Search Results

You are looking at 1 - 10 of 14 items for

  • Author or Editor: M. Newman x
Clear All Modify Search

The effects of night temperature (NT) and photosynthetic photon flux (PPF) on time to flower and flower yield in `Bristol Fairy' and `Bridal Veil' Gypsophila paniculata L. (perennial baby's breath) were studied in controlled environments. Plants were grown with nights at 8, 12, 16, and 20C and 450 or 710 μmol·s-1·m-2 photosynthetic photon flux (PPF). Days were at 20C. In both cultivars, the times from the start of treatments to visible bud and from visible bud to anthesis were delayed at the lower PPF and at an NT <20C. The delays in `Bristol Fairy' were greater than those in `Bridal Veil'. Failure of `Bristol Fairy' plants to reach anthesis was common at SC NT and either 450 or 710 μmol·s-1·m-2 PPF; whereas in `Bridal Veil', nearly all plants flowered, regardless of environmental conditions. Flower yield (measured as fresh weight of inflorescences) decreased with NT in `Bristol Fairy' but was highest at 8 or 12C in `Bridal Veil'. In a second experiment using the same cultivars, the effect of curtailing long-day (LD) conditions at various stages on stem elongation and flower yield was investigated. `Bristol Fairy' required more LD cycles (>56) than `Bridal Veil' for maximum stem elongation and flower yield. Terminating LD conditions before the start of inflorescence expansion resulted in lower yields and shorter plants in both cultivars.

Free access

Winter greenhouse production of perennial baby's breath (Gypsophila paniculata L.) is hampered by short daylength, low PPF and low temperatures. Flowering of the popular cultivar `Bristol Fairy'(BF) can be improved by supplemental assimilation lighting, but the costs are rarely justifiable. `Bridal Veil' (BV) is a new cultivar with similar flower morphology to BF. BF and BV were grown under long day (LD) conditions at 8, 12, 16 and 20C night (20C day) and either 450 or 710 μmol s-1 m-2 in controlled environments. Most BF plants failed to lower at 8C in both PPF. Nearly all BV plants flowered irrespective of growth conditions. Flower yield decreased with night temperature in BF but was greatest at 8 or 12C in BV. BF required more LD cycles (>56) than BV for maximum stem elongation and flower yield. Termination of LD conditions before the start of inflorescence expansion resulted in reduced yields in all plants.

Free access

The objective of this study was to determine if blackspot (Diplocarpon rosae, Wolf) resistance and susceptibility is expressed in callus derived from known resistant and susceptible genotypes of roses. Established callus lines of blackspot susceptible hybrid tea roses `Pascali' and `Tropicana' and blackspot resistant species roses Rosa roxburghii and R. setigera were inoculated directly with a blackspot conidia suspension. Uninoculated callus served as controls. Cultures were incubated at 25°C for 28 days in the dark. An evaluation of the appearance and precent change in fresh weight indicated that for all genotypes tested, inoculation resulted in a decline in tissue appearance and rate of weight increase. These results indicated that in vitro. resistance to blackspot differs from the resistance found in whole plants.

Free access

Strawberry fruit were inoculated with the human pathogen E. coli O157:H7, and the bacteria were recovered from the fruit over a 3-day period of storage at room temperature. The bacterial population was maintained on fruit when the inoculation level was relatively high and increased when the inoculation level was low. The volatile metabolites of E. coli O157:H7 growing on plate count agar (PCA) and on inoculated strawberry fruit were collected by a headspace trapping system and analyzed by gas chromatography and GC-mass spectrometry. E. coli O157:H7 grown on PCA produced a variety of volatile compounds including indole as a major component and a series of methyl ketones. A nonpathogenic E. coli also produced these compounds. However, there was not an appreciable amount of indole collected from E. coli O157:H7 inoculated strawberry fruit as compared to the large amount of volatiles produced by the fruit. Strawberry fruit were able to capture over 95% of the vapor phase indole fed to them from a neat source.

Free access

Three application rates of two new growing medium surfactants were tested under two different irrigation systems on Dianthus barbatus plants. The objectives of the study were to determine if either of the surfactants influenced plant growth and development and to determine if surfactant applications decreased irrigation frequencies. The three levels of surfactant tested were 0 mg·L–1 (control), 10 mg·L–1 applied at each watering, and 100 mg·L–1 applied once a week. Each surfactant and rate was tested on hand-watered and ebb-and-flood irrigated plants. D. barbatus plants were grown for 8 weeks in 875-ml (12.7 cm) pots. Plants were watered when at least one plant per treatment showed visible wilt. Results showed that phytotoxicity symptoms occurred with repeated applications of both surfactants tested, especially at the 10 mg·L–1 rate at each watering. Application of either surfactant at 10 mg·L–1 at each watering decreased plant heights, dry weights, and plant widths, and increased phytotoxicity symptoms over the controls and the 100 mg·L–1 weekly treatments. Fewer waterings were required in surfactant-treated containers.

Free access

Our objective was to determine the feasibility of using waste tire rubber and fiber from the processing of waste tires as a root-zone medium for greenhouse crops. Two cultivars of zonal geraniums, `Danielle' and `Kim' were grown in media containing three grind sizes of rubber (10, 6, and 2.4 mm) and fiber from the fabric belting processed from waste tires in three proportions (1 rubber: 1 peat moss, 1 rubber: 1 vermiculite: 2 peat moss, and 2 rubber: 1 vermiculite: 1 peat moss, by volume). Two control media were also included: 1 vermiculite: 1 peat moss and 1 rock wool: 1 peat moss, by volume. The largest plants were grown in the 1 vermiculite: 1 peat moss medium, whereas the smallest plants were grown in the media containing the rubber grinds 2.4 mm and 6 mm making up 50% of the media. The media 1 rubber: 1 vermiculite: 2 peatmoss, regardless of grind or fiber, produced plants equal to the 1 rock wool: 1 peatmoss medium. All plants grown in media containing rubber by products had elevated levels of Zn and Cu in the foliage, but was greatest in media containing 50% rubber. Foliar P: Zn ratio was less for plants grown in media where rubber was 50% of the volume. The P: Zn ratio also was lower in plants grown in media with smaller grind sizes of rubber. Geranium plants can be successfully grown in media containing up to 25% rubber waste products without reducing plant quality.

Free access

The objective of this study was to determine whether tissue culture can be used for studying the blackspot resistance found in some roses. Callus was initiated from leaves, petioles, and stems of resistant and susceptible genotypes. Good callus formation for susceptible roses (hybrid teas) was obtained on a medium containing MS basal salts, vitamins, sucrose, and 8 g/L agar supplemented with 2 mg/L 2,4-D, 1 mg/L NAA, and 0.2 mg/L BA. Callus formation for resistant roses (species roses) was best when the concentrate ions of growth regulators in the medium were halved. Browning in species rose cultures, was decreased with the addition of 0.05 g/L ascorbic acid to the medium followed by incubation in the dark. The subculture calli were inoculated with the fungal conidia and were analyzed for proteins by SDS-PAGE. These protein profiles were compared to those of whole leaf samples. The results are discussed in terms of similarities and differences in the biochemical responses of callus cultures versus whole leaves to the blackspot infection.

Free access

Most modern roses are highly susceptible to the disease blackspot caused by the fungus Diplocarpon rosae. This contrasts to species roses that are resistant to the disease. To gain information on the biochemical factors in this resistance mechanism, we are studying the involvement of proteins. Soluble proteins of modern roses and species roses were extracted and analyzed by SDS-PAGE. When healthy leaves were examined, there were no distinct differences in the protein patterns, indicating that there are no constitutive proteins involved in the disease resistance mechanism. There were no differences between healthy and infected leaves of resistant genotypes. When detached leaves of some susceptible types were infected with the fungus new proteins seemed to appear in the healthy region surrounding the blackspot lesion. These proteins may be involved in resisting the spread of the pathogen.

Free access

The objective of this study was to determine which combination of three types of irrigation systems, three fertilization method, and four growing media produced optimum growth of flowering vinca, Catharanthus roseus. Irrigation systems used included ebb-and-fl ood, drip, and pulse; fertilization methods included slow release, prepackaged, and custom mixed; and the four growing media were peatmoss:perlite:vermiculite (1:1:1, by volume), peatmoss:rockwool (1:1, by volume), and 0.6-cm diameter shredded rubber or fabric from waste tires: vermiculite:peatmoss (1:1:2, by volume). Four replications of five plants each were used in each of the 36 treatment combinations. Plants were potted 29 and 30 May 1996 in 10-cm containers, grown for 10 weeks, and harvested 6 Aug. 1996. The drip-irrigated benches were irrigated once per day for 15 s. Pulse-irrigated benches were watered twice per day for 6 s. This resulted in the drip- and pulse-irrigated plants receiving a similar volume of water daily. Ebb-and-fl ood benches were filled once per day with drainage occurring 15 min after filling. Ending plant heights and dry weights indicated that those plants in the prepackaged fertilizer/drip or ebb-and-fl ood irrigation/shredded tire fiber growing medium were comparable to plants grown in the peatmoss:rockwool medium with the same fertilizer and irrigation methods.

Free access

Hydroponic greenhouse tomato production’s popularity has grown in the United States to meet the demands for year-round availability of fresh tomatoes. Although Salmonella has been the cause of several foodborne illness outbreaks linked to tomatoes, the potential for contamination in hydroponic production is not well understood. The objectives of this study were to determine whether biweekly inoculation of Salmonella in a hydroponic tomato nutrient solution would lead to Salmonella survival and contamination of the tomato fruit and plants, hydroponic nutrient film technique (NFT) troughs, and water receptacles. An avirulent strain of Salmonella Typhimurium was used to contaminate the nutrient solution at a concentration of 105 colony-forming units (CFU)/mL. Inoculation was conducted on day 0 and biweekly until the termination of project at 12 weeks; samples were filtered and plated on selective media. Leaves and biofilm coupons were collected on day 0 and every 2 weeks postinoculation. Leaf samples were analyzed using culture methods. The biofilm coupons were analyzed using tape fluorescence in situ hybridization (FISH) method. Fruit samples were collected 6 weeks postinoculation until termination of project and analyzed using culture methods. Typical Salmonella morphology of colonies on plates streaked from overnight cultures from plant samples were confirmed by automated ribotyping. A 2-log10 reduction of cells was observed in water samples 2 days post initial inoculation. Reduction continued over the 2-week period with few cells surviving until the next inoculation. S. Typhimurium was observed on the surface of the root systems. However, a splash incident resulted in low-level contamination of selected leaves and fruit samples. The results of the study indicate that although contaminated hydroponic nutrient solution led to surface contamination of roots, such an event may not pose a high risk of contamination of hydroponically grown fruit.

Free access