THE PHYSIOLOGY OF STOMATA: I. CARBON DIOXIDE FIXATION IN GUARD CELLS

Abstract

The guard cells of Tulipa gesneriana L. were found to contain both chlorophylls a and b. The total chlorophyll content was estimated to be of the order of 0.5 × 10−12 gm, per cell. By exposure to radioactive carbon dioxide followed by microautoradiography, selective carbon dioxide uptake in the light was demonstrated in the stomatal cells of Allium, Hordeum, Nicotiana, Sedum, Tradescantia, Tulipa, and Vicia, A less intense uptake was observed in darkness with Allium, Sedum, Tulipa, and Vicia. The rate of guard-cell photosynthesis was estimated to be of the order of 0.02 × 10−12 M. carbon dioxide per cell per hour at 500 ft-c. and in 0.04% (v/v) carbon dioxide. It was concluded that this rate was too low to account for the increase in osmotic potential caused by illumination.