[Caffeine synthesis in fruits and tissue cultures of Coffea arabica].
During fruit development the relative caffeine content of the pericarp falls from 1.68% to 0.24% on a dry weight basis, but remains more or less constant in the seed (about 1.25%). On an absolute basis, the pericarp has twice as much and the seed twenty times as much caffeine at maturity as at the beginning of fruit development. Tissue cultures of seed tissue (endosperm) produce caffeine and release it into the growth medium. Both pericarp and endosperm fed with NaH(14)CO3 synthesize ring-labelled caffeine. Light strongly stimulates the methylation step of caffeine synthesis in the pericarp.