Cytological effects observed in plant material grown on irradiated fruit juices

Abstract

Germinating seeds of barley and onion were treated for different durations with fruit juices (orange and apple) irradiated with 200,000 rad of γ-rays, a dose suggested for the pasteurization of juices. One treatment, lasting 24 hr, was split into three fractions each lasting 8 hr given on consecutive days. Controls involving treatment for identical duration with unirradiated juices were kept in all cases. Mitosis was studied in root tips fixed 24 hr after the end of the treatment. The pH and total peroxide values of the juices were determined immediately before and after irradiation. Mitosis was normal in root tips treated with unirradiated juices, only two cells in about 1000 studied containing one break each. In treatments with irradiated juices, on the other hand, varying numbers of chromosome breaks, ranging from 1-15 per cell, were found. Fractionation of the 24 hr treatment led to an increase in the yield of chromosome aberrations. Growth of roots and shoots was stimulated in the 4 hr treatment and retarded in the 24 hr treatment. There was a slight decrease in the pH value and an increase in the peroxide content of irradiated juices. About 20 per cent of the chromosome breaks occurred at the region of the centromere resulting in both equal and unequal distribution of the centromeric chromomeres. The rarity of chromatid aberrations suggested that the first part of interphase may be the most sensitive period to the action of irradiated fruit juices. Since it is difficult to think of an effect caused by ionizing radiations in the meristematic cells of plants which does not have a close analogue among the responses of mammalian tissues, the radiomimetic properties of irradiated fruit juices deserve consideration with regard to the assessment of the wholesomeness of fruit juices pasteurized by irradiation. Studies on the effects of storage of irradiated juices on the expression of radiomimetic effe cts would, however, be needed before the practical implications of this study can be determined.