Effects Of Exogenous Spermidine(Spd) On Seed Germination And Physiological And Biochemical Characteristics Of Pepper Seedling Under Salt Stress

The effects of spermidine(Spd) on pepper seed germination and growth,oxidative damages,osmotic adjustments,chlorophyll fluorescence parameters,exchange of gases parameter in pepper seedlings under 100mmol/L NaCl stress were investigated,in order to clarify the possible mechanisms of enhancing salt-tolerance in plants.Pepper cultivar(Minxin zaojiao) was selected as a basic testing material.The main results were presented as follows:1.Under 100mmol/L NaCl stress condition,the effects of spermidine(Spd) at the concentration of 0.01-1.0mmol/L on seed germination and physiological characteristic of pepper seedling were investigated.The results showed that the effects of 0.05-0.1mmol/L Spd treatment on the alleviation of NaCl stress damage were the most obvious.At the two concentration levels,the seed germination force, germination index,activity index were significantly increased.Furthermore,the treatment of 0.1mmol/L Spd could also alleviate the rise of membrane permeability and increase the root activity in pepper seedlings under salt stress.2.The growths of pepper seedlings were limited under 100mmol/L NaCl stress. 0.1mmol/L Spd could increase height,fresh weight and dry weight of pepper seedling under salt stress.Meanwhile,relative water content in leaves and root activity of pepper seedlings were increased under salt stress.The above results indicated that exogenous spermidine(Spd) could significantly improve the growth of pepper seedlings.As a result,alleviate the growth inhibition of pepper seedling under salt stress.3.0.1mmol/LSpd could apparently alleviate the accumulation of malondialdehyde(MDA) and decrease membrane permeability in leaves of pepper seedling under salt stress.Meanwhile,the activity of protective enzymes(including SOD,POD and CAT) and contents of praline and soluble protein in leaves of pepper seedling were significantly increased under salt stress.It could be concluded that lower membrane permeability,MDA content and higher protective enzyme activieties,osmotic adjustment substances contents in salt-stressed leaves induced by Spd addition may protect the plant tissues from membrane oxidative damage under salt stress,thus mitigating salt toxicity and improving the osmotic adjustment of pepper plants. 4.NaCl stress could significantly decrease content of chlorophyll,Fv/Fm,Fv/Fo,ФPSâ…¡,Fv′/Fm′and qP in leaves of pepper seedling under salt stress.0.1mmol/LSpd could apparently increase content of chlorophyll,Fv/Fm,Fv/Fo,ФPSâ…¡,Fv′/Fm′and qP in leaves of pepper seedling under salt stress.And there was a relation between the increase of salt tolerance and photochemical efficiency in pepper seedling.5.NaCl stress could decrease the photosynthesize(Pn),the blowhole leading(Gs), transpiration rate(E) and rose in the intercellular CO₂ concentration(Ci) in leaves of pepper seedling under salt stress.0.1mmol/LSpd could apparently increase the photosynthesize(Pn),the blowhole leading(Gs),transpiration rate(E) and decrease the intercellular CO₂ concentration(Ci) in leaves of pepper seedling under salt stress.And there was a certain relation between the increase of salt tolerance and the photosynthetic capacity in pepper seedling.