The mechanism of bicarbonate assimilation by the polar leaves of Potamogeton and Elodea. CO 2 concentrations at the leaf surface

The mechanism of bicarbonate assimilation by the polar leaves of Potamogeton and Elodea. CO 2... Abstract. Photosynthetic utilization of HCO, in leaves of Poiamogeton and Elodea occurs at the lower leaf side, with subsequent OH∼ release at the upper side. It is accompanied by transport of cations, in the present experiment K +, across the leaf. The resulting pH and K+ concentration changes near the leaf surface were recorded with miniature electrodes. From the pH and K+ concentration the concentrations of the different inorganic carbon species were calculated and compared with photosynthetic O, production. HCO−3 utilization is accompanied by a drastic increase in the free CO2 concentration near the lower epidermis. Experiments with CO2− and HCO3−free solutions showed an oscillating acidification near the lower epidermis and alkalinization near the upper epidermis. It is concluded that the acidification results from the activity of light‐dependent H+ pumps. The finding that an increase in pH at the upper side always coincided with a decrease at the lower in these experiments shows that the H+ pumps and the OH− extruding mechanism are coupled although occurring in different cell layers. Previously we have suggested that the first step in the process of photosynthetic HCO3− utilization is external conversion of HCO3−” by acidification caused by light‐dependent H+ pumps. The present results strongly support this hypothesis. Two possible pathways for the accompanying K + transport are discussed. The model presented here explains the known inhibiting effects of buffers and high pH on photosynlhetic HCO3− utilization. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Cell & Environment Wiley

The mechanism of bicarbonate assimilation by the polar leaves of Potamogeton and Elodea. CO 2 concentrations at the leaf surface

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Publisher
Wiley
Copyright
Copyright © 1982 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0140-7791
eISSN
1365-3040
D.O.I.
10.1111/1365-3040.ep11571916
Publisher site
See Article on Publisher Site

Abstract

Abstract. Photosynthetic utilization of HCO, in leaves of Poiamogeton and Elodea occurs at the lower leaf side, with subsequent OH∼ release at the upper side. It is accompanied by transport of cations, in the present experiment K +, across the leaf. The resulting pH and K+ concentration changes near the leaf surface were recorded with miniature electrodes. From the pH and K+ concentration the concentrations of the different inorganic carbon species were calculated and compared with photosynthetic O, production. HCO−3 utilization is accompanied by a drastic increase in the free CO2 concentration near the lower epidermis. Experiments with CO2− and HCO3−free solutions showed an oscillating acidification near the lower epidermis and alkalinization near the upper epidermis. It is concluded that the acidification results from the activity of light‐dependent H+ pumps. The finding that an increase in pH at the upper side always coincided with a decrease at the lower in these experiments shows that the H+ pumps and the OH− extruding mechanism are coupled although occurring in different cell layers. Previously we have suggested that the first step in the process of photosynthetic HCO3− utilization is external conversion of HCO3−” by acidification caused by light‐dependent H+ pumps. The present results strongly support this hypothesis. Two possible pathways for the accompanying K + transport are discussed. The model presented here explains the known inhibiting effects of buffers and high pH on photosynlhetic HCO3− utilization.

Journal

Plant Cell & EnvironmentWiley

Published: Jun 1, 1982

References

  • Apparent bicarbonate uptake and possible plasmalemma proton efflux in Chara corallina
    Ferrier, Ferrier
  • Exogenous inorganic carbon sources in plant photosynthesis
    Raven, Raven
  • The influence of environmental factors on apparent photosynthesis and respiration of the submersed macrophyte
    Simpson, Simpson; Eaton, Eaton; Hardwick, Hardwick
  • Localization of hydrogen ion and chloride ion fluxes in Nitella
    Spear, Spear; Barr, Barr; Barr, Barr
  • Comparison of the photosynthetic characteristics of three submersed aquatic plants
    Van, Van; Haller, Haller; Bowes, Bowes

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