Thermal Stress Photosynthetic Response of Picea pungens
[Objective]The continuous global warming will be detrimental to the growth of Picea pungens.Studying the growth and photosynthetic response mechanism under high temperature stress would provide a reference for the introduction and cultivation of P.pungens.[Methods]Three temperatures were set at 45,50 and 55℃,and treated for 6 hours using P.pungens seedlings.Among them,three different durations of 12,18 and 24 hours were also set under 45℃treatment,and room temperature was used as a control.The growth phenotype,relative water content and chlorophyll fluorescence parameters of P.pun-gens seedlings after treatment,7 and 28 days of recovery were studied,and the effects of high temperat-ure and stress duration on the growth and photosynthesis of P.pungens were analyzed.[Result]The growth of P.pungens could basically be restored after 6 hours treatment at 45℃,while those treated at 50 and 55℃,their needles turned yellow,withers and falls,accompanied by the decrease of relative water content.The fluorescence parameters photochemical efficiency for photosystem Ⅰ(Y(Ⅰ)),relative electron transfer rate of photosystem Ⅰ(ETR(Ⅰ)),non-photochemical energy dissipation due to donor-side restriction(Y(ND)),non-photochemical energy dissipation due to receptor-side restriction(Y(NA)),photochemical effi-ciency for photosystem Ⅱ(Y(Ⅱ)),the relative electron transfer rate of photosystem Ⅱ(ETR(Ⅱ)),PSⅡ maxim-um light energy conversion efficiency(Fv/Fm)and the maximum quantum yield of electron transport between PSⅡand PSⅠ(φEO)were significantly lower than those treated and controlled at 45℃.Although the phenotypic change could not be seen after treatment at 45℃for 6,12,18 and 24 hours,it was found that the needles continued to lose water and turn yellow at 12 hours and 18 hours during the recovery peri-od,and the whole needles turned yellow after 24 hours treatment,basically dried up and fell off,and the relative water content of the needles was the lowest.When recovering for 28 days,φEo at 18 and 24 hours was almost 0.[Conclusion]P.pungens can withstand high temperature treatment at 45℃for 6 h,but it is not resistant to high temperature of 50℃and 55℃.The seedlings with a high temperature treatment time of 45℃for more than 12 hours will suffer severe water loss and dry needles,which will have a significant impact on the photosynthetic characteristics and make it difficult to resume normal growth.
Picea pungensheat resistanceneedle water contentphotosystem Ⅰ and Ⅱfluorescence parameters
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