The Effect of Various Growth-Regulators on Embryos of Capsella bursa-pastoris Growing in Vitro

1. The effect of three growth-regulators on the growth in vitro of Capsella bursa-pastoris embryos was studied. 2. Gibberellic acid increases the growth rate of “torpedoes” considerably. It also stimulates the root-meristem activity, and induces epinastic curvatures of the cotyledons. As these phenomena are part of the process of germination, we may classify GA as a promotor of germination. It is unlikely that GA functions as an agent controling embryogenesis. 3. Our experiments with indole-3-acetic acid make it improbable that IAA acts as a natural growth-regulator during embryogenesis. 4. The effect of kinetin on embryo growth in vitro is twofold: it causes an inhibition of the root meristem and an increased cell division in the very young embryo. The latter leads to a modified growth pattern. 5. From experiments with combinations of the three growth-regulators we conclude that these substances influence the growth of the embryo through different mechanisms. 6. In the general discussion attention was paid to the fundamental differences between embryo growth in vitro and embryo growth in the ovule. One has to be careful in applying results obtained with embryo growth in vitro on embryo growth in the ovule.