Proceedings of the Biochemical Society

Abstract

The well-known oxygen requirement for the synthesis of starch and sucrose from glucose by leaf tissue in the dark may be explained if synthesis depends on the coupling of oxidative phosphorylation in mitochondria with the formation of phosphorylated intermediates, at the expense of adenosine triphosphate (ATP) (Porter, 1953). The discovery by Arnon (1956) and colleagues that illuminated chloroplasts also effect phosphorylation but by a process which neither produces nor requires oxygen, suggested that in intact tissue it should be possible to circumvent the oxygen requirement for starch synthesis simply by illuminating under anaerobic conditions.Synthesis of starch, sucrose and fructose has been accomplished in tobacco leaf disks infiltrated with 5 % radioactive glucose and held at a reduced air pressure of 2-0 cm. Hg for 24 hr. in light of about 600 foot-candles. The anaerobiosis existing in this 'vacuum' completely prevented synthesis in darkness, and compared with many plant tissues