The Monitoring Of "Heat-forced Maturity" Index In Xiangnan And The Response Of Heat And Irradiance Stress On Photosynthetic Physiology In Tobacco

Based on the field monitoring test of the main ecological index,agronomic index and physiological index of Hunan tobacco“heat-forced maturity”,we initially constructs the index of field ecological factors of occurrence of tobacco“heat-forced maturity”.By using the artificial climate chamber,through precise control of temperature,light and wet,we studied the effects of different light and temperature stress on Photosynthetic Physiology of upper leaves of flue-cured tobacco.Test results show that:(1)Hunan tobacco heat forced maturity phenomenon is caused by the comprehensive climate factors.The early excessive rainfall is the leading factor of heat forced maturity phenomenon;maturity high temperature is the second main factors to cause the heat forced maturity phenomenon;Light intensity at mature stage is a promotive factor for the occurrence of“heat-forced maturity”.The light intensity can lead to excessive heat forced maturity phenomenon aggravating.(2)The main ecological indexes of avoiding the occurrence of“heat-forced maturity”phenomenon in the south of Hunan Province are as follows: The rainfall during root-extended period should be less than 100~130 mm/months compared with the perennial;Days of Midday temperature more than 35? during mature period is 0~10 d;Days of Midday light intensity more than 100000 lux during mature period is 0 d.The main ecological indexes of mild“heat-forced maturity”phenomenon in the south of Hunan Province are as follows: The rainfall during root-extended period should be more than 150~180 mm/months compared with the perennial;Days of Midday temperature more than 35? during mature period is 5~15 d;Days of Midday light intensity more than 100000 lux during mature period are 0~2 d.The main ecological indexes of severe of“heat-forced maturity”phenomenon in the south of Hunan Province are as follows: The rainfall during root-extended period should be more than 200 mm/months compared with the perennial;Days of Midday temperature more than 35? during mature period are 10~20 d;Days of Midday light intensity more than 100000 lux during mature period are more than 0 d.(3)Tobacco leaf of“heat-forced maturity”average thickness are 12% thinner than the normal tobacco leaf and the average weight of tobacco leaf of“heat-forced maturity”generally light 11.8% than the normal,Maturity is generally 5-7 D ahead of schedule.The average leaf thickness of“heat-forced maturity”after baking was 15% than normal,and the average weight of single leaf was 6.4% lighter than that of normal.(4)Compared with normal tobacco,the contents of chlorophyll,chlorophyll a,chlorophyll b and carotenoid were significantly decreased in the case of high temperature ripening.The intensity of photosynthesis,respiration and root activity decreased significantly,the content of total sugar,conventional chemical composition in reducing sugar content decreased significantly,between different varieties to CZ-43 "high temperature forced ripening" smoke down the most,the total sugar and reducing sugar were decreased by 46% and 47%.(5)At the same temperature,the transpiration rate,stomatal conductance and photosynthetic intensity of the upper leaves of flue-cured tobacco increased first and then decreased with the increase of light intensity,and reached the peak at about 80000 lux.With the same light intensity treatment,the high temperature treatment will lead to the decrease in transpiration rate,stomatal conductance and photosynthetic intensity of the upper leaves of flue-cured tobacco.High temperature(38 ?)is the main factor limiting the gas exchange parameters of photosynthesis in upper leaves of flue-cured tobacco.(6)Light intensity is the main limiting factor of F0 value change in the upper leaves of flue-cured tobacco.The change of Fm value is influenced by high temperature stress.The effect of high temperature and strong light on the upper leaf of flue-cured tobacco was higher than that of high temperature or strong light.Strong light(120000 lux)is the main factor to limit the photosynthetic fluorescence parameters of the upper leaves of flue-cured tobacco.(7)Both high temperature and strong light could enhance the expression of VDE gene and ZE gene in the upper leaves of flue-cured tobacco during mature period.The expression level of ZE gene had a positive correlation with the expression of VDE gene.