10. Indoleacetic acid response of corn coleoptiles.

In view of the extensive work with Avena coleoptiles, it was surprising to find that no one had reported the effects of indoleacetic acid (IAA) on corn coleoptile elongation. A few simple experiments were therefore carried out. Corn seeds were germinated on the dark and when the tip beyond the first node was 1 to 1.2 mm. long, 5 mm. sections were cut with parallel razor blades beginning 2 to 3 mm. back from the tip. The primary leaf was withdrawn and batches of ten to twenty coleoptile sections floated on buffered sucrose solutions to which IAA was added. The average increase in length over controls was 0-25 mm./10 sections for the range of .1 to 3 mg. IAA per liter, a definitely usable sensitivity, which could probably be increased by rejecting 5 mm. of tip instead of 2‑3 mm. The results are reported here since they suggest the possibility of using corn coleoptiles for IAA assay as well as their application in the study of coleoptiles of mutants in which differences of IAA metabolism are suspected.

Howard J. Boroughs