Study On Cause Of Formation, Mechanism And Prevention To Grey Disorder Leaves Of The Flue-cured Tobacco

Growth of tobacco is subject to a variety of biological and non-biological effects of stress on the quality of tobacco production and availability of a dramatic impact. There have been appeared a great deal of flue-cured tobacco of grey disorder leaves of in Yunnan Baoshan in the late 1990s.Gray severe flue-cured tobacco was cured in the early dust-color,which is of less value.Those leaves even were grey-black,and of less usability.However,Because without knowing the reason and lack of effectively prevention measure.The pathogenesis areas and incidence rate increase year by year. Some tobacco-growing areas even have no harvest.In order to search for prevention measure of grey disorder leaves,the cause and mechanism of those have been studied. The results are as follows.1,Base on field experiment and potted plant test,physiologic and biochemical indexes of grey tobacco leaves and the soils occurring grey disorder were measured, the cause and mechanism of occurrence of grey disorder leaves were discussed.The results showed that the occurrence of grey disorder leaves correlate with the low soil pH,high water content of root layer soil,its occurrence and severity degree positive correlate with the Fe2+ and Mn2+ content of soil and tobacco leaf。2,In that condition,charged ions of tobacco leaves from higher oxidation state to lower oxidation state,which leading to uptake accumulation excessly and distribution of Fe²⁺ and Mn²⁺ in flue-cured tobacco.These caused nutrition equilibrium maladjustment,finally,flue-cured tobacco leaves were intoxication.3,Plot trials were carried to explore the effects of some agricultural practices on the prevention of grey flue-cured tobacco.The results showed that the occurrence of grey flue-cured tobacco was mainly due to the excessive uptake of Fe2+ and Mn2+ by tobacco plant.However,the agricultural practices,such as plowing high ridge in the field to improve soil drainage ability,applying lime to increase soil pH,no plastic film covering or uncovering film in season,or increasing P and decreasing K fertilizer,had obvious effect to decrease the uptake of Fe²⁺ and Mn²⁺ by tobacco plant and controlled the occurrence of grey flue-cured tobacco.