Thermal Stability Of PS ? Of Main Picea Species In China

Photosystem ?(PS ?)is one of the most sensitive components in plant photosynthetic apparatus to environmental changes,its stability determining the light absorption and electron transport rates,thus affecting the accumulation organic matter in plant.However,the raising of atmospheric temperature result from global climate change will have effects on the plant PS ? stability,thereby affects the ability of the plant carbon accumulation,ultimately influence the growth and survival of plants.Hence,the response of structural and functional of PS ? to rising temperature is commonly used for understanding the influence of climate change on the plant.Picea is the important forest constitute tree species in our country,which are mainly distributed in the northeast low latitudes and western high altitude cold regions and highly sensitive to climate change.Therefore,the research about rising temperature effects on Picea taxa PS ? would has important scientific significance.In this study,we chose nine main Picea taxa as the research materials.The rapid chlorophyll fluorescence induction kinetics method was used to analysis the response of PS ? to the rising temperature and the difference of the PS ? thermal stability and its main influencing factors was then analyzed.Finally,the data of climate from original habitat of Picea taxa was combined to testify the adaptive evolutionary relationship between Picea taxa and the environment.The main results were as follows:(1)With the increase of temperature,the decrease of maximal photochemical efficiency(Fv/Fm),maximal fluorescence(Fm),active number of reaction center(RC/CSo),unit reaction center electron transmitted energy(ETo/RC),PQ library heterogeneity index(Vi)and PQ library size index(Sm)were observed in different Picea taxa.In contrast,minimal fluorescence(Fo),unit reaction center absorbed energy(ABS/RC),unit reaction center energy dissipation(DIo/RC),unit reaction center captured energy(TRo/RC),relative variable fluorescence(Vj)increased with the increase of temperature.Besides,the K point of fast chlorophyll fluorescence induction kinetics curve was invisible apparently in Picea taxa.In conclusion,warming mainly inhibited the activity of PS ? reaction center as well as the electron transfer of receptor side,and changed the allocation of energy flow in reaction center while have less effects on donor side in Picea taxa.(2)With the increase of temperature,the decreasing amplitude of Fv/Fm among different Picea taxa was significant different,which can be quantified as the difference of lethal temperature(FT50).This suggests the thermal stability of different Picea taxa is different.Among them,Picea smithiana had the highest value of FT50 while its value in P.koraiensis was the lowest,for the remaining taxa,however,exhibited intermediate between them.Further analysis showed that this difference is mainly result from the response difference of PS ? reaction center RC/CSo,DIo/RC and receptor side Vj to warming.In addition,a positively relationship was also observed between FT50 and the annual mean temperature of original habitat in different Picea taxa.This phenomenon may be the results of adaptation of Picea species to the environment of its original habitat.These results not only facilitated the understanding of Picea species response to global warming but also provided the theoretical basis for screening high resistance tree species in Picea taxa.Moreover,this study also provides the important clues for exploration the adaptive evolutionary relationship between Picea species and its habitat environment.