Effects Of Ethephon On Openness Condition And Curing Characteristics Of Flue-cured Tobacco Upper Leaves During Curing

In view of the problem of insufficient openness and low availability of the upper tobacco leaves in which place,this study used a randomized block design for ethephon application testing to determine field agronomic traits and indoor curing characteristics.From February to August,field trials were conducted in Shi xing County,Shao guan City,Guang dong Province to investigate the effect of different concentrations of ethephon on the opening degree and curing characteristics of the upper leaves and ethephon pairs with different petiole soaking concentrations.The influence of curing characteristics of flue-cured tobacco was proposed,so that to meet the requirements of the application concentration of ethephon to provide technical basis for the application of ethephon in upper leaves.The main findings are as follows:(1)When ethephon treatment concentration is 120~170 mg/kg(T1~T2),the opening degree of the upper leaves of tobacco have no obvious effect,the concentration is 230~290mg/kg(T3~T4),the tobacco leaves have good opening,and the concentration is more than350 mg/kg(T5),the effect is not obvious,the tobacco leaves become soft and fast yellow.(2)When spraying ethephon on the leaves,the water content of the tobacco leaves decreases faster during the baking,the water loss rate is directly proportional to the ethephon treatment concentration,and the dry matter content is lower than the water treatment;the ethephon treatment concentration is at 170~230 mg/kg(T2~T3),the pigment content of tobacco leaf is good,,the degradation is fast;when the concentration of ethephon is 230 mg/kg(T3),the brightness values L,the redness value a,the yellowness value b and saturation C increases rapidly,the hue angle H°decreases rapidly,the tobacco leaves turn yellow quickly,and the yellowing time is shortened at least for more than 12 hours.The tobacco leaves are easy to bake and have a good yellowing property,the color changes better during the baking of the tobacco leaves;the activity of Polyphenol(PPO)oxidase and the content of Malondialdehyde(MDA)in tobacco leaf are directly proportional to the concentration of ethephon,the PPO Oxygenase activity and MDA content are low,cell membrane damage is small,the tobacco leaf have good resistance to baking when the concentration is at 120~170 mg/kg(T1~T2).When the foliar spraying ethephon concentration is 230 mg/kg(T3),the amylase activity of tobacco leaves is the highest,and starch fully degraded.Ethephon treatment at a concentration of 170 mg/kg(T2),tobacco leaf reduction sugar,total sugar content,and nicotine content are the most suitable;therefore,when the concentration of ethephon applied on the leaves is 170~230 mg/kg,the tobacco has good baking properties.(3)When the petioles is soaked in ethephon and the treatment concentration is 600mg/kg(E3),the loss of water is slower,the rate of water loss is stable,the accumulation of dry matter is faster and the content is larger.The physical properties'variation is small,such as shrinkage,curl,etc.The color difference between the front and back of tobacco leaves is stable,the degradation of chlorophyll a is fast,the chlorophyll b degradation of each treatment is increased by an average of 9.68%compared with the untreated,when the ethephon soaking concentration is 800 mg/kg(E4),the degradation rate of carotenoid content in tobacco leaves is fastest,0.31%?h~-11 faster than CK,followed by 600 mg/kg(E3).Therefore,the soaking concentration of ethephon is controlled within the range of 600~800mg/kg,the tobacco leaves is easier to bake and yellowing properties is good,which will help to improve the appearance quality of the tobacco leaves.When the ethephon concentration is 400m/kg,the content of petroleum ether extract is most suitable.When the concentration of ethephon is 400~600 mg/kg,the activity of PPO oxidase is high,the content of MDA is low,the resistance to baking of tobacco leaves is good,and the coordination of chemical composition is good.When the petiole soaking ethephon concentration is controlled at 400~600 mg/kg,the tobacco has good baking properties.(4)There is significant difference in the curing characteristics of leaves with foliar spraying of ethephon and petioles,petiole soaking treatment method is more easy to promote the application of tobacco leaf baking production.