Key Time For Fiber Develepment Response To High Temperature Stress And Its Mechanism

Withglobal wanling,more and moreextreme weather of high temperature happened world widely.Short-term high temperature stress would become one of the most important natural disasters which would impact the production and quality of China Cotton Belt.Fiber developmentis extremely sensitive to temperature,andat different developmental stageit has different responses tohigh temperaturestress.Therefore,the study of key time region of fiber quality formation and its mechanism in response to short-term higher temperature stress can help us tinely and moderately assess the tolerant rang of cotton under this stress,and provide a theoretical basis for the arise of high temperature resilience cultivation techniques.It will also make a good contribution to China’s ability of cotton suppIy.By taking two cotton cultivars with different temperature-sensitivity(PHY370WR temperature-insensitive cultivar.Sumian 15,tenperature-sensitivecultivar)as materials,a experiment with two different temperatures regimes(high temperature:34℃[38/30℃]and control:26℃[30/22℃])were set in climate chamber in Nanjing Agricultural University to study the changes of the key physiological matters and fiber qualities in different genotypes in response to high temperature.In order to study key timeof fiber quality formation and physiological changes in response tohigh temperature stress.The main findings are as follows:1.The determination of thekey time window and the critical duration of cotton fiber development in response to high temperature stressAs treated in the 34.0oC high-temperature regime for 5 days at different DPA,significant changes in fiber quality would be observed in the temperature-sensitive cultivar Su、ian 15.Fiber length decreased,while fiber strength increased and Micronaire decreased,and the general fiber quality deteriorated.Thekey time window of 2014wasl2.7-16.3 DPA,it was 11.9-16.1 DPAin 2015.Based on different indicators and the critical standard to calculate the critical stress time,the critical durations of Sumian 15 are shorter than PHY370WR.Based on fiber quality,the critical duration of PHY370WR was 5.0d in 2014,and it was l.9d for Sumian 15.It was 4.8d and 2.0d in 2015.Based on matters,the critical duration of PHY370WR was 6.4d in 2014,and it was 5.6d for Sumian 15.It was 6.1d and 5.4d in 2015.2.The influence of source-sink capability on different high temperature stress durations and fiber qualityAs treated with different high temperature stress durations,the net photosynthetic rate and the total chlorophyll a content and chlorophyll b content of leaves subtending to boll in two cotton cultivar decreased,while.the ratio of chlorophyll a and chlorophyll b increased in 2014 and 2015.The sucrose content of cellulose fiber declined under the condition of high temperature,sucrose content decreased,callose content raised,and with the high temperature stress duration increasing,the resilience of the above indicators weakened gradually.As 5%for difference standard,PHY370WR achieved the high temperature tolerance limit in 5d,5d,sd,the recovery times were 5.6d,11.5d,1.8d.Sumian 15 achieved high temperature tolerance limit in 4d,4d,5d,the recovery times were 4.5d,10.2d,2.4d.Beyond the limit,fiber development related matters cannot recover to normal level.The change of weak temperature sensitive variety is same as temperature sensitive variety,just the change is smaller.Resilience of PHY370WR significantly stronger than Sumian 15 after high temperature stress.Correlation analysis showed that the chlorophyll a + b dramatically affected the net photosynthetic rate,fiber sucrose could significantly influence the formation of the fiber quality,cellulose and callose could only affect micronaire and strength.3.The influence of different high temperature stress durations on enzyme activityAs treated with different high temperature stress durations,Sucrose synthase declined,the activity of sucrose phosphate synthase increased firstly then decreased,β-1,3-glucanase activity decreased.As 10%for difference standard,PHY370WR achieved the high temperature tolerance limit in 5d,6d,N/A,the recovery times were 6.3d,7.2d,N/A.Sumian 15 achieved high temperature tolerance limit in 4d,6d,5d,the recovery times were 6.0d,8.3d,6.7d.Beyond the limit,fiber development related enzyme activity cannot recover to normal level.The change of weak temperature sensitive variety was same as the temperature sensitive variety,just change is smaller.Thekey time window of 2014wasl2.7-16.3 DPA,it was 11.9-16.1 DPAin 2015.As treated with different high temperature stress durations,the net photosynthetic rate of leaves subtending to boll in two cotton cultivar decreased.And sucrose synthase declined,the activity of sucrose phosphate synthase increased firstly then decreased,β-1,3-glucanase activity decreased.Which hindered sucrose synthesis and callose degradation.Meanwhile,fiber sucrose could significantly influence the formation of the fiber quality,cellulose and callose could only affect micronaire and strength.The change of weak temperature sensitive variety was same as the temperature sensitive variety,just change is smaller.