Response Of Different Winter Wheat Varieties To Water Deficit And Re-Watering From Regreening To Jointing Stage

During the 2017-2018 growth season,the experiment was conducted in the rainproof shed of Xuanzhuang village test station,Daolang town,Tai'an City,Shandong province,and covered up when it rains.The pot experiment was conducted with dryland variety Heng 0628 and irrigated variety Shannong 29 as materials.Three-factor cracking zone design was adopted in the experiment.The main-treatment was winter wheat varieties,and the sub-treatment was the water supply level from regreening to jointing stage.Three water supply(drought)levels were set in this stage,and the relative moisture content of soil was 65-70%(Mild drought),55-60%(moderate drought)and 45-50%(severe drought),respectively.The water supply(re-watering)level from jointing to anthesis was taken as the deputy-treatment.Two water supply levels were set,and the moisture content of soil was 65-70% and 75-80%,respectively.The relative water content of soil from sowing period to regreening and from anthesis to maturity period was 75-80%.In addition,the treatment of 75-80% was set as the control in the whole growth period.The response of different winter wheat varieties to water deficit and re-watering after drought from regreening to jointing stage has important theoretical significance for the research,and it can develop the water-saving and high-yield irrigation technology for wheat.The main results were as follows:1 Effects of water deficit and re-watering on tiller yield and its components.Compared with the control group,mild and moderate drought stress at the regreening to jointing stage and rehydration to 75-80% at the jointing stage increased the panicle number and grain number per spike of the two varieties,and the yield increased.Re-watering to65-70% at the jointing stage,the panicle number increased but grain number decreased,and there was no significant difference in yield between the treatment and control.No matter which supplementary irrigation level at the jointing stage,severe drought stress reduced the thousand-grain weight and decreased the yield.The yield reduction in Shannong 29 was significantly greater than Heng 0628.The yield of re-watering to 65-70% was higher than to75-80% in two varieties.Grain number per spike of main stem of the two cultivars decreased significantly with the increase of drought degree from regreening to jointing stage.Compared with the control group,mild and moderate drought stress occurred in the regreening to jointing stage,and re-watering to 75-80% in jointing stage,which increased the grain number per spikeof tillers,while re-watering to 65-70%,which was lower than the control group.Under severe drought,the grain number per panicle for different tillers of the two varieties decreased,and the grain number under treatment with rehydration to 65-70% decreased less than that rehydration to 75-80%.The spike number was increased by drought and re-watering from regreening to jointing stage,and the number of panicles was increased more by re-watering to75-80%.2 Effects of water deficit and re-watering on population dynamics and earbearing tiller percentage.Drought during the regreening to jointing stage inhibits the occurrence of tillers of the two varieties.With the drought degree increased,the number of tillers decreased.The inhibited degree of tillers growth of Heng 0628 was higher than that of Shannong 29.After rehydration at jointing stage,drought stress was relieved and tiller quantity increased.With the increase of tiller position,the tiller heading rate of both varieties reduced.Compared with the control group,drought and water treatment during the regreening to jointing stage delayed the polarization of tillers and increased the final panicle number.When re-watering to 75-80% at jointing stage,compared with re-watering to 65-70%,tiller extinction was delayed,tiller heading rate was improved,and the final panicle number was increased.3 Effects of water deficit and re-watering on dry matter accumulation and earbearing tiller percentage.Compared with the control group,mild and moderate drought stress during the period from regreening to jointing resulted in the stable growth of main stem matter weight of Shannong 29 and a slight decrease of main stem matter weight of Heng 0628.Severe drought stress significantly reduced the main stem dry matter weight of the two varieties.The dry matter accumulation of each tillering decreased with the increase of drought degree.Mild and moderate drought stress occurred during regreening to jointing,and re-watering to 75-80% at jointing,which promoted the increase of tillering matter weight of each tillers,and was higher than that of control treatment and rehydration to 65-70%.Under severe drought stress,re-watering to 65-70% promoted the dry matter accumulation of each tillers.Under the conditions of this experiment,when the average dry matter weight of single stem exceeded0.17g/stem at jointing stage and 0.61g/stem at flowering stage,the tiller heading rate reached about 60%,and the heading rate gradually increased with the increase of the dry matter weight of single stem.The net photosynthetic rate and transpiration rate were reduced by drought stress from regreening to jointing stage.And the higher the drought degree was,the more significant the reduction was.The net photosynthetic rate and transpiration rate were restored after re-watering,and the recovery degree was higher after rehydration under severe drought stress in the early stage.With the increase of tiller position,the net photosynthetic rate and transpiration rate of tillers decreased gradually.Different tillers were affected by drought and re-watering,which varied with varieties.Shannong 29 showed mild drought would increase the net photosynthesis and transpiration rate of each tiller,but Heng 0628 did not show this characteristic.After rehydration,compared with the control group,the lower tillers such as the main stem and tiller I of Shannong 29 showed photosynthesis and transpiration compensation.However,Heng 0628 showed this rule in high tillers such as tiller in IV and IP.At the same time,the net photosynthetic rate and transpiration rate of both varieties were higher in the treatment of re-watering to 75-80% than that to 65-70%.5 Effects of water deficit and re-watering on tiller nitrogen accumulation in wheatThe accumulation of nitrogen in single stem increased gradually with the growth period.With the increase of tiller position,nitrogen accumulation in single stem decreased gradually.Compared with the control group,mild and moderate drought stress increased the nitrogen accumulation of Shannong 29 during the regreening to jointing stage,and mild drought stress increased the nitrogen accumulation of Heng 0628 in the early stage.Mild and moderate drought stress occurred during the period from regreening to jointing stage,and re-watering to75-80% at jointing stage,which promoted the accumulation of nitrogen in single stem,and was higher than that in the control and jointing stage when re-watering to 65-70%.After severe drought,re-watering to 75-80% promoted the accumulation of high tiller nitrogen,and re-watering to 65-70% promoted the accumulation of low tiller nitrogen.6 Effects of water deficit and re-watering on antioxidant enzyme system of tillers in wheatDuring the period from regreening to jointing,MDA content and SOD activity increased with the increase of drought degree.After re-watering,SOD activity and MDA content decreased,but were still higher than the control.Mild and moderate drought stress occurred during the period from regreening to jointing stage,and re-watering to 65-70% at jointing stage,Shannong 29 showed higher SOD and MDA than that re-watering to 75-80%.Under severe drought stress,SOD and MDA of rehydration to 75-80% at jointing stage were high.In Heng 0628,the plant recovered slowly under the influence of drought,and showed no effect of reducing plant aging within 10 days after re-watering.With the increase of tiller position,SOD4 Effects of water deficit and re-watering on the photosynthetic characteristics oftillers in wheatactivity of Shannong 29 showed a gradually increasing trend,while MDA content decreased.The SOD and MDA of Heng 0628 decreased with the increase of tiller position.