title: A sporulation-inhibiting substance from vegetative thalli of the green alga Ulva mutabilis, Føyn.
abstract: The formation of zoospores or gametes in the green alga Ulva mutabilis Føyn is shown to be blocked by some substance(s) which can be extracted into fresh growth medium from a suspension of living thallus fragments. The inhibiting power of thallus extract is greatly reduced by heat treatment, but heat-stable components may also be present since active extracts can be produced by boiling algal thalli in growth medium. Separation of the extract on a Sephadex G25 column gave two peaks of inhibitory activity which corresponded with the fraction's content of high molecular carbohydrate (probably ulvin). Various mono- and disaccharides were inactive. In order to block meiotic zoospore formation completely, thallus extracts must be applied at least 6-7 h prior to the cells' visible entry into the meiotic prophase.
authors.affiliation: Zoological Institute, University of Oslo, Blindern, Post Box 1050, Oslo-3, Norway.
authors.forename: G
authors.initials: G
authors.lastname: Nilsen
authors.forename: O
authors.initials: O
authors.lastname: Nordby