STUDIES ON PENICILLIUM CHBYSOOENUM THOM, IN RELATION TO TEMPERATURE AND RELATIVE HUMIDITY OF THE AIR

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Abstract
SUMMARY.: (i) Germination and viability of conidia of P. chrysogenum.1. Conidia were found to germinate in moist air on glass in atmospheres ranging in relative humidity from 100 to 81 per cent, and in temperature from 1 to above 35 but below 40° C, with the optimum temperature lying near 25° C.2. At constant temperature the latent period of germination generally shortened as the relative humidity of the air rose, and when liquid or gaseous water was replaced by 2 per cent, malt agar.3. The latent period of germination in water of conidia from old cultures (120 or 210 days old) tended to be longer than that of conidia from young cultures (3 days old). Variations in the intrinsic characters of the conidia caused irregularity in the results which was not shown when the conidia were germinated on 2 per cent, malt agar.4. Conidia were exposed for periods up to 136 days to atmospheres of temperatures 20 and 30° C. and of relative humidities 72–6, 26 and 0 per cent, (approx.). The percentage germinations in water and on agar within 24 hours, and in water, after submersion for periods up to 216 hours, were determined. No correlation was found between the length of exposure of conidia to various atmospheres and the ultimate germination in water, though during the first 24 hours of germination on agar and in water increased length of exposure generally resulted in decline in percentage germination.5. Exposure of conidia to atmospheres of 0–100 per cent. R.H. and 1–100° C. showed that conidia possess considerable powers of resistance to heat for temperatures up to 30° C. in atmospheres of relative humidity 0 and 26 per cent, and can live in the latter for more than 129 days; at temperatures above 40° C. the time required to kill the conidia at the same temperature falls with rise in relative humidity, and at the same relative humidity falls with rise in temperature.

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