BREAKING DOWN THE WALLS - A ROLE FOR ENDO-BETA-MANNANASE IN RELEASE FROM SEED DORMANCY

Dormancy is imposed in some seeds by the tissues that surround the emb ryo, which act as a mechanical barrier to the emergence of the radicle . Thus it has been proposed that germination is completed following th e production of hydrolases within the surrounding tissues: these are s ecreted into the cell walls, causing weakening and so allowing the rad icle to break out. Mannose is a prominent component of the endosperm c ell walls of dormant seeds of several species and, in these, productio n of endo-beta-mannanase has been suggested to be essential for germin ation. It is possible that this is the case in Datura ferox seeds, but evidence for a causal link between the enzyme and germination in seed s of tomato and lettuce is more equivocal.