Studies On The Mechanism Of Growth And Potassium Uptake Of Tobacco Root System Under Low Potassium Stress By Auxin

It is of great significance for agricultural production to improve the plant’s potassium absorption efficiency.Auxin is mainly synthesized at the top of the plant.Numerous studies have found that auxin is a major factor in signaling under low potassium stress,and It is also an important substance that affects the absorption and transport of potassium for plants roots.There are many experiments have confirmed that exogenous auxin is involved in the regulation of plant potassium absorption under the apical regulation.In this experiment,tobacco was used as the experimental material by the method of hydroponics.The main research of this experiment are:(1)the influence of exogenous auxin and inhibitor on the growth of plant root system under different potassium supply levels;(2)Effects of exogenous auxin and inhibitors on auxin distribution characteristics in plants at different potassium levels;(3)Effects of exogenous auxin and inhibitor on potassium accumulation,distribution and potassium absorption kinetic parameters in plant;(4)Non-invasive micro-testing(NMT)was used to analyze the characteristics of potassium currents of plant roots under the condition of low potassium(5)The effects of auxin on the key regulatory genes of potassium uptake and transport in plants were analyzed at transcriptional level.1.After the addition of exogenous auxin,the root morphology of the regular potassium and low potassium plants improved significantly with the increase of auxin concentration;After the addition of auxin transport inhibitors,with the increase of auxin inhibitor concentration,the dry weight of underground and aboveground roots,the values of root scan indexes,and the number of lateral roots of grade 1 and 2 were significantly decreased.The effect was most pronounced when the concentration of auxin was 10 μmol/L.2.Low potassium stress can significantly increase the concentration of endogenous auxin in the main root tips,lateral root tips and leaves.When exogenous auxin is added,the concentration of endogenous auxin in the main and lateral root tips is significantly increased.When the auxin transport inhibitor was added,the concentration of endogenous auxin in the main root tip decreased and that in the lateral root tip increased,as the concentration of auxin inhibitor increased.3.Low potassium stress can significantly reduce potassium content in aboveground parts of tobacco plants and the potassium absorption kinetic parameters of in tobacco roots;After the addition of exogenous auxin,the potassium absorption kinetics of the roots of the normal potassium and low potassium plants increased with the increase of auxin concentration,but the potassium content of the low potassium plants increased more obviously;When the auxin transport inhibitor was added,the potassium concentration in tobacco plants decreased obviously,no matter at normal potassium level or low potassium level.4.From the results of NMT,we can concluded that low potassium plants are characterized by obvious phenomenon of k+ uptake,normal potassium concentration plants are often characterized by obvious phenomenon of potassium efflux,and when exogenous auxin was added,the absorption of k+by roots of low potassium tobacco plants was more obvious than that of no treatment,and the efflux of k+from roots of constant potassium tobacco plants decreased so as to promote the retention and absorption of k+.The results indicated that exogenous auxin could promote the uptake of potassium by root system.After adding auxin transport inhibitor,the rate of potassium uptake by roots of low potassium tobacco plant was lower than that of no addition treatment,and the phenomenon of root efflux of constant potassium tobacco plant was more obvious,which indicated that the addition of inhibitor was not conducive to the absorption and retention of potassium.5.Low potassium stress decreased the expression of 6 key regulatory genes for potassium uptake and transport in roots.After exogenous auxin was added,the expression levels of NKT1,NtKC1,NtTPK1 and NtHAK1,NtKT12,which regulated the influx of potassium ions in roots and leaves,were significantly increased.The expression level of the gene NTORK1 controlling the potassium ion outflow was lower than that of the control group.After adding inhibitor,the expression of NKT1 gene in root decreased,the expression of NTORK1 increased,and the expression of gene NtHAK1 in leaves decreased.