The germination of mould spores at controlled humidities

Observations have been made on the influence of humidity on spore germination, the rate of elongation of the germ tubes and the production of asexual and sexual fructifications of various mould fungi. The humidity range at which the different species developed is given. Some of the Mucorales and certain pathogenic moulds required high humidities (100-93%) for their successful growth. Penicillium spp. had a wider humidity range (100-80%). Aspergillus spp. were able to grow under conditions of even more restricted moisture supply. Spores of members of the A. glaucus group, particularly, germinated and developed at humidities as low as 70-64%. The reasons for variations in the humidity range of the different species are discussed. The influence of the supply of nutrients on spore germination and subsequent mould growth is considered.