The Effect of Gravity on Root Emergence from Cuttings of Some Tree Species

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Abstract
Poplar shoots trained horizontally and normally growing shoots were used to compare the effect of horizontal and vertical orientation in summer on the subsequent rooting of terminal cuttings; a significantly greater number of preformed roots emerged from cuttings of vertical shoots. This difference in rooting ability may be due to the lower concentration of indolyl-acetic acid in the upper than in the lower half of horizontal poplar stems as shown by Leach and Wareing (1967). Decapitation of a series of these poplar cuttings ( Populus × robusta Schn. ) showed that wound-root production was influenced by the larger terminal buds on vertical than on horizontal shoots. From a comparison of horizontal and vertical storage of apple rootstock cuttings at 45 °F in the autumn, 29 per cent more of the horizontal cuttings than the vertical ones had a basal callus in the following February. Of these cuttings which made satisfactory shoot growth (over 5 cm) in the following summer, horizontal cuttings exceeded vertical ones by 80 per cent; a result which was correlated with root production. In a second experiment with M II apple rootstocks in which cuttings were both stored and grown at the same angle more roots occurred on cuttings placed horizontally rather than vertically, and this orientation also induced the rootings of a greater proportion of leafy Worcester Pearmain apple cuttings.

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