Relationship between Photosynthesis and Plasmalemma Transport

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Abstract
Hansen, U.-P., Kolbowski, J. and Dau, H. 1987. Relationship between 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 of plasmalemma potential (V) were measured in the presence of red (633 nm) background light with blue or far-red (720 nm) sinusoidally modulated actinic light. The kinetic study based on curve-fitting of the measured frequency responses led to the following: the response of chlorophyll-fluorescence (F) to blue actinic light comprises four time-constants located at 2·7,50,400 and 4000 s. Membrane potential (V) displays five time-constants: 2· 50, 160±330, √—1, 4000 s. These time-constants were assigned to the reactions involved as follows: from the comparison of the effects of blue and far-red actinic light the time-constants of 2·7 s and 400 s were related to the plastoquinone pool and to the state-transition controller. The time-constant of 4000 s was not investigated. The complex time-constants of V are known to be related to the controller of cytoplasmic pH from previous studies. The time-constant of 50 s was common to V, F, and PAS. From the sign of the 50 s component in F and in PAS (qE-component), the following model of the light action on membrane transport was developed: the uptake of protons into the inner space of the thylakoids causes an alkalinization of the cytoplasm which slows down the plasmalemma H+-pump via a substrate effect.

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