Caffeine, caffeine derivatives and chromosomal aberrations I. The relationship between ATP-concentration and the frequency of 8-ethoxycaffeine-induced chromosomal exchanges in Vicia faba

By exposing plant root tips to aqueous solutions containing 0.75 - 1 X 10-2M 8-ethoxycaffeine (EOC), a high frequency of “subchromatid” and chromatid exchanges are produced. The exchange reaction is induced during prophase and late interphase and can be completely suppressed by anoxia and by inhibitors of oxidative phosphorylation. We have studied the relationship between the frequency of EOC-induced exchanges and the ATP level in root tips of Vicia faba. Treatments were performed on intact lateral roots (cytological studies) and on excised main root tips (ATP determinations). The concentration of ATP in the roots was increased by pre-treatments with adenine or adenosine and decreased by exposing the roots to sodium azide. No exchanges were produced by EOC when the concentration of ATP was reduced to 40 % of the normal. An adenine-induced 70 % increase of the concentration of ATP resulted in a frequency of exchanges which was three times higher than the frequency obtained at a normal level of ATP. Pre-treatments with adenine counteracted the reduction of ATP concentration and EOC-induced exchange frequency which is obtained in the presence of sodium azide.