SEQUESTRATION OF CYTOPLASMIC ORTHOPHOSPHATE BY MANNOSE AND ITS DIFFERENTIAL EFFECT ON PHOTOSYNTHETIC STARCH SYNTHESIS IN C₃ AND C4 SPECIES

Abstract

SUMMARY Leaf tissues from many C3 species respond to exogenous mannose in the light by a marked stimulation of starch synthesis. This is attributed to a decreased movement of triose phosphate from the chloroplast following sequestration of cytoplasmic orthophosphate as mannose phosphate and interference with the phosphate translocator. By contrast, in most C 4 species, feeding of mannose inhibits starch synthesis. It is concluded that, in these plants, the principal effect of sequestration of orthophosphate is interference with the regeneration of the CO 2 ‐acceptor.