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 CrossRef Citing Articles via Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Fu, C. F. Articles by Gibbs, M. Search for Related Content PubMed PubMed Citation Articles by Fu, C. F. Articles by Gibbs, M. Agricola Articles by Fu, C. F. Articles by Gibbs, M.

Environmental and Stress Physiology

CO₂ Photoassimilation by the Spinach Chloroplast at Low Temperature ^1,2

Institute for Photobiology of Cells and Organelles, Brandeis University, Waltham, Massachusetts 02254

Spinach chloroplasts were used to study the relationship between photosynthetic CO₂ fixation and temperature from 30 to –15°C. In saturating light and high concentrations of CO₂, the temperature coefficients (Q₁₀) above 20°C were less than 2 in the intact chloroplast. Below 15°C, the Q₁₀ values were greater than 2 and gradually increased with decreasing (down to 0°C) temperature to approximately 4.4. Photosynthesis responded similarly to temperature in a reconstituted chloroplast preparation fortified with ribose 5-phosphate. In the intact chloroplast, temperature did not alter the Q₁₀ value in low light and high CO₂. Elevating the temperature to 25°C after photosynthesizing at –15°C (46 minutes) or 0°C (17 minutes) restored the temperature-depressed photosynthetic rate without a lag in the intact chloroplast to the rate of a chloroplast continually at 25°C. At 0°C, the intact chloroplast photosynthetic rate responded slightly to the inorganic phosphate concentration (0.1-1.0 millimolar) and to pH (7.0-8.6). Relative to 25°C, the levels of ribulose 1,5-bisphosphate and glycerate 3-phosphate were increased 1300 and 200%, respectively, whereas glycolate decreased 57% during intact chloroplast photosynthesis at 0°C. Chilling temperature impeded the transport of photosynthetic intermediates from the stromal compartment to the external medium. Ethylene glycol was shown to be an appropriate additive to prevent freezing of the reaction mixture down to –15°C for photosynthetic CO₂ assimilation.

¹ Supported by National Science Foundation PCM 83-04147.

² Dedicated to Professor F. L. Wynd on the occasion of his 82nd birthday.