Abstract—Red light can promote (a) the straightening of the curvature (Phaseolus vulgaris, Pisum sativum) (b) the formation of a loop (Phacelia tanacetifoliaandPicea 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 ph