Comparative microsporogenesis and anther development of selected species from Magnoliaceae

Abstract

Stamen development and microsporogenesis of four species from Magnoliaceae was investigated in order to provide additional data from this family. Stamen bases were found to be wide and short, without morphological diff erentiation in Magnolia moto , M. paenetalauma and Woonyoungia septentrionalis . In contrast, stamens are distinctly diff erentiated into anther and fi lament regions in Michelia crassipes. Th e orientation of dehiscence is introrse, introrse-latrorse and latrorse in M. moto , M. paenetalauma and M. crassipes , respectively. Th e vascular bundles range from three to fi ve ( M. moto , M. paenetalauma ) to one ( M. crassipes ). Th e amount of the connective tissue has been reduced from three to two times of the sporogenous tissue in M. moto and M. paenetalauma . Th e two parts are nearly equal in M. crassipess . In W. septentrionalis , the orientation of dehiscence, the vascular bundles and the size of the connective tissue vary in diff erent parts of the fl oral receptacle. Th e endothecium and endothecial-like cells form a ring that encloses the entire anther. Th e middle layer cells originate from both the outer and inner secondary parietal layers, and start to degenerate gradually at the microspore interphase stage or meiosis stage. Th e tapetum is of the secretory type, derived from the inner secondary parietal cells. Th e mature anther wall is composed of one epidermal, one endothecial, three to four middle layer(s) and one glandular tapetum. Only one epidermis, one endothecium, and the remnants of the middle layer and tapetum are left before anther dehiscence. Microspore tetrads appear as isobilateral, tetrahedral, decussate and T-shaped, produced by a modifi ed simultaneous microsporogenesis, which have evolved from the common ancestor of all Magnoliaceae. Our results support an ancestral state with stamens with non-marginal sporangia and the amount of sterile tissue exceeding the amount of sporogenous tissue, and evolutionary trends toward equalization of the amount of fertile and sterile tissue on the stamen.

Ontogeny of Different Tetrad Types in the Single Microsporangium of Mitrephora tomentosa (Annonaceae)

“…By contrast, in basal angiosperms, e.g., Magnoliaceae Juss. [22], Annonaceae Juss. [21], and Monimiaceae Juss.…”