Effects Of High Temperature Treatment At Flowering Stage On Plant Growth,Yield And Quality Of Cotton

June to August is the key period for cotton growth in the Yangtze River Basin,and high temperature stress will also begin at this period,during which the temperature is generally28℃-35℃,and sometimes it can reach 40 ℃.Cotton will also experience important growth periods such as flowering and boll setting during this period.As a thermophilic crop,suitable temperature within a certain range can promote the growth and development of cotton.However,when the ambient temperature exceeds this range,the seed survival rate,germination rate,seedling plant growth rate,plant height,stem width,leaf number size,flowering rate,boll setting rate at flowering and bolling stage,lint yield and seed cotton yield of fiber will be seriously affected,and eventually lead to cotton yield reduction and even plant death.In this experiment,38 cotton germplasm resources were used as experimental materials,and high temperature stress treatment was carried out at flowering stage.The agronomic traits,yield and quality traits of 38 varieties of upland cotton materials at flowering stage were compared.The changes and significance and correlation of each trait were studied,and the differences in heat resistance of different cotton varieties were analyzed.Finally,through a large number of data analysis,excellent high temperature resistant cotton varieties suitable for planting in the Yangtze River Basin were screened,aiming to achieve high yield of cotton and improve its economic value.The main research results are as follows :(1)The plant height of 38 cotton varieties were measured before high temperature treatment at flowering stage.The plant height of 31 varieties in the experimental group was between 59cm-67 cm,and that of 32 varieties in the control group was between 59cm-70 cm.On the 20 th day after high temperature stress at 40-42℃ for 10 days,the plant height of 38 cotton varieties was measured,of which 25 varieties in the experimental group were between 70cm-90 cm and 27 varieties in the control group were between 90cm-100 cm.The average number of buds in the experimental group was 5.14,and that in the control group was 10.06.The average first fruit branch position was 10.3 in the experimental group and8.4 in the control group.The average number of fruit branches was 4.6 in the experimental group and 6.3 in the control group.The average number of buds in the experimental group was 0.96,and the control group was 0.36.The budding rate of the experimental group ranged from 2.40 % to 64.33 %,and that of the control group ranged from 0 to 12.24 %.Therefore,high temperature stress at flowering stage could inhibit the growth of cotton plants,reduce the number of buds and fruit branches of cotton plants,and increase the first fruit branch node of cotton plants,the number of buds and the budding rate.(2)Under the high temperature stress of 40-42℃ for 10 days,the average flowering number in the experimental group was 25.96,and the flowering number of 19 varieties was more than 25.The average flowering number in the control group was 43.11,and the flowering number of 26 varieties was more than 35.The average number of bolls was37.34 in the experimental group and 59.21 in the control group.Within 10 days,the average number of flowers in the experimental group was 6.41 and that in the control group was 1.71.The flower drop rate of the experimental group was 1.94 %-71.11 %,and that of the control group was 0-15.63 %.The average shedding rate of bud and boll was25.98 % in the experimental group and 13.4 % in the control group.The average seed cotton yield(25 bolls)in the experimental group was 74.12 g,and that in the control group was 94.17 g.The average lint yield(25 bolls)in the experimental group was 27.94 g,and that in the control group was 40.41 g.The average clothing score of the experimental group was 37.28 %,and that of the control group was 42.66 %.Therefore,high temperature stress at flowering stage could inhibit the increase of flowering number,boll setting number,flower falling number,flower falling rate and bud and boll shedding rate of cotton,and reduce the yield and lint percentage of seed cotton and lint cotton.(3)Under the high temperature stress of 40-42℃ for ten days,the average length of the upper half of cotton fiber in the experimental group was 29.86 mm,and that in the control group was 28.19 mm.The average uniformity of the experimental group was 84.37 %,and that of the control group was 85.06 %.The average fracture specific strength of the experimental group was 29.09 g / tex,and that of the control group was 32.98 g / tex.The average elongation of the experimental group was 6.65 %,and that of the control group was 6.74 %.The average value of the experimental group was 4.57,and the control group was 4.14.Therefore,high temperature stress at flowering stage will increase the length of the upper half of cotton fiber,decrease the uniformity,breaking strength and elongation,and increase the micronaire value and deviate from the better grade range.(4)Correlation analysis : Under the high temperature stress of 40-42℃ for 10 days during the flowering period of cotton,the correlation analysis was carried out on the three indexes of agronomic shape,yield during boll opening period and cotton fiber quality,and it was concluded that the number of buds,the number of fallen buds,the number of flowering,the number of fallen flowers and the number of bolls were significantly correlated with seed cotton yield,lint yield and lint percentage.There was no significant correlation between yield and quality indicators,but there was a significant correlation between cotton fiber quality indicators.(5)Screening of resistant varieties : Through principal component analysis,the comprehensive evaluation system of high temperature resistance was established.According to the comprehensive score of high temperature resistance,38 cotton varieties were divided into four high temperature resistance categories : high temperature resistance,high temperature resistance,high temperature sensitivity and high temperature sensitivity.The high temperature resistant cotton varieties are : NL018(Yujing 3),NL010(Shanmian7),NL030(Jinzimian),NL028(Chuan 57-681),NL034(Zhongmian 1279♂).The high temperature sensitive cotton varieties are : NL033(Zhongmian 1279♀),NL002(Zhong9018),NL004(1638),NL019(Zhong 7263),NL031(Fuzimian).