| Annual seedlings of Phoebe bournei were used as experimental materials in this paper.The effects of drought stress on Phoebe bournei and the mitigation effects of exogenous polyamines on Phoebe bournei under drought stress were studied.The effects of drought on Photosynthetic Physiology and nutrient uptake of Phoebe bournei were studied by using weighing method to control soil water content.The effects of polyamines on the drought resistance of Phoebe bournei were studied by spraying different concentrations of spermine and spermidine on the leaves.The results showed that:(1)Phoebe seedlings can normally under drought stress and mild drought stress,so as to reduce the damage to Phoebe bournei due to high temperature at noon.Under severe stress,Pn and Cond remained at a relatively low level due to excessive water deficit in the seedlings of Phoebe bournei.At the early stage of the trial.Ls of Phoebe bournei seedlings was higher than that of moderate drought and severe drought when there was no drought and mild drought.Tr did not change significantly among the grougs.and Tr was higher when temperature was higher in the early stage of drought.Tr of Phoebe bournei seedlings decreased with the aggravation of drought,in the late stage of drought.(2)The FO of Phoebe bournei seedlings was positively correlated with the degree of drought.On the 32nd day,the FO of the severe drought group was 50.88%higher than that of the control group.Fm,Fv/Fm and ETR decreased with the intensification of drought stress.The decreases were smaller under mild stress and moderate stress and the greatest under severe stress.The change range of Y(?)of Phoebe bournei under mild stress was small,while the reduction under moderate and severe stress was more;The qP of Phoebe bournei decreased significantly with drought aggravation and time extension.Under mild stress,Y(NPQ)of Phoebe bournei increased first and then decreased as time went on.Under moderate and severe drought,Y(NPQ)of Phoebe bournei showed a downward trend(3)The content of N and P in Phoebe bournei decreased with the aggravation of drought and extension of time,while the content of K increased slightly in mild drought and decreased significantly in severe drought.In the early stage of mild and moderate drought,Ca content in Phoebe bournei increased,decreased slightly in the late stage of drought,and presented a downward trend in the severe drought.During mild and moderate drought,Mg content increased significantly compared with that without drought,and decreased slightly during severe drought.(4)A11 indexes of Phoebe bournei seedlings were significantly affected by exogenous polyamine treatment.Different types and concentrations of polyamine had different effects on drought relief of Phoebe bournei seedlings in different periods.At the 24th day of drought,the effect of 0.lmmol/L Spd on maintaining Pn of Phoebe bournei seedlings was the best,and the difference was not significant at the 32nd day.Polyamines had slight relief effect on Phoebe bournei Cond,but the effect was not obvious.In the early stage of drought,the Tr of Phoebe bournei group without polyamine was higher than that of other groups,and the Tr of Phoebe bournei group without polyamine was lower than that of most groups with polyamine.Spm with 0.01mmol/L can reduce the damage of Phoebe bournei stomata in long-term drought.(5)Different concentrations in alleviating drought of Spd and Spm had different influence on chlorophyll fluorescence effect,the tendency for 0.lmmol/L of Spd in promoting Fm,Fv/Fm)and Y(NPQ)effect was the largest during drought,The effect of 0.01 mmol/L SPD on Y(?)and ETR of Phoebe bournei under drought was better;Spm of 0.01mmol/L and Spd of lmmol/L had the best alleviating effect on qP and F0,respectively.(6)Polyamine can effectively increase the content of soluble sugar and chlorophyll under drought,so that Phoebe bournei can increase osmotic pressure during drought to reduce the rate of water loss and increase the intensity of photosynthesis;The activities of POD,SOD and CAT were improved to reduce the degree of membrane lipid peroxidation and the content of MDA.In addition,the soluble protein and Pro content can be reduced to maintain the normal protein metabolism in Phoebe bournei plant,so as to improve various physiological and biochemical reactions.(7)According to the value of the drought resistance membership function under different treatments,it can be found that,on the whole,the drought resistance of Phoebe bournei was significantly improved by various concentrations of polyamines,among which the effect of 0.1mmol/L Spd on the drought resistance of Phoebe bournei was the most obvious,while the effect of lmmol/L Spd was the least. |
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