Abstract
The effects of the triazole compound paclobutrazol on the mycorrhizalfungi and production of droppers (tuber stalks) in three species of terrestrialorchids of southwestern Australia were investigated. Seedlings ofDiuris laxiflora Lindley (bee orchid), Microtismedia R. Br. (common mignonette orchid), and Pterostylissanguinea D. Jones & M. Clements (dark banded greenhood orchid)were cultured symbiotically with specific mycorrhizal fungi invitro. The mycorrhizal fungi of the study species were grown on mediacontaining paclobutrazol at 0, 1.7, 3.4, 10.2, or 17.0 μM(corresponding to 0, 0.5, 1.0, 3.0, or 5.0 mgL−1). Paclobutrazol at all concentrations evaluateddecreased the growth rates of the mycorrhizal fungi of M.media and P. sanguinea below that of thecontrol. However, paclobutrazol did not adversely affect the growth of themycorrhizal fungus of D. laxiflora, and low concentrations(1.7 or 3.4 μM) stimulated the growth of this fungus. Symbiotic seedlings of the study species were exposed to paclobutrazolat 0, 1.7, 3.4, 10.2, or 17.0 μM. Paclobutrazol at allconcentrations evaluated increased dropper (tuber stalk) production inD. laxiflora, but had no effect on M.media and P. sanguinea.
This suggests that, for species in which paclobutrazol has no fungicidaleffect on mycorrhizal fungi, it has the potential to stimulate early andefficient tuberization of symbiotic orchid seedlings.
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Hollick, P., Senaratna, T., McComb, J. et al. Response to paclobutrazol of symbiotic mycorrhizal fungi and dropper (tuber stalk) formation of host orchid seedlings. Plant Growth Regulation 36, 31–39 (2002). https://doi.org/10.1023/A:1014799008459
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DOI: https://doi.org/10.1023/A:1014799008459