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Abstract

Ethylene (C2H4) and CO2 levels and callus formation were influenced by photoperiods (8 hours-SD; 16 hours-LD) under which ‘Nita’ dahlia stock plants were grown and leaf segments incubated in vitro. Larger callus and higher levels of C2H4 and CO2 were detected when tissues from stock plants under SD were incubated under SD (SD-SD) than when incubated under LD (SD-LD). Tissue under LD-LD or LD-SD formed similar amounts of callus to SD-LD cultures, but C2H4 and CO2 levels were higher. Compared to water-sprayed controls, 2500 mg/liter butanedioic acid mono-(2,2-dimethylhydrazide) (daminozide) sprayed on SD stock plants one day before explant removal promoted callus formation, and C2H4 and CO2 production in tissue incubated under either SD or LD. Daminozide sprayed on LD stock plants had no influence on callus or C2H4, but CO2 was increased under SD or LD incubation.

Open Access

Abstract

Encapsulated 2-chloroethyl-trimethylammonium chloride (chlormequat) stimulated and retarded growth of tomatoes, petunias, snapdragons, and mar-igolds. Low rates (3-6 g of 1, 2 oi 4% active ingredients/liter of growing medium) stimulated earlier bloom up to 14 days in these crops and doubled stem diameter in tomato. Conversely, higher levels of encapsulated chlormequat (12-25 g/liter) retarded plant height to 50% of controls and produced stocky more symmetrical bedding plants without deleterious effects.

Open Access

Rosemary (Rosmarinus officinalis) belongs to the Lamiaceae family, and is native to the Mediterranean and one of the most important medicinal herbs containing antioxidants in its leaves. One of the most important antioxidants is rosmarinic acid (RA). The aim of this study was to test the concentration of (RA) and chlorophyll content in leaves and callus of five successive subcultures of five different genotypes of rosemary. They were: 1) `Majorca'; 2) Rosmarinusofficinalis; 3) `Pine Scented'; 4) `Madeline Hill', and 5) APR. It was found that the highest concentration of RA in leaves was in `Pine Scented', while the lowest concentration was for APR and `Madeline Hill'. However, in the callus the highest RA concentration was for Rosmarinusofficinalis in the second subculture and `Madeline Hill' in the third subculture, while the lowest RA concentration was for `Majorca', `Pine Scented', and APR. The RA concentration in callus declined after the second and the third subculture for Rosmarinusofficinalis and `Madeline Hill', respectively. We concluded that it is preferred to use `Pine Scented' for RA extraction from the leaves while for RA extraction from callus it is better to use Rosmarinusofficinalis in the second subculture or `Madeline Hill' in the third subculture.

Free access

The American Chestnut Foundation (ACF) has conducted a breeding program aimed at developing blight-resistant chestnut trees exhibiting the phenotype of American Chestnut [Castanea dentata (Marsh) Borkh]. Because such plants are difficult to propagate, we developed a protocol for in vitro multiplication of candidate blight-resistant plants resulting from the ACF breeding programs. Dormant shoots were taken from 5- to 8-year-old trees and forced, producing softwood growth for use as a source of explants for shoot multiplication. Best shoot proliferation took place on WPM containing 0.2 mg BA/L. Explant material for the rooting experiments was taken from 6- to 12-month-old proliferating cultures. The basal rooting medium consisted of WPM containing 0.01 mg IBA/L and was overlaid with a thin opaque layer. Rooting was enhanced overall with this bilayer approach. A “D/W” medium (DKW and WPM) was also used as a rooting medium containing 0.01 mg IBA/L and 0.2 mg BA/L, which further enhanced leaf quality and rooting for some genotypes. After several transfers on the bilayer system, explant growth appeared to become less juvenile in stem and leaf development and more analogous to mature later-season growth. The rooting responses and the time for rooting to be induced were highly variable among the different genotypes.

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Buffalograss is native to the Great Plains of North America. Its excellent drought resistance and low growth habit make it a good choice for a low-maintenance turf. A reproducible and efficient regeneration protocol of buffalograss is critical for further genetic transformation. By using immature inflorescences as explants, we have achieved the regeneration of buffalograss of two female clones, `315' and `609', a male clone, NE 84-45-3, and a synthetic cultivar, `Texoka'. Somatic embryogenesis was observed. The medium used for callus initiation was MS basal medium supplemented with various concentrations of 2,4-D and BA. After 4 weeks of dark culture, calli with nodular structures were transferred to the same basal medium supplemented with BA and either a reduced rate of 2,4-D or no 2,4-D. It was demonstrated that 2,4-D at 2 or 3 mg/L is optimal for embryogenic callus production. The presence of BA from 0.1 mg/L to 0.5 mg/L was required for the regeneration of `315', `609', and NE 84-45-3. For `Texoka', 2,4-D at 0.5 mg/L with BA at 0.3 mg/L in the regeneration medium favored normal development of somatic embryos that were capable of germination. A genotypic effect was observed with regard to embryogenic callus production; explants of the male genotype NE 84-45-3 exhibited a higher percentage of embryogenic callus formation than was found for the two female genotypes. A significant seasonal effect was also observed with inflorescences collected in early May exhibiting a higher percentage of callus formation than those collected in the summer and fall.

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Abstract

Biologically active levels of ethylene were accumulated in flask atmospheres of leaf segments and callus of dahlia cultured in vitro. The ethylene levels were dependent on concentrations of α-naphthaleneacetic acid (NAA) and 6-fur-furylamino purine (kinetin) in the medium. NAA promoted ethylene levels to a greater degree than kinetin. NAA at 1 mg liter, but not 5 or 10 mg liter, interacted with kinetin to stimulate ethylene synthesis. Reducing ethylene concentrations in the flasks by potassium permanganate absorption had no effect on callus formation from leaf tissue.

Open Access

Abstract

Interlocular Cavitation (IC) in snap bean pods was studied in 8 commercial cultivars under several irrigation regimes on a sandy soil. In susceptible cultivars, IC was consistently associated with heavy irrigation during pod growth. Little or no IC was found when no more than 1.27 cm of water was applied per week. Irrigation also influenced pod yield, plant weight, ratio of pod weight to plant weight, pod composition, and seed number. Cultivars susceptible to IC showed rapid increase in pod weight when irrigated after 2-3 weeks of moisture stress conditions. However, this rapid increase in pod weight did not induce IC under the conditions tested. Proportion of pod P and K in relation to Ca and Mg increased as irrigation levels were increased. Seed number was related to irrigation and the severity of IC, depending upon cultivar.

Open Access

A new in vitro protocol was developed for multiple bud induction and plant regeneration from embryonic axis explants of four common bean (Phaseolus vulgaris L.) and two tepary bean (P. acutifolius A. Gray) lines. The explants were prepared from two embryo sizes, 3 to 4 mm and 5 to 7 mm, corresponding to pods collected after 15 and 25 days from flowering, respectively. The embryonic axis was cultured on Gamborg's B5 basal medium with 0, 5, 10, or 20 μm BA in combinations with 0, 1, or 2 μm NAA. The cultures were maintained at 24 to 25C under continuous light or incubated in darkness for 2 weeks followed by continuous light before transfer to the secondary B5 medium (0 or 2 μm BA or 2 μm BA plus 4 μm GA3). Adventitious roots or a single shoot with roots formed on the explants cultured on media without plant growth regulators. Multiple buds were induced on all BA media, but more were produced with 5 or 10 μm for most lines. Dark incubation greatly enhanced multiple bud initiation. Shoot buds were not produced on media containing NAA alone or in combinations with BA. On the secondary medium, six to eight shoots per explant for common bean and up to 20 shoots per explant from tepary bean were observed after 3 weeks. Mature, fertile plants were produced from these shoots. Chemical names used: benzyladenine (BA); 1-naphthaleneacetic acid (NAA); gibberellic acid (GA3).

Free access

Dry seeds from two lines of common bean (Phaseolus vulgaris L.) and one cultivar of faba bean (Vicia faba L.) were germinated on Murashige and Skoog (MS) medium containing B vitamins, 30 g sucrose/liter, and either 2.5, 5.0, or 7.5 μm benzyladenine (BA). Axenic seed cultures were grown at 22 to 24C in darkness and under continuous light from cool-white fluorescent tubes (40 μmol·m-2·s-1). Explant tissues were prepared from cotyledonary nodes (CN) and primary nodes (PN) of 14-day-old seedlings. Explants were cultured on corresponding seedling growth medium and maintained under continuous cool-white light (40 μmol·m-2·s-1). The percentages of CN and PN (in one line of common bean) explants that regenerated shoots and the number of shoots per explant (in all germplasm) were highest when nodal tissues were prepared from seedlings germinated in darkness. These responses were optimal on medium containing 5 μm BA during seedling growth and subsequent culture of explants. The number of shoots per explant was two to five times higher on explants cultured on medium with 0.25 to 1.0 μm forchlorfenuron (CPPU) or thidiazuron (TDZ) than on medium with 5 μm BA. Higher (2.5 and 5 μm) CPPU and TDZ concentrations inhibited shoot elongation and stimulated callus production. Histological analyses indicated that adventitious meristems formed 6 to 8 days after explant culture. Progenies from regenerated plants appeared similar to plants raised from the original seed stocks. Chemical names used: N- (phenylmethyl) -1 H- purin-6-amine (benzyladenine, BA); N- (2-chloro-4-pyridyl)-N'- phenylurea (forchlorfenuron, CPPU); N- phenyl -N' -1,2,3-thiadiazol-5-ylurea (thidiazuron, TDZ).

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Plant regeneration has been achieved in two common bean lines from pedicel-derived callus that was separated from the explant and maintained through successive subcultures. Callus was induced either on B5 or MS medium containing 2% sucrose and enriched with 0.5 or 1.0 mg thidiaznron/liter alone or plus various concentrations of indoleacetic acid. The presence of 0.07 or 0.14 g ascorbic acid/liter in the maintenance media prolonged the maintenance time. Up to 40 shoot primordia were observed in 4-week-old cultures obtained from 40 to 50 mg callus tissues on shoot-induction medium containing 1-mg benzyladenine/liter. These shoot primordia developed two to five excisable shoots (>0.5 cm) on medium with 0.1-mg BA/liter. A histological study confirmed the organogenic nature of regeneration from the callus tissues. The R2 line from a selected variant plant showed stable expression of increased plant height and earlier maturity. Chemical names used: ascorbic acid, N- (phenylmethyl)-1H-pnrin-6-amine [benzyl-adenine, BA], 1H-indole-3-acetic acid (IAA), N- phenyl-N'-1,2,3-thiadiazol-5-ylurea [thidiazuron, TDZ].

Free access