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| - The Role of the Lens in Controlling Heat-induced Breakdown of Testa-imposed Dormancy in Native Australian Legumes
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| - A high proportion of seeds of most species of the Fabaceae have testa-imposed dormancy, which prevents them from imbibing water even under favourable environmental conditions. This allows seeds to accumulate in a persistent soil seed bank. Dormancy is usually considered to be broken only when the testa is disrupted, particularly at the lens. In Mediterranean-type ecosystems, the primary natural mechanism causing the breakdown of this dormancy is the disruption of testas in the soil seed bank by heat from fires that warms the soil in which the seed bank occurs. We examined experimentally the role of the lens in controlling this heat-induced breakdown of dormancy in 16 native Australian species of the Faboideae and Mimosoideae. Two groups of patterns are recognized: species of the Mimosoideae: Acacieae and Faboideae: Mirbelieae, where water permeability is regulated by the lens; and species of the Faboideae: Bossiaeeae, where water permeability apparently occurs at non-localized regions of the testa. The species in these two groups differ in the structure of their testas. Thus, testa-imposed dormancy does not represent a single dormancy mechanism in legumes, as is often assumed when dormancy is broken artificially.Copyright 1998 Annals of Botany Company
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