DEVELOPMENT OF THE RECALCITRANT (HOMOIOHYDROUS) SEEDS OF AVICENNIA-MARINA - ANATOMICAL, ULTRASTRUCTURAL AND BIOCHEMICAL EVENTS ASSOCIATED WITH DEVELOPMENT FROM HISTODIFFERENTIATION TO MATURATION

Early histodifferentiation of the embryo of Avicennia marina (Forssk) Vierh was characterized by the formation of endosperm haustona Once the growth phase was initiated, subsequent embryo development was extra-ovular The mature seed, therefore, was enclosed by a pericarp originating entirely from the ovary wall Growth and reserve deposition was not initiated until 45-50 d after fruit set (DAFS), when respiratory activity had peaked Water content remained constant from the earliest stages of embryogenesis to seed abscission and respiratory activity, although declining somewhat after the completion of histodifferentiation, remained relatively high throughout seed development The ultrastructure of the menstematic root pnmordia was indicative of metabolic activity, remaining essentially similar in all respects from the end of histodifferentiation until the mature seeds were abscised During this phase cotyledon cells became highly vacuolated and the soluble sugars, which constituted the major nutrient reserves of mature seeds, increased considerably Seeds of A, marina initiate germination, without the requirement for additional water, as soon as they are shed It is proposed that the accumulation of soluble sugars, rather than insoluble complex reserves, is a major factor in the developmental strategy of these highly recalcitrant seeds. © 1992 Annals of Botany Company.