ABSTRACT
From the main groups of hormones in higher plants only auxins and cytokinins are documented as natural signal substances in mosses. Not only do both hormone groups exist in mosses, but they also have basic functions in the regulation of normal development. Among the three groups of growth regulators abscisic acid and ethylene have been identified in moss protonema. Protonema development starts in the same way from spores, single cells, cells from protoplasts, or as regeneration products from small pieces of tissue. They usually produce a single filament from one cell. However, a few primary filaments can originate from spores, one of which is a small primary rhizoid. Several effects of auxins on moss development have been known for more than 30 years. These include inhibition of protonema growth, stimulation of rhizoid formation, transformation of buds to filaments, torsion of young stems, and complete suppression of leaves on gametophores.
