Study On The Responses Of Endogenous Hormone And Polyamine Of Flue-Cured Tobacco To Water Stress And Nitrogen Forms And Their Regulation

Phytohormone and polyamine are belong to plant growth regulators. They can accelerate or restrain or change plant growth course at very low density When plants get menaced, phytohormone and polyamine commonly adjust the growth and form build of plant by changing their density. This paper studied the effect of osmotic stress on endogenous hormone and polyamine content in flue-cured tobacco under nitrogen forms by hydrocultivate examination using PEG(6000) as infiltrator,and discussed the effect of external polyamine on endogenous polyamine content and activities of their metabolize enzyme under drought press. The result as follows:(1).There was significant effect of osmotic stress on the changes of endogenoushormone and polyamine content .With the osmotic stress time prolonging and menace degree increasing,the content of abscisic acid (ABA) in flue-cured tobacco leaves increased,but the changes of heteroauxin (IAA), gibberellin (GA3) and iPA are falling at first, increasing after that and falling again to a certain stress.The content of ABA in flue-cured tobacco roots rapid accumulate under osmotic stress,but the content of IAA GA3 and iPA increased only under -0.25Mpa.The contents of polyamine in flue-cured tobacco leaves and roots increased at first and then failed under osmotic stress,and the range of their change was largen with osmotic potential falling.Osmotic stress can heighten the activities of ADC and PAO and decrease the activities of ODC in flue-cured tobacco leaves,even the increase of the activities of PAO is almost in-phase with the accumulation of polyamine content.(2).There are obvious difference in the contents of endogenous hormone and polyamine content under osmotic stress and different nitrogen forms.The content of PRO, ABA and GA3 in the leaves was higher and the content of IAA was lower when tobacco was fertilized with ammonium (NH4-N) than that of nitrate (NO3-N) without osmotic stress, and that the content of ribosylzeatin (ZR) was increased when tobacco was fertilized with ammonium + nitrate (NO3-N + NH4-N). It was observed that allthe nitrogen forms could significantly increase the content of PRO in the leaves under osmotic stress when the osmotic potential was at -0.3MPa. At the same time, the content of ABA tended to raise, and the content of IAA, GA3 and ZR obviously decreased respectively when tobacco fertilized with both NH4-N and NO3-N, while the content of all the endogenous hormones determined were increased in varying degrees when tobacco was fertilized with NO3-N + NH4-N. With the increasing of osmotic stress, it was found that NH4-N could significantly decline the content of PRO, and increase the content of GA3 and ZR, but had not significant effect on the changes of ABA and IAA, and NO3-N did not significantly affect the changes of endogenous hormones in tobacco leaves though the content of PRO could be increased continuously. It was also found that the content of PRO, ABA, GA3 and ZR could be decreased by NO3-N + NH4-N, but no significant change on IAA was observed. The content of nicotine in flue-cured tobacco leaves is the highest under fertilized with NH4-N,but the content of polyamine is the highest under fertilized with NO3-N + NH4-N.The content of nicotine and three polyamines are increasing with different degrees under osmotic stress and different nitrogen forms,thereinto the change scope under fertilized with NO3-N + NH4-N is bigger than that under fertilized with NH4-N,and the change scope under fertilized, with NO3-N is the least.On the side,the ratio of put/ (spd+spm) is smaller under fertilized with N03-N,we can presume that the tobacco under fertilized with NO3-N has obvious ability to resist osmotic stress.(3).There is significant effect of external polyamine on endogenous polyamine content and activities of their metabolize enzyme in tobacco leaves under drought press, external polyamines promote the synthesize of nicotine in tobacco leaves under no water stress,but decrease the content under water press, external polyamine can engance the a...