Response of strawberry leaves photosynthesis to strong light and its mechanism

Abstract

Abstract: In this paper,PAM-2000 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: Strawberry, Strong light stress, Photoinhibition, Chlorophyll fluorescence, Xanthophyll cycle

CLC Number:

XU Kai, GUO Yanping, ZHANG Shanglong, ZHOU Huifen, ZHENG Yi . Response of strawberry leaves photosynthesis to strong light and its mechanism [J]. Chinese Journal of Applied Ecology, 2005, 16(1): 73-78.

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