Embryonal dormancy in apple seeds is controlled by free and conjugated gibberellin levels in the embryonic axis and cotyledons

Abstract

Halińska, A., Sińska, I. and Lewak, St. 1987. Embryonal dormancy in apple seeds is controlled by free and conjugated gibberellin levels in the embryonic axis and cotyledons. Free and conjugated gibberellins (GAs) A 4+7 and A 9 were determined in embryonic axes and in cotyledons of seeds of apple ( Malus domestica Borb., cv. Antonó wka) during breaking of dormancy under cold stratification. In both organs, the maximum level of free GA 4+7 was found at day 30 of stratification, but the concentration was 700 times higher in axes than in cotyledons. Comparison of changes in free and conjugated GA 4+7 levels during stratification allow us to suggest that the accumulation of free hormone in axes is, at the most, to 40% due to release from conjugates already present in the axis; that maximally 20% is derived from hydrolysis of cotyledonary conjugates translocated to axes; and that at least 40% originate from the novo biosynthesis of the hormone. Free and conjugated GA 9 levels were similarly altered in axes and in cotyledons, markedly increasing at the end of afterripening. Both release of the free hormone from conjugates and biosynthesis of GA 9 , appeared to be involved in that increase; no translocation of free or bound GA 9 , between axes and cotyledons was demonstrated.