Regeneration in Fucus vesiculosus L. has been studied using light microscopic, autoradiographic, and electron microscopic techniques.
Segments of vegetative tissue from mature Fucus plants were cultured in sea-water. Histological sections of this material were prepared at various intervals up to eight months of culture in order to follow the development of adventitious branches from the wound surfaces. In both cultured segments and whole, naturally wounded plants, existing filament and cortical cells in the midrib region of wound surfaces differentiate a new epidermis. Several loci on this new epidermis undergo increased rates of periclinal division to produce structures which are morphologically very similar to normal Fucus embryos and which ultimately acquire apical grooves and apical cells and become flattened in the manner of normal vegetative thallus branches.
Thin sections of regenerating tissue segments were prepared at intervals up to thirty days of culture and examined with the electron microscope. Soon after wounding, a new cell wall is formed within existing walls of filament cells located adjacent to wounded cells. Plastids and Golgi bodies appear to be involved in the production of some of the new wall material, and an effective barrier to damage is produced by cells which are exposed during wounding. One to two weeks after wounding, these cells expand near their outer end by a process in which the new cell wall protrudes through the old wall. The expansion and subsequent cellular divisions produce a layer of cells at the wound surface which differentiate into new epidermal and cortical cells similar to equivalent cells in unwounded plants.
A radioisotope of sulfur was used, by autoradiography, to determine changes in fucoidan production at the wound surface. Fucoidan is synthesized within 6 hours after wounding and concentrated near filament cross-walls which separate wounded and unwounded cells. Autoradiographic experiments utilizing radioactive thymidine failed to indicate the location or time at which cell divisions are Initiated during the formation of new epidermis.
An apparatus was designed which permitted the continuous culture of mature Fucus plants in an artificial inter tidal environment.