Ignatov, M.S., U.N. Spirina, E.V. Maslova, O.V. Ivanov &E.A. Ignatova. On the leaf development in Oedipodium griffithianum (Oedipodiopsida, Bryophyta)

Arctoa (2015) 24: 431-451

doi: 10.15298/arctoa.24.35

Leaf development in Oedipodium griffithianum was studied based on herbarium and living material, using microscopic observations of plants at different stages of development and series of sections. It turned out that the apical cell may lose its bifacial structure, thus the leaves develop the bilaterally symmetric areolation pattern, similar to that seen in Oedipodium protonemata. Young leaves never have zones of small, actively dividing cells in their basal parts, similar to those seen in leaves of most other mosses. Contrary to the common pattern of leaf forming by means of groups of 4´4, 4´8, 8´8 cells (descending from a single cell), the leaf development in Oedipodium has an opportunistic model of growth, where the cell divisions proceed randomly throughout the lamina, being not obviously correlated one with another in time, nor having a definite direction and position where it is performed. The leaves in Oedipodium are bi- to multistratose at very early stages of growth, not overlapping each other by their corners and only later develop the basal decurrency. The similarity and possible affinity of Oedipodium with the Upper Permian fossil mosses of Angaraland are discussed.