Morphogenetic response of Lilium michiganense to four auxin-type plant growth regulators in vitro
Shoot, root, and callus induction were examined in the North American lily Lilium michiganense in response to treatment with four auxin-type plant growth regulators (PGR). Seed from controlled crosses were aseptically excised from slightly immature capsules and cultured in vitro on Murashige and Skoog basal medium and vitamins with 30 g·L-1 sucrose, 7.0 g·L -1 agar, and a pH = 5.7. Seed were maintained at 20°C with a 14-h photoperiod. After 5.0 to 5.5 months, leaves and roots were removed from seedlings, the bulbs transversely sectioned, then the bulb sections cultured cut-surface down on the identical medium supplemented with 0.0, 1.0, 2.0, 4.0, or 8.0 μM dicamba, picloram, K-NAA, or 2,4-D. Morphogenetic response was tabulated 4 months after treatment. Shoot formation was promoted by treatment with dicamba, picloram, and K-NAA in comparison with the control (2.5 shoots/explant). Shoot formation varied significantly in response to individual dicamba, picloram, and 2,4-D concentrations. A maximum of 7.9 shoots per expiant was promoted by 4.0 μM K-NAA and 1.0 μM dicamba, respectively. Root and callus formation also varied significantly between PGR treatments. Root formation was inhibited by dicamba, picloram, and 2,4-D treatments in comparison with the control (100% rooting); callus formation was promoted by dicamba, picloram, and K-NAA treatments in comparison with the control (15% callusing).