Welwitschia mirabilis: Fine Structure of the Germinating Seed III. The Quiescent Gametophyte

Abstract

Summary More than half of a gametophyte cell's volume is taken up by protein (1–9 μm in diameter) and lipid bodies (0.2–0.7 μm). In an almost obscure cytoplasm a few amyloplasts are the most obvious organelles. Ribosomes are present as unaggregated monosomes. No ER or dictyosomes are observed. The polymorphic nucleus is scalloped, compact and dense. Fibrous, presumably proteinaceous, inclusions ramify profusely throughout nucleoplasm and nucleolar lumina. Globoid inclusions are rare and most have no outer envelope; the bounding membrane of those that do does not appear to have a unit structure. Some globoids are pitted. Protein body matrices are mottled with non-uniform electron transparent areas, suggesting digestion prior to germination. Lipid bodies appear to be surrounded by a halfunit membrane. Most striking effect of imbibition is increased clarity of membranes and disappearance of fibrous inclusions from the nucleus.