Effects Of Drought Stress On Root Properties,Physiological Characteristics And Grain Yield Of Dryland Winter Wheat Of Shaanxi Province

Shaanxi Province is located in a semi–arid and semi–humid area and is an important winter wheat(Triticum aestivum L.)production area in the northwest region.Drought is one of yield–limiting factors of winter wheat.This study used five winter wheat genotypes with different release time widely planted in Shaanxi Province.Soil column techniques and laboratory analysis were used to systematically study the root morphology,soil water consumption,leaf photosynthesis,ABA concentration,the effects of assimilates transport and yields of drought stress on dryland winter wheat.Thus this study provides a scientific basis for future studies aiming to improve grain yield and drought resistance of winter wheat in dryland areas.Two experiments were conducted in this study:Experiment 1: Conducted in 2017–2018 with two water treatments(well–watered and drought stressed)during the whole plant growth period.The adaptability difference of five winter wheat genotypes in dryland in Shaanxi Province to drought stress was examined.The grain yield,root water use efficiency and root morphological characteristics were analyzed.The main findings of Experiment 1 are as follows:1.The yield and harvest index of dryland winter wheat increased significantly with the genotype replacement(increase in released years).Under drought stress,the yield increased from 5.32 g/plant of the 50–60s genotype(Xinong 6028)to 6.60 g/plant of the 2010 S genotype(Changhang No.1);the harvest index increased from 0.40 to 0.54.2.The total root length of dryland winter wheat increased significantly with the genotype replacement.Under drought stress,the total root length at flowering stage increased from 29.7 m/plant(Xinong 6028)to 42.2 m/plant(Changhang No.1).The total dry weight at flowering stage did not change regularly with genotype replacement,but that of Fengchan No.3 was significantly lower than other genotypes.3.During the replacement of winter wheat genotypes in dry land,the water consumption during the growing period was changed.The main performance is the decrease of water consumption before flowering and the increase of water consumption after flowering.Winter wheat water consumption before flowering decreased from 1.73 kg/plant(Xinong 6028)to 1.28 kg/plant(Changhang No.1);water consumption after flowering increased from 1.08 kg/plant(Xinong 6028),to 1.46 kg/plant(Changhang No.1).Experiment 2: Based on the results from Experiment 1,two wheat genotypes with constructing grain yield and root morphological characteristics were selected as the test materials.The second experiment was conducted in 2018–2019 consisting of three water treatments(well–watered,early–season drought with water recovery when leaves started wilting,and terminal drought started from flowering).The growth and physiology of dryland winter wheat in response to drought stress at different growth stages were investigated.The main findings of Experiment 2 are as follows:1.Both early drought and terminal drought reduced the yield of the two winter wheat genotypes,but terminal drought stress had a greater reduction in grain yield.Compared with well–watered treatment,the early drought stress decreased grain yields of the two genotypes by 7.7% and 7.0%,respectively;the terminal drought stress decreased grain yield by 9.8% and 9.2%,respectively.2.Early drought increased the post–anthesis dry matter accumulations of the two winter wheat genotypes by prolonging post–anthesis photosynthetic time.The post–anthesis dry matter increased by 76.4% and 10.7%,respectively.Terminal drought increased dry matter translocation and dry matter translocation efficiency.The contribution of pre–anthesis assimilates to grains of the two winter wheat genotypes was increased.Fengchan No.3(FC3)increased the contribution of pre–anthesis assimilates to grains by 38.2%,while Changhang No.1 increased 1.18 times.3.Under early drought,the two winter wheat genotypes increased the specific root length after rewatering,and the root to shoot ratio decreased.The root to shoot ratio under early drought at the anthesis stages was significantly lower than that under well–watered,and the specific root length at the maturity was significantly higher than that under well–watered;the terminal drought significantly increased the specific root length of the two winter wheat genotypes at maturity.4.Early drought has a compensatory effect on winter wheat after rewatering.Compared with well–watered,the two winter wheat genotypes of the eraly drought treatment with rewatering,increased the specific leaf area by 23.7% and 19.7%,ABA concentration decreased by 68% and 81%,and photosynthetic rate increased by 41.4% and 56.6%,respectively.