Abstract: | Lucas, W. J. and Ogata, K. 1985. Hydroxyl and bicarbonateassociatedtransport processes in Chara corallintr. Studies on the lightdarkregulation mechanism.J. exp. Bot. 36: 19471958.Experiments were undertaken on the fresh water alga Chara corallinato investigate the nature of the coupling between the chloroplastsand the lightdependent OH and -associated plasmalemma transport systems. Electrophysiologicalexperiments, in which DCMU was employed, revealed that thischemical could elicit a hyperpolarization of the membrane potentialthat was identical to that normally obtained by turning offthe light. This DCMUinduced hyperpolarization was obtainedunder control () and phosphatedecoupled conditions (). Measurements of the extracellular electric potentialswhich are associated with the acidic () and alkaline (OH) regions, indicated that, in the presenceof control ()or phosphatedecoupled conditions, normal profiles were established under air, oxygenor nitrogen environments. These results indicate that the generationof the control signal(s) is related to events associated withchloroplast electron transport, rather than to changes in theflow or levels of carbon intermediates within the reductivepentose phosphate or photorespiratory cycles. Although the levelof oxygen was found to have no effect on the lightinducedactivation of the OH regions, we found that in pure oxygen thedarkinduced inactivation of the OH efflux systemwas delayed, and that partial transport function could be maintainedin the dark. The possible involvement of changes in either theratio of oxidized to reduced ferridoxin or NADP? to NADPH, aspart of this lightmediated control signal, is discussed. Key words: Chara corallina, Plasma membrance transport, OH and , regulation |