Date of this Version
HORTSCIENCE 27(2):182. 1992
Penstemon (beard tongue) is a native genus of U.S. wildflower that is used for landscape plants (Lindgren, 1984a, 1984b, 1990), for cut flowers (Lindgren, 1986), and for ecological studies (Stubbendieck et al., 1982). Tissue culture techniques could be useful for propagating cultivars and species in this genus as some do not breed true from seed, require special seed germination conditions, or are difficult to propagate using other vegetative methods (Lindgren, 1984b, 1990; Stubbendieck et al., 1982). Penstemon haydenii is also the only listed endangered plant species in Nebraska.
The Penstemon spp. P. digitalis Nutt. ‘Husker Red’ (Lindgren, 1984b); P. grandiflorus Nutt. ‘Prairie Snow’ (Lindgren, 1990); P. barbatus (Cav.) Roth ‘Schooley’s Yellow’ (Lindgren, 1984a), and P. haydenii S. Wats (Stubbendieck et al., 1982) were evaluated for their growth response to five levels of N- (phenylmethyl)-1H purine-6-amine (BA).
Lateral buds from greenhouse-grown plants of each of the four species were surface sterilized by sequential immersion in 75% ethanol for 1 min and 0.53% NaOCl for 15 min, followed by rinsing three times in sterile water. Explants were then placed in 120-m] baby food jars with polypropylene closures that contained 30 ml Woody Plant Medium (Lloyd and McCown, 1980) with 0.1% (w/v) Gelrite, 0.3% (w/v) Sigma agar, 2% (w/v) sucrose, 6 mM calcium gluconate, and 0.4 μM BA. Shoots were grown on this medium for 8 weeks, then transferred to Murashige and Skoog (MS) basal medium (Murashige and Skoog, 1962) without BA and grown for 6 weeks. Shoot sections with one node each were then transferred to 30 ml MS medium, placed vertically, and supplemented with either 0, 0.01, 0.1, 1.0, or 10.0 μM BA. At the end of 4 weeks, shoot tips (1 cm) were transferred to fresh MS media supplemented with the same concentrations of BA and, at the end of 6 weeks, plant growth was measured. All tissue culture media were adjusted to a pH of 5.7. Growth rooms were maintained at 27 ± 1C with 24 h continuous light provided by cool-white fluorescent bulbs (20 μmol·m–2·s–1). The experimental design was a randomized complete block with five replicates per treatment. One replicate consisted of one jar with one shoot per jar. Statistical comparisons were made between BA levels only within each species.