Flower-bud formation and shoot growth in apple as affected by shoot orientation

In the spring of 1965, 20 one year old Golden Delicious trees planted in pots were placed horizontally and 20 were kept in the vertical position. At the time of growth termination, half of the horizontal trees were placed vertically and half of the vertical trees were shifted to the horizontal position. In December, all trees were returned to the upright position. In 1966 the treatments were repeated. In 1965 and 1966 flower-bud formation increased in the trees kept horizontal throughout the season; in 1966 flower-bud formation also showed a marked increase in the trees placed in the horizontal position for only half of the season. In the first year growth was considerably reduced in the trees kept horizontal during the growth period. In the second year growth was weak and irregular in relation to treatments. Data on the time of flowering indicate that flowering was advanced slightly in trees held in the horizontal position for the whole or only half of the season. It is concluded that in all probability tree orientation in relation to gravity has an influence on the intensity of flower-bud formation and the time of flowering independent of its effect on growth vigour.