?????????????????????? ?????????????????? ???????????????????????????? ???????????????????? ?? ???????????????????? ?????????????????????? ?????????????? Linum usitatissimum, ???????????????????????? ???????????????? ???????????? ?????? ?????????????? ???????????????????????????? ?? ????-?? ??????????????????. ?????????????????????? ?????????????????????? ?????????????????? ???????????????????????????? ???????????????????? ???? ?????? ?????????????????? ?? ???????????? ???????????????????? ?????????????????????? ??????????????. ?????????????????????? ???????????????????????????? ?????????????????? ???????????????????????? ???????????????? ???????????????? ????????????????.

????????i?????????? ????i???? ???????????????????????????? ??????????????????i ?? ??????????????????i ??i????????????????????? ??????????i?? Linum usitatissimum, ??i???????????? ??i?? ??i???????? ?????? ???????????????? ??????????????i?????????????? ???? ????-?? ??????????i??????????. ?????????????????????? ????????????i?????? ??i???????????????? ???????????????????????????? ??????????????????i ??i?? ?????? ??????????i?????????? ???? ????????i?? ???????????????????? ??i????????????????????? ??????????i??. ???????????????????? ??i????????????????i ??????????i?????? ??????i????i???????? i??????????i?? ????????i?????? ????????????.

We investigated changes of the ribonuclease activity in ontogenesis of cotyledon leaves Linum usitatissimum irradiated by different doses of acute X-ray and UV-B radiation. The dependence of the ribonuclease activity increase on the doses and the stages of ontogeny of cotyledon leaves is found. Some hypothetical mechanisms of radiation induction of senescence are considered.