Resumo

WANG, XL; ZHAO, Z  e  QUAN, JE. Indole-3-butyric acid on rooting and endogenous plant hormones in tetraploid and diploid Robinia pseudoacacia hardwood cuttings. Phyton (B. Aires) [online]. 2011, vol.80, n.1, pp.93-100. ISSN 1851-5657.

Robinia pseudoacacia (locust hereafter) is an ornamental tree with various uses. Both homologous tetraploid (tetraploid hereafter) and diploid cultivars are commercially available. The tetraploids have advantageous traits, but poor germinability, and cuttings are difficult to root. Since auxin applications can promote rooting, we evaluated the effects of dipping cuttings in various indole-3-butyric acid (IBA) concentrations for four hours on rooting parameters. IBA significantly affected all measured parameters of both tetraploid and diploids cuttings. Tetraploid cuttings produced no roots without IBA. The effects were strongest at 1000 and 800 mg/L IBA for tetraploids and diploids, respectively. Values for tetraploids and diploids respectively, were (1) 75.6 and 100% for rooting percentages, (2) 11.74 and 13.5 for average root numbers, and (3) 5.24 and 5.5 cm for average root lengths per rooted cutting. We also examined the content of endogenous hormones in cuttings treated with (1) IBA at optimal concentrations or (2) water (controls). Diploids seemed to require high indole-3-acetic acid (IAA) levels during root primordia initiation, but IAA contents were substantially and consistently higher in tetraploids. Trends in IAA levels were opposite to those of abscisic acid (ABA) in tetraploids; however, this did not happen in diploids. Root induction was negatively or positively related to IAA content and IAA/ABA ratio in tetraploids or diplods, respectively. Rooting was associated with high ABA contents in tetraploids, but low ABA contents in diploids. Zeatin riboside contents were proportional to numbers of roots per cuttings and root length. The results demonstrate clear physiological rooting-related differences between tetraploid and diploid locust cuttings, indicating that high IAA contents constrain rooting in tetraploids.

Palavras-chave : Abscisic acid; Indole-3-acetic acid; Indole-3-butyric acid; Robinia pseudoacacia; Zeatin riboside.

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