The metabolism of photosynthetically fixed carbon by isolated chloroplasts from Codium fragile (Chlorophyta: Siphonales) and by Elysia viridis (Mollusca: Sacoglossa)

Abstract

The metabolism of photosynthetically fixed 14C by isolated chloroplasts from Codium fragile is compared with that by Elysia viridis (which contains C. fragile chloroplasts). There are marked differences between the two in the formation and subsequent metabolism of both soluble and insoluble products. Less than 6% of the carbon fixed by the isolated chloroplasts during a 15 min pulse of 14C-bicarbonate in the light is released into the medium over the succeeding 24 h. During photosynthesis glycollate and glucose monophosphate are the only labelled compounds released; after the pulse very little glycollate is released and over 24 h only glucose monophosphate and an unidentified compound are found in the medium. In E. viridis photosynthetically fixed carbon can be recovered from compounds of all major classes found in animals. Soon after the pulse, hexoses are the most heavily labelled compounds, but two hours later amino acids are more heavily labelled than hexoses. The unidentified compound is not found in the animals. E. viridis can absorb and metabolize exogenous glycollate and glucose. Earlier authors' suggestions that glucose is the compound which moves from the chloroplast to the animal cell are discussed, and it is proposed that both glucose monophosphate and glucose are formed outside the chloroplast from triose phosphate exported from it.