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Influence of Certain External Factors on Spore Germination in the Myxomycetes

Robert F. Smart
American Journal of Botany
Vol. 24, No. 3 (Mar., 1937), pp. 145-159
Stable URL: http://www.jstor.org/stable/2436830
Page Count: 15
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Influence of Certain External Factors on Spore Germination in the Myxomycetes
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Abstract

Seventy species and varieties of Myxomycetes representing all types of fruiting bodies known to this group of organisms were studied in an effort to correlate the relation of external factors to spore germination. The present paper is a report on the influence of such factors as (1) the nutritional condition of the medium, (2) the hydrogen-ion concentration of the medium, (3) temperature, and (4) the mutual effect of spores sown in mass as indicated by single spore and multi-spored cultures. Though the spores of most Myxomycetes are known to germinate in pure distilled water or in tap water, the results of the present investigation show conclusively that the percentage and rate of germination are promoted to a greater degree when the spores are sown in weak decoctions of natural substrata such as rotting wood and bark of various trees, decaying leaves, worm casts, hay, humus from mixed woods, etc. The pit range in which the spores of all species studied germinate is between pti 4.0 and 8.0. The spores of Fuligo septica germinate in all solutions ranging from pit 2.0 to 10.0, and the spores of Physarum Serpula germinate in all solutions from pH 2.0 to 8.5. The optimum pH for the germination of the spores in all species studied falls between pit 4.5 and 7.0, with Physarum Serpula and Badhamia rubiginosa germinating better at pH 4.5 and Physarum didermoides at pH 7.0. The optimum temperature for spore germination in all species tested ranges from 22⚬ C. to 30⚬C. with most species germinating more readily at the higher temperatures of the optimum range. The temperature range for germination is from 2⚬C. to 36⚬C. At 10⚬C. or lower and above 30⚬C. the rate and percentage of germination are greatly reduced. Temperature not only affects the percentage and rate of germination, but the method of emergence of the protoplast from the spore membrane as well. Spores which germinate typically by the pore method as in Enteridium Rozeanum are caused to merge into the split type as exemplified by Fuligo septica by holding the temperature of the culture above the maximum temperature for a time and then lowering the temperature to the optimum for the species being tested. Evidence is presented to show that some "autocatalytic" agent is probably freed by the spores of some species to stimulate spore germination. Single spores of species which otherwise failed to germinate can be induced to do so by sowing them in a medium filtered off of a culture in which many spores have been sown and allowed to germinate.

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