This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (17) Citing Articles via Google Scholar Google Scholar Articles by Baer, G. R. Articles by Schrader, L. E. Search for Related Content PubMed PubMed Citation Articles by Baer, G. R. Articles by Schrader, L. E. Agricola Articles by Baer, G. R. Articles by Schrader, L. E.

Articles

Relationships between CO₂ Exchange Rates and Activities of Pyruvate,Pi Dikinase and Ribulose Bisphosphate Carboxylase, Chlorophyll Concentration, and Cell Volume in Maize Leaves ¹

Department of Agronomy, University of Wisconsin, Madison, Wisconsin 53706

The relationships between CO₂-exchange rate (CER), DNA and chlorophyll (Chl) concentrations, pyruvate,Pi dikinase (PPDK) and ribulose bisphosphate carboxylase (RuBPCase) activities in ten maize (Zea mays L.) genotypes were investigated. The in vivo degrees of activation of PPDK and RuBPCase were estimated to make meaningful comparisons with CER. In leaves at a photosynthetic photon flux density (PPFD) of 720 micromoles per square meter per second, in vivo PPDK degree of activation was 80% of that of PPDK fully activated in vitro, whereas RuBPCase could not be further activated in vitro, suggesting that RuBPCase was fully activated in vivo. CER varied about 50% among the genotypes tested. Significant genetic differences were observed for the average weight of a cell (estimated by gram fresh weight per milligram DNA), but this character was not correlated with CER expressed on a fresh weight basis. CER was correlated with Chl concentration, and with estimates of the in vivo degree of activation of PPDK and RuBPCase. We concluded that in maize, CER is controlled by the metabolic components of photosynthesis rather than by membrane resistances to CO₂. If the latter factor were controlling CER, then smaller cells with higher amounts of exposed cell surface area per unit cell volume would have lower resistance to CO₂ diffusion, and therefore higher CER. When data were expressed on a DNA basis (proportional to a per cell basis), results indicated that larger cells (i.e. those with higher fresh weight per milligram DNA) have a higher content of Chl, and higher PPDK and RuBPCase activities, resulting in higher CER than in smaller cells.

¹ Supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison. Research conducted by senior author in partial fulfillment of requirements of the Ph.D. degree.

This article has been cited by other articles:

				S. L. Naidu, S. P. Moose, A. K. AL-Shoaibi, C. A. Raines, and S. P. Long Cold Tolerance of C4 photosynthesis in Miscanthus x giganteus: Adaptation in Amounts and Sequence of C4 Photosynthetic Enzymes Plant Physiology, July 1, 2003; 132(3): 1688 - 1697. [Abstract] [Full Text] [PDF]