PROTONEMAL MORPHOGENESIS OF THE MOSS TETRAPHIS-PELLUCIDA HEDW IN CULTURE AND IN THE WILD

In axenic culture, the protonemal filaments of Tetraphis pellucida derived from either spores and gemmae, or excised stems and leaves, share a mixture of attributes of chloronemata and caulonemata. Indirect immunofluorescence reveals that the tip cells contain cortical and endoplasmic arrays of microtubules at interphase, and phragmoplasts associated with cell plate formation, but pre-prophase bands are absent. Protonemal plates originate from the same sites as filamentous protonemal side branches or directly from young gemmae or excised stem fragments. These plates have a cylindrical base, the latter producing a single gametophore bud, and a unistratose lamina. The gametophores produce gemma cups in culture with the vegetative life cycle taking approximately 28 d. Gibberelhc acid (GA3) has no visible effect on protonemal morphogenesis whereas the auxin naphthalene acetic acid (NAA) suppresses plate and side branch formation. In the presence of kinetin the plates are callus-like and produce supernumerary buds. Abscisic acid (ABA) induces malformed plates and filaments with swollen cells, similar to those found in ageing cultures. Rhizoids are produced in abundance from gametophores and protonemal plates in nature hut were never seen in culture. In the wild, rhizoids produce numerous protonemal plates and occasional gametophore buds. The former are the main source of new shoots. The filamentous protonemal phase in nature mainly comprises upright filaments containing one or more abscission cells. The protonemal plates in Tetraphis are homologous with those in the allied genus Tetrodontium but are very different from those in Diphysctum and Sphagnum. Differences between culture and nature are attributed to lower nutrient levels and irradiances in the wild. © 1992 Annals of Botany Company.