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Hard-seededness and seed bank dynamics of six pasture legumes

Published online by Cambridge University Press:  19 September 2008

L. Russi*
Affiliation:
International Center for Agricultural Research in the Dry Areas (ICARDA), PO Box 5466, Aleppo, Syria
P. S. Cocks
Affiliation:
International Center for Agricultural Research in the Dry Areas (ICARDA), PO Box 5466, Aleppo, Syria
E. H. Roberts
Affiliation:
Department of Agriculture, University of Reading, Earley Gate, PO Box 236Reading RG6 2AT, UK
*
* Present address and correspondence Istituto di Miglioramento Genetico VegetaleUniversita di Perugia, Borgo XX Giugno, 74 06100 Perugia, Italy

Abstract

Six pasture legumes, common in Syrian grasslands, were investigated. Medicago orbicularis and M. rotata had the largest number of hard seeds, with >90% still hard 5 months after shedding; Trifolium stellatum had the least with <30% of hard seeds; T. campestre, M. rigidula and T. tomentosum were intermediate. Hard-seededness in M. orbicularis and M. rotata varied between years. Scarification of hard seeds resulted in almost complete germination in all species. Alternating temperatures (10/20°C) reduced the rate of germination of scarified T. campestre seeds, but had no effect on germination of scarified or unscarified seeds of T. stellatum. The breakdown of hard-seededness in the field in Syria did not begin until 3 months after shedding and greatly increased when seeds overwintered. Breakdown of hard-seededness was slower when seeds were buried at 5 and 10 cm than when seeds remained on the soil surface. Seedling emergence after the rains started in November was highly correlated with the number of soft seeds observed in October. Similarly, a high correlation was found between the percentage of hard seeds in October and carry-over in the seed bank. In small-seeded species (Trifolium spp.), 39% of the initial seed bank was lost in 2 years by causes other than emergence as seedlings. Such losses were only 7% in larger-seeded species (Medicago spp.). The implications of hard-seededness on the utilization and survival of legumes in grasslands are discussed.

Type
Research Papers
Copyright
Copyright © Cambridge University Press 1992

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Footnotes

Present address Crop and Pasture Science Department, University of Western Australia, Nedlands, Perth, WA 6009, Australia

References

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