Relationship between banding and photosynthetic activity in Chara corallina as studied by the spatially different induction curves of chlorophyll fluorescence observed by an image analysis system

Abstract

Image analysis was applied for studying the kinetics of chlorophyll fluorescence in the alkaline and acid zones of internodal cells of Chara corallina Klein ex Willd., in order to test the hypothesis that in the acid bands an outward proton current yields a conversion of HCO3− ions to CO2, thus facilitating inward diffusion of CO2.The analysis of the responses of chlorophyll fluorescence induced by changes in light intensity from 0.15 W m−2 to 2.0 W m−2 (λ <580 nm) revealed different kinetic behaviour. In the alkaline zones, the amplitude of the variable components of fluorescence was smaller than in the acid zones. Curve fitting by a sum of exponentials showed that the 4 time constants of about 2, 22, 48 and 140 s were not significantly different between the alkaline and acid zones. In contrast the related amplitude factors were smaller in the alkaline zones. by a factor of about 1.6 to 2.0 in old calcified cells and by a factor of about 1.2 in young cells without acrustations.The interpretation of these results in terms of a better supply of carbon dioxide in the acid zones was supported by investigations on leaves of tobacco. Lowering the CO2 concentration of an artificial atmosphere below 20 ppm resulted in a similar reduction of the variable component of chlorophyll fluorescence as found in the alkaline zones of Chara.