Pre-imbibition: Effects in the germination, seedling growth and content of caffeine in coffee seeds (Coffea arabica L.)

Abstract

Coffee seeds ( Coffea arabica L.) contains from 1% to 2% of caffeine, a highly water-soluble alkaloid, which inhibits germination of several species. This work was undertaken to evaluate the effects of treatments of pre-imbibition and running water washing on physiological performance and caffeine content of coffee seeds, with the following treatments: pre-imbibition in water under stirring for 6, 12 and 24 hours, followed by fast washing in running water; washing in running water for 6, 12 and 24 hours; pre-imbibition in water for 6, 12, 24, 48, 72 and 96 hours, followed by fast washing in running water, and dry seeds witout parchment. The percentage of root protrusion, of normal seedlings at 30 days, of cotiledonary leaves at 45 days and of the root protrusion velocity index were evaluated. The contents of caffeine, aminoacids and total soluble sugars present in the imbibition solution, as well as the caffeine contents in seeds were also determinated. There were no significant differences in the root protrusion evaluation at fifteen days and the best treatments, evaluated by means of radical protrusion at seven days and of index of germination velocity, were pre-imbibited in water for 48, 72 and 96 hours. As to the percentage of seedlings with cotyledonary leaves opened at 45 days, the pre-imbibition treatments for both 24 and 48 hours provided the best physiological performances of seeds, and in these treatments there were significant reductions of caffeine content between 10% and 18%, respectively. Nevertheless, the detrimental action of caffeine on the physiological performance of coffee seeds, associated with the pre-imbibition treatments should be better investigated.