Study On Polyamine Metabolism And Its Physiological Role Under Osmotic Stress In Rice

Rice cultivars of Han 116,Jiaozao935 and Xiangzaoxian32 were used as experimental materials, treated rice cultivars with different concentration PEG-6000 and natural drought,followed by treatment of polyamine,polyamine synthesis inhibitor to the solution.Then studied on growth,polyamine metabolism,active oxygen and change of some related enzymes activity and signal transduction of rice under osmotic stress.Physiological regulation role of polyamine in its adaptation to osmotic stress was explored.Main reseach results were as follows:1. Accumulation of dry weight in roots,R/S and contents of Put,Spd and Spm of rice seedlings were significantly increased under osmotic stress,and Han116 increased more markedly than Xiangzaoxian32,positive correlation between Put,Spd and Spm contents and R/S ,which showed that Put,Spd and Spm were involved in adaptation metabolism.Exogenous Spm treatment could significantly promote Put,Spd and Spm contents and alleviate harm of osmotic stress,but MGBG and D-Arg treatment significantly inhibited Put,Spd and Spm contents and aggravated it.Exogenous Put could reverse inhibitory effect of D-Arg.Change of Put,Spd and Spm contents of seedlings would be regarded as an indicator of identifying drought -resistance at seedling stage under osmotic stress2.Osmotic stress led to notable increase of Put,Spd and Spm contents in coleoptiles and young roots of rice,and Han116 and Jiaozao935 increased more markedly than Xiangzaoxian32. Exogenous MGBG and D-Arg inhibited Put,Spd and Spm contents and aggravated harm on coleoptiles and young roots under osmotic stress,while exogenous Spd treatment remarkably enhanced Put,Spd and Spm contents in coleoptiles and mitigated harm degree of osmotic stress. Though exogenous Spd treatment could increase Put,Spd and Spm levels in young roots , aggravate harm degree of osmotic stress on young roots. Change of PAs contents in coleoptiles could be considered as a physiological indicator of identifying drought - resistance at bud stage under osmotic stress .3. Osmotic stress mainly effected tillering number at tillering stage and then effected yield . Significantly positive correlation between Put,Spd and Spm contents and change rate of tillering numbers and yield maintenance ratio under exogenous Spm and MGBG treatment demonstrated that increase of Put,Spd and Spm levels helped improve drought - resistance of rice at tillering stage,which agreed with experimental results at seedling stage.It manifested that change of Put,Spd and Spm levels could be believed as an indicator of identifying drought - resistance at tillering stage under osmotic stress. 4.PAO activity changed with the change of Put,Spd and Spm levels under osmotic stress.It found there was some correlation between PAO activity and Put,Spd and Spm contents. Cell wall-localized PAO activity was notably higher than free PAO,which was 9.8-15.65 times higher than that of free PAO.There was also certain correlation between binding PAO activity and free PAO activity (R=0.952) ,which illuminated that PAO of rice largely located cell wall.5.There was nearly the same tendency between the change of SAMDC,ADC activity and Put,Spd and Spm contents under osmotic stress, exogenous Put and MGBG treatment while ODC activity essentially remained unchanged. It declared that synthesis of Put mainly went through decarboxylation of ADC6.Osmotic stress induced to raise contents of Put,Spd and Spm , encouraged to enhance activity of SOD,POD and increase content of Vc in order to decrease levels of MDA and H₂O₂-Then reduced harm of active oxygen on rcie seedlings.7.The osmotic stress-induce accumulation of Put,Spd and Spm in roots of rice seedlings was regulated by ABA,H₂O₂ and Ca²⁺,while Put,Spd and Spm might regulate the activity of plasma membrance-bound NADPH oxidase.The results implied that there might be a signaling pathway which include osmotic stress→ABA→PAs→PM NADPH oxidase→H₂O₂→Ca²⁺,and there might be cross-talk between PAs and NADPH oxidase-induces ROS and Ca²⁺,and there might be alsocross-talk between ROS and Ca(2+).