Relationship between Photosynthesis and Plasmalemma Transport

Hansen, U.-P., Kolbowski, J. and Dau, H. 1987. Relationshipbetween photosynthesis and plasmalemma transport.—J. exp.Bot. 38: 1965–1981. The yield of chlorophyll-fluorescence (F), of oxygen evolution(PAS, photo-acoustic signal) and the light-induced changes ofplasmalemma potential (V) were measured in the presence of red(633 nm) background light with blue or far-red (720 nm) sinusoidallymodulated actinic light. The kinetic study based on curve-fittingof the measured frequency responses led to the following: theresponse of chlorophyll-fluorescence (F) to blue actinic lightcomprises four time-constants located at 2·7,50,400 and4000 s. Membrane potential (V) displays five time-constants:2· 50, 160±330, —1, 4000 s. These time-constantswere assigned to the reactions involved as follows: from thecomparison of the effects of blue and far-red actinic lightthe time-constants of 2·7 s and 400 s were related tothe plastoquinone pool and to the state-transition controller.The time-constant of 4000 s was not investigated. The complextime-constants of V are known to be related to the controllerof cytoplasmic pH from previous studies. The time-constant of50 s was common to V, F, and PAS. From the sign of the 50 scomponent in F and in PAS (q_E-component), the following modelof the light action on membrane transport was developed: theuptake of protons into the inner space of the thylakoids causesan alkalinization of the cytoplasm which slows down the plasmalemmaH₊-pump via a substrate effect. Key words: Chlorophyll-fluorescence, frequency responses, kinetic analysis, plasmalemma potential, photo-acoustic effect, proton flux, spinach, state-transitions, thylakoid membrane, time-constants