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Christopher S. Cramer and Mark P. Bridgen

Disinfected midrib sections of Mussaenda `Queen Sirikit' ≈3 to 4 mm in size were cultured on a basal medium of Murashige and Skoog salts and vitamins, 87.7 mm sucrose, and 5 g Sigma agar/liter supplemented with several concentrations of indole-3-acetic acid (IAA) (0, 5.0, 10.0, 20.0 μm) and 6-benzylaminopurine (BAP) (0, 0.5, 1.0, 2.5, 5.0, 10.0, 25.0, 50.0 μm). Cultures were subculture onto the same treatment after 5 weeks and observed weekly for 15 weeks for the presence of somatic embryos. As somatic embryos were produced, they were subculture onto basal medium supplemented with 0.5, 1.0, 2.5, or 25.0 μm BAP. Callus was first observed at 2 weeks in cultures grown on basal medium supplemented with 5.0–20.0 μm IAA and 0–50.0 μm BAP. Somatic embryos were observed at 8 weeks on basal medium supplemented with 5.0–10.0 μm IAA and 2.5–5.0 μm BAP. Callus cultured on 0–10 μm IAA and 5.0–10.0 μm BAP produced the greatest number of somatic embryos by 15 weeks. Somatic embryos subculture to basal medium supplemented with 25.0 μm BAP proliferated shoots, while eliminating BAP from the medium resulted in root and callus production. Shoots and entire plants were removed from in vitro conditions and successful] y acclimated to greenhouse conditions. Somatic embryo-derived plants flowered sporadically 25 to 35 weeks after removal from in vitro conditions. Variations in sepal number and leaf number per node were observed at 1% to 5%.

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Christopher S. Cramer and Mark P. Bridgen

Mussaenda, a tropical ornamental shrub developed in the Philippines is being examined as a potential greenhouse potted crop in the United States. Showy sepals of white, picotee, pink or red and fragrant, yellow flowers make Mussaenda an attractive patted plans however, the profuse upright growth habit of some Mussaenda cultivars is undesirable for pot plant culture. With this in mind experiments were conducted to determine the effects of three growth regulators at two concentrations each, as well as the application method and the number of applications on Mussaenda plant height.

Three growth regulators, daminozide (B-Nine), ancymidol (A-Rest), and paclobutrazol (Bonzi) were applied at two commercially recommended rates and two application methods (spray or drench). The treatment were daminozide at 2500 ppm and 5000 ppm (spray), ancymidol at 33 and 66 ppm (spray) and at 0.25 and 0.50 mg/pot (drench), and paclobutrazol at 25 and 50 ppm (spray) and at 0.125 and 0.25 mg/pot (drench). In subsequent experiments, the same growth regulators were applied with an increase in concentration and either two or three applications. The treatments were daminozide at 5000 ppm (spray), ancymidol at 66 and 132 ppm (spray) and at 0.50 and 1.0 mg/pot (drench), and paclobutrazol at 50 and 100 ppm (spray) and at 0.25 and 0.50 mg/pot (drench).

The most attractive potted plants were produced with two applications of daminozide at 5000 ppm or two applications of ancymidol at 0.5 mg/pot (drench). Higher concentrations or additional applications excessively reduced plant height. Three spray applications of 132 ppm ancymidol also produced an attractive potted plant. Paclobutrazol sprays or drenches at any concentration or application number were ineffective for reducing Mussaenda `Queen Sirikit' plant height.

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Elizabeth L. Kollman and Mark P. Bridgen

Alstroemeria, the Inca Lily or Lily-of-the-Incas, is becoming a popular garden plant in the United States. In past years, the primary interest in Alstroemeria has been for its cut flowers. However, recent cold-hardy introductions (USDA hardiness zone 5) have expanded the interest of this colorful plant as a garden perennial throughout the United States. Previously, garden interests were restricted to warmer zones in the southern United States where Alstroemeria could overwinter. This research describes a breeding procedure that has been used with the objective to develop a cold-hardy, white-flowered Alstroemeria. The interspecific hybrids were bred with the use of in ovulo embryo rescue. Reciprocal crosses were made between several white-flowered cultivars and the cold-hardy Chilean species Alstroemeriaaurea during Summer 2004. Ovaries were collected 10–23 days after hand pollination and their ovules were aseptically excised. Ovules were placed in vitro on 25% Murashige and Skoog (MS) medium under dark conditions until germination. Three weeks after germination, they were then placed on 100% MS medium, and subcultured every 3–4 weeks thereafter until they were large enough for rooting. After rooting and acclimation, plants were transferred to the greenhouse. Successful hybrids that were produced in 2004 were evaluated under greenhouse and field trials during 2005, and the number of plants with white-colored flowers was noted. Although certain morphological characteristics indicate if plants are coldhardy, the hybrids will be overwintered outside in Ithaca, N.Y. (USDA zone 5), during the next several years to determine winter hardiness.

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Christopher S. Cramer and Mark P. Bridgen

Mussaenda, a tropical, hybrid ornamental plant from India and the Philippines, is being evaluated as a potential greenhouse ported crop in the united States. Showy sepals of white, picotee (White with rosy edges), light pink, dark pink, or red complemented by fragrant, yellow flowers and dark green, pubescent foliage make Mussaenda a very attractive potted plant. However, sometimes the height of Mussaenda is unsuitable for pot plant culture. With the use of chemical growth regulators. plant height is reduced thus making Mussaenda a more feasible potted crop.

In the summer of 1992, a growth regulator study was conducted to evaluate three growth regulators and concentrations capable of reducing plant height in Mussaenda. Daminozide (B-Nine SP), ancymidol (A-Rest), or paclobutrazol (Bonzi) was applied at two concentrations each. Daminozide was tested as a spray at 2500 ppm and 5000 ppm. Ancymidol was applied as a spray at 33 ppm and 66 ppm or as a drench at 0.25 mg/pot and 0.50 mg/pot. Paclobutrazol was tested as a spray at 25 ppm and 50 ppm or as a drench at 0.125 mg/pot and 0.25 mg/pot. Growth regulators were applied as a single application or a double application with two weeks separating applications.

Daminozide at 2500 ppm and 5000 ppm was most effective in controlling plant height. Ancymidol as a drench at 0.25 mg/pot and 0.50 mg/pot was also effective in plant height control. Two applications of these growth regulators were more effective in controlling plant height than a single application.

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Chad T. Miller and Mark P. Bridgen

The dormancy mechanism in achimenes (Achimenes hybrids) has not been thoroughly characterized. Rhizomes of five recently developed achimenes cultivars were stored for 0, 4, 8, 12, or 16 weeks at 68 °F. Cultivar A09 demonstrated a strong decrease in the time to root after 4 weeks of storage, rooting after 13 weeks postplanting. The rooting response for cultivars A16, A21, and A22 was significantly less than cultivar A09; they developed roots between 2.6 and 7.6 weeks after 4 weeks of storage. Rhizomes stored longer than 8 weeks resulted in decreased rooting responses for all cultivars. Shoot emergence was delayed in all cultivars with cultivars without any storage period; cultivars A09, A16, and A23 exhibited a stronger delay than other cultivars. After 4 weeks of storage, the number of weeks to shoot development decreased for all cultivars and after each additional 4-week storage period, the number of weeks to shoot development decreased or remained the same. After 16 weeks of storage, shoots developed in less than 4 weeks for all cultivars. Pupation occurred in four of five cultivars on rhizomes given no storage or with only 4 weeks of storage. The results obtained suggest that the dormancy period of some newer achimenes cultivars is abbreviated in comparison with older cultivars.

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Mark A. Smith, George C. Elliott, and Mark P. Bridgen

The effects of Ca and N on cut flower production of Alstroemeria were determined in separate greenhouse experiments. Calcium was supplied as Ca(NO3)2 and CaCl2 at 0, 1, 2, 4, 8, and 12 mmol·L-1 added to tap water containing Ca at ≈0.2 mmol·L-1. Nitrogen was supplied as KNO3 and Ca(NO3)2 providing total N at 0, 3.5, 7, 14, 28.5, and 57 mmol·L-1 in tap water containing N <0.2 mmol·L-1. Nutrient solutions were applied at 7- or 10-day intervals to plants growing in a soilless medium in 2.6- or 5.5-L containers. Flowering stems were harvested when the primary florets opened. Total N concentration was measured in leaf tissue from the upper portion of flowering stems. Flower production was not affected by Ca supply, but increased with N supply to a maximum of about four stems per plant on a weekly basis at 28.5 mmol·L-1, then decreased to less than three stems per plant at 57 mmol·L-1. Nitrogen concentration in leaf tissue on a dry mass basis was maintained at 45 ±3 g·kg-1 in plants supplied with N at 28.5 mmol·L-1, 52±5 g·kg-1 at 57 mmol·L-1, but <40 g·kg-1 with N supply of 14 mmol·L-1 or lower. Nitrogen fertilization of Alstroemeria should be managed to maintain leaf tissue N close to 45 g·kg-1.

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Masood Z. Hadi, Mark P. Bridgen, and John P. Sanderson

Procedures were developed to determine if live, adult two-spotted spidermites (Tetranychus urticae Koch) could be surface disinfested before being introduced into in vitro cultures of torenia (Torenia fournieri L.). Three time periods (5, 10, and 15 minutes) and five levels of sodium hypochlorite (0.05% to 0.25%) were evaluated. Surface disinfestation was accomplished by agitating 2 × 3 cm pieces of infested bean leaves in sodium hypochlorite solutions and then drying in a mite drier apparatus. All sodium hypochlorite concentrations disinfested the mites completely, however high concentration levels were lethal to the mites. Exposure periods of 10 and 15 minutes also significantly increased mortality. For optimum disinfestation of two-spotted spidermites with minimum mortality, a concentration of 0.05% sodium hypochlorite and 0.05% Tween-20 for 5 minutes should be used.

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Alessandro Chiari, George C. Elliott, and Mark P. Bridgen

Seven resin-coated fertilizers (RCF) (Osmocote 19–6–12, 18–6–12, 14–14–14, 13–13–13, and 19–6–12, and Polyon 19–6–12, 17–17–17, and 13.5–13.5–13.5) were applied to marketable potted Alstroemeria hybrid FL101 plants to determine their effects on postproduction flowering and growth. The nonfertilized control produced the greatest number of floral stems, total florets, and mean number of florets per stem, but these plants were extremely chlorotic and spindly, and had the lowest fresh weight and number of vegetative stems. In a subsequent experiment, plants were fertilized with low, medium, and high concentrations of either Osmocote 19–6–12 or Sierra HighN 24–4–8. Nonfertilized controls were again chlorotic and spindly, but produced as many florets as fertilized plants. Plants fertilized with Osmocote 19–6–12 had greater fresh weight and more vegetative stems, but fewer total florets than those fertilized with Sierra HighN 24–4–8. We concluded that potted Alstroemeria do not need fertilizer for continued flowering, and fertilization favors production of vegetative stems relative to flowering stems. However, application of RCF to marketable plants prevents chlorosis, increases fresh weight, and, if low to moderate rates of formulations with N–P ratios of at least 6:1 are applied, does not inhibit flowering.

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Chad T. Miller, Krystal Snyder, and Mark P. Bridgen

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Mark P. Bridgen, Masood Z. Hadi, and Madeleine Spencer-Barreto

A laboratory exercise on direct and indirect organogenesis from leaf explants is presented for students of plant tissue culture or plant propagation. Torenia fournieri, the wishbone flower, is used for this laboratory exercise because the in vitro production of adventitious shoots from Torenia is easy to control, seeds are easy to obtain, and plants are easy to grow. Direct shoot organogenesis results from leaf explants without an intervening callus phase, and indirect shoot organogenesis is possible after 4 to 6 weeks of callus production from leaf explants. The basal medium for all forms of organogenesis contains Murashige and Skoog (MS) salts and vitamins, 30 g sucrose/liter, and 7 g agar/liter at pH 5.7. To obtain direct shoot organogenesis, leaf explants should be placed on the MS basal medium with 1.1 μM (0.25 mg·liter-1) 6-benzylaminopurine (BAP) and 0.25 μM (0.05 mg·liter-1) indole-3-butyric acid (IBA). If leaf explants are placed on MS medium with 2.3 μM (0.5 mg·liter-1) 2,4-dichlorophenoxyacetic acid (2,4-D), callus formation will occur. Callus can be subcultured onto a MS medium with 8.88 μM BAP (2.0 mg·liter-1) plus 2.5 μM IBA (0.5 mg·liter-1) for indirect shoot organogenesis to occur.