Starch content of etiolated radish (Raphanus sativus L.) hypocotyls as affected by chloramphenicol and external sucrose

Abstract

Starch was enzymatically assayed in the hypocotyls of radish (Raphanus sativus L.) seedlings grown in water or chloramphenicol (CAP) 1 × 10^4. CAP inhibits starch formation and its effect is related to the concentration. Both CAP- and water-grown hypocotyls are able to accumulate starch when sucrose is supplied in the medium, thus suggesting that the damage caused by CAP to the amyloplast is not irreversible. Apical segments of both water- and CAP- grown hypocotyls accumulate starch upon incubation in sucrose solutions while basal segments are unable to accumulate starch even in the presence of sucrose. The authors suggest that the basal segments are unable to perform sucrose uptake or that the amyloplast is incapable to starch synthesis. In any case the inability of the basal segment to perform sucrose uptake is independent of CAP. These findings confirm that the radish hypocotyls is not homogeneous along its axes.