STUDY ON THE GROWTH AND DEVELOPMENT OF TH E COMMON ASH, FRAXINUS-EXCELSIOR, CULTIVATED UNDER CONTROLLED CONDITIONS

Under controlled conditions (14 h light : 10 h dark; 27 +/- 1 and 19 /- 1 degrees C), common ashes, Fraxinus excelsior L., display a rhythm ic growth. The average duration of the first growth flush is 106 days, followed by a phase of nonlengthening from 9 to 11 months, depending on individuals. This rhythm was materialized in the shoot organization . The end of each growth stage was characterized by progressively shor ter internodes and by the presence of scales around the bud. Histologi cal studies reveal that no leaf is preformed at the embryo stage and t hat the meristem activity carried on after the stem growth stops. The common ash growth rhythm is therefore not the direct consequence of th e arrest of meristem activity. The nonlengthening phase is an apparent resting phase during which the initiation of new leaves carries on.