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  • Author or Editor: Dennis P. Stimart x
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Abstract

Bulblets from bulb-scale explants of Lilium longiflorum Thunb. cvs. Ace and Nellie White cultured in darkness on a semisolid Linsmaier-Skoog medium supplemented with 0.03 mg/liter α-naphthalene-acetic acid (NAA) bore no leaves when produced in vitro at constant 30°C but often did when produced at constant 25°. In vitro temperature regimes involving both 25 and 30° resulted in the largest number of leaves per explant. Time in vitro in each temperature regime was calculated to provide equal heat units so that differences could not be explained by a linear relationship between development and temperature × time. Physiological state of explants, measured by time lily bulbs were stored at 4° before tissue culture, interacted with in vitro temperature. Explants from bulbs stored 110 days or less produced significantly fewer but significantly larger bulblets at constant 25° as compared to constant 30°. This difference was not apparent when explants were taken from bulbs stored at 4° more than 110 days. In an experiment with explants from bulbs stored 80 days, there was no significant difference between ‘Ace’ and ‘Nellie White’ in number of scales per bulblet at either 25 or 30° but bulblets of both cultivars contained significantly fewer scales if generated at 30°. Mean width of meristems in ‘Ace’ bulblets was significantly greater when produced in vitro at 30°. Neither initiation of bulblets nor bulblet development appeared controlled by apical dominance.

Open Access

Abstract

Anatomical and phytochemical studies of Zinnia angustifolia HBK, Z. elegans Jacq., and their interspecific hybrids were initiated to define factors affecting ray floret color. Clones of Z. angustifolia with ivory, orange, or white ray florets, and Z. elegans lines with orange, pink, red, white, or yellow ray florets were crossed intraspecifically to produce S1 and F1 progeny. Interspecific hybrids were produced by crossing orange- or white-flowered Z. angustifolia clones (as ♀♀) with Z. elegans lines (as ♂♂). In both species and interspecific hybrids, pigments were present mainly in the upper epidermis, more dilute in the lower epidermis, and not observed in internal parenchyma. Variation in ray floret color in Z. elegans was primarily due to presence or absence of carotenoids in chromoplasts and anthocyanidins in vacuoles. Quantitative differences in the anthocyanidins pelargonidin and cyanidin were detected among Z. elegans lines; in vivo expression of anthocyanins was influenced by epidermal cell pH. Ray floret color in Z. angustifolia was due to presence or absence of two novel anthocyanidins and ivory-colored flavonoids, with no attributable effect of epidermal cell pH on anthocyanin expression. Carotenoids were not present in ray florets of Z. angustifolia × Z. elegans hybrids, regardless of whether carotenoids were expressed in the Z. elegans parent line. Presence or absence of the two novel anthocyanidins from Z. angustifolia and cyanidin from Z. elegans permitted unique combinations of floral pigments in interspecific hybrids not previously found in either species.

Open Access

Abstract

An average Easter lily bulb with 100 scales may produce 8000 or more bulbs in 6 weeks when 1 mm thick cross sections from the scales are cultured in the Linsmaier-Skoog medium as modified by Sheridan and supplemented with 0.03 mg/liter NAA. Continuous darkness at 25°C increased bulb number and size at the expense of leaf number and size while a cycle of 16 hours cool white fluorescence at 1.6 klx (150 ft-c) and 8 hours dark at 25°C suppressed bulb formation but enhanced leaf formation, root weight, and fresh weight of callus. Root numbers were equal in both environments. Cultures incubated at 18.3° exhibited no measurable growth after 6 weeks. Explants from the distal part of the bulb scale will grow only with growth regulators present.

Open Access

Direct shoot organogenesis (DSO) on Antirrhinum majus L. (snapdragon) was evaluated in vitro to determine the inheritance of genes conditioning this response. One-centimeter-long hypocotyls excised from 2-week-old seedlings started in vitro in the dark on Murashige and Skoog medium served as explants. Optimal conditions for DSO on explants included hypocotyl excision from 10-day-old seedlings, 2.22 μmol BA in the culture medium, and a 21-day culture duration. An adventitious shoot was counted once it developed a stem terminated by at least one leaf appearing to have originated from an apical meristem. Seven populations were evaluated for DSO: parent 1 (P1) with lowest DSO (0.3 shoots); parent 2 (P2) with highest DSO (13.9 shoots); F1 (P1 × P2); F1 (P2 × P1); F2 (self-pollination of F1); P1 × [P1 × P2]; and P2 × [P1 × P2]. P1 and P2 were chosen as parents based on DSO counts being lowest and highest, respectively, of inbreds evaluated. DSO appears to be a trait under nuclear genetic control. High DSO appears to be dominant over low DSO. The trait appears to be simply inherited through one or two genes.

Free access

Abstract

In vitro shoot proliferation of Pyrus calleryana Decne. ‘Bradford’ was investigated on medium containing BA at 0, 1, 2, 10, or 20 µM in factorial combination with IBA at 0, 0.5, or 5.0 µM. Shoot proliferation increased as BA level increased but the magnitude was reduced as IBA level increased. Greatest shoot proliferation was on medium excluding IBA. Shoots were longest on medium containing 1 or 2 µM BA. Medium with 2 µM BA and 0.5 µM IBA was optimum for shoot proliferation and length. Shoot fasciation increased as BA level increased, but addition of IBA to BA reduced fasciation. Rooting of microcuttings with IBA and sucrose was unsuccessful. Chemical names used: N-(phenylmethyl)-1H purin-6-amino (BA); 1H-indole-3-butanoic acid (IBA).

Open Access

Abstract

Irrigation interruptions of 0, 2, 4, or 8 weeks were imposed on actively growing ‘Red Lion’ amaryllis (Hippeastrum × hybridum) bulbs to determine the influence of water stress on flowering. Withholding irrigation for 4 or 8 weeks was effective in promoting early flowering of first and second scapes compared to continuously irrigated plants. Irrigation interruptions of 2, 4, or 8 weeks resulted in first scape flowering on all plants by 160, 140, or 60 days, respectively, after resumption of irrigation. Only 83% of continuously irrigated plants flowered within 160 days. Water stress treatments did not influence total number of flowering scapes per plant produced in 160 days nor number of flowers per umbel. Irrigation interruption affected timing of flowering by promoting scape extension and floral development.

Open Access

Abstract

Propagation time, N, and shoot growth were studied for their effects on overwinter survival of newly rooted stem tip cuttings of Acer palmatum Thunb. ‘Blood-good’ and Cornus florida L. var. rubra. Propagation of A. palmatum and C. florida in May and June, respectively, resulted in a greater number of plants with shoot growth after rooting compared to those propagated later. Removal of a terminal leaf on A. palmatum after rooting increased the percentage of plants with shoot growth. Nitrogen application after rooting decreased survival before winter storage for A. palmatum propagated in May and C. florida propagated in June and July. May propagation of A. palmatum reduced overwinter survival, whereas propagation date did not affect overwintering of C. florida significantly. Plants with shoot growth and not given N had best overwinter survival, followed by plants with shoot growth given N. Poorest overwintering occurred on both species given N that failed to grow prior to winter storage. Nitrogen application to these plants when newly propagated should be avoided until the role of N is better understood.

Open Access

Abstract

Callus culture establishment and adventitious shoot development from callus of Rhododendron × ‘Gibraltar’ (G) and R. × ‘Old Gold’ (OG) after serial subculture were determined. Callus grew on Anderson's Rhododendron medium containing 2,4- D at 0.0045, 0.009, or 0.018 mm, but was optimum at 0.018 mm, since shoot organogenesis was suppressed at that level. After two callus subcultures, adventitious shoot development from callus on media containing 0, 0.017, 0.034, 0.068, or 0.136 mm zeatin (mixed isomers) was optimum at 0.034 and 0.068 mm zeatin for G and OG, respectively. After 17 weeks (five subcultures), 70- to 75-mg pieces of G and OG callus regenerated ≈20 shoots each. Adventitious shoot regeneration from callus declined with prolonged callus subculture. Regenerated plants are currently being evaluated for somaclonal variation. Chemical names used: (2,4-dichlorophenoxy)acetic acid (2,4-D); (E)-2-methyl-4-(1H-purin-6-ylamino)-2-buren-1-ol (zeatin).

Open Access

Abstract

Stem pieces from expanding spikes of Liatris spicata (L.) Willd. were cultured in vitro on a Murashige and Skoog medium containing BA to establish proliferating cultures for use in comparing BA and IBA effects on shoot proliferation. Both compounds promoted multiple shoot development. The optimum level for micropropagation was 2.7 μm BA without IBA. Greatest rooting was at 5.0 μm IBA without BA.

Open Access

Abstract

Postharvest flower fresh weight of Zinnia elegans Jacq. increased when held in solutions containing 200 mg liter-1 8-hydroxyquinoline citrate (8-HQC) and sucrose and decreased when held in deionized water. Ethylene biosynthesis was enhanced by holding flowers in solutions of 8-HQC + 1, 2% or 3% sucrose compared with deionized water where ethylene release was low initially and remained low. Carbon dioxide evolution declined sharply the first 2 days postharvest and remained low for flowers held in deionized water, but remained at initial levels for those held in 200 mg liter-1 8-HQC + 3% sucrose. Glucose, fructose, and sucrose in ray florets declined to levels barely detectable if flowers were held in deionized water but increased if held in 200 mg liter-1 8-HQC + 3% sucrose. The induction of ethylene biogenesis may be an injury response caused by sucrose.

Open Access