Seed dormancy in Acer: abscisic acid as a factor in the control of precocious germination and the induction of dormancy

Abstract

AbstractImmature embryos isolated from fruits of Acer pseudoplatanus L. at various stages during a 24-week development period, showed a sharply defined transient accumulation of endogenous free ABA, with peak levels at 10 weeks postanthesis (wpa). When this ABA peak occurred isolated embryos showed a high level of germinability when incubated in sterile culture; however, germinability fell rapidly thereafter, reaching minimum values at 14 wpa before recovering as maturity approached. Halfembryos and excised embryonic axes, although showing consistently higher germinability than whole embryos, also showed a similar progressive reduction in germination capacity up to 14 wpa, followed by a recovery in germinability. This peak of free ABA in the embryo also correlated with the start of the most rapid phase of both embryo mass and volume increase. The possibility that endogenous ABA is the causal agent of this short-lived embryo dormancy in A. pseudoplatanus is discussed, as is the possibility that by suppressing precocious germination, ABA frees the embryo to initiate or accelerate its normal developmental processes.