Effects Of Warming At Late Winter And Early Spring Stage On Plant Morphology And Yield Formation Of Winter Wheat

The winter wheat in North China Plain is vulnerable to the harm of hot and dry wind in the late growth period,which shortens filling duration and advances maturity,thus resulting in the wheat yield reduction.Therefore,a two years field experiment was conducted to explore a new management method that makes full use of light and heat resources reasonably and effectively during the growing period of wheat in this region by creating different heating conditions during the late winter and early spring,which would achieve high yield of wheat.We changed warming intensity by altering the length of film mulching time and the number of film mulching layers during the late winter and early spring stage(from 25th January to 25th March).In 2016-2017,the tested varieties for warming treatments were Shi Mai 18 and Heng Guan 35.Five warming treatments were set:covering on 25th January with 3 layer film(T1),25th January with 2 film(T2),1st February with 2 film(T3),8th February with 2 film(T4)and 15th February with 1 film(T5),respectively.Similarly,the tested materials in this warming treatment were Shi Mai 18 and Heng 4399 in 2017-2018.Different warming treatment,which covering on 25th January with 1 film(T1),1st February with 1 film(T2),8th February with 1 film(T3)and 15th February with 1 film(T4),respectively.Normal growth condition(CK)was used as the control in two years.The results show that:1.Compared with CK,warming treatments increased the accumulated temperature by 27.37-662.61? during late winter and early spring stage in 2016-2017,and which was 66.04-101.05? higher than CK in 2017-2018.The increase of accumulated temperature accelerated the growth process of wheat,leading to the advance of the time of each major phenological period.In 2016-2017,flowering period of warming treatments were 2-11 days earlier than CK,and the filling duration in each warming treatment increased by 6 days,5 days,5 days,4 days and 1 day respectively compared with CK.And in 2017-2018,each treatment advanced the flowering period by 2-9 days than CK,and the filling duration of each warming treatment was increased by 4 days,2 days,2 days and 1 day respectively compared with CK.The extension of wheat filling period ensured sufficient grout time and increased wheat yield.2.Late winter and early spring temperature changed the winter wheat morphology.Compared with CK,the flag leaf area of each warming treatment of Shi Mai 18 increased by 2.3%to 43.8%in 2016-2017,and which was 14.5%to 65.8%for Heng Guan 35.Likewise,the flag leaf area of Shi Mai 18 was increased by 0.1%to 37.9%compared with CK,which was 9.6%to 34.3%for Heng 4399.Flag leaf is the main organ of photosynthesis in winter wheat during the filling period.The increase of flag leaf area is beneficial to photosynthesis of winter wheat.The length of the fifth inverted internode of T1 of Shi Mai 18 and Heng Guan 35 was the shortest and T2 was the second in 2016-2017.In 2017-2018,the length of the fifth inverted internode of each warming treatment of Shi Mai 18 and Heng 4399 is shorter than that of CK.The shortening of basal internode is beneficial to the lodging resistance of winter wheat plants.3.With the increase of heating strength,the spike number,kernels per spike,1000-kernel weight and grain yield of winter wheat increased.Compared with CK,the spike number,kernels per spike,1000-kernel weight and grain yield of each warming treatment of Shi Mai 18 increased by 2.9%-16.5%,6.1%-18.2%,0.3%-6.3%and 2.4%-16.2%respectively in 2016-2017,and which was 2.9%-16.5%,2.6%-13.2%,0%-10.4%and 5.4%-24.0%respectively for Heng Guan 35.In addition,in 2017-2018,the spike number,kernels per spike,1000-kernel weight and grain yield of each warming treatment of Shi Mai 18 increased by 4.2%-12.7%,6.1%-15.2%,1.3%-5.1%and 6.7%-14.5%respectively compared with CK,and which increased by 5.0%-23.0%,6.3%-15.6%,1.3%-9.0%and 6.7%-18.2%respectively for Heng 4399.4.The gradual warming in late winter and early spring increased the chlorophyll content and net photosynthetic rate of wheat flag leaves,promoted the transfer of dry matter in the vegetative organs,reduced the contribution rate of assimilates to the grains during the whole growth period of wheat,increased the transfer rate of nutrient elements to the grains,and promoted the increase of wheat yield.