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The Stability of the Growth Pattern of Young Apple-trees under Four Levels of Illumination

D. H. MAGGS
Annals of Botany
New Series, Vol. 24, No. 96 (OCTOBER 1960), pp. 434-450
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/42908583
Page Count: 17
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The Stability of the Growth Pattern of Young Apple-trees under Four Levels of Illumination
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Abstract

As part of a programme on the characterization of the growth pattern of the apple-tree, uniform 1-year-old plants carrying two new shoots were grown for a season under 100, 78, 41, or 24 per cent, natural light. Weights of leaf, new stem, old stem, and root were determined by sampling on 6 occasions. The dryweight increments over the whole season ranged from 17 to 151 g. of which, in full light, 22 per cent, was leaf and 22 per cent, was root; in deep shade, 32 per cent, was leaf and 8 per cent, was root; and under all conditions 56-60 per cent, was stem. These percentages were the cumulative result of current rates of growth of leaf, stem, and root over the whole growing period. The rates were not constant relative to one another, but the much greater quantity of growth made over the period 100-200 days from bud-break swamped earlier differences. All treatments showed the same basic pattern of growth with minor differences increasing with the intensity of shading. These differences are discussed in relation to utilization of reserves and the demands of the various regions of the plant. The response to shading was analysed into the effects of reduced light interception, increased leaf dispersion, increased leaf proportion, reduced length of growing season, and lighter leaf weight at the beginning of the 20-leaf stage. The result of these factors was a doubling of the growth expected in the absence of response. It was concluded that the pattern of growth is stable, and the conditions for the perpetuation of such stable patterns as a necessary qualification for tree growth are briefly discussed.

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