Light-induced polar pH changes in leaves of Elodea canadensis. I. Effects of carbon concentration and light intensity

• Published in: Plant physiology (Bethesda) Vol. 91; no. 1; pp. 62 - 67
• Main Authors: Elzenga, J.T.M. (University of Groningen, Haren, The Netherlands), Prins, H.B.A
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.09.1989
• Subjects: Acidification; Adenosine triphosphatases; Bicarbonates; Biological and medical sciences; Carbon dioxide; CARBONE; CARBONO; Cell membranes; Cell physiology; COMPOSE MINERAL; COMPUESTOS INORGANICOS; Cytoplasm; FEUILLE; FOTOSINTESIS; Fundamental and applied biological sciences. Psychology; HELOBIAE; HOJAS; Leaves; LUMIERE; Luminous intensity; LUZ; PHOTOSYNTHESE; Plant physiology and development; Plants; Plasma membrane and permeation; POLARIDAD; POLARITE; Light effect; Monocotyledones; Elodea canadensis; ATPase; Carbon dioxide; Hydrocharitaceae; Acidity; Plant leaf; Hydrogencarbonates; Absorption; Angiospermae; PH; Polarity; Spermatophyta; Photosynthesis
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.91.1.62

Leaves of the submerged aquatic Elodea canadensis Michx. exhibit a light induced polar pH reaction. In this study, the effects of light intensity and dissolved inorganic carbon concentration on this polar reaction were examined. At a light intensity of 100 watts per square meter the leaf showed a polar pH response when the dissolved inorganic carbon concentration was less than about 1 millimolar. The polar reaction was suppressed at a higher dissolved inorganic carbon concentration. This suppression was not due to the buffering capacity of bicarbonate. Because another weak acid, acetate, did not inhibit the polarity, but even had a small stimulatory effect, the effect of bicarbonate is also not due to acidification of the cytoplasm. The suppression of the polar reaction by CO2/HCO3- was relieved when the light intensity was increased. Apparently there is competition for product(s) of the photosynthetic light reactions between processes generating the polar reaction and the carbon fixation reactions. The possibility that the redox state of the cell regulates the generation of the polar reaction is discussed