Study On The Effects Of Temperature-light Factors At Seedling Stage On Premature Flowering Of Flue-cured Tobacco And Mechanism

Tobacco is a kind of industrial crop for leaves.Because of the different environmental conditions.It is easy to occur premature flowering when tobacco seedling encounter adverse weather during the critical period of growth and development. In the southern tobacco region of Hunan,spring tobacco occur different dgree of premature flowering every year. In the study we analyzed recent a decade the main meteorological conditions of temperature-light in the southern tobacco region of Hunan by Principal Component Analysis(PCA),then we performed a series of simulation and regulation experiments to test.The main results were as follows:1 The budding time could be advanced with the low-temperature and short-day at seeding stage.The premature flowering of NC82 is less than the temperature and day-length were 12℃and 8h/d at seedling stage.When the temperature and day-length were 8℃and 6h had the most obvious effect seriously.The NC82 was not sensitive to the low-temperature and short-day before the 20th day of treatments.(1) ZR content of NC82 during seedling in terminal-bud was very low,and different treatments of temperature and light had no significant effect on its.(2) IAA content of NC82 during seedling in terminal-bud appeared two peaks.It was speculated that the first peak may be related to state change of cell growth in terminal buds.The second peak was critical period of tobacco seedling growth.The low-temperature and short-day could lead to IAA content of tobacco seedling decreased.The lower temperature and shorter day,the effect was more obvious.IAA content of tobacco during seedling in terminal-bud was decreased by the low-temperature and short-day were 12℃and 8h. When 8℃and 6h/d had the most obvious effect. seriously.(3) GA3 content of NC82 during seeding in terminal-bud appeared continuous peak time at earlier time,and then decreased.Probably,it was a ealier signal that vegetative growth changed to the reproductive growth,and the low-temperature can lead to a early peak and GA3 content of tobacco seedling increased was induce,but the concrete critical value was not obvious.The short-day had no obvious effect to GA3 content of tobacco seedling.3 It showed that except for stem thickness there was no significant difference,most of the main agronomic characters of NC82 were downtrend with the decrease of temperature and day-length at seedling stage.There were significant differences less than the temperature and day-length were 12℃and 8h.When 8℃and 6h/d had the most obvious effect seriously.4.The different treatments of temperature and light had significant effects on some chemical and quality index,but no influence on the nicotine,protein,ratio of nitrogen to nicotine and ratio of sugar to protein. When the temperature were 12℃or 8℃,the total nitrogen somewhat increased and other chemical components declined.When the day-length were 8h/d or 6h/d,total nitrogen and ratio of nitrogen to nicotine increased and other chemical components declined.The results indicated that the low-temperature and short-day could lead to other chemical components declined except for the total nitrogen and ratio of nitrogen to nicotine.The total nitrogen increased with different treatments and the protein content was no significant difference.It was speculated that the increase of total nitrogen caused by other nitrogen compounds.5 It was suggested that the temperature,light,humidity and rainfall conditions during seedling to buding stage might be the influencing factors for premature flowering of southern tobacco region of Hunan.