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 5-³H]tryptophan to ³H]indole-3-acetic acid (IAA). Both a chloroplast and a crude cytoplasmic fraction, isolated from protoplasts that had previously been fed 5-³H]tryptophan, contained ³H]IAA. Chloroplast and cytoplasmic preparations, isolated from protoplasts and thereafter incubated with 5-³H]tryptophan, also synthesized ³H]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 ³H]IAA that accumulated in protoplast and chloroplast preparations incubated in light and darkness.Abbreviations HPLC high-performance liquid chromatography - IAA indole-3-acetic acid - RC radiocounting