13C/12C Ratios of carbon dioxide from peanut and sunflower seedlings and tobacco leaves in light and in darkness

Shoots of intact peanut and sunflower seedlings evolved CO₂in the light which was enriched more than 10 per mille in ¹³Ccompared with simultaneous CO₂ evolution from the roots. Carbondioxide collected from tobacco leaves in the light was 10 permille enriched in ¹³C compared with that collected in the dark.Anaerobic conditions inhibited photorespiration but did notchange isotopic ratios of dark respiration. ¹ Department of Biology, Fresno State College, Fresno, California93710, U. S. A. ² Deceased. (Received February 29, 1972; )