Eingegangen am 10. November 1966 TANNINS AND GROWTH III. ANALYSIS OF THE IAA/TANNIN-ANTAGONISM IN OAT-COLEOPTILE CYLINDERS
Summary. An analysis of the IAA/Tannin-Antagonism which occurs in oatcoleoptiles was carried out. The investigations were done with 10 mm coleoptile sections of 4-day-old seedlings of Avena 8ativa L. var. "Fl~mingsgold".
First it was shown that the IAA/Tannin-antagonism which could be established with a tannin-preparation by "Fluka" resembled very much that caused by "Merck-Tannin". Whereas the antagonism which was demonstrated by "Merck-Tannin" seemed to be independent of the IAA concentration, the antagonism induced by "Fluka-Tannin", showed a strict correlation to the applied amount of IAA. An increase of the IAA concentration resulted in a decrease of the antagonistic tannin effect. A 5" 10 -5 molar tannin solution reduced the activity of an IAA-oxydase preparation by 71--92 %.
Oat-coleoptile cylinders which were preincubated for 4 hours in a 10 ~ molar or a 10 -4 molar IAA solution and subsequently treated with tannin for 16 hours showed no growth inhibition at all.
After a preincubation period with tannin solutions (5.10 -s up to 5. l0 -~ M) for 3 hours the uptake of IAA during 20 hours by oat-coleoptile cylinders was lowered by 1245%. It seems to be clear that the IAA/Tannin-antagonism in buffered solutions is due to a remarkable drop in the IAA uptake by the coleoptile tissue.