Distributions of the growth rate of the germ tubes and germination time of Penicillium chrysogenum conidia depend on water activity

The effects of water activities for sporulation (awsp) and germination (awge) on the distributions of the growth rate of the germ tubes (μ) and the germination time (tG) of Penicillium chrysogenum conidia were determined by monitoring the length of the same germ tubes throughout the experiments automatically. No relationship between the individual tG's and μ's could be established. Irrespective of the water activity for germination, μ was greater and tG was less for conidia produced at 0.95awsp than that at 0.99awsp. At 0.99 awge the mean and the standard deviation of tG were smaller than those obtained at 0.95awge. At 0.99awge, normal distributions for μ and tG were exhibited, but not at 0.95awge. The cumulative frequencies were used to reconstruct the germination curves. Great differences in the percentage of spores capable of germination (PG) and in the mean germination times between conidia produced at 0.95awsp and at 0.99awsp were clearly exhibited at 0.95awge, thus demonstrating the paramount influence of sporulation conditions on germination kinetics.