Photosynthetic Carbon Metabolism in the Palisade Parenchyma and Spongy Parenchyma of Vicia faba L.

Abstract

Palisade parenchyma cells and spongy parenchyma cells were isolated separately from V. faba L. leaflets. Extracts of the cell isolates were assayed for several enzymes involved in CO2 fixation and photorespiration. When compared on a chlorophyll basis, the levels of enzyme activities either were equal in the different cell types or were greater in the spongy parenchyma; this difference may be a reflection of the higher protein-chlorophyll ratio in the latter tissue. The distribution of radioactivity in the products of photosynthesis by each cell type was the same at various times after exposure to NAH14CO3, and the kinetics of 14C incorporation into these compounds was similar. However, a larger percentage of radioactivity was incorporated by the cell isolates into the 80% ethanol-insoluble fraction and correspondingly less into the neutral fraction as compared to whole leaf. Photosynthetic CO2 fixation apparently is similar in the different mesophyll tissues from which these cells were derived.