Study On The Relationship Of Soil Water Conditions And Physiological Characteristics Of Winter-wheat Under Drought Stress

China,as a vast agricultural country,agriculture consumes a large percentage of water resourses.However,it usually lacks effective management measures,which has resulted in a serious waste of water resourses.In order to develop water-saving agriculture,we must improve the management of water resources and strengthen relevant scientific researches to enhance water use efficiency of crops,which is very important for the construction and sustainable development of ecological agriculture.Here,for the purpose of studying the quantitative relationship of soil water content and soil water potential,soil water potential and leaf water potential of wheat,soil water and chlorophyll fluorescence parameters,and wheat yield and drought stress,respectively,we designed pot experiments and tank experiments with winter wheat(sichuan wheat No.104),and measured physiological indexes of wheat(including leaf water potential and chlorophyll fluorescence parameters)and meteorological and environmental information(including soil water potential and soil volumetric water content)under soil progressive drought and re-watering.In summay,this result can be used in water-saving irrigation,which can be conducive to reduce the waste of water resource and increase water use efficiency,and gives some advice for the government section's establishing relevant policies.It also provides the theoretical foundation for the study on the movement law of in the metabolism process of crops,and relationship between the physiological indexes of wheat and soil water under drought stress.According to the test scheme that we have done for the test.we can conclude the following main results:(1)The soil water content could be well described by an exponential function with the soil water potential in the tank experiments.Although the PF curves of soil are diverse in the different tank,the trend is identical,usually,the soil water suction increased with soil moisture decreasing.The saturated soil volumetric water content is 3 5?40%,and field capacity is 25?30%,which is the upper limit of farmland irrigation in the yucheng,in Jianyang County.Therefore,the specific yield of soil is about 7?10%.(2)The leaf water potential of wheat decreased with soil water suction increasing in the whole growth period(including seedling stage,jointing to heading stage,flowering to grain filling stage)under different degrees of drought stress.However,the leaf water potential loss rate decreased variously under the different water potential gradient,and the relationship is T1<T2<T3<T4<T5.Leaf water potential of wheat and soil water suction would be in a quadratic function relationship at the seeding stage,but would be in a quadratic function relationship firstly,and then become in a cubic function relationship from jointing to grain filling stage.As a consequence,there seems to be a threshold effect in this process.(3)In the field experimental observation,we found that leaf water potential of wheat decreased gradually with the soil water suction increasing on account of rising temperature and intense light between 9 a.m and 1 p.m,but it did not change significantly after 1 p.m.The wheat could maintain water balance through morphological and physiological adjustment when the temperature and light intensity changed.For instance,they would close pores in order to avoid excessive water loss.(4)The research shows that chlorophyll fluorescence parameters of plant had obvious differences in different physiological stages under drought stress.When the soil water content is 18%,drought stress had a great influence on the efficiency and the activity of PSII photochemical reaction of wheat from seedling to grain filling stage.However,the efficiency of photochemical reaction showed no difference in different physiological stages under the condition(soil moisture content is 21%,24%and 27%,repectively).But,at the same time,we also observed that drought stress in varying degrees had no significant effect on chlorophyll fluorescence parameters of wheat.(5)In the present study,we found that there is a dramatic change of the chlorophyll fluorescence parameters in a day,and Fm,Fv and Fv/Fm were likely to be the minimum due to the peak of the light,solar total radiation and air temperature at 1 p.m.The lower air humidity and intense transpiration led to stomatal closure of plant,which would result in reducing the C02 inflow,and then lowering system II(PS II)activity,light system II photochemical efficiency and energy conversion efficiency of PS II original light.Thus,this may explain that values of Fm,Fv and Fv/Fm are lower at 1 p.m.(6)Based on the analysis of production data,drought stress had the growing influence on thousand kernel weight from seedling to grain filling stage.Meanwhile,drought stress had varied impact on yield of wheat in the different physiological stages,and had the largest effect from flowering to grain filling stage.Moreover,it also affected the harvest index of wheat significantly,and harvest index of wheat under drought stress from jointing to heading stage was significantly higher than that from seedling stage and flowering to grain filling stage.