Effect Of Foliar Spraying Plant Growth Regulator On Quality Of Upper Leaf Of Flue-cured Tobacco

Field trials were conducted in Pangu Township,Biyang County,Zhumadian City,Henan Province in 2018 to study the effects of foliar application of gibberellin,monopotassium phosphate and sucrose fatty acid ester on the physiological growth and physical properties,chemical quality and aroma content of the upper leaves of flue-cured tobacco influence,discuss the treatment measures to improve the quality and availability of the upper leaves of flue-cured tobacco.Totally 8 treatments are set:CK:spray water;CK1:spray gibberellin;CK2:spray monopotassium phosphate;CK3:spray sucrose fatty acid ester;T1:spray gibberellin+monopotassium phosphate;T2:spray gibberellin+sucrose fatty acid ester;T3:spray monopotassium phosphate+sucrose fatty acid ester;T4:spray gibberellin+monopotassium phosphate+sucrose fatty acid ester.The main research results are as follows:1.With the growth and development of flue-cured tobacco after topping,the upper leaf area of flue-cured tobacco under different treatments showed a gradual increase trend,and basically showed that the results of T4 treatment were basically greater than T1,T2,T3 treatment with pairings and CK1,CK2,CK3 treatment with spraying alone.The leaf area of the upper part of flue-cured tobacco was the highest under T4 treatment in each period.Compared with the condition of pairwise application,it was particularly significant(P<0.05)higher than that of CK2,CK3 and T1 treatments,with average increases of 25.43%,35.53and 12.40%respectively.From the above analysis,it can be seen that the exogenous spray treatment of gibberellin,monopotassium phosphate,and sucrose fatty acid ester can effectively increase the upper leaf area of flue-cured tobacco,especially when three treatments are mixed.2.Under T4 treatment,the SPAD value of flue-cured tobacco decreased 15 days and 30 days after topping compared with CK treatment,but the difference was not significant(P>0.05).Compared with the combined application of gibberellin,monopotassium phosphate and sucrose fatty acid ester,the SPAD value of flue-cured tobacco 45 days after topping was significantly lower than that of T1 and T2 treatments.With the extension of the growth period,the SPAD value of flue-cured tobacco under different treatments gradually decreased,showing aging characteristics.Under different spraying of different exogenous materials and compound treatment,the flue-cured tobacco under CK2 treatment,T3 treatment and T4 treatment matured and fell yellow at a later stage.3.Under T4 treatment,the net photosynthetic rate,stomatal conductance and transpiration rate of flue-cured tobacco leaves decreased significantly in the late topping period.Combined with the performance of SPAD value,it can also be seen that the combination of three exogenous substances in the late stage of ripening and yellowing is better.There is also a corresponding performance in photosynthesis rate.Compared with CK treatment and CK2 treatment,the intercellular CO2 concentration of flue-cured tobacco leaves decreased to different degrees 45 days after topping.While compared with the combined application of gibberellin,monopotassium phosphate and sucrose fatty acid ester,the increases were 16.30%,23.50%and 13.34%respectively,and the differences were significant.At this time,the upper leaves of flue-cured tobacco were nearly in mature status.4.With the extension of the growth period,under different treatments,the activity of amylase in flue-cured tobacco increased first and then decreased,while the nitrate reductase activity in flue-cured tobacco decreased gradually.Under T4 treatment,the activities of flue-cured tobacco amylase and nitrate reductase were higher at 15,30,and 45 days after topping.Compared with the contrast,spraying alone and applying gibberellin,monopotassium phosphate and sucrose fatty acid ester in combination,the activities of flue-cured tobacco amylase and nitrate reductase were basically higher than other treatments.5.Under T4 treatment,all physical properties of flue-cured tobacco leaves were significantly improved compared with CK treatment,among which single leaf weight,tensile strength,leaf specific weight and filling value were the highest among the treatments,and the stem ratio was relatively low.It shows that the combined application of gibberellin,monopotassium phosphate and sucrose fatty acid ester can effectively improve the physical characteristics of flue-cured tobacco leaves.6.Under T4 treatment,the content of reducing sugar,total sugar and potassium in flue-cured tobacco leaves was the highest among all treatments,while the content of total nitrogen,nicotine and chlorine was the lowest in each treatment,and there was also a significant difference compared to CK treatment and CK1,CK2 and CK3 treatment.It indicated that the combined spraying of gibberellin,monopotassium phosphate and sucrose fatty acid esters had the most significant beneficial improvement on the conventional chemical components of flue-cured tobacco leaves,which could effectively increase the content of reducing sugar,total sugar and potassium in flue-cured tobacco leaves,and effectively reduce the total nitrogen,Nicotine and chlorine content.Under T4 treatment,the flue-cured tobacco sugar ratio,sugar-alkali ratio,nitrogen-alkali ratio and potassium-chlorine ratio were improved to different degrees compared with other treatments to improve the coordination of tobacco leaf chemical composition.7.The total content by combined application of gibberellin and monopotassium phosphate and sucrose fatty acid esters in flue-cured tobacco neophytadiene and aroma>combined treatment of both>sprayed separately>control treatment.The combined application of gibberellin,monopotassium phosphate and sucrose fatty acid ester can obviously promote the accumulation of neutral aroma substances in flue-cured tobacco leaves,and it has the best effect compared with other treatments.