Drought stress reduced the distribution ratio of leaf,increased the distribution ratio of stem and ear,but had little effect on sheath.Rewatering during flowering stage weakened the effect of dry matter distribution under drought.Drought stress before flowering increased the contribution rate of stems and sheaths to grains in winter wheat,thereby improving the transport efficiency of stem and sheath.The changes of dry matter accumulation,distribution,and transport in winter wheat under drought stress mainly led to an increase in infertility spikelet rate and a decrease in the spikelet number,which in turn led to a decrease in yield.Drought stress promoted the transfer of stem and sheath to ear,so thousand grains weight was not significant.?3?Based on the development period and yield data of Taian agricultural meteorological observation station and drought experiment,the localization application of WOFOST model and drought simulation correction were realized.The WOFOST model was used to simulate the growth indexes of winter wheat in different development periods and different drought degrees.The effects of drought at jointing stage and flowering stage on TAGP were the greatest.The decrease of TAGP in slight drought above 15d and in medium or severe drought above 10d were more than10.0%.The biggest loss of TAGP was that the severe drought lasting for 20d at jointing stage,with a decrease of 57.8%.The effect of drought at seedling stage was the second.The decrease of slight or medium drought for 20d and severe drought above 15d were more than 10.0%,ranging from 10.3%to 28.5%.According to the simulation of TWSO,the effect of drought at flowering stage was the greatest.TWSO in slight drought above 10d decreased by 20.1%?49.9%.The decrease in medium and severe drought above 5d were more than 10.0%.The biggest loss of TWSO was that the severe drought lasting for 20d,with a decrease of 86.4%.The effect of drought at jointing stage was the second.The decrease of medium drought for 20d and severe drough above 15d were ranging from 23.1%to 57.9%.The effect of drought at seedling stage was the weakest.After suffering from short-term slight drought at seedling stage,TWSO of winter wheat increased slightly.The drought period with the greatest effect on TWLV and TWST were seedling stage and jointing stage,with the decrease of 5.2%?61.4%and 4.2%?68.1%,respectively.The drought at flowering stage had no influence on TWLV and TWST of winter wheat.According to the simulation of MAXLAI,the effect of drought at seedling stage was the greatest.The decrease of MAXLAI in slight drought for 20d,medium drought above 15d and severe drought above 5d were more than 10.0%,while drought at flowering stage had no influence on MAXLAI.