Action du rayonnement X sur la croissance des cellules internodales de l'algueChara vulgaris L

Summary We have irradiated internodal cells ofChara vulgaris L. at different doses of X rays from 50 to 600 kr. These internodal cells never show mitotic activity and are of plasmodial constitution. When elongations are measured 7, 14 and 21 days after irradiation, we observe increased clongations from 0 to 150 kr. Then, elongations diminish when doses increase from 150 to 600 kr. This absence of proportionality between doses and biological effect is believed to be in relation to the increased amount of certain enzymes liberated by X rays.