Water content, a_w, and enzyme activity (xaa-prolyl-dipeptidyl aminopeptidase) during the germination process of cocoa beans (Theobroma cacao L.)

Cacao seeds demonstrate epigeal (or epigeous) germination in which the hypocotyl elongates and forms a hook, pulling rather than pushing the cotyledons and apical meristem through the soil. Once it reaches the surface, it straightens and pulls the cotyledons and shoot tip of the growing seedlings above the ground (Bewley 1997). After the cocoa seeds are removed from the fruit they germinate rapidly, 4–6 days after planting. The root and the hypocotyle emerge first, which causes the cotyledons to elevate above the substrate (10 or 15 days after planting). The cotyledons then open and expose the plumule, which begins to grow at the same time as the root, but it is much smaller. The first phase of growth is completed with the maturation of the first leaves (López-Andrade 2003). This means that germination commences with the uptake of water by dry seed imbibition and is completed when a part of the embryo, usually the radicle, extends to penetrate the structures that surround it (Bewley 1997).