Figure 8.

IEF gels showing the effects of GA₃ and ABA on PME isoform activities in isolated embryos and megagametophytes excised from dormant seeds (A) and in embryos and megagametophytes (B) of intact seeds following a full dormancy-breaking treatment and during the germinative and post-germinative stages. A, Megagametophytes and embryos were excised from mature dormant seeds (subjected to only a 3-d soak) and then placed on water, 0.1 mm ABA, or 0.5 mm GA₃ for 6 d. To test whether the acidic PME isoforms in the embryos and megagametophytes excised from dormant seeds were due to wounding during their excision, the seed parts were kept within the intact seed and wounded by piercing them with forceps (wound). The control is the partially purified PME from intact germinated seeds. B, Intact yellow cedar seeds were subjected to a full dormancy-breaking treatment (after m.c., moist chilling) or were subjected to the dormancy-breaking treatment and then transferred to germination conditions for 4 d (germ.) or until the seeds had achieved radicle lengths of 1 mm (post-germ.). Following moist chilling or during the germinative and post-germinative phases, seeds were incubated in water, 0.1 mm ABA, or 0.5 mm GA₃ for 6 d and the PME isoform activities determined in the embryo and megagametophyte of the intact seeds.