Effect of Peeling on IAA-induced Growth in Avena Coleoptiles

The act of peeling removes the epidermis exclusively from Avenacoleoptiles. Peeling inhibits IAA-induced growth, by inhibitingthe growth of segments incubated in the presence of IAA, andpromoting that of those incubated in water. The magnitude ofthe inhibition of IAA-induced growth is proportional to theamount of epidermis removed. It is shown that neither lateralswelling, wounding, anaerobiosis, nor exposure to supraoptimalconcentrations of IAA cause the inhibition. It is concludedthat in Avena coleoptiles the epidermis regulates the rate ofexpansion of the underlying parenchyma cells and is the principaltarget of IAA-action. Avena sativa L., oat, coleoptile, indol-3-ylacetic acid, auxin, extension growth