Analysis On The Disaster Process And Influence Of Spring Wheat Drought In Ningxia Irrigation District

Spring wheat is the main food crop in Ningxia,Inner Mongolia and Gansu.Drought is one of the most important disasters affecting wheat growth and yield formation,and is also an important limiting factor affecting wheat yield and yield texture.Global warming leads to the increase of climate temperature,the decrease of precipitation,the increasing trend of drought region and frequency in northern China,and the aggravation of the influence on wheat yield and quality.According to the actual situation of Ningxia,the field experiment of Yongchun 4,a spring wheat variety,was carried out in Yongning County of Yinchuan,Ningxia,using random block design.The irrigation period of wheat was set as tillering stage,jointing stage,flowering-filling stage,and filling-maturing stage.The experiment treatment was divided into four stages: whether or not irrigation was fully arranged at four growth stages,with a total of16 experimental treatments.The effects of drought stress on morphological and structural parameters photosynthesis indexes and biochemical indexes of spring wheat in different periods were studied and the disaster-causing process and influence of wheat were discussed.The main results and conclusions are as follows:1 The effects of drought stress on the growth period are postponed.Drought during flowering-filling period had the greatest impact on the shortening of developmental period,followed by drought at jointing stage.The drought in the tillering and jointing stage will cause wheat to die tillering,the length of the underarm stems will be shorter,the leaves will be poorly developed,and the leaf area and plant height will decrease.Rewatering after the early drought can delay the aging rate of the leaves.Continuous drought and early drought had a great effect on the decrease of leaf water content.Drought at tillering stage and jointing stage would change the pattern of dry matter distribution in wheat.The dry weight of dry leaves and sheath decreased rapidly in the late growth stage.The early drought significantly increased the grain weight per spike,and the grain weight per ear decreased significantly during the grain filling period.Guaranteed flowering-filling stage irrigation,wheat 1000-grain weight is higher.The experiment showed that the yield of the control group was the highest,and the wheat yield of the early drought and late rehydration treatment had no significant decrease.No matter whether the other periods were drought or not,the wheat yield would decrease significantly as long as the flowering-filling period suffered drought.2 The chlorophyll content of wheat showed an overall trend of increasing at first and then decreasing under different periods of drought stress.When wheat was subjected to slight drought,the relative chlorophyll content would increase slightly,but if the drought time was longer in the early stage,the relative chlorophyll content would decrease rapidly at the filling stage.Drought stress could significantly decrease the photosynthetic capacity of spring wheat.The diurnal changes of photosynthesis in wheat treated with different treatments were studied.The results showed that the net photosynthetic rate decreased and the transpiration rate was much lower than that in the control group after continuous drought treatment.The changes of photosynthesis with light intensity were different in different stages and treatments.Drought at tillering stage could improve photosynthesis of plants.Persistent drought at heading stage decreased the net photosynthetic rate and the transpiration rate changed parabola with the increase of light intensity.During the continuous drought to the filling period,the drought stress was serious and photosynthesis was strongly inhibited.The change of grouting rate of each treatment was "S" curve.Early drought treatment,the completion of the filling process will also be ahead of schedule.The results showed that high1000-grain weight could be obtained by irrigation at flowering stage.3 The chlorophyll content of wheat increased continuously before heading stage,stabilized at flowering stage,and began to decrease with yellowing and degeneration of leaves in filling stage.The malondialdehyde(MDA)and proline(proline)contents of spring wheat increased in different periods of drought.The activities of SOD,POD and CAT increased gradually from tillering stage to flowering stage.The activity of SOD decreased in the treatment of continuous drought during the filling period,while the activity of SOD in the other treatments increased.POD showed that the more severe drought,the greater the increase of POD activity in later stage.The activity of CAT decreased at filling stage,and the more severe drought was,the lower the activity of CAT was.