Abscisic Acid and Apple Seed Dormancy1

Abstract

c,t-Abscisic acid (ABA) was identified in methanol extracts of mature apple (Malus domestica Borkh.) seeds by gas chromatography-mass spectrometry, and concentrations of both free and base-hydrolyzable (bound) ABA in immature and mature seeds were quantified by electron capture gas chromatography. Immature embryos failed to germinate regardless of time of sampling unless seed coats were removed. Germination of excised embryos reached a maximum in early August, then gradually declined to nil in mid-September. Although ABA content of the embryonic axes rose sharply at maturity, the rise occurred only after germination capacity declined. Premature defoliation reduced ABA content of the axes, but did not prevent the induction of embryo dormancy. ABA content of mature seeds declined during stratification at both 5° and 20°C, with maximum differences occurring in the embryonic axis, but dormancy was broken only at 5°. Induction of secondary dormancy by high temperature (27°) was accompanied by a slight decline in ABA content of whole seeds.

The Relationship of Apple Embryos and Their Cotyledons to Maturity, Dormancy, and the Potential to Form Shoots in Vitro

“…31' (GN31) x 'Blue Lake', resistance of GN31 to an Oregon isolate of the BYMV type strain was conditioned by 3 recessive genes with modifiers (2). Similar results were obtained from the cross 'Blue Lake' x BYMV resistant P. coccineus (1). These results differ from those of Dickson and Natti (4) who found resistance to BYMV (isolate 1 of Hagedom and Walker) to be controlled by a single, dominant gene when lines deriving resistance from P. coccineus were crossed with several susceptible lines and cultivars.…”

“…Jones and Hopgood (4) reported that the free abscisic acid (ABA) content of the seed reached a peak on 30 June (under their climatic conditions) and then dropped, whereas indoleacetic acid levels of the seed continued to increase throughout the period of fruit growth and maturation. Thus, it may be that the ABA levels of the embryo in our study were reduced when the endosperm and seed coats were removed (1). The formation of adventitious shoots from cotyledons was independent of the presence of the embryonic axis, indicating that the full potential for plant regeneration was present within the cotyledon itself.…”

Hormones in Pear Seeds. II. Levels of Abscisic Acid, Dihydrophaseic Acid, and Their Metabolites in Relation to Seed Dormancy in Several Pyrus Species1

“…ABA fell during imbibition, as was expected in view of the high level in the water used for soaking the seeds (Table 3). The constant level during stratification was not expected, however, on the basis of previous work with apple seeds (1,11). Bound ABA content of seeds was not measured in this study.…”

“…Rudnicki (11) observed that levels of ABA in diffusates from apple seeds declined during low temp stratification, and suggested that ABA content might be a controlling factor in dormancy. However, Balboa-Zavala and Dennis (1) found the decline in ABA content of apple embryonic axes to be inde pendent of temp, suggesting that factors other than ABA content control dormancy.…”