title: The effect of ionic stress on photosynthesis in Dunaliella tertiolecta : Chlorophyll fluorescence kinetics and spectral characteristics.
abstract: A comparison of the effects of ionic stress and an uncoupler on long-term fluorescence transients (the 'Kautsky effect') in the green alga Dunaliella tertiolecta indicated that the large quenching induced by ionic stress was caused by a pH gradient across the thylakoid membrane. This possiblity was given support by the increase in the slow phase of 3-(3',4'-dichlorophenyl)-1,1-dimethylurea-induced fluorescence relaxation in algae subjected to ionic stress. Low-temperature fluorescence emission spectra indicated that salt stress enhanced photosystem-I emission in the dark, and a comparison of simultaneous emissions at 695 and 720 nm at room temperature indicated a further increase in photosystem-I emission during the fluorescence transients. Taken together with the decrease in the fast phase of 3-(3',4'-dichlorophenyl)-1,1-dimethylurea-induced fluorescence relaxation in stressed algae, our results indicate that ionic stress stimulates cyclic electron flow, and that non-cyclic flow is inhibited. The effect of sucrose-induced osmotic stress was similar to, but less marked than, the effects of NaCl and KCl; the effect of decreasing the external salinity was small.
authors.affiliation: Department of Botany, University of Glasgow, G12 8QQ, Glasgow.
authors.forename: D J
authors.initials: DJ
authors.lastname: Gilmour
authors.forename: M F
authors.initials: MF
authors.lastname: Hipkins
authors.forename: A N
authors.initials: AN
authors.lastname: Webber
authors.forename: N R
authors.initials: NR
authors.lastname: Baker
authors.forename: A D
authors.initials: AD
authors.lastname: Boney