THE DEVELOPMENT OF EMBRYO DORMANCY AND TESTA-IMPOSED DORMANCY DURING SEED ONTOGENY IN THE GENUS ACER

Excised immature embryos of both Acer platanoides and Acer pseudoplatanus cultured in sterile conditions gave high levels of germination when isolated from very young developing fruits at 10 weeks post anthesis (wpa), but germinability in both species fell rapidly to minimum values at 14 wpa and 18 wpa, respectively, as development proceeded.Although remaining low until maturity in the former species, germinability subsequently increased in the latter until comparatively high levels of embryo germinability were present at seed maturity and testa-imposed dormancy was established.This is not the way testaimposed dormancy develops in all genera and the similarity between these two Acer species suggests the existence of a common mechanism for dormancy induction in Acer species, irrespective of whether they show embryo dormancy on testa-imposed dormancy at maturity. The cotyledons of developing embryos of each species had some inhibitory effect on germination, but a well defined dormancy also developed in the embryonic axis and results indicate that embryo dormancy is largely regulated within the axis itself. © 1990, Gustav Fischer Verlag, Stuttgart. All rights reserved.