Studies of the effects of stem poise and bending in young and older fruit trees showed clear responses to gravity in the outgrowth of lateral buds, terminal shoot growth, and cambial activity. A distinctive seasonal pattern in the outgrowth of shoots was found in upright maiden apple trees. This pattern was also evident in trees grown in the inclined, horizontal, and inverted positions, but was modified by the effects of gravity. These effects included changes in the symmetry of bud growth about the axis, changes in the relationship between growth in different portions of the trunk, and tropistic reactions. Using a stem-splitting technique, shoots were induced to grow out from buds on the under sides of horizontal branches, and in an experiment with bent stems rotated about a horizontal axis the outgrowth of "gourmand" shoots was shown to be an effect of bending, rather than a response to gravity. Bending also affected bark anatomy. Effects of gravity on flowering in apple trees were far less clear. In some young non-fruiting trees, inclination and bending of the trunk resulted in increased flowering, but in other young trees, and in older orchard trees, no effects of gravity on flower bud formation were observed. It was concluded that a horizontal or pendulous branch poise in bearing apple trees is mainly a result of fruiting rather than a cause of fruitfulness. It was suggested that the stimulative effects of gravity on the flowering of inclined apple shoots may be obscured by countervailing factors such as the inhibitive eff~cts of the presence of fruits on flower bud formation, effects of vegetative growth, and effects of variety. From the practical aspect, branch bending techniques are likely to have their greatest effects in inducing precocious flowering in vigorously growing trees of shy-bearing varieties.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:594256 |
| Date | January 1963 |
| Creators | Mullins, Michael Gordon Charles |
| Publisher | University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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