Spatial Coordination of Photosynthesis and H+Transport in Chara corallina as Studied with the Use of Local and Whole-Cell Illumination

Abstract

In experiments with the alga Chara corallina Klein ex Willd., the appearance of subcellular domains with different photosynthetic activities, as well as formation of alkaline and acid zones near the cell surface were monitored with pulse-amplitude modulated microfluorometry and pH microelectrodes. After transfer of a dark-adapted cell to actinic light, the effective yield of PSII photochemistry (ΔF/Fm′) underwent different induction changes in cell regions where acid and alkaline zones were produced. The PSII effective yield decreased for 5–15 min of illumination in cell regions forming the alkaline bands but increased after the initial decline in the acid regions. The photoinduced decrease in ΔF/Fm′ in the alkaline regions occurred faster than or concurrently with the change in local pH near the cell surface (pH0). The light-induced change in pH0 was manifested as a steep transition after a latent period of variable lengths. The kinetics of ΔF/Fm′ and Fm, specific for alkaline regions, were replaced by those typical of acid regions, when the illumination area was narrowed to 2 mm. The results show that the formation of subcellular domains with different photosynthetic activities is not strictly bound to particular cell regions but is a dynamic event determined by spatial coordination of photosynthesis in a long cylindrical cell.