Effect Of Topping On The Content Of Six Mineral Elements In The Upper Leaves Of Flue-cured Tobacco

Potassium is a crucial nutrient for the growth and development of tobacco leaves.It plays a significant role in promoting photosynthesis,respiratory efficiency,and energy metabolism of the leaves.Additionally,it also helps in maintaining the water balance and physiological metabolism of the leaves,resulting in improved quality and yield of tobacco leaves.In order to promote the opening of upper tobacco leaves,topping is necessary after harvesting the lower and middle leaves in tobacco cultivation.However,this practice can cause a rapid decrease in potassium ion content,ultimately leading to a decrease in tobacco quality.To address this issue,it is crucial to study the destination of potassium ions after topping and the factors that influence it.By doing so,we can improve the potassium ion content of the upper tobacco leaves.Interactions between potassium ion uptake and transport and other mineral elements occur during tobacco growth under normal conditions.In this study,nine varieties of roasted tobacco(High Agar K326,Concentrated Falling Yellow K326,K326,China Tobacco 300,China Tobacco Special Aroma 301,Special Aroma 18,Zhongchuan 208,Yunnan Tobacco301,NC55)were utilized as research materials,which were provided by the Institute of Tobacco Research,Chinese Academy of Agricultural Sciences.The research focused on determining the potassium ions present in the upper tobacco leaves before and after topping,as well as the rapid potassium ions in the soil layers at different depths(0-10 cm,10-20 cm).In addition to measuring potassium ions,the study also analyzed the levels of calcium,magnesium,sodium,copper,and chloride ions in tobacco leaves.The study aimed to investigate the correlation between potassium ions and other mineral elements.To investigate the temporal pattern of potassium ions and other mineral elements after topping,we conducted further testing using NC55,a prominent tobacco variety in Shandong.Samples were collected on the day of topping(day 0)and subsequently every two days(days 2,4,6,8,and 10)to observe the changes in ion content over time.The results of the testing are presented below:(1)After topping off the roasted tobacco,there was a significant reduction in potassium ions in the upper leaves of all varieties.The highest reduction rate of 5.17% was observed in high agar K326,while the smallest reduction rate of only 1.47% was observed in CCS 300.The study found that after topping,the potassium ion content of the soil at depths of 0-10 cm and 10-20 cm increased by 17.69% and 19.40%,respectively.This suggests that the potassium ions from the upper leaves moved back towards the root system,leading to an ion exchange between the root system and the soil.Ultimately,this resulted in an increase in the soil’s potassium ion content.(2)After topping,there was a decrease in copper ion content as well as potassium ion content.On the other hand,the calcium,magnesium,sodium,and chloride ion contents increased.The highest reduction rate of copper ions in the upper leaves after topping was50.65% for Special Aroma 18,while the lowest was 7.67% for China Tobacco Special Aroma301.After topping,the upper leaves of Cigarette Special 301 showed the highest increase rate of calcium ion content at 31.97%,whereas NC55 had the lowest increase rate at 0.97%.In terms of magnesium ion content improvement rate,K326 had the highest rate at 7.65% while K326 had the lowest rate at 0.99%.Among the varieties tested,Concentrated Yellow K326 showed the highest increase rate of sodium ions at 15.65%,while China Tobacco Special 301 had the lowest increase rate at 3.32%.On the other hand,Concentrated Falling Yellow K326 exhibited the highest improvement rate in chloride ion content at 40.03%,while Zhongchuan208 had the lowest improvement rate at 6.64%.Although there were variations in the changes of mineral elements among different roasted tobacco varieties,the overall trend remained consistent.(3)In our study of NC55 material,we analyzed the dynamic trend of mineral elements in the upper leaves after topping.Our findings indicate that all mineral elements exhibited significant changes within 48 hours of topping,followed by a leveling off period.The concentration of potassium ions in the upper leaves decreased by 12.11% within 48 hours after topping,and then gradually leveled off;the concentration of calcium,magnesium,sodium,and chloride ions experienced a rapid increase within 48 hours after topping,followed by a gradual leveling off.Specifically,the concentration increased by 7.21%,4.02%,21.32%,and 34.60%,respectively.Similarly,the concentration of copper ions also increased sharply within 48 hours after topping and then stabilized over time.The concentration of copper ions decreased rapidly within 48 hours after topping,and then gradually stabilized,resulting in a decrease of 69.04%.This indicates that the optimal time frame to prevent the reflux of potassium from the upper leaves is within 48 hours after topping.Implementing appropriate measures during this period can effectively inhibit the reflux of potassium ions from the upper leaves.(4)The study found that there was a negative correlation between potassium ions and calcium ions,magnesium ions,sodium ions,and chloride ions.This means that as the levels of potassium ions increased,the levels of these other mineral elements decreased.On the other hand,copper ions were found to have a positive correlation with potassium ions,meaning that as the levels of potassium ions increased,so did the levels of copper ions.After topping,calcium ions were absorbed and accumulated,resulting in a significant reflux and outflow of potassium ions.Magnesium ions had a relatively minor impact on the reflux and efflux of potassium ions.The levels of sodium and chloride ions increased simultaneously.The correlation between copper and calcium ions was the strongest among all ions,and they showed a negative correlation.After the topping process,there was a significant decrease in the copper ion content,which directly affected the calcium ion content and indirectly impacted the return of potassium ions.The conclusion of this experiment proved that the change of potassium ion content in the upper tobacco leaves after topping occurred within 48 hours and was mainly influenced by copper and calcium ions,and the upper tobacco leaves mainly returned to the 10-20 cm soil layer.