INFLUENCE DE LA LUMIÈRE SUR LES MOUVEMENTS DE NUTATION DES PLANTULES

Abstract— Red light can promote (a) the straightening of the curvature ( Phaseolus vulgaris, Pisum sativum ) (b) the formation of a loop ( Phacelia tanacetifolia and Picea abies ) or (c) the induction of a curvature which does not occur in the darkness ( Lactuca sativa ). Thesc red-light induced movements could be reversed by following each brief red exposure with short irradiation by far-red light. These reactions are controlled by the phytochrome system.
On the other hand, exposure to far-red and blue light during a long period can induce other movements:
(a) The light re-opens the hook which has been closed by red radiation ( Lactuca sativa ).
(b) The light induces the straightening of the dark-induced curvature ( Phacelia tanacetifolia ). These facts may be due to an unknown property of phytochrome or to the action of another photoreceptor.