Influence of Aryl Esters of Indole‐3‐acetic and Indole‐3‐butyric Acids on Adventitious Root Primordium Initiation and Development

Abstract

AbstractSynthetic aryl esters of indole‐3‐acetic acid (IAA) and indole‐3‐butyric acid (IBA) greatly enhanced adventitious root primordium initiation in bean (Phaseolus vulgaris L. cv. Top Crop) and jack pine (Pinus banksiana Lamb.) cuttings, respectively. Bean cuttings produced 95 to 154% more macroscopically visible root primordia in 2 days when treated with phenyl indole‐3‐acetate (P‐IAA), in comparison with an equal concentration of IAA. Substantial but lesser increases occurred when treatment was done with 3‐hydroxyphenyl indole‐3‐acetate (3HP‐IAA). On a molar basis, either P‐IAA or 3HP‐IAA were 10 or more times as efficient as IAA in inducing adventitious root primordium initiation in bean cuttings. Methyl indole‐3‐acetate was no more effective than IAA in these tests.Phenyl indole‐3‐butyrate (P‐IBA) consistently enhanced the number of rooted jack pine seedling cuttings by 11 to 12% in comparison with a 27% higher concentration of IBA.The number of elongated roots (2 mm or more) after 5 days was 165 to 276% greater for P‐IAA than for IAA‐treated bean cuttings. Similar but lesser increases occurred as a result of 3HP‐IAA treatment. P‐IBA in comparison with IBA treatment did not influence either the number of roots or length of the longest root per rooted jack pine cutting.Enzymes in bean and jack pine cuttings hydrolyzed the aryl esters. However, check experiments showed that initial integrity of the esters was required for enhanced activity in inducing root primordium initiation. Treatment of bean cuttings with hydrolysates of P‐IAA, or with IAA and phenol, alone or combined, did not influence root primordium initiation or development in a manner different from treatment with IAA alone.