The Effect of Relative Humidity and Light on Air-Dried Organisms

S ummary : The effect of relative humidity (RH) and inositol on the lethal action of artificial sunlight has been studied. The lethality of these radiations is shown to be strongly dependent on RH provided the intensity of the light is not too great. A critical region between 55 and 65% RH exists in which there is an abrupt change in the sensitivity of airborne cells to all wavelengths tested. Not only does the death rate change suddenly in this RH region but so also does the rate of mutant production. This critical RH region corresponds to the RH level at which bound water is removed from the nucleic acid bases and it is suggested that these water molecules are able to prevent lethal excitations or migration of excitation energy. Inositol is shown to prevent radiation damage and, because of its structure, it is assumed to replace water in the dried cells. Some ramifications of these findings with respect to the maintenance of cell integrity are discussed.