Portal de Periódicos da CAPES

Spore wall development in the liverwort, Haplomitrium hookeri

1986; Canadian Science Publishing; Volume: 64; Issue: 6 Linguagem: Inglês

10.1139/b86-159

1480-3305

Roy C. Brown, Betty E. Lemmon,

Lichen and fungal ecology

Spore wall development in Haplomitrium hookeri (Calobryales) is initiated while the sporocyte is in meiotic prophase. Extracellular exine precursor material is preferentially deposited within the sporocyte wall in a highly specific pattern that is predictive of the pilate – retiplilate ornamentation of the mature exine. Tripartite structures characteristic of hepatic exine are polymerized in exine precursors that become elevated on stalks of projecting cytoplasm. Plasma membranes of the cytoplasmic projections become extremely contorted and membrane displacement eventually isolates stalks from cytoplasm. An inner multilaminar layer is formed by apposition of tripartite lamellae. By the late tetrad stage the distinctive wall layers of the mature spore are present; capitula of heavily coated lamellae that cap projections of the continuous foveolate layer, a multilaminar inner exine layer of approximately 20 alternating light and dark bands, and a fibrillar intine. All but the intine become acetolysis resistant indicating the presence of sporopollenin. During maturation the sporopollenin framework of the capitula and foveolate layer become obscured by the addition of electron-dense, non-acetolysis-resistant materials. Based on spore wall micromorphology, Haplomitrium hookeri appears most closely allied to certain of the Metzgeriales, e.g., Pallavicinia.