Characters Of Dry Matter And Potassium Accumulation Of Flue-cured Tobacco After Decapitation And Its Regulatory Measurement In Yunnan

Field experiments were conducted in red soil from 2000 to 2002 in Yuxi, Yunnan to understand the mechanism of dry matter production and potassium accumulation and distribution in flue-cured tobacco after decapitation, in order to increase the potassium concentration and improving the quality of flue-cured tobacco leaves. The main results are as follows:The accumulation of dry matter and potassium of flue-cured tobacco plants was increased after decapitation until the leaves had its ripeness fit for harvest compared to those at decapitation. During harvest of leaves, the dry matter accumulation of tobacco plants showed the decreasing tendency for variety K.326 in 2000 and 2002 due to the respiration consumption and translocation of carbohydrates from leaves to other organs, while tobacco of variety Yun 85 may need a relatively longer period of time to show the same tendency. Sustaintial net K+ export occurred from lower and middle and upper leaves, resulting in decreasing the potassium accumulation of whole plant. The K+ concentration in upper, middle and lower leaves decreased not only for the reason of dilution of dry matter increment, but also mainly for the net loss of K+ in tobacco, in addition to the lower partitioning of K+ into the leaves.The dominant phloem sink could be kept for tobacco plants without decapitation or with replacement by 1-naphthylacetic acid (NAA) on the cut surface of the stem stump, altering the translocation and partitioning of dry matter and potassium in plants. In these plants K+ uptake were increased and more increment of dry matter and potassium were allocated into shoot, meanwhile the lateral buds' growth were more effectively controlled than control plants, which resulted in increasing the K+ concentration in upper and middle leaves.The lateral roots' growth was stimulated by cutting root at one direction and top-dressing of potassium fertilizer after decapitation, which increased the K+ uptake and stimulated the partitioning of K+ into the upper and middle leaves, making the K+ concentration of leaves increasing correspondingly.The potassium content and quality of flue-cured leaves had been improved as the remaining of bottom leaves enhanced the translocation and supply of carbohydrates to roots, and uptake of potassium from soil, in addition to the translocation of potassium from bottom leaves to others. It is recommended that bottom leaves could be remained up to its senescence in condition that tobacco is planted in a less dense.The K+ uptake by tobacco plants and the K+ concentration in leaves, as well as efficiency in potassium utilization, could be increased by improving supply intensity of nutrients in root zones through mixing the fertilizer with the soil of root zones (25cm×25cm×20cm ) under the same dose of potassium fertilization.Film covering simulated the accumulation of dry matter and potassium in tobacco. Removal of film after decapitation caused marked changes in accumulation of dry matter and potassium. Tobacco keeping film-covering had more net increment of dry matter and potassium than those removing film in the early stage after decapitation. But due to increasing of root fitness to environment and improvementof soil aeration, tobacco with film removed had more advantage of growth than those keeping film.In the demonstration trial, flue-cured tobacco leaves with superior quality and high K+ concentration had been obtained when NAA was applied on the cut surface of the stem stump or cutting roots at one direction while with potassium fertilizer top-dressed after decapitation respectively.