Metabolism and Excretion of Caffeine during Germination of Coffea arabica L

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