Seed Dormancy in Avena fatua. II. Evidence of Embryo Water Content as a Limiting Factor

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Abstract
A study was conducted under controlled conditions of changes in the water content of the embryo of the caryopsis of Avena fatua in relation to the development of dormancy and the experimental induction of germination. Dormancy developed rapidly between 18 and 22 days from anthesis and was associated with a reduction in embryo water content (% DW) from 119% at 18 days from anthesis to 13% at maturity. During 10 days of imbibition by the mature caryopsis, the embryo water content increased to a constant maximum level of 121%, but the seed remained dormant. When dormant embryos were excised from the fully imbibed caryopses and placed on wet filter paper, their water content increased by ca. 10% within 30 min, and this response was followed, after a further 18 h, by germination. A similar increase in embryo water content occurred 12-18 h after a hole was pierced in the imbibed caryopsis and ca. 72 h prior to the resumption of growth and elongation of the radicle. These results are consistent with the hypothesis that seed dormancy in A. fatua is caused by factors that prevent the uptake of imbibed water by the embryo in the amount required for the induction of germination.

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