Key Time Region For Fiber Quality Formation Response To Short-term Heat Stress And Its Mechanism

Fiber development is extremely sensitive to temperature,and at different developmental stage it has different responses to heat(high temperature)stress.With global warming,more and more extreme 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.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 timely 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 supply.By taking two cotton cultivars with different temperature-sensitivity(Sumian 15,temperature-sensitive cultivar and Kemian 1,temperature-insensitive cultivar in 2013,PHY370WR temperature-insensitive cultivar form USA in 2014)as materials,a experiment with two different temperatures regimes(high temperature:34?[38/30?],HT and control:26?[30/22?],CK)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 time region of fiber quality formation and physiological changes in response to short-term high temperature stress.The main findings are as follows:1.Changes of cotton fiber quality in response to the high temperature stress which stared at different DPAs and the determination of key time region for fiber quality formation.As treated in the 34.0 ? high-temperature regime for 5 days at different DPA,significant changes in fiber quality would be observed in the temperature-sensitive cultivar Sumian 15.Fiber length decreased,while fiber strength increased and Micronaire decreased,and the general fiber quality deteriorated.The "key time region" of 2013 for fiber length,fiber strength and Micronaire in response to the high temperature stress were 0 to 18.3 DPA,10.9 to 26.1 DPA and 10.5 to 34.0 DPA,respectively.The "key time region" of 2014 for fiber length,fiber strength and Micronaire in response to the high temperature stress were 0 to 20.6 DPA,13.5 to 27.1 DPA and 11.2 to 33.2 DPA,respectively.Similar changes and trends could also be observed in the temperature-insensitive cultivar except that the variation degree was comparatively lower.So it could be concluded that the general fiber quality deteriorated by high temperature stress and the "key time region" of cotton fiber development in response to high temperature stress was around 10 to 20 DPA.2.Effect of high temperature stress which stared at different DPAs on the photosynthesis ability of subtending leavesAs treated in the 34.0? high-temperature regime for 5 days at different DPA in 2013 and 2014,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.When subjected the two different temperature-sensitivity cotton cultivar to the high temperature stress at the "key time region",the content of sucrose,soluble sugar,amino acid in subtending leaves of the temperature-sensitive cultivar all decreased,while the content of starch increased.Similar changes and trends could also be observed in the temperature-insensitive cultivar except that the variation degree was comparatively lower.So it could be concluded that the "source capacity" of leaves subtending to boll affected by the high temperature stress which stared at different DPAs,and the production,transport and distribution of photoassimilate in leaves subtending to boll affected by the high temperature stress at the "key time region".3.Effect of high temperature stress which stared at different DPAs on the substance content and enzyme activity related to fiber developmentWhen force two temperature-sensitive type cotton cultivar to the high temperature stress at the "key time region" in 2013 and 2014,the content of sucrose in fiber decreased firstly then increased as compared with those in control,the content of callose increased and cellulose decreased.While the activity of sucrose synthase,sucrose phosphate synthase and ?-1,3-gulcanase all decreased firstly then increased,and the activity of acidic invertase decreased as compared with those in control.Similar changes and trends could also be observed in the temperature-insensitive cultivar except that the variation degree was comparatively lower.So we speculate that the changes of substance content and enzyme activity related to fiber development would be effected by the high temperature stress at the"key time region",and then affect fibroblasts cellulose synthesis and accumulation,and ultimately affect the quality of fiber formation.