Changes in IAA, tryptophan and activity of soluble peroxidase associated with zygotic embryogenesis in Araucaria angustifolia (Brazilian pine)

In A. angustifolia seeds the highest values of freeIAA occurred in the embryonic axis, at the initial phases of development. Thesevalues decreased sharply coincident with the increase of IAA with thedifferentiation of cotyledons and seed elongation. During seed development,tryptophan concentrations varied inversely with free IAA and directly withconjugated IAA. An increase in peroxidase activity was followed by a decreaseinfree IAA in the embryo axis, and in conjugated IAA in the megagametophyte.Megagametophyte tissues did not exhibit significant variation in free IAAduringseed development. Following the stage where cotyledons arise, tryptophandecreased in the megagametophyte and increased in the cotyledons and embryonicaxis.