Effects of Temperature, Moisture, and Oxygen on the Induction of Chromosome Damage in Seeds of Barley, Broad Beans, and Peas during Storage

Abstract

The effects of temperature, seed moisture content, and oxygen level on the production of chromosome aberrations during seed storage have been investigated. It has been found that an increase in any of these factors increases the rate of loss of seed viability and that any treatment which leads to a loss of viability also leads to an accumulation of aberrant cells in the embryo. Under most storage conditions, irrespective of the combination of factors which leads to loss of viability or the rate at which viability is lost, the relationship between percentage viability and mean frequency of aberrant cells in the surviving seed population is always the same. Under very severe storage conditions, which result in half-viability periods of about a week or less, however, the relationship is altered so that for any given percentage viability the mean frequency of aberrant cells in the surviving seeds is less than is typical of more normal storage conditions. In all treatments (except the most severe) the curve showing mean frequency of aberrant cells in surviving seeds against time eventually became asymptotic to a critical value peculiar to the species. It is suggested that these results are compatible with the hypothesis that under most storage conditions death of the embryo is the result of the accumulation of nuclear damage which is reflected in chromosome breakage; it is emphasized, however, that the visible chromosome breakage itself is probably not critical to the seed's survival. When the nuclear damage has reached a critical level, of which the frequency of aberrant cells is an index, the seed is no longer capable of germinating. Under very severe storage conditions, additional factors appear to be involved. An effort was made to test the frequently suggested hypothesis that chromosome aberrations produced during the ageing of seeds are the result of the accumulation of automutagenic substances. Attempts to demonstrate the presence of mutagenic substances in water-, ethanol-, and ether-extracts of fresh and aged seeds gave negative results. Aqueous extracts showed antimitotic and germination inhibitory activity, but this was the same from both aged and fresh seeds.