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Seed dormancy and germination in Rottboellia exaltata

Published online by Cambridge University Press:  27 March 2009

P. E. L. Thomas  and
J. C. S. Allision
P. E. L. Thomas
Affiliation:
Henderson Research Station, Private Bag 222 A, Salisbury, Rhodesia
J. C. S. Allision
Affiliation:
Department of Agriculture, University of Rhodesia, Salisbury, Rhodesia
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Summary

Eight laboratory and three field experiments were made on seed of Rottboellia exaltata, a grass weed of maize.

Seed stored dry, indoors or outside, either on the soil surface or buried, was unable to germinate for 5–6 months after being shed. Its ability to germinate then increased rapidly, reaching 50–70% by 8–9 months, and, indoors, continued to increase slowly to reach 80% by about ayear after being shed. Periodic wetting hastened the increase in ability to germinate of seed kept indoors or on the soil surface, but slowed down that of buried seed. When germination was tested with husks removed the ability of the caryopses to germinate began increasing soon after seed was shed, reaching 60% after 3 months and, later, up to 85–95% in different experiments. Dehusking was only effective if the inner bracts as well as the outer husks were removed, but pricking a hole through the husk and inner bracts had an effect similar to removing them. Germination decreased when in-husk seed was immersed in water before being incubated, whether this was done in air or oxygen, or in light or light/darkness, and increased again when seed was dried or its husks pierced before incubation. Wetting and drying in light, but not in darkness, increased germination of in-husk seed, and constant high temperature enhanced the increase.

When seed was buried in soil at a range of depths between 2·5 and 30 cm, the more deeply situated seed remained viable for longer than that near the surface, but there was little viable seed at any depth after 4 years. Many seedlings emerged in the first two rainy seasons after shedding of seed was prevented in an infested field which was ploughed each dry season, but by the third season the number of seedlings had greatly decreased and in the fifth season no seedlings emerged. Most of the seedlings emerging in maize fields came from seeds situated near the surface of the soil.

Type
Research Article
Information
The Journal of Agricultural Science , Volume 85 , Issue 1 , August 1975 , pp. 129 - 134
Copyright
Copyright © Cambridge University Press 1975

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