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Plant Physiology 49:218-223 (1972)
© 1972 American Society of Plant Biologists

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Articles

Photorespiratory Phenomena in Maize

Oxygen Uptake, Isotope Discrimination, and Carbon Dioxide Efflux 1

R. J. Volk and W. A. Jackson

a Department of Soil Science, North Carolina State University, Raleigh, North Carolina 27607

Concurrent O2 evolution, O2 uptake, and CO2 uptake by illuminated maize (Zea mays) leaves were measured using 13CO2 and 18O2. Considerable O2 uptake occurred during active photosynthesis. At CO2 compensation, O2 uptake increased. Associated with this increase was a decrease in O2 release such that a stoichiometric exchange of O2 occurred. The rate of O2 exchange at CO2 compensation was directly related to O2 concentration in the atmosphere at least up to 8% (v/v).

When illuminated maize leaves were exposed to saturating CO2 concentrations containing approximately equal amounts of 12CO2 and 13CO2, the latter was taken up more rapidly, thus depressing the atom% 13C in the atmosphere. Moreover, upon exposure to CO2 containing 96 atom% 13C, there occurred a directly measurable efflux of 12CO2 from the leaves for at least 15 minutes. During this period an equimolar evolution of 16O2 and uptake of 13CO2 was observed. Thereafter, although the rate of 16O2 evolution remained unchanged, the rate of 13CO2 uptake declined markedly, suggesting continual 13C enrichment of the photorespiratory substrate.

It is concluded that a finite photorespiratory process occurs in maize and that the CO2 generated thereby is efficiently recycled. Recycling maintains the internal CO2 concentration at a level difficult to detect by most photorespiratory assays.

1 Paper No. 3515 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh, N. C. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Experiment Station of the products named nor criticism of similar ones not mentioned.




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I. Zelitch
Improving the Efficiency of Photosynthesis
Science, May 9, 1975; 188(4188): 626 - 633.
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Copyright © 1972 by the American Society of Plant Biologists