Alkaline Earth Elements and Zoospore Release and Development in Protosiphon botryoides

Abstract

O'Kelley, Joseph C., and Walter R. Herndon. (U. Alabama, University.) Alkaline earth elements and zoospore release and development in Protosiphon botryoides. Amer. Jour. Bot. 48(9): 796–802. Illus. 1961.—Cells of Protosiphon botryoides Klebs from depleted nutrient medium containing Ca were washed and resuspended in fresh complete medium with Ca; or in media with a Sr, Ba or Na replacement, respectively, for Ca; or in an equivalent CaCl2 solution or deionized water. Zoospore release was observed in these media upon illumination following a 12-hr dark period. Free zoospores were less abundant in Sr-, Ba- and Na-replacement media than in the Ca medium. Zoospore production and release also were depressed in solutions of only CaCl2 and in deionized water. In the Sr and Ba media, zoospores were formed but not released from the parent cell, as a rule; some zoospores were released in mass within a gelatinous vesicle which did not liquefy and set the zoospores free; these zoospores lost motility and continued development in Sr, producing characteristic, spheroidal clusters of aplanospores. In the Na medium, protoplasmic cleavage preceding zoospore formation was severely inhibited. A study of the reversibility of Sr inhibition of the zoospore-release mechanism revealed evidence of reversion 12 hr after replacement of Sr by Ca. Walls of cells produced in Ca are rich in ruthenium red-positive materials, whereas cells produced under conditions of Sr replacement lack these materials. The significance of these findings in relation to the Ca requirement of other algal species is discussed.