Abscisic acid and indole‐3‐butyric acid regulation of maturation and accumulation of storage proteins in somatic embryos of interior spruce

Abstract

The ontogenetic course followed by somatic embryos of interior spruce is highly dependent on the media concentration of abscisic acid (ABA). Little or no organized development occurs in the absence of ABA and as the level of ABA is increased, a range of embryo types is produced. “Shooty embryo” structures predominate in many callus lines at low levels of ABA (1‐10 μM), while 10‐20 μM ABA promotes the formation of bipolar embryos that germinate precociously. When ABA is increased to 30‐40 μM, precocious germination is inhibited and opaque cotyledonary embryos characteristic of their zygotic counterparts are formed which enter a period of quiescence. Only “mature” somatic embryos contain significant amounts of storage proteins and the level to which these proteins accumulate is dependent on the concentration of ABA. Indole‐butyric acid (IBA) included with ABA increases the number of mature embryos. Root elongation, which was used as a measure of embryo quality, was never observed from shooty embryo Structures and was 2‐3 fold higher in mature embryos compared to those that germinated precociously.