The responses to shade of seedlings of very small-seeded tree and shrub species from tropical rain forest in Singapore

Authors

  • D. J. METCALFE,

    1. Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK and ,
    2. Department of Botany, National University of Singapore, Lower Kent Ridge Road, Singapore 0511
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  • P. J. GRUBB

    1. Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK and ,
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Abstract

1. Newly germinated seedlings of six tree and shrub species with very small seeds (31–460 μg dry mass), one light-demanding and five shade-tolerant at the stage of establishment in the wild, were grown for 5 months in neutral shade houses with 0·5, 1, 3·5 and 7·5% daylight.

2. The ratio of yield in 7·5% to that in 1% was 8:1 for the light-demanding Melastoma malabathricum but only 2:1 for the confamilial shade-tolerator Pternandra echinata. The Pternandra, Urophyllum hirsutum, Ficus chartacea, Ficus grossularioides and Pellacalyx saccardianus showed a graded series of responses to irradiance, generally consistent with their apparent demands for light in the wild. In contrast, survival of very deep shade was not clearly related to light demand in nature.

3. The results support the conclusion drawn from observational studies that large seed size is not primarily adaptive in resisting shade but in resisting the associated risks of burial by litter, desiccation during dry spells, uprooting by birds and other kinds of damage by animals or falling debris.

Footnotes

  1. Present address: CSIRO Tropical Forest Research Centre, PO Box 780, Atherton, Queensland 4883, Australia.

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