Biosynthesis of indole-3-acetic acid in protoplasts, chloroplasts and a cytoplasmic fraction from barley (Hordeum vulgare L.).

Protoplast preparations from barley (Hordeum vulgare L.) enzymatically converted [5-(3)H]tryptophan to [(3)H]indole-3-acetic acid (IAA). Both a chloroplast and a crude cytoplasmic fraction, isolated from protoplasts that had previously been fed [5-(3)H]tryptophan, contained [(3)H]IAA. Chloroplast and cytoplasmic preparations, isolated from protoplasts and thereafter incubated with [5-(3)H]tryptophan, also synthesized [(3)H]IAA, although, in both instances the pool size was less than 50% of that detected in the in-vivo feeds. There were no significant differences in the amounts of [(3)H]IAA that accumulated in protoplast and chloroplast preparations incubated in light and darkness.