Effects Of Soil Moisture During Returning Green And Jointing Stages On Spike Formation And Yield Of Main Stem And Tillers In Winter Wheat And Its Physiological Characters

The experiment was conducted from 2017 to 2019 in Xuanzhuang Village(116°54?E,36°12?N),Daolang Town,Tai'an City,Shandong Province under pot conditions,the winter wheat varieties Shannong 29 and Heng 0628 were used as experimental materials.in total nine water treatments were set up during returning green and jointing stage.Full irrigation treatment during whole growing season was designed as control(CK,maintaining soil relative water content of 75~80%,the effective soil water content is 42.2~46.7 mm),0~10 d light drought stress after returning green(R1,maintaining soil relative water content of 65~70%,soil availability water content is 33.4~37.8 mm),0~10 d severe drought(R2,maintaining soil relative water content of 45~50%,available soil water capacity is 15.6~20.1mm),10~20 d light drought stress after returning green(R3,maintaining soil relative water content is65~70%,soil availability water content is 33.4~37.8 mm),10~20 d severe drought stress(R4,maintaining the soil relative water content 45~50%,availability water content is15.6~20.1mm),0~5 d light drought stress after jointing(T1,maintaining soil relative water content of 65~70%,soil availability water content is 33.4~37.8 mm),0~5 d severe drought(T2,maintaining soil relative water content of 45~50%,available soil water capacity is15.6~20.1 mm),0~10 d light drought stress after jointing(T3,maintaining soil relative water content is 65~70%,soil availability water content is 33.4~37.8 mm),0~10 d severe drought stress(T4,maintaining the soil relative water content 45~50%,availability water content is15.6~20.1mm).The effects of soil moisture before and after jointing on the development of young spike,ear formation and seed setting,physiological characteristics of the main stem and tillers were studied.The main results were as follows:1 Effects of returning green and jointing stage on winter wheat tillering development dynamics and panicle formation rateThe number of stems and tillers in the whole pot of Heng 0628 before the standingstage was greater than Shannong29.There was no significant difference in the number of stems and tillers in the whole period of the two varieties from the standing to the jointing.It showed that Heng 0628 had fewer tillers in spring,and the invalid tillers died together,and the final number of panicles was less than Shannong29.Drought can regulate the number of stems andtillers of the two wheat varieties.With the increase of the degree of drought and the extension of the time of drought,the number of stems and tillers in the whole pot showed a decreasing trend.Mild drought had no significant effect on the ear differentiation period,and severe drought delayed the differentiation process of tiller and ear.Shannong 29 and Heng 0628 reduced tillers by 9.20% and 11.72% in R1 treatment,the final panicle rate increased by1.48% and 0.33%,respectively,and tillers decreased by 3.39% and 7.63% in R3 treatment,and the final panicle rate increased by 3.50% and 3.12%,respectively.The final spike rate of T1 increased by 3.29% and 2.01%,respectively.This indicated that R1 and R3 treatment effectively inhibited the occurrence of ineffective tillers,and T1 treatment controlled the rate of tiller death.The above three treatment can reasonably improve the group environment,and increase the ear formation rate of the high tiller and increase the number of ear formation in the whole pot,while ensuring that the main stem and low tiller formation rate remain unchanged.2 Effects of drought before and after jointing on photosynthesis and senescence of winter wheat stems and tillersDifferent degrees of drought before and after jointing can increase the activity of superoxide dismutase(SOD)and the content of malondialdehyde(MDA),reduce the net photosynthetic rate of the leaves,and the degree of the impact increases with the backward movement during the drought period.After normal water supply,the net photosynthetic rate of the stem and tiller leaves under mild drought treatment returned to the control level,which was consistent with the recovery of SOD activity and MDA content.The SOD activity and MDA contents of the stem and tiller leaves under severe drought treatment still increased significantly,and the active oxygen balance system was gradually Broken,the cell membrane was destroyed resulting in a net photosynthetic rate significantly lower than the control.Light drought treatment can reduce the MDA content of leaves during flowering,and increase the net photosynthetic rate and SOD activity of leaves during flowering.It showed that the mild drought before and after jointing increased the net photosynthetic rate and active oxygen scavenging ability of the leaves in the late growth stage,and the proper delay of senescence could provide better growth conditions in the later stage,which was beneficial to the improvement of ear traits and yield.Severe drought treatment still has a certain effect on the flag leaf photosynthetic characteristics and antioxidant enzyme system.The reduction of photosynthetic rate inhibits the production of assimilation,and the ear traits and yield are suppressed.3 Effects of drought on carbon and nitrogen metabolism of winter wheat stems and tillers before and after jointingWith the intensification of drought,soluble sugar and soluble protein increased significantly,the total nitrogen content did not decrease significantly,the ratio of sugar and nitrogen was imbalanced,the main stem and tillers performed the same,drought had less effect on the main stem than tillers,and had a greater impact on the jointing stage.Different degrees of drought before and after jointing also affected the normal operation of carbon and nitrogen metabolism of stem and tillers during flowering.R1 treatment reduced soluble sugar and soluble protein content.R3 and T1 treatment restored soluble sugar and soluble protein to normal levels and increased total nitrogen content.The soluble protein and soluble sugar were still significantly higher than the control,and the total nitrogen content of T4 treatment was significantly reduced.This study found that the tillering rate was significantly negatively correlated with soluble total sugar,soluble protein content,and sugar-nitrogen ratio at the flowering stage,and weakly correlated with total nitrogen content.4 Effects of dry matter accumulation on stem and tillers of winter wheat before and after jointingThe dry matter quality of two winter wheat stems and tillers showed a significant increase with the growth period,and the increase of tillers was significantly lower than that of the main stems.With the increase of drought,the dry matter accumulation rate of stem and tillers decreased significantly,and the decrease of tillers was greater than that of the main stem.Compensation effect occurs after rewatering.The dry matter accumulation rate of stem and tillers in a short period of time shows severe drought>mild drought>CK,and later becomes mild drought>CK>severe drought.The R1 and R3 treatment increased the dry matter accumulation intensity of joint-flowering and flowering-maturity,and the T3 treatment increased the flowering-mature dry matter accumulation intensity.This indicates that the effects of severe drought and prolonged mild drought in the jointing period seriously inhibited the accumulation of biomass during the drought,delayed the differentiation process of young ears,and led to a reduction in the number of ears.At the same time,it also affected the accumulation rate of dry matter after anthesis,not conductive to the development of ear traits.5 The effect of drought on yield and yield components before and after jointingThe effects of drought stress on yield before and after jointing were the same in both varieties.The short-term mild drought treatment at the greening stage and the jointing stage increased the yield.The severe drought before and after the jointing and the long-term mild drought at the jointing stage significantly reduced the yield.R1 and R3 treatment can increasethe number of panicles and 1000-grain weight.Severe drought 0~10 d after returning green(R2)significantly reduced the number of ears,and 10~20 d severe drought after returning green(R4)significantly reduced the number of grains of the ears 10~20 d after returning green.0~5 d light drought after jointing(T1)increased the number of spikes,0~5 d severe drought after jointing(T2)significantly reduced the number of spikes,and the number of spikes,0~10 d light and severe drought after jointing(T3 and T4)were significantly reduced spikes,grain per spike and 1000-grain weight.The increase in yield per panicle under mild drought conditions during the greening stage is beneficial to the increase in grain yield.In summary,on the basis of the mild drought(relative water content 65~70%,soil effective water content 33.4~37.8 mm)during the returning green stage and 0~5 d after jointing stage,on the basis of ensuring that the main stem and the low tillering rate are unchanged,increasing the tillering rate of high tillers to increase the number of spikes per unit area.At the same time,R1,R3 and T1 treatment increased the net photosynthetic rate of the leaves during flowering,slowed down the senescence of the leaves,increased the total nitrogen content,and reduced the ratio of sugar to nitrogen.With coordinated development,the output per unit area can be improved.