Carbon dioxide fixation by epidermal and mesophyll tissues ofTulipaandCommelina

摘要

Rates of14CO2fixation by epidermal tissue ofTulipa gesneriana(tulip) andCommelina diffusaare only slightly higher in the light than in the dark while in mesophyl tissues rates are much greater in the light. The first products of14CO2fixation by epidermal tissue ofTulipa gesnerianaandC. diffusain the light and dark are malate and aspartate. In addition to these dominating dicarboxylic acids, 3-phosphoglyceric acid and sugar phosphates appear in the light, while in the dark only the amino acids, glutamate and glutamine become labelled. Mesophyll tissue of tulip andC. diffusa, however, gives typical CO2fixation patterns of the labelled products of C3plants. Furthermore, a period of dark14CO2fixation followed by a light12CO2chase carried out with epidermal tissue suggested that malate can act has the precursor of phosphorylated compounds of the Calvin cycle and consequently of starch. The data are consistent with the view that guard cells are able to exhibit Crassulacean acid metabolism.