Incorporation of ³²P and ¹⁴C into Photosynthetic Products of Ankistrodesmus braunii as Affected by X-Rays

Abstract

Sunmtmary. The incorporation of 32p and 1"C into organic compounds by Ankistrodesmitus is strongly inhibited by X-rays. In the same phosphorylated compounds 39P-incorporation apparently is more severely inhibited by X-rays than the "4C-labelling. The 32P-incorporation into organic compounds is more strongly inhibited than 3"P-labelling of inorganic phosphate in the cell. The inhibition of 32P-incorporation into a number of compounds is strikingly tuniform. It is concluided that the inhibition of "P-incorporation and of _4C-incorporation into phosphorylated compounds in vivo is due to an uncoupling by X-rays of photophosphorylation as in vitro. The difference in X-ray sensitivity of 14C-and "2P-incorporation into one organic phosphorous compound is attributed to a dual action of X-rays on "P-incorporation in organic compounds (both via the uncoupling of photophosphorylation) and only a single effect on 14C-incorporation and 32P-labelling of inorganic phosphate. The effect of X-rays on 14C-incorporation into organic compounds included inhibition in most cases but also stimulation as in the case of glycolic acid. These differences may be due to interference in the intercellular regulations following the application of X-rays. The inhibition of 14C-incorporation in many cases exhibits different behaviour at low (<200 krad) and high doses. These chaiiges are (liscussecd on the assuimption that at the lower doses X-rays cause uncoupling of photophosphorylation and at the higher doses an additional inhibition of electron transport.

The Warburg Effect in a Chloroplast-Free Preparation from Euglena gracilis

“…There is data in the literature which can be interpreted to support this suggestion 1 (6,7,8,10,11). The proportions of glycolate and glycine labeled in this Euglena system (without chloroplasts) is dramatically altered by light.…”