Regulation of root formation by auxin‐ethylene interaction in pea stem cuttings

The possibility was investigated that the inhibition of rooting in pea ( Pisum sativum L. cv. Weibull's Marma) cuttings caused by low indol‐3yl‐acetic acid (IAA) concentrations is due to ethylene produced as a result of IAA treatment. Treatment with 10 uμ IAA reduced the number of roots to about 50% of the control and increased ethylene production in the stem bases by about 20 times the control value during the two first days of treatment. Ethylene‐releasing compounds (ethephon and 1‐amino‐cyclopropane‐1‐carboxylic acid, ACC), in concentrations giving a similar ethylene release, inhibited rooting to the same extent or more strongly than IAA. These results indicate that IAA‐induced ethylene is at least responsible for the negative component in IAA action on root formation in pea cuttings. A higher IAA concentration (100 μ) and indol‐3yl‐butyric acid efficiently counteracted the negative effect of ethylene on root formation.