Dormancy studies in seed of Avena fatua. 6. Germinability of the immature caryopsis

Abstract

Caryopses of a dormant strain of Avena fatua L. fail to germinate on moist filter paper when immature whereas non-dormant caryopses germinate at 10 days after fertilization and at later stages of development. Embryos of the dormant strain excised at any stage of development fail to germinate in a complex nutrient medium which supports germination and growth of non-dormant embryos at, and after, 10 days following fertilization. Gibberellicacid (GA) promotes germination of dormant caryopses and excised dormant embryos before and at maturity in the presence of either endosperm or the nutrient medium. This requirement for gibberellin is not absolute, since germination of dormant embryos in mid-development occurs when the nutrient medium is solidified with agar in the absence of gibberellin. The stimulatory effect of solidifying the medium is probably due to differential leaching action upon embryos affecting levels of endogenous gibberellins. The genetic source of endosperm does not influence germinability of the embryo, and endosperms of both dormant and non-dormant strains show an increasing capability of supporting postgerminal growth of non-dormant embryos. A block to the use of these nutrients by the embryo, reversible by gibberellin, is present at maturity in endosperm of the dormant strain.