Preliminary Study On Enhancing Potassium Content In Tobacco By Using Ion-Channel Regulators

Tobacco is an important cash crop in China. However, the tobacco leaf with high quality can only produce high grade, good quality tobacco products. As a quality element, Potassium (K) content in tobacco leaf is one of the important quality indices for flue-cured tobacco.The focal point on Potassium nutrition of flue-cured tobacco was to increase leaf K content. Because of the present low K content in tobacco leaves in China, many scholars have done a lot of studies to improve potassium content, and achieved some results.To search a new way to enhance the potassium content in tobacco leaf, the aim of the present study was expected to realize it by adjusting potassium channel activity. The paper mainly studied on regulating effection of three ion channel regulators A:IAA, B:Ba(NO3)2 and C:Ca(NO3)2 on tobacco growth, potassium auptake and accumulation, and the expression of K-channel genes, using solution cultures and pot cultures experiments. Main results of the research were reviewed as follows:1.Effects of different regulators on the growth of tobacco plants. The investigation on tobacco growth, including girth, stem from, the largest leaf length, leaf width, leaf area, root volume, root fresh weight and dry weight of organs showed that three kinds of regulators made no much difference on plant growth, although regulator A stimulated the growth to a certain promotion (increasing the maximum leaf area).2.Effects of different regulators on the potassium content and accumulation of tobacco leaves. After top exisionfor two weeks, K content of tobacco leaves decreased distinctly in all treatments.However, all of the regulator treatments showed a slow decline trend, resulting in an increase of K accumulation in tobacco leaves.And the K content and K accumulation were raised by the regulators in mature leaves. The similar results were gained in solution culture experiment. K content decreased observably in leaves after top excision, comparing with the intact plants (no excision) in which K content increased slowly during the culture period. While the regulators could inhibit the decrease of K content a certain extent. By monitoring the K content changes of solution in the solution culture, we found that K content decreased observably in the solution with intact plant, but the trend was more gentle in the culture solution of top excision plant. As to the regulator treatments, the situation K content was between the two contasts, this result indicated that the potassium accumulation was increased by regulators on the other hind.3.Effects of different regulators on the tobacco quality. All the regulator treatments improved several main quality evidently, including increasing sugar content, decreasing nicotine content, and harmonizing the ratio of nitrogen/nicotine, sugar/nicotine and so on. The result on correlation coefficient ananysis between chemical components and potassium content in leaves showed that tobacco leaf main quality was correlated closely to K content in tobacco leaves.This result supported our conclusion that the K conten was enhanced by regulators.4. Effects of different regulators on the expression of potassium channel genes.The effects of the regulators treatments on the relative transcript levels of potassium channel genes in leaves and roots after the shoot apex excision was determined by real-time PCR with a inward-rectifying K-channel gene NKT1 and a outward-rectifying K-channel gene NTORK1.Relative expression levels of the NKT1 and NTORK1 was higher in tobacco leaves and roots after IAA treatment. The expression change of NKT1 was greater than NTORK1,and the increase of inward-rectifying K-channel expression will results in an increase in the K conten of leaves.The expression of the NKT1 and NTORK1 was inhibited by Ba2+, though the effect of NTORK1 was more obvious, especially in roots.As outward-rectifying K-channel gene was inhibited, the potassium loss will decline, and it will lead to the potassium content increase in leaves.As to Ca2+, it did not make too much difference in the two genes.Only 5 h after treatment, the expression of NKT1 in leaves was higher, while NTORK1 declined in leaves and roots obviously. And this result will also help to enhance potassium content in leaves.