to sucrose takes place at or near the surface of the haustorium. The enzymes responsible for mannan catabolism are endo-p-mannanase and p-mannosidase. Both are thought to be secreted by the haustorium, but the possibility that they are also produced by the (living) cells of the endosperm cannot be ruled out (Bewley and Reid, 1985).
The cellulose component of the endosperm walls remains intact during the mobilization of mannan. The biological significance of mannan as a carbohydrate reserve in species such as date palm should be considered in the context of the sugary fruit in which the seed is embedded and of the dry subtropical region in which the date palm grows.
The nature of the fruit suggests that the seed would be dispersed by mammals and possibly by birds, and so the advantages to the seed of having a hard texture and storage material in a form resistant to digestive tract enzymes are clear. The relatively large bulk of storage carbohydrate may relate to the problems of seedling estab¬lishment in a harsh environment. No commercial use of seed mannans has yet been developed. The economic value of mannan deposits may well be negative because they have been responsible for many broken teeth!