II. Exine development in Passiflora racemosa Brot.: post-tetrad period. Overlooked aspects of development

Developmental stages during the post-tetrad period are examined in detail with TEM and SEM, with emphasis upon substructure. Our purpose was to find out whether the sequence of sporoderm developmental events gives additional evidence for our recent hypothesis on the underlying cause of exine ontogeny as a sequence of self-assembling micellar mesophases, initiated by genomically given physico-chemical parameters. Four different layers of the endexine are developed in the post-tetrad period. The first one is a layer of white line centered lamellae which appear as a demarcation line between ect- and endexine. The second layer is sponge-like and consists of “roots” of columellae and a layer between them. The third layer consists of basally disposed radially elongated granules which appear in the aperture sites only. The fourth layer emerges in interapertural sites only and is formed as stacks of uneven lamellae. Therefore, the sequence of substructural units in primexine is the next: white-lined lamellae, a layer of honeycombed substructure, globule-to-rod-like granules, stacks of wavy lamellae. These sequences correspond to the next four mesophases of self-assembling micelles: neat (=laminate) micelles, high-concentrated emulsion of sponge-like (=foam-like) substructure, spherical-to-cylindrical micelles, and laminate micelles with fenestrated laminae. Reiteration of the micellar mesophases, participating in endexine development, is observed during the post-tetrad period.