Rooting, growth and ethylene evolution of pea cuttings in response to chloroindole auxins

In pea cuttings (Pisum sativum L. cv. Alaska) we measured shoot and root growth and ethylene production in response to 4‐chloroindole‐3‐acetic acid (4‐CI‐IAA) or 4,6‐dichloroindole‐3‐acetic acid (4,6‐Cl2‐IAA). Leafy cuttings treated basally with either of the chlorinated auxins in high concentrations showed permanent epinasty, loss of apical growth and dominance resulting in the outgrowth of laterals from the lower‐most axillary bud. The naturally occurring 4‐CI‐IAA was a better root promoter than the synthetic 4,6‐Cl2‐IAA which inhibited rooting. Both chloroindole auxins induced very high ethylene evolution, which lasted much longer than the ethylene evolution after IAA treatment.