| Cotton((Gossypium hirsutum L.))is an important economic crop in china,which is mainly concentrated on Xinjiang,the Yellow River basin and the Yangtze River Basin.The reproductive process includes the stages of bud development,flowering,pollination,fertilization and boll development.The pollen germination and pollen tube growth in the stigma were sensitive to high temperature.the optimum temperature of floral organ development is tycally 3 0℃,high temperature of June to August is harmful to pollen development、fertilization and boll development,and leading to abscission,boll and seed retarded,reducing yield and quality of cotton.Breeding and extension heat-tolerance varieties is a important ways to improve the yield of cotton.However,the research progress of this area is slow and relevant issues need to be resolved.Such as lack of high temperature resistant technology standard in the process of cotton reproduction,the risk of high temperature to cotton growing areas is not clear.This study selected different levels of heat-resistant material and measured variety pollen germination rate for 37 days continuously to explore the effects of environment temperature and cultivation temperature on germination rate of pollen.established the technology standard of select heat-tolerance cotton varieties,screened the region which is suitable for extension different kinds of varieties.High temperature will limit plant photosynthesis and affect plant growth and development.Compared with other stress photosynthetic system,stress reaction is more sensitive to high temperature.high temperature may destroy light system first and drop the PSⅡ system significantly.The chlorophyll fluorescence parameters can reflect the structure and state changes of the photosynthetic apparatus.Most of research focus on the change of chlorophyll fluorescence parameters when plant were treated with different plant stress.It is still rare to use chlorophyll fluorescence parameters to breed high efficiency and heat-tolerance varieties.In this study,we measured chlorophyll fluorescence parameters to in provide reference for selection of excellent varieties for breeders.in different species and temperature.The mian results were as follows:1.The pollen germination rate were determined at 26℃,28℃,30℃,32℃,34℃ and 36℃,analysised the difference of pollen germination rate when.pollen were cultivate in different temperature,how environmental temperature affect on bud pollen development.how relationship of pollen germination rate、boll setting rate and boll weight.The results showed that 30℃ was the most suitable temperature for pollen germination,the pollen germination rate was the highest.The germination rate was decreased significantly during the 10 day of budding period,heat-resistant varieties decreased 44%,heat-sensitive species decreased 54%.2.we determined pollen germination rate at 30℃ with different kinds of materials,and found that the pollen germination rate will decrease under 3 consecutive days beyond 35℃high temperature which was last 2 hours.the short time(1 day)above 35℃ high temperature will not significantly affect pollen activity.3.Base on the model of high temperature affect pollen germination rate and the occur of high temperature degree which above 35℃,Cotton production areas can be divided into 5 different high risk areas.The first level,high temperature risk-free zone:Mongolia Saier ute pull flag,Booker Etuokeqi,Yanchi The second level,mild high temperature risk area:Aletai,Yumen and Xi’an.The third level,moderated high temperature risk areas:Urumqi,Taiyuan and Chengde The fourth level,highly temperature-risk areas:Yining,Hanzhong,Fuyun,Qitai,Huimin County,Weifang and Yanzhou.The fifth level,high temperature risk areas:Ganyu,Kashgar,Kuqa,Karamay,Jinghe,Anyang,Tianjin,Zhengzhou,Zhumadian,Xinyang,Xuzhou,Bozhou,Bengbu and eastern Taiwan,Hami and Hotan,Yarkand,Ruoqiang,iron Doral,Bachu,Dunhuang,Shijiazhuang,Yuncheng,Jinan,Enshi,Yichang,Wuhan,Changde,Changsha,Hefei,Anqing,Nanjing and Nanchang.4.We use PEA measured chlorophyll fluorescence parameters at Liuhe and Huaian which was treated with different temperature.The results showed that the maximal rate chemical Fv/FM,performance index P.I.,electron transfer rate ETo/CS showed drop trend under high temperature stress.The level of heat dissipation DIo/CS increased.the Performance index of Zhengdan 958,Xundan 20,Suyu 31 was higher than other varieties,indicating that the photosynthetic apparatus of three varieties which resistant high temperature was higher than other varieties,and with a stronger regional adaptability.This study established a evaluation of technical standards on heat-resistant varieties,defined the high temperature risk degree of cotton producing regions.Clarified the areas which suitable for different kinds of species.It have important significance to evaluation heat-resistant varieties,determination the warning standard of high temperature and formulation high temperature hazard defense measures.Screening of a chlorophyll fluorescence parameters which able to identify heat-resistant maize varieties.Provided additional basis for breeders to select superior maize varieties. |
