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The Reactions of Claviceps purpurea to Variations of Environment

Adelia McCrea
American Journal of Botany
Vol. 18, No. 1 (Jan., 1931), pp. 50-78
Stable URL: http://www.jstor.org/stable/2435724
Page Count: 31
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The Reactions of Claviceps purpurea to Variations of Environment
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Abstract

1. The studies of Claviceps purpurea herein reported have shown that under controlled experimental conditions, both physical and physiological, an unprecedented mycelial growth of this fungus can be obtained in saprophytic culture. 2. A nutrient synthetic agar was selected and used as a standard medium for securing a maximum mycelial development of this organism. 3. Of the stimuli tried, oxygen was found to have the greatest effect upon mycelial growth, also for increased size of the conidia and for earlier appearance and greater size of the pseudosclerotia. 4. The optima of heat, light, and moisture were determined, and reactions to other physical stimuli such as mechanical pressure and aëration are reported. 5. Sunlight produces a marked chromogenic effect upon the mycelium of this fungus by causing an intense coloration, Carrot red (R.). This greatly exceeded the faint trace of color produced by means of any other stimulant tried. 6. It has been shown in this and in a previous work by the writer (23) that the favorably stimulating rays for color production lie in the blueviolet region of the spectrum, and that the ultra-violet rays, although not markedly injurious to C. purpurea, have no special effect upon growth or reproduction. 7. Light has been found to increase the ergosterol content of the mycelium of this fungus growing in saprophytic culture. 8. No true sclerotia have been developed in culture, but the production of definite mycelial knots herein designated as pseudosclerotia is a constant phenomenon in properly nourished mycelium. It is suggested that these structures are possibly primordia of true sclerotia which have failed to reach their full development through lack of some essential conditions. 9. A partially sclerotioid mycelium is readily obtained on standard medium. Such tissue, however, does not develop the morphological characteristics of true sclerotia nor does it pass through a stage analogous to the stroma formation and subsequent germination of the natural sclerotia. 10. The experiments with paired cultures give strong indication of homothallism in C. purpurea. 11. It has been demonstrated for the first time that this fungus develops in saprophytic culture the three chief active principles which are characteristic of the extracts made from the natural sclerotia; viz., ergotoxin, histamine, and tyramine; and that they are obtainable to an extent sufficiently large to be of economic significance. 12. Field demonstrations have shown it to be improbable that parasitic culture of C. purpurea on a large scale would be desirable, under prevailing conditions in Southern Michigan.

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