Developmental potentialities of leaf primordia of Osmunda cinnamomea. V. Toward greater understanding of the final morphogenetic expression of isolated set I cinnamon fern leaf primordia

Abstract

Arguments supported by the data given favor the interpretation that (1) adaxial buds are produced by Osmunda cinnamomea leaf primordia; (2) they are produced in addition to the leaf which bears them; (3) they are to be considered adventitious rather than axial; (4) they are of a strictly foliar rather than cauline nature; and (5) they are produced only when a primordium has been isolated from the rest of the shoot system.In O. cinnamomea, the bud, which is formed in addition to the leaf primordium, is evident at the end of the fifth to sixth week on singly cultured P3 and P4 leaf primordia. With younger leaf primordia, e.g. P2’s, often the only evidence of bud formation at the termination of an 8-week culturing period is the presence of the new apical meristem (the SAM′). In the case of older primordia, however, such as P4’s, whether cultured singly or isolated from the shoot apical meristem (SAM) on a plug of tissue, the bud is observed to consist of the SAM′, and from one to seven new leaf primordia. At this stage, the meristematic outgrowth can be considered to be in the true bud state. If the culturing period is extended beyond 8 weeks, the SAM′ develops from the bud state into the plantlet state bearing miniature juvenile leaves, and roots.