Metabolism and Excretion of Caffeine during Germination of Coffea arabica L.

Abstract

To investigate the physiological role of the purine alkaloids during germination, seeds of Coffea arabica were allowed to germinate under aseptic conditions on agar at 26°C, either in the dark or in the light. After imbibition for 7 days less than 1% of the seed caffeine is found in the agar, indicating a strong diffusion barrier at the surface of the coffee bean. After 56 days, when the radicle has grown deep into the agar support, a considerable amount (22%) of caffeine is excreted. The total caffeine content increases during germination for 56 days by 83% in the dark and by 51% in the light, whereas the soluble protein falls drastically. We propose that caffeine is not a nitrogen reserve for germination and acts against competitors (release into the soil) and against predators (concentration increase in the tissue).