Some Aspects of the Chemical Protection against Radiation Damage to Vicia Faba Chromosomes.

INCE 1933 when CRABTREE and CRAMER first reported that anaerobiosis S decreased the effects of radium treatment on cancerous tumors, there have been numerous reports on the recovery of living cells, both animal and plant, from the effects of ionizing radiations. LEA (1945) and GRAY (1952) have reviewed the literature concerning these effects. An excellent area for the study of these effects has been the production of chromosomal aberrations in plant tissues. THODAY and READ (1947) discovered that low oxygen tensions reduced the amount of chromosomal aberrations in actively growing Vi& faba roots ; GILES and RILEY ( 1950) found a reduction in the chromosomal aberrations of Tradescantia microspores if the microspores were irradiated in nitrogen; and HAYDEN and SMITH (1949) showed a reduction of chromosomal aberrations in barley seed irradiated in vacuo. The above work, however, is of theoretical interest only, as it seems impractical to keep aerobic organisms in oxygen-free atmospheres for lengthy periods of time. Thus much of the recent work has centered on tihe method of reducing the internal cellular oxygen tension by chemical means. Chief among the chemicals that do this are : sulfhydryl compounds, alcohols, glycols, and sodium hydrosulphite (BURNETT et al. 1951). In light of this, MICHAELSON (1952) was able to decrease the amount of chromosomal aberrations caused by X-rays in Tradescantia root tips by pretreatment with glutathione solutions. And RILEY (1952) was able to decrease the number of aberrations in onion roots by treating with sodium hydrosulphite. Ostensibly, these chemicals work by reducing the number of active radicals formed in irradiated water as postulated by WEISS (1944, 1947) and thus they can protect against the " indirect effect " of ionizing radiations as first described by DALE (1943). This present paper is concerned with the protective effects of some of the chemical reducing agents against chromosome damage in Vicia faba. The study is divided into three parts ascertaining 1) whether or not the agents can reduce damage if given to resting cells in the seed ; 2) whether or not there is an additional effect of the chemicals beyond that of simple oxygen removal ;