Effects Of Drought Stress On Photosynthesis,growth And Yield Of Winter Wheat At Jointing Stage

This article adopts the method of pot experiment,through setting up control(CK)in winter wheat jointing stage,mild drought(G1),moderate drought(G2)and-severe drought(G3)four different water levels,observing the photosynthetic characteristics of winter wheat under different drought treatment,plant morphology,grouting rate and the change of the production index,comprehensive research systematically jointing stage drought stress on the photosynthetic characteristics of winter wheat jointing stage to the mature period,the influence of the growth and yield.The results showed that different degrees of drought at the jointing stage inhibited the growth indexes of winter wheat to some extent.The main research results are as follows:(1)The net photosynthetic rate of winter wheat decreased significantly under drought stress.CK?G1>G2>G3,and G1 and G2 show a "bimodal" pattern in the three development stages.G3 is a less obvious "unimodal" pattern.The higher the drought grade was,the lower the net photosynthetic rate was.(2)Transpiration rate of winter wheat was negatively correlated with drought grade.G1,G2 and G3 show a "bimodal" pattern in each period.The daily average Tr of CK>G1>G2>G3 in all three periods,but CK and G1 have no significant difference,G2 and G3 have extremely significant difference compared with CK.With the growth and development of winter wheat,the difference of Tr between different treatments became smaller and smaller.(3)The diurnal variation of WUE in each treatment mostly presents a "double peak"characteristic similar to "M" type,and some presents a "single peak" or "triple peak" type.WUE of winter wheat from G1 and G2 increased gradually with the aggravation of drought.The daily mean value of WUE in all three periods is G1?G2?CK>G3.G3 is significantly lower than other treatments throughout the development period.CK increased slightly compared to G1 and G2.(4)The daily mean values of Gs at jointing stage,heading stage and grouting stage were CK>G1>G2>G3.The drought grade was aggravated,and the mean values of stomatal conductance days of winter wheat were decreased.At the jointing stage,the difference between different treatments was the largest,while the difference between different drought treatments at the mature stage and the grouting stage and CK gradually narrowed,indicating that the influence of drought stress on winter wheat Gs at the jointing stage was gradually weakened as the development stage advanced.(5)There was an extremely significant negative correlation between Ci and drought grade of winter wheat.The daily mean of Ci in the three periods is generally shown as CK>G1>G2>G3.The worse the drought grade is,the lower the daily mean of Ci is.There was no significant difference between G1 and CK in the three development stages,and the Ci value of G2 and G3 decreased rapidly after drought stress in the joint stage,with a large gap with CK.The gap between G3 and CK increased further in the heading stage,but the gap between different drought treatments and CK decreased significantly in the grouting stage.All the photosynthetic indexes of winter wheat showed the adaptability to drought and stress along with the development stage.(6)Under drought stress,the leaf area,plant height,stem diameter,root dry weight,secondary rooting number and root-crown ratio of winter wheat were significantly reduced.The effects of drought on winter wheat plant morphology at jointing stage run through every development stage from jointing stage to maturity stage,and the root-crown ratio shows adaptability after heading stage,while the root-crown ratio of winter wheat gradually reduces the gap between different treatments after jointing stage,indicating that drought stress has a greater effect on the above-ground part of winter wheat than on the root system.lt also showed that drought and stress had a great influence on plant morphology of winter wheat,and other plant morphology indexes except secondary rooting and root-cap ratio were difficult to recover.(7)Drought will cause the flowering delay of winter wheat,and the difference of different treatments is significant.CK begins on or about April 11,G1 on April 13,G2 on April 16,and G3 on April 18 at the latest.Compared with the control group,mild drought delayed the beginning of flowering flowering by about 2 days,moderate drought by about 5 days,and severe drought by about 7 days.Grout duration of G1,G2 and G3 decreased by 2.2 days,6.46 days and 10.36 days,respectively.This indicates that drought stress can reduce the duration of winter wheat grouting,which also causes the early maturity of winter wheat with heavier drought grade.Drought increased the average grouting rate of winter wheat.The average grout rate of G3 is about 0.93mg/grain·d,which is the maximum value of each treatment.G2 and G1 are relatively close,and the average grout rate is 0.91mg/grain·d,while CK is 0.87mg/grain·d,which is the minimum value of each treatment.Drought is inversely proportional to the maximum grouting rate.The maximum grout rate of CK was 1.43mg/grain·d,G1 was 1.36mg/grain·d,G2 was 1.25 mg/grain·d,and G3 was 1.21mg/grain·d.The maximum grouting rates of CK,G1,G2 and G3 are 23.33 days,21.83 days,21 days and 18.97 days respectively after flowering.This indicated that drought stress would lead to the advance of the maximum grouting rate from the days after flowering,and G1,G2 and G3 were advanced by about 1.5 days,2.33 days and 4.36 days respectively.(8)There was an extremely significant correlation between drought grade and the number of spikelets per plant,the number of grains per ear,the rate of infertile spikelets,the 1000-grain weight and the grain weight per plant,among which there was an extremely significant negative correlation with the number of spikelets per plant,the number of grains per ear,the 1000-grain weight and the grain weight per plant,and an extremely significant positive correlation with the rate of infertile spikelets.The higher the drought level was,the higher the number of spikelet per plant,the number of grains per panicle,the 1000-grain weight and the grain weight per plant were all significantly decreased,while the rate of infertile spikelet was significantly increased.G1 1000-grain weight reached 36.64g,slightly higher than CK's 36.51g,G2 and G3 averaged 31.55g and 28.28g,respectively.The control reduction rate of the three kinds of drought treated winter wheat 1000-grain weight was-0.36%,13.58%and 22.53%,respectively.When the drought degree reached G3,winter wheat 1000-grain weight was the lowest.There was a negative correlation between drought grade and grain weight per plant of winter wheat.The average plant weight of CK was about 1114mg,G1 was 856.64mg,G2 was 619.01mg,and G3 was 480.19mg on average.Compared with CK,G1 had a reduction rate of about 15.48%,G2 had a reduction rate of about 38.92%,and G3 had a reduction rate of about 52.62%.