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  • Author or Editor: Dennis P. Stimart x
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Nicotiana alata Link and Otto (Jasmine tobacco) was transformed with an autoregulated senescence-inhibition gene construct PSAG12-IPT encoding isopentenyl transferase via Agrobacterium-mediated transformation. Transformation was confirmed by polymerase chain reaction. Transgenic plants exhibited up to 2- to 4-fold fewer senesced leaves, 29% longer in situ flower life, 26% more shoot dry weight, and a 32% to 50% reduction in flowers per branch. Additionally, transgenics were 28% shorter and had up to 174% more branches, indicative of cytokinin overproduction and a lack of tight autoregulation of PSAG12-IPT. Variation among independent transgenics suggests selection for enhanced PSAG12-IPT is feasible. Our observations of increased branching and in situ flower longevity, as well as reduced plant height and flowers per branch provide new information on PSAG12-IPT and its potential value for biological study and horticultural application.

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Abstract

Shoot tips of Exbury azalea (Rhododendron sp.) were proliferated on Anderson's Rhododendron medium supplemented with 6-benzylamino purine (BA), 6-(= ϒ, = ϒ-dimethylallylamino) purine (2iP), 6-(= ϒ, = ϒ dimethylallylamino) purine riboside (2iP-riboside), 6-furfurylaminopurine (kinetin), or 6-(4-hydroxy-3-methylbut-2-enylamino) purine (zeatin). The greatest number of shoots was produced on medium containing zeatin, a lesser number on 2iP and 2iP-riboside, and the least on BA and kinetin. Shoot proliferation was affected by genotype. Few adventitious shoots formed on detached cultured leaves. Shoot tips rooted when subcultured on medium without cytokinin or when inserted in moist milled sphagnum.

Open Access

Abstract

Callus initiated from bulb-scale expiants of the interspecific hybrid Lilium ‘Black Beauty’ on a Linsmaier-Skoog (LS) semisolid medium containing 4 mg/liter 2,4-dichloro-phenoxyacetic acid (2,4-D) was transferred to liquid LS with or without 4 mg/liter 2,4-D and incubated in darkness on a gyrorotary shaker at 100 rpm. Every 7 to 10 days the callus was transferred to fresh medium. The culture was maintained for 3 years. Plants were generated from the callus on semisolid LS at 1 year and 30 months after initiation of the liquid culture. Differentiation began with root formation, then shoots were produced. Supplementing the semisolid medium with 0.3 mg/liter α-naphthaleneacetic acid (NAA) stimulated root formation but shoot production was best on medium without growth regulators or medium containing 0.03 mg/liter NAA. Eleven of the 58 plants recovered (19%) bore variegated foliage but none of the 40 which flowered, including 2 with variegated leaves, deviated from the floral phenotype of ‘Black Beauty’.

Open Access

Ammonium and NO3 uptake from hydroponic solutions containing 1 mm each of (NH4)2SO4 and Ca(NO3)2 were measured during development of Dendranthema ×grandiflorum (Ramat.) Kitamura `Iridon', `Sequoia', and `Sequest'. Nitrogen depletion from solutions approximated a 1 NH4: 1 NO3 ratio throughout a 90-day growth cycle (r = 0.96). Although harvest date cultivar interactions were significant for both forms of N, overall patterns of N uptake were similar among cultivars. Nitrogen removal from hydroponic solutions (milligrams per plant) was greatest from days 40 to 60; however, N removal (milligrams per gram of tissue dry weight) was greatest in the first month of development and decreased steadily until day 90. From day 40 to 60, new leaf development ceased while inflorescence buds developed to ≈1.0 cm in diameter. After this time, N uptake decreased rapidly as inflorescences expanded. Correlations between morphological changes and N demand could maximize the efficiency of applied N by matching form and application timing with plant needs.

Free access

Adventitious shoot formation in vitro from Antirrhinum majus L. hypocotyls was investigated using two inbred lines, the most and least regenerative lines selected from screening. Time course analysis indicated cell division in the most regenerative line occurred first in one or a small number of epidermal cells with periclinal and anticlinal divisions. Subsequently, cortical then vascular cells were recruited beneath the dividing epidermal cells. Once shoots formed, their vascular system was continuous with the original hypocotyl explant. The least regenerative line had no cell division directed toward organogenesis. Shoot formation on hypocotyls of A. majus was adventitious in origin, by direct organogenesis and genotype dependent.

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Expanding shoot tips of Pulmonaria `Roy Davidson' and Pulmonaria saccharata `Margery Fish' were cultured in vitro on a modified Murashige and Skoog medium containing BA to establish proliferating cultures for use in comparing BA concentrations on shoot proliferation and rooting. The optimum level for shoot proliferation was 8.8 μm BA. Greatest rooting was on medium without BA. Genotype and time in culture influenced shoot and root counts. Chemical names used: N6-benzyladenine (BA)

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Impatiens (Impatiens walleriana) are currently among the most valuable and widely cultivated floriculture crops in the world. Attractive floral display is a primary goal for breeders of impatiens. Although breeders have selected for this trait, little consideration has been given to floral longevity as a means to increase the floral display of bedding crops. In this study, 259 commercial inbred lines of impatiens were grown in a greenhouse and evaluated for floral longevity as defined by the time between when a flower was completely open to when all of the petals abscised from the pedicle. Mean floral longevity of inbreds ranged from 3.3 ± 0.4 to 15.8 ± 2.5 days. Twelve inbreds (six with long floral longevity and six with short floral longevity) were chosen and crossed in a half diallel to create 66 hybrids that were analyzed for floral longevity in three greenhouse environments. Mean floral longevity of hybrids across greenhouse environments ranged from 2.8 ± 0.4 to 14.1 ± 2.8 days. Significant general (GCA) and specific (SCA) combining abilities for floral longevity were detected. GCA mean squares were 37 times larger than SCA mean squares, revealing that additive genetic effects play a more important role in the inheritance of floral longevity in impatiens. This information, coupled with the significant amount of variation for floral longevity among inbreds, indicates that there is good potential for breeding for floral longevity in impatiens to improve the floral display of hybrids.

Free access

Abstract

Zinnia is a relatively small genus of the tribe Heliantheae (Asteraceae) comprising 17 species endemic to North and South America (19). Two cultivated species, Z. elegans Jacq. (2n = 24 or 48) and Z. angustifolia HBK (2n = 22), are classified within the subgenus Zinnia, a taxon of annual and perennial herbs with base chromosome numbers of n = 11 and n = 12. The subgenus Zinnia is subdivided further into sections, with Z. elegans in the section Zinnia and Z. angustifolia in the section Mendezia.

Open Access