Auxin promoted rooting in 70% to 95% of in vitro shoot cultures of Cheiranthera volubilis compared with 25% on auxin-free medium. The type of auxin in the medium affected root morphology, which, in turn, affected plantlet survival on transfer to soil. IBA in the medium caused thickened roots or callusing, with poor survival of rooted plantlets (10% to 40%). NAA or NOA alone stimulated thread-like root growth and increased survival (60%). A low gelrite concentration (0.125%) gave good rooting (84%), but reduced plantlet survival (27%), whereas a high concentration of gelrite (0.5%) inhibited rooting (51%) but increased survival (70%). The best combination was 1 µM of NOA in 0.375% gelrite, giving 82% rooting and 65% survival. Chemical names used: 1H-indole-3-butanoic acid (IBA); naphthaleneacetic acid (NAA); β-naphthoxyacetic acid (NOA).
A number of Australian woody species are shown to differ widely in adventitious root production in vitro in response to the type and combination of hormones applied, although the most effective combinations usually included IBA. Shoots of Eremophila lanii F. Muell produced roots on a medium containing cytokinins and no auxin. Two species, Prostanthera striatiflora F.v.M and Correa decumbens F.v.M., required reduced pH and a period of darkness for root induction, whereas these conditions inhibited Grevillea biternata Meissner. There also is an interaction among hormone treatment, media pH, and the effect of continuous light vs. a period of darkness. Chemical names used: 1H-indole-3-butanoic acid (IBA); naphthhalene acetic acid (NAA); indole-3-acetic acid (IAA); B-naphthoxyacetic acid (NOA); 6-furylaminopurine (KIN); N-(phenylmethyl)-1H-purin-6-amine (BA).