Effects Of Organic Acids Secreted By Tobacco Roots On Soil Potassium In The Rhizosphere

K is one of the major elements of plant.The content of K in China have a large amount of K,but the uptake of K is limited.,plant roots secrete a large amount of organic acid to release the stress of bad effects under the lack of K.The organic acid in root can be used to activate the mineral K in soil and the slow-release potassium into the plant change that which can directly absorb and utilize the available potassium.To improve the content of available potassium in soil and in order to make the tobacco plant could absorb more potassium,so as to enhance the potassium content in tobacco leaves.Under the normal conditions,the secretion of organic acid was different in Y6 and NC89,and secretion of organic acid was greater without fertilizer.Without the application of potassium fertilizer,there was a decreasing tendency of the slow-release potassium in the soil,and the available potassium maintained at the normal level.Under the condition of without potassium fertilizer,the root activity of Y6 and NC89 decreased,and respectively decreased 0.191 mg/(g· h),0.714 mg/(g· h).The results showed that the content of organic acid about different varieties in the soil was different because of the different of available potassium.The secretion of organic acid was a kind of anti reverse method for tobacco plant under the condition of potassium deficiency.The amount of organic acid in different varieties was different.The secretion of more and less of organic acids(K326,LN3 and NC89)varieties were screened from 12 tobacco varietie.Under normal conditions,different varieties of root length had great differences,the potassium that under normal conditions had longer of root length when compared with the lake of potassium,the K326 and LN3 in normal conditions long around 50% compared with the lake of potassium conditions,it means that K is important to the growth of root.That will be benefit to the further genetic research.The potassium content,available potassium content and physiological characteristics of tobacco about different tobacco varieties were analyzed by using malic acid and citric acid.The results of the determination of available potassium in tobacco soil by the application of malic acid and citric acid showed that the organic acid significantly increased the content of available potassium in the soil.The potassium content in tobacco leaves were significantly increased.It proved that the secreting of organic acid by roots is one of the main reasons for the difference of K content in soil.The contents of citric acid and malic acid in root about different tobacco varieties were different under the condition of normal potassium.The root length of the same species in lacking of potassium were significantly lower than the normal ones,and the root length of LN3,NC89 and K326 in condition of normal potassium were respectively increased by 56.24%,29.30% and59.74% with the lacking of potassium.Root stress enzyme activity is higher than that of normal conditions,POD activities of Luoning 3,K326 and NC89 in the lacking increased by 44.73%,13.32% and 45.72% than the normal,that indicated that lacking potassium treatment improved the tobacco plant in antioxidant defense mechanism.Under the condition of lacking potassium,the relative expression of MATE and ALMT gene in tobacco varieties were significantly increasing.In the potassium stress condition,the MATE of K326 increased by 0.82 than normal K,while LN3 was about 4.5 higher.The ALMT of K326 increased by 1.32 than normal K,while the NC89 is higher than 0.63.The citric acid channel and malic acid channel opened in the stress of potassium,citric acid and malic acid drained away,in order to resist stress,there was a positive correlation between MATE and ALMT genes in tobacco varieties and the contents of citric acid and malic acid in root.