Studio Cito-Istologico sulle Curvature Prodotte dalle Radiazioni Ultraviolette in Apici Radicali diScilla ObtusifoliaPoir

Abstract

Summary The Author studies the cyto-histological effects produced by ultraviolet radiations on root tips of Scilla obtusifolia Poir. and finds that the most frequent effects are negative curvatures, i. e., the ones causing the withdrawal of the root tip from the irradiating source. The cyto-histological effects produced by ultraviolet radiations are as follows: 1) The root tip is normal; 2) The zone of elongation is normal too; only the dermatogen, which is limited by the piliferous layer on the irradiated side, is replaced by a necrotic tissue on the non irradiated side; 3) In the piliferous layer, on the irradiated part the epidermis produces a lot of root hairs; the cells of the cortex are very large, elongated and greatly vacuolised; the stele, at the level of the piliferous layers looks normal; on the contrary the cells of the cortex on the opposite side of the irradiation-source are degenerating and the epidermis seems to be necrotic. If irradiation time is very long and fixation is made 14–24 days ...