Abstract: In this paper,PAM2000 portable chlorophyll fluorometer and HCM1000 photosynthesis measurement system were applied to measure the apparent quantum efficiency(AQY),initial fluorescence (Fo),maximal photochemical efficiency of PSII (Fv/Fm),maximal fluorescence(Fm),photochemical quenching(qP),nonphotochemical quenching(qN),actual quantum yield of PSⅡ electron transport (ΦPSII),electron transport rate (ETR),amount of inactive PSⅡ reaction centers (FiFo),QA reduction rate,proportion of QBnonreducing PSⅡ reaction centers［(FiFo)/（FpFo）］,and energydependent quenching (qE),photoinhibitory quenching (qI) and statetransition quenching (qT) of nonphotochemical quenching of strawberry leaves.The results showed that the Fv/Fm,Fm,FiFo and QA reduction rate decreased in strong light and increased during subsequent dark recovery,but （FiFo）/（FpFo） was in reverse.They changed drastically within the first 10 minutes in strong light or in subsequent darkness.In strong light,ΦPSII,ETR and qP increased firstly and then decreased,while qN decreased drastically firstly and then increased slightly.After exposure to strong light for 4 hours,the AQY of two varieties “Toyonoka" and “Houkouwase" decreased by 20.9% and 37.5%,respectively,and qE was 89.1% and 87.1%, respectively in NPQ (qE+qI+qT).In strong light,“Toyonoka" showed less changes than “Houkouwase" in Fo,Fv/Fm,Fm,ETR,ΦPSII and AQY.After treated with DTT,the Fv/Fm and Fm were lower,but Fo was much higher than control.It is deduced that in strong light,xanthophyll cycle-dependent non-radiative energy dissipation and pH-dependent heat dissipation could play an important protective role against photo-damage to the photosynthetic apparatus in strawberry leaves.

Key words: Spring-sown wheat, Grain quality, Growing period, Climatic conditions