Flower Bud Atrophy in Baccara Roses

Changes in gibberellin content and of the production of ethylene in the two upper shoots of roses were measured as affected by decreasing temperature and light intensity, factors which encourage flower atrophy. Decreases in temperature or light intensity to the whole plant reduce the endogenous content of gibberellin in the leaves of the two shoots. The decrease is more rapid and occurs earlier in leaves of the second shoot from the top, where “blindness” is more common. There was also a drop in the gibberellin content, when individual shoots were shaded, although the decrease was more moderate. A lowered light intensity reduced the production of endogenous ethylene by the two shoots, but in the second shoot this production increased after a number of days, before atrophy of the flower bud took place. It is suggested that gibberellin participates in the endogenous control of rose flower development, and the possibility is discussed that it acts by directing the translocation of metabolites to the flower bud.