bluuebunny/crossref_metadata_2025 huggingface dataset:
Industrial Mineral Aggregate Amendment Affects Physical and Chemical Properties of Pine Bark Substrates
Authors: Owen James S. , Warren Stuart L. , Bilderback Ted E. , Albano Joseph P.
Published: February 2019

Nonpoint source effluent containing nitrate N (NO3-N) and phosphorus (P) from containerized nursery production has garnered local, regional, and national concern. Industrial minerals have long been used as absorbents, agrochemical carriers, and barriers to retain heavy metals. Our objective was to determine the effects of a palygorskite–bentonite industrial mineral aggregate on the physical and chemical properties of a soilless substrate and the resulting impact on water and nutrient efficiency. The mineral aggregate had two particle size ranges (0.25 to 0.85 mm or 0.85 to 4.75 mm) in combination with two temperature pretreatments [low volatile material (LVM) or regular volatile material (RVM)]. A representative substrate (8 pine bark:1 coarse sand) of the southeastern United States nursery industry was also included in the study as a control. Cotoneaster dammeri C.K. Schneid. ‘Skogholm’ was grown in all substrates on collection pads that allowed for the quantification of daily influent and effluent volumes to calculate cumulative NO3-N, ammonium N (NH4-N), and dissolved reactive phosphorus (DRP) loss for 112 days. There was a 13% to 15% decrease in daily water application volume with no effect on Skogholm cotoneaster growth, which equated into a savings of 22 to 26 L per 14-L container in mineral aggregate-amended substrates compared with a sand-amended substrate (control). Mineral aggregate-amended substrates decreased NH4-N and DRP effluent 39% and 34%, respectively, compared with the control. In addition, LVM and particle size 0.25 to 0.85 mm reduced effluent DRP compared with the 0.85 to 4.75-mm RVM aggregate. Plant dry weight was unaffected by any of the treatments. Substantial nutrient content reduction in effluent and reductions in water application were achieved with amending pine bark with 0.25 to 0.85 mm LVM industrial mineral aggregate. A 0.25 to 0.85-mm LVM industrial mineral aggregate pine bark-amended substrate reduced effluent DRP and NH4-N greater than 40% and reduced water application 15% or 26 L when compared with the industry representative substrate.
Ontogenesis of the Somatic Embryogenesis of Habanero Pepper (Capsicum chinense Jacq.)
Authors: Santana-Buzzy Nancy , López-Puc Guadalupe , Canto-Flick Adriana , Barredo-Pool Felipe , Balam-Uc Eduardo , Avilés-Viñas Susana , Solís-Marroquín Daniela , Lecona-Guzmán Carlos , Bello-Bello Jericó Jabín , Gómez-Uc Eunice , Mijangos-Cortés Javier O.
Published: February 2019

The ontogenesis of direct high-frequency somatic embryogenesis of C. chinense induced from hypocotyl was characterized through a histological analysis of the different phases in the histodifferentiation process during the development of the somatic embryo. The anatomical analysis was carried out since the hypocotyl segments were placed in the culture medium until 45 days of culture. The somatic embryos were induced and maintained in Murashige and Skoog medium supplemented with 2,4-dichlorophenoxyacetic acid (9.5 μm). Samples of tissues and organs were taken every 24 h, fixed in formalin acetic alcohol, and embedded in plastic resin. They were cut into serial sections (5 μm) and stained with toluidine blue. The analysis revealed that the proembryogenic cells originated just from provascular hypocotyl cells. Provascular cells acquired the embryogenic competence 48 h after induction and an intense mitotic division was observed and embryogenic structures were generated first along the vascular strands, which subsequently evolved into somatic embryos. After 2 weeks, there were observed embryos at different stages of development (preglobular, globular, heart-shaped, torpedo-shaped, and cotyledonary). This is the first report dealing with the ontogenesis of the direct somatic embryogenesis of C. chinense, and it is the most complete histological characterization carried out on somatic embryogenesis in the Capsicum genus to date.
After-ripening, Light Conditions, and Cold Stratification Influence Germination of Marula [Sclerocarya birrea (A. Rich.) Hochst. subsp. caffra (Sond.) Kokwaro] Seeds
Authors: Moyo Mack , Kulkarni Manoj G. , Finnie Jeffrey F. , Van Staden Johannes
Published: February 2019

Marula [Sclerocarya birrea (A. Rich.) Hochst. subsp. caffra (Sond.) Kokwaro (Anacardiaceae)] is used in many African countries as a food crop and is also in demand for industrial purposes. The fruit pulp has high vitamin C levels and the nuts have a high protein and oil content. The fruit pulp is commercially used in the production of an alcoholic beverage (Amarula Cream) and the oil is gaining importance in the cosmetic industry. Although attempts are being made to domesticate this high-value indigenous tree, there is very limited information available on aspects of seed germination. Our study investigated the role of light, temperature, cold stratification, and after-ripening on seed germination of S. birrea. Temperatures between 25 and 35 °C favored germination of opercula-removed seeds under continuous dark conditions. White light completely inhibited seed germination with the inhibitory effect being reversed when seeds were transferred to dark conditions. This photoinhibitory effect on opercula-removed seeds was lost after 12 months of seed storage at room temperature in the dark. Cold stratification (5 °C) of intact seeds for 14 days significantly improved germination (65%) as compared with nonstratified seeds (32%). Pregermination treatments (acid scarification, boiling water, dry heat, soaking, and plant growth regulators) of S. birrea seeds did not promote germination. Seeds of S. birrea can be considered orthodox because they tolerated desiccation without significant loss of viability. Both intact and opercula-removed seeds readily imbibe water suggesting physiological rather than physical dormancy. The highest germination percentage was recorded under constant dark conditions at 25 °C for opercula-removed seeds exposed to an after-ripening period of 12 months. This study indicates that after-ripening, light conditions, and cold stratification are critical factors for germination of S. birrea seeds.
The Impacts of Yield on Nutritional Quality: Lessons from Organic Farming
Authors: Benbrook Charles
Published: February 2019

A majority of well-designed studies comparing nutrient density (milligrams of a given nutrient per kilogram of food) in organically and conventionally produced fruits and vegetables show modest to moderately higher concentrations of most nutrients in organic produce. Likewise, organic produce is either as flavorful as or more flavorful than conventional produce and often tends to store better. Physiological factors that may account for these differences include the levels and form of nitrogen applied to crops, the balance of macro- and micronutrients in the soil, soil quality, average cell size, glycosylation status, and concentrations of plant secondary metabolites.
Hypoxia Controls Hypocotyl and Radicle Length in Germinated Impatiens Seeds
Authors: Waterland Nicole L. , Gladon Richard J.
Published: February 2019

Sowing germinated seeds for bedding plant production can decrease the production time and reduce profit losses from sporadically or poorly germinating seeds. Low concentrations of O2 have been used to control radicle length in Impatiens wallerana Hook. F., but only a brief exposure period could be used (12 to 24 h). The effects of prolonged exposures are unknown. Our first objective was to determine if impatiens seedlings could be acclimated to an extreme hypoxic environment by a preliminary exposure to a less severe hypoxic exposure. Our second objective was to determine the effects of longer-duration (greater than 24 h) treatments at low-O2 concentrations on hypocotyl and radicle length, abnormal seedling development, and subsequent plant growth and development. Our third objective was to provide a commercial recommendation of a low-oxygen treatment or treatments that could be used for temporary storage of unused germinated seeds. Germinated seeds were placed in various combinations of 0.5%, 1.0%, and 1.5% O2 for either 4 days (Expt. 1) or 3 days (Expt. 2) followed by 24 h in air to simulate shipping. Germinated seeds were less tolerant of 0.5% O2 than greater O2 concentrations, especially during the first 2 days of treatment, and more abnormal seedlings developed at 0.5% O2. Germinated seeds were more tolerant of 0.5% O2 during Days 3 and 4 of the treatment period or when days at 0.5% O2 were interspersed between days of 1.0% or 1.5% O2. This indicates that germinated impatiens seeds can tolerate extremely low-O2 for longer durations (greater than 24 h) when first acclimated to lower O2 concentrations. Treatment of 1.5% O2 for Days 1 and 2 followed by 0.5% O2 for Day 3 is recommended for commercial use. Hypocotyl and radicle length was controlled to 1 mm without development of abnormal seedlings. Fully grown plants from seedlings that received low-O2 treatments were not different from control plants with regards to hypocotyl and radicle length, percentage abnormal seedlings, and plant growth and quality, ensuring there were no long-term detrimental effects.
Red to Far-red Ratio During Seed Development Affects Lettuce Seed Germinability and Longevity
Authors: Contreras Samuel , Bennett Mark A. , Metzger James D. , Tay David , Nerson Haim
Published: February 2019

Thermoinhibition and photosensitivity are two characteristics of lettuce seed that frequently affect its stand. The main objective of this study was to evaluate the hypothesis that lettuce seed germinability and longevity are affected by the red to far-red light ratio (R:FR) under which seeds maturate. ‘Tango’ lettuce seeds were produced in growth chambers under one of two treatments: 1) red-rich light (R treatment) and 2) far-red-rich light (FR treatment). For both treatments, the percentage of normal seedlings germinated at 20 °C–light was ≈100%. When germinated under the light, seeds from the R treatment exhibited a higher germination percentage and a faster germination (under a broader range of temperatures) than seeds from the FR treatment. When germinated in the dark, seeds from the R treatment germinated 100% between 12 and 23 °C and over 50% at 30 °C, whereas seeds from the FR treatment germinated less than 35% between 12 and 23 °C and less than 5% at 30 °C. Seeds from the R treatment had lower abscisic acid (ABA) content and were better able to germinate when exposed to external ABA concentrations than seeds from the FR treatment. Seed longevity as assessed by the accelerated aging test was higher in seeds from the FR treatment, indicating that red-rich light was detrimental to longevity. In another experiment, lettuce seeds that developed under similar conditions were harvested at approximately the moment of maximum dry weight accumulation and desiccated in dark, far-red, red, or fluorescent + incandescent light. Seeds desiccated under red light exhibited higher dark germination than the other treatments; however, no differences were observed in thermoinhibition or longevity. These results suggest that lettuce seed produced in an environment with a high R:FR light ratio will exhibit reduced thermoinhibition and photosensitivity as compared with production in a lower R:FR light environment.
Response of Young and Maturing Citrus Trees Grown on a Sandy Soil to Irrigation Scheduling, Nitrogen Fertilizer Rate, and Nitrogen Application Method
Authors: Morgan Kelly T. , Wheaton T. Adair , Castle William S. , Parsons Laurence R.
Published: February 2019

This study examined the effect of irrigation rates, nitrogen (N) fertilizer rates, and methods of applying N on growth and productivity of young (3 to 5 years old) and maturing (8 to 10 years old) citrus trees. A long-term study was conducted with the following objectives: 1) to measure the main effects of N rate, N application method, and irrigation on citrus tree growth and production from planting to maturity; 2) to establish growth and production relationships for long-term N rates and irrigation on well-drained sandy Entisols; and 3) to determine the effect of split fertilizer applications at two soil moisture regimes on citrus growth and production for two tree age classes as trees mature. Irrigation was applied using two selected ranges of soil moisture tensions and annual N rate varied by tree age as percentages of recommended. Methods of applying N included a dry granular fertilizer (DGF) containing soluble N applied four times annually or a controlled-release fertilizer (CRF) applied once per year and fertigation applied either four (FG04) or 30 (FG30) times annually. Canopy size and yield were higher with the moderate irrigation rate compared with the low rate for both young and maturing trees. Critical N rates for both canopy volume and yield were between 178 and 200 kg·ha−1. The CRF and FG30 treatments produced larger trees and higher yields compared with FG04 and DGF in the young tree study, indicating that younger trees benefitted from frequent split fertilizer applications. As the trees matured and filled their allocated space, the two irrigation rates were continued and N was applied at six rates using either DGF or FG30. For these 8- to 10-year-old trees, critical values of N application rates were 210 and 204 kg·ha−1 for DGF and FG30, respectively. The absence of a significant interaction between N rate and application method indicated that N uptake efficiency was similar for all application methods tested. DGF and FG30 treatments resulted in similar maturing tree yields and fruit total soluble solids. Canopy volumes, for the same trees, were significantly greater all 3 years with the FG30 treatment compared with DGF. Thus, if increase in tree size is desired, increased number of split applications will likely promote tree growth; however, little increase in fruit yield may be obtained.
Response of Container-grown Nursery Plants to Chlorine Used to Disinfest Irrigation Water
Authors: Cayanan Diane Feliciano , Dixon Mike , Zheng Youbin , Llewellyn Jennifer
Published: February 2019

The recycling of irrigation water may cause the dispersal of plant pathogens. Irrigation water disinfected with 2.4 mg·L−1 of free chlorine for 5 min was overhead-applied to 17 container-grown nursery plants for 11 weeks in a commercial nursery to evaluate the response of container-grown nursery plants to chlorine. No visual symptoms of injury or growth reduction were observed on the evergreen shrubs (Juniperus horizontalis, Thuja occidentalis, Buxus microphylla, Picea glauca, Rhododendron catawbiense, Taxus media, and Chamaecyparis pisifera), but there were visual injuries and/or growth reduction on some of the deciduous shrubs (Salix integra, Hydrangea paniculata, Prunus ×cistena, Weigela florida, Physocarpus opulifolius). Symptoms of anthracnose were reduced on Cornus alba plants treated with chlorinated water. The chlorine treatment did not affect leaf chlorophyll content. The chlorine treatment killed all fungi and oomycetes in the irrigation water (DNA multiscan). Although there were visible leaf injuries and growth reduction on some of the deciduous plants, chlorine injury did not render them unsalable. Results suggest that irrigation water treated with 2.4 mg·L−1 free chlorine for 5 min will effectively control the dispersal of common plant pathogens without reducing the market value of container-grown plants.
Apple Root Growth, Turnover, and Distribution Under Different Orchard Groundcover Management Systems
Authors: Yao Shengrui , Merwin Ian A. , Brown Michael G.
Published: February 2019

Minirhizotrons were used to study root emergence, turnover, and depth distribution of apple (Malus ×domestica Borkh.) rootstocks (M.9/MM.111) under four groundcover management systems (GMSs)—pre-emergence herbicide (Pre-H), postemergence herbicide (Post-H), mowed sod grass (Grass), and hardwood bark mulch (Mulch)—that had been maintained since 1992 in an orchard near Ithaca, NY. Two root observation tubes were installed on both sides of one tree in three replicates for each GMS treatment. Roots were observed by camera at 2- to 3-weekly intervals during the growing seasons of 2002 and 2003 and from whole tree excavations in Apr. 2000. Tree growth and yield observations from 1992 to 2003 showed that Mulch and Post-H treatments produced more tree growth and higher yields than other treatments during most years; the Grass treatment usually had the smallest trees and lowest yields. More root emergence was observed in a light crop year (2002) than in a heavy crop year (2003). Pre-H treatment trees had more total roots and new roots than all other treatments, and trees in Grass plots had fewer total roots than others. Trees in Mulch plots had more shallow roots, and trees in Grass plots had more deep roots than others. Root diameter was positively correlated with overwintering root survival. The Pre-H treatment trees had greater root mortality than other trees during an unusually hot and dry growing season (2002) and this was attributed to higher shallow soil temperatures in this treatment. The GMS treatments affected root number and root depth distribution patterns. Despite microsprinkler irrigation, hot, dry weather conditions coincided with decreased root growth, increased root mortality, and reduced root median lifespan. GMS treatments affected root growth, turnover, and distribution at this orchard, and these differences were linked with long-term trends in tree growth and fruit production in this study.
Impacts of Handling and Transport on the Growth and Survival of Balled-and-burlapped Trees
Authors: Koeser Andrew K. , Stewart J. Ryan , Bollero Germán A. , Bullock Donald G. , Struve Daniel K.
Published: February 2019

Transplanted trees are exposed to numerous stresses from the time of harvest until establishment in the landscape. Although an individual stress factor may be the sole cause of plant death or decline, it is more likely a combination of stress factors cause reduced growth or death after planting. In an effort to isolate the stresses associated with three critical stages in the transplanting process (i.e., initial harvest, handling, and transport), 5-cm-caliper, balled-and-burlapped Acer rubrum L. ‘Red Sunset’ (red maple) and Acer platanoides L. ‘Pond’ (Norway maple) trees at three sites (Urbana, IL; Union, IL; and Manitowoc, WI) were subjected to three treatments: root-pruned, handled, and transported. Effects of water stress, root severance, and root-ball disruption on twig elongation and tree survival were measured for each treatment and compared with unaltered control trees. Twig elongation was greater in unaltered control trees when compared with root-pruned trees. In addition, root-pruned trees exhibited greater twig elongation when compared with either handled or transported trees suggesting that although initial root severance did affect growth, it was not as detrimental as lifting and handling. In addition, twig elongation was not different between handled and transported trees. Water potential measurements ranged from –0.2 to –2.0 MPa, suggesting water stress was not a critical factor during the time of transplanting. Similarly, root-ball soil moisture varied little between treatments over the course of transplanting. Results suggest rough handling before and after transport should be minimized in an effort to maximize growth and transplant success.
Maximum Potential Vegetative and Floral Production and Fruit Characteristics of Watermelon Pollenizers
Authors: Dittmar Peter J. , Monks David W. , Schultheis Jonathan R.
Published: February 2019

Triploid (seedless) watermelon [Citrullus lanatus (Thunb.) Matsum. and Nak.] pollen is nonviable; thus, diploid (pollenizer) watermelon cultigens are required to supply viable pollen for triploid watermelon fruit set. The objective of this research was to characterize maximum potential vegetative growth, staminate and pistillate flower production over time, and measure exterior and interior fruit characteristics of pollenizer cultigens. Sixteen commercially available and numbered line (hereafter collectively referred to as cultigens) pollenizer and two triploid cultigens were evaluated in 2005 and 2006 at Clayton, NC. Vegetative growth was measured using vine and internode length, and staminate and pistillate flower development was counted weekly. Fruit quality and quantity were determined by measuring individual fruit weights, soluble solids, and rind thickness. Based on vegetative growth, pollenizer cultigens were placed into two distinct groups. Pollenizers, which produced a compact or dwarf plant were ‘Companion’, ‘Sidekick’, ‘TP91’, ‘TPS92’, and ‘WC5108-1216’. Pollenizers having a standard vine length were ‘Jenny’, ‘High Set 11’, ‘Mickylee’, ‘Minipol’, ‘Pinnacle’, ‘Summer Flavor 800’ (‘SF800’), ‘Super Pollenizer 1’ (‘SP1’), and ‘WH6818’. Cultigens with compact growth habit had shorter internodes and vine lengths compared with the cultigens with standard growth habit. Cultigens with the greatest quantity of staminate flower production through the entire season were ‘Sidekick’ and ‘SP1’. The lowest number of staminate flowers was produced by ‘TP91’ and ‘TPS92’. Based on fruit quality characteristics and production, pollenizers currently or possibly marketed for consumption include ‘Mickylee’, ‘SF800’, ‘Minipol’, ‘Jenny’, and ‘Pinnacle’. The remaining cultigens evaluated in this study should be used strictly as pollenizers based on fruit quality. Arrangement of diploid pollenizers in a commercial planting of triploid watermelons is an important consideration depending on plant vegetative development. Based on staminate flower production, cultigens with higher staminate flower production are potentially superior pollenizers and may lead to improved triploid quality and production. Furthermore, pollenizer selection by fruit characteristics should include a rind pattern easily distinguished from triploid fruit in the field.
Mechanical Hedge Pruning of Pecan in a Relatively Low-light Environment
Authors: Wood Bruce W.
Published: February 2019

Long-term productivity of commercial pecan [Carya illinoinensis (Wangenh.) K. Koch] enterprises in relatively low-light environments such as the southeastern United States are limited by excessive tree crowding as orchards age. An effective horticultural strategy for countering this problem in relatively high-light environments is mechanical hedge-type pruning; however, uncertainty persists regarding the best strategies in low-light environments. This report describes the results of a 4-year study regarding the response of ≈25-year-old ‘Desirable’ pecan trees to different mechanical hedgerow-type, moderate canopy width (i.e., 2.43-m cuts from tree axis) pruning strategies. Canopy treatments were nonpruned control (NPC), annual dormant season side-hedge pruning on two faces, annual summer season side-hedge pruning on two faces, and alternating annual dormant season side-hedge pruning on a single alternating face. Relative to the NPC treatment, all three pruning strategies: 1) reduced in-shell nut yields by roughly 19% to 38%; 2) reduced marketable nut-meat yield by ≈19% to 36%; 3) failed to stimulate shoot development or fruiting within the central interior zone of tree canopies; 4) increased kernel percentage of nuts; 5) increased nut-meat grade; 6) substantially reduced alternate bearing intensity (I = 0.51 to ≈0.20); and 7) reduced orchard crowding. Pruning-associated reductions in nut yield appear sufficient to limit the commercial usefulness of annual or biennial mechanical hedgerow-type pruning of ‘Desirable’ pecan orchards at moderate canopy widths in relatively low-light environments such as the southeastern United States.
Photoregulation of Bioprotectant Content of Red Leaf Lettuce with Light-emitting Diodes
Authors: Stutte Gary W. , Edney Sharon , Skerritt Tony
Published: February 2019

Lactuca sativa cv. Outredgeous was grown under either fluorescent lamps or light-emitting diodes (LEDs) to test the hypothesis that antioxidant potential could be regulated by light quality. Red leaf lettuce was grown at 300 μmol·m−2·s−1 of photosynthetically active radiation, 1200 μmol·mol−1 CO2, 23 °C, and an 18 h-light /6-h dark photoperiod in controlled-environment chambers. The LED treatments were selected to provide different amounts of red (640 nm), blue (440 nm), green (530 nm), and far-red (730 nm) light in the spectra. Total anthocyanin content and the oxygen radical absorbance capacity of the tissue were measured at harvest. The source of light had a dramatic effect on both plant growth and production of radioprotective compounds. LEDs resulted in 50% greater bioprotectant content per plant at the same light level over triphosphor fluorescent lamps. Blue LEDs (440 nm) appeared to regulate the metabolic pathways leading to increased concentration of bioprotective compounds in leaf tissue. LED lighting induced a number of effects on morphology that increased both accumulation of bioprotective compounds and total yield.
Comparison of Citrus Sector Competitiveness between Turkey and EU-15 Member Countries
Authors: Fidan Halil
Published: February 2019

A missing component of existing research on Turkey's citrus products is examination of their revealed comparative advantage (RCA). Such information would enable a comparison of Turkey and EU-15 countries in regard to citrus sector competitiveness. Therefore, this study calculates the RCA for citrus products and explores their competitiveness as well as components of their competitive performance. RCAs for citrus trade performances of both EU-15 countries and Turkey are examined, and the sources of export performance and competitiveness are newly presented. The results indicate that the principle of comparative advantage is a useful tool for understanding the future of citrus agriculture in EU-15 countries and Turkey. In line with the assumption that the dynamics of comparative advantage have become increasingly transparent as citrus markets have become less fettered by government trade, this study uses an RCA index to investigate the patterns of comparative advantage in the EU-15 countries and Turkey in regard to citrus exports. Since the beginning of the Entry Price System in the European Union in 1995, significant changes in citrus export performance have occurred. The RCA index of the Turkish citrus sector within EU-15 countries (RCAe) shows that Greece, Spain, Italy, and Portugal are Turkey's main competitors. The RCAe index and relative trade advantage index indicate that Turkey's competitive power is greater than those of Spain, Italy, Greece, and Portugal in lemon/limes and grapefruit exports.
Modified Ethylene Signaling as an Example of Engineering for Complex Traits: Secondary Effects and Implications for Environmental Risk Assessment
Authors: Little Holly A. , Grumet Rebecca , Hancock James F.
Published: February 2019

The next wave of genetically engineered crops will use genes that modify gene regulation, plant metabolism, or signal transduction. The potential for these genes to have cascading effects on metabolism, physiology, and development increases the possibility for unintended effects that influence crop performance or environmental impact. This review examines altered ethylene signaling as an example of a complex trait with many horticultural applications. Genes for modified ethylene production or perception intended to regulate ripening, senescence, or stress or disease resistance have been observed to cause a broad range of secondary effects, including modified growth and development and increased severity to biotic and abiotic stresses. Successful use of complex traits in crop varieties will frequently require methods to reduce secondary effects, including the use of targeted gene expression. Risk assessment will need to consider observed pleiotropic effects on fitness within the context of potential environmental impacts.
Sesquiterpene Lactones and Bitterness in Korean Leaf Lettuce Cultivars
Authors: Seo Myeong Whoon , Yang Dong Sik , Kays Stanley J. , Lee Gung Pyo , Park Kuen Woo
Published: February 2019

The principal bitter sesquiterpene lactones (BSLs; latucin, 8-deoxylactucin, and lactucopicrin) in six red and four green-pigmented leaf lettuce (Lactuca sativa L. var. crispa L.) cultivars were identified and quantified using high-performance liquid chromatography, proton nuclear magnetic resonance, and liquid chromatography–mass spectrometry and the contribution of each to the overall bitterness was determined. The concentration of each BSL and the total varied significantly among cultivars and there were significant differences resulting from leaf color (green versus red) and morphology (cut versus curled leaves) with red and curled leaf cultivars having higher BSL concentrations. The concentrations of lactucin, 8-deoxylactucin, and lactucopicrin ranged from 2.9 to 17.2, 2.8 to 17.1, and 8.8 to 36.1 μg·g−1 dry weight, respectively, with the total concentration ranging from 14.6 to 67.7 μg·g−1. Bitterness of the cultivars was assessed using a bitter activity value calculated using the concentration and bitterness threshold value for each BSL. Lactucopicrin was the primary contributor to bitterness as a result of its concentration and lower bitterness threshold; its relative proportion of the total bitterness activity value across all cultivars was over 72%. The concentration of individual BSLs differed with leaf location on the plant (i.e., basal, midstalk, and flower stalk). The concentrations in lactucin, 8-deoxylactucin, and lactucopicrin in flower stalk leaves were significantly higher (i.e., 2.9, 12.4, and 5.4 times, respectively) than in basal leaves, with the concentrations increasing acropetally. Genetic differences among cultivars and with leaf location on the plant contribute to the wide range in bitterness in lettuce.
Development of a Range of Polyploid Lines in Petunia hybrida and the Relationship of Ploidy with the Single-/Double-flower Trait
Authors: Ning Guo-Gui , Shi Xue-Ping , Hu Hui-Rong , Yan Yan , Bao Man-Zhu
Published: February 2019

A set of Petunia hybrida plants encompassing a range of ploidy levels was developed through colchicine-mediated induction of chromosome doubling. The resulting double-flower tetraploid plants were cross-hybridized with inbred single-flower diploid lines to generate F1 populations with segregation for ploidy level and flower type. The initial in vivo application of colchicine to seedling apical tips produced mixoploid plants of petunia at a high rate of efficiency. Thus, 95% of the shoot tips treated with colchicine for 48 h resulted in polyploid mutant plants, and no difference in this efficiency was observed using concentrations of colchicine between 0.2 and 2.0 mg·mL−1. Of the polyploid plants, 10% were found to be tetraploid and 85% were mixoploid (chimeric). Compared with their diploid counterparts, polyploid plants underwent reduced elongation growth during the first 2 weeks and had thicker stems and shorter internodes resulting in dwarfing of the whole plant. In extreme cases, very slow growth rates produced stunted plantlets. Polyploid plants also had larger, thicker leaves and, in some cases, the leaves that developed after 1 month of growth appeared seriously malformed. Octoploid plants were also obtained and these tended to have more extreme phenotypes. Pure tetraploid plants of double-flower petunia were isolated by the in vitro culture of explants from the initial chimeric tetraploid mutants. These were crossed with three inbred single-flower diploid lines (S1, S2, and S3) thereby generating F1 populations that showed segregation for flower type and ploidy level and included the generation of triploid plants. In the tetraploid plants, flower diameter and the number of flower petals were not changed significantly (P > 0.05) compared with the original diploid double-flower plants, but observation of the pollen grains revealed segregation for size consistent with the increased ploidy level. Analysis of the F1 progeny plants also indicated that chromosome number is not necessary but sufficient to cause the production of semidouble-flowered plants. Flower color and flower diameter were also analyzed in the F1 progeny and complex patterns of inheritance were inferred. In addition to single and double flowers, semidouble-flowered plants were also suggested to be generated by the hybridization of 2n or 3n pollen from the double-flower tetraploid plants with the single-flower diploid lines.
Organic Orchard Floor Management Systems for Apple Effect on Rootstock Performance in the Midwestern United States
Authors: Stefanelli Dario , Zoppolo Roberto J. , Perry Ronald L. , Weibel Franco
Published: February 2019

In organic apple production systems, orchard floor management is of prime importance because it determines weed management and soil fertility. In this experiment, we evaluated the response of the cultivar Pacific Gala on three rootstocks of different vigor: M.9 NAKB 337, M.9 RN 29, and Supporter 4 (in respective order of vigor from dwarfing to semivigorous). The rootstocks were also evaluated for the response to three orchard floor management systems (OFMSs): mulching using alfalfa hay, flame burning, and shallow strip tillage using the Swiss sandwich system (SSS). The experiment was conducted in an experimental orchard planted in 2000.
Identification of Crucifer Accessions from the NC-7 and NE-9 Plant Introduction Collections That Are Resistant to Black Rot (Xanthomonas campestris pv. campestris) Races 1 and 4
Authors: Griffiths Phillip D. , Marek Laura Fredrick , Robertson Larry D.
Published: February 2019

Black rot, caused by Xanthomonas campestris pv. campestris (Pam.) Dawson (Xcc), is a serious disease of vegetable crucifers worldwide. The USDA NC-7 and NE-9 regional PI stations maintain vegetable, mustard, and oilseed crucifers, of which 4084 accessions were available for testing, representing 23 genera and 125 species. These accessions were evaluated for resistance to black rot after wound inoculation with race 1 of the pathogen. Accessions that were symptomless for race 1 of Xcc were replanted and inoculated with race 4 of the pathogen to identify accessions with resistance to both races. Symptomless responses were observed in 362 accessions of the mustard species (Brassica juncea, Brassica carinata, and Brassica nigra), in particular, B. juncea for which 353 of the 389 accessions tested were symptomless. Resistance was identified in five accessions of B. carinata out of 63 evaluated (PI 193460, PI 193959, PI 194254, PI 280230, PI 633077) determined by repeated symptomless responses after inoculation and four accessions of B. nigra from the 83 evaluated (PI 197401, A 25399, A 25401, PI 458981). Five accessions of Brassica rapa (PI 633154, A9285, PI 340208, PI 597831, PI 173847) were identified, which represent promising new sources of resistance to Xcc. Incomplete resistance was identified in an accession of Eruca sativa (PI 633207), an accession of Lepidium spp. (PI 633265), an accession of Sinapis arvensis (PI 296079), and two accessions of B. napus (PI 469733 and PI 469828). These identified accessions represent germplasm that can be used in breeding for resistance to Xcc in vegetable crucifers through interspecific crossing.
Lignan and Nutrient Concentrations in American Mayapple (Podophyllum peltatum L.) in the Eastern United States
Authors: Zheljazkov Valtcho D. , Jones Andrew M. , Avula Bharathi , Maddox Victor , Rowe Dennis E.
Published: February 2019

Podophyllotoxin is an anticancer compound found in Indian mayapple (Podophyllum emodii Wall.), American mayapple (Podophyllum peltatum L.), and other species. Podophyllotoxin and its derivatives are used in several commercially available pharmaceutical products such as the anticancer drugs etoposide, teniposide, and etopophos. Currently, the commercial production of podophyllotoxin is based on Indian mayapple. The objective of this study was to estimate podophyllotoxin concentration in American mayapple across its natural habitats in the eastern United States and to identify high podophyllotoxin types that could be used for further selection and cultivar development. Analyses of American mayapple leaves collected from 37 mayapple colonies across 18 states indicated a significant variation in podophyllotoxin, α-peltatin, and β-peltatin content and the presence of chemotypes. Overall, the concentrations of podophyllotoxin, α-peltatin, and β-peltatin in the collected accessions ranged from below detectable levels to 45.1, 47.3, and 7.0 mg·g−1 dry weight, respectively. We classified American mayapple accessions into seven groups: 1) with very high concentration of podophyllotoxin (greater than 20 mg·g−1) and no α- or β-peltatin; 2) high podophyllotoxin (greater than 10 mg·g−1) and no α-peltatin but trace amounts of β−peltatin; 3) medium podophyllotoxin (1 to 10 mg·g−1) and no α- or β-peltatin; 4) low podophyllotoxin (0.05 to 1 mg·g−1) and high α-peltatin; 5) trace amounts of podophyllotoxin and high concentration of α-peltatin and α-peltatin; 6) high α-peltatin and trace amounts of podophyllotoxin or β−peltatin; and 7) high α−peltatin and no podophyllotoxin or β-peltatin. American mayapple was found to grow on various soil types with a range of pH (4.6 to 7.6) and dissimilar concentrations of phytoavailable soil nutrients. Tissue zinc concentration was positively correlated to podophyllotoxin, whereas soil and tissue phosphorus was positively correlated to the concentration of α-peltatin. The results from this study may contribute toward the development of high podophyllotoxin-containing varieties of American mayapple and the development of a new cash crop for American farmers.
Organic or Local? Investigating Consumer Preference for Fresh Produce Using a Choice Experiment with Real Economic Incentives
Authors: Yue Chengyan , Tong Cindy
Published: February 2019

Determining consumers' preferences and willingness to pay (WTP) for organically grown and locally grown fresh produce is very important for stakeholders because it helps them figure out what type of fresh produce to grow and sell, what to emphasize in marketing efforts, and what are reasonable prices to charge. However, the literature that studies and compares consumers' preference and WTP for both organically and locally grown fresh produce is sparse. The objective of this study was to investigate consumers' WTP for organically grown and locally grown fresh produce and the marketing segmentation of these two types of produce. We combined a hypothetical experiment and nonhypothetical choice mechanism to investigate consumers' WTP for the attributes organic, local, and organic plus local for fresh produce. We found that when real products were used in the hypothetical experiment, the hypothetical bias (the difference between what people say they will pay and what they would actually pay) was not high. We found that consumers' WTP for the organic attribute was about the same as their WTP for the local attribute. Consumers' sociodemographics affected their choice between organically grown and locally grown produce. Furthermore, we found that consumers patronized different retail venues to purchase fresh produce with different attributes. The findings of the research have great importance for fresh produce stakeholders to make correct production and marketing decisions; the findings also contribute to experimental method choice in consumers' WTP research.
Making the Choice between Rewholesalers and Other Nursery Market Channels
Authors: Velástegui Andrade Marco A. , Hinson Roger A.
Published: February 2019

Alternative market channels that include garden centers, landscapers, mass merchandisers, and rewholesalers have contributed to the growth of ornamental crops sales in the United States. Knowledge about growers' use of these channels is indispensable for the development of appropriate strategies to achieve goals. This study estimated the impacts of growers' business characteristics on market channel choice by firm size. The explanatory variables were evaluated separately but were grouped by regions of the United States, kind of plant, kind of contract sales, and promotion behavior. Growers' location had limited effect on channel choice when compared with growers in the south. Growers with a more diversified marketing strategy were associated with higher likelihood of using the mass merchandiser and garden center channels. Trade show attendance had a strong negative impact on choice to the mass merchandiser compared with the rewholesaler channel. Generally, there appeared to be differences in the groups of variables that were related to channel choice. By channel, plant groups were important in explaining the mass merchandiser and landscaper channels, and the contracts group affected the garden center choice. By size, the contracts variables impacted the mass merchandiser channel, plant groups variables impacted the garden center channel, and promotions variables impacted the landscaper channel.
Organic Matter Application Improves Posttransplant Root Growth of Three Native Woody Shrubs
Authors: Price Julie Guckenberger , Wright Amy N. , Tilt Kenneth M. , Boyd Robert L.
Published: February 2019

The need for reliable planting techniques that encourage posttransplant root growth in adverse conditions has prompted research into planting above soil grade (above-grade). Container-grown Morella cerifera (L.) Small (syn. Myrica cerifera L.) (wax myrtle), Illicium floridanum Ellis (Florida anise tree), and Kalmia latifolia L. (mountain laurel) plants were planted in Horhizotrons (root observation chambers) in a greenhouse in Auburn, AL, on 1 Mar. 2006, 6 June 2006, and 3 Jan. 2007, respectively. The experiment was repeated with all three species being planted 18 June 2007. Horhizotrons contained four glass quadrants extending away from the root ball providing a nondestructive method for measuring root growth of the same plant into different rhizosphere conditions. Each quadrant was filled with a native sandy loam soil in the lower 10 cm. The upper 10 cm of the quadrants were filled randomly with: 1) milled pine bark (PB); 2) peat (P); 3) cotton gin compost (CGC); or 4) more native soil with no organic matter (NOM). Horizontal root lengths (HRL, length measured parallel to the ground from the root ball to the root tip) of the five longest roots visible along each side of a quadrant were measured weekly for M. cerifera and I. floridanum and biweekly for K. latifolia. These measurements represented lateral growth and penetration of roots into surrounding substrates on transplanting. When roots of a species neared the end of the quadrant, the experiment was ended for that species. M. cerifera had the fastest rate of lateral root growth followed by I. floridanum and then by K. latifolia. In most cases, roots grew initially into the organic matter rather than the soil when organic matter was present. In general, HRL and root dry weight (RDW) of I. floridanum and K. latifolia were greatest in PB and P, whereas for M. cerifera, these were greatest in P. Differences in root growth among substrates were not as pronounced for M. cerifera as for the other species, perhaps as a result of its rapid increase in HRL. Increased root growth in PB and P may be attributed to the ideal physical and chemical properties of these substrates. Results suggest that planting above soil grade with organic matter may increase posttransplant root growth compared with planting at grade with no organic matter.
The Impact of Interior Plants in University Classrooms on Student Course Performance and on Student Perceptions of the Course and Instructor
Authors: Doxey Jennifer S. , Waliczek Tina Marie , Zajicek Jayne M.
Published: February 2019

The main objective of this research was to investigate the impact of plants within a university classroom setting on course performance and on student perceptions of the course and instructor. The study was designed to include a minimum of two classes of the same coursework taught by the same professor in the same room during one semester. Three sets of two classes each and 385 students were included within the study. Throughout the semester, the experimental class of students was treated by including an assortment of tropical plants within the classroom. Plants were not present in the control classroom of the study. The official university course and instructor evaluation survey was administered at the end of the semester. Additionally, each student provided demographic data, including class rank, gender, and ethnicity. To measure course performance, the professor for each course reported each student's grade for the course. No statistically significant differences were found in comparisons of grades/student course performance (P = 0.192). However, statistically significant differences were found in comparisons of overall course and instructor evaluation scores of treatment and control groups (P = 0.065). Statistically significant differences were found in comparisons of the individual courses/classrooms between control and treatment groups on statements in subsections of the course and instructor evaluation survey, including the areas of “learning,” “enthusiasm (of instructor),” and “organization (of instructor).” In these comparisons of the treatment and control groups, the differences that were most apparent were in students who had class in the classroom that was windowless and stark. The plants appeared to have the greatest impact on students in the room that was void of other natural elements.
Substrate Depth Influences Sedum Plant Community on a Green Roof
Authors: Getter Kristin L. , Rowe D. Bradley
Published: February 2019

Because the waterproofing membrane beneath green roofs is estimated to last at least 45 years, long-term plant performance beyond initial establishment is critical. Plants that survive initially on a green roof may not exist in the long term because of variability in climate and other factors. This study evaluated the effect of green roof substrate depth on substrate moisture, plant stress as measured by chlorophyll fluorescence, and plant community development and survival of 12 Sedum species over 4 years in a midwestern U.S. climate during 4 years of growth. Plugs of 12 species of Sedum were planted on 8 June 2005 and evaluated biweekly for absolute cover (AC). Most species exhibited greater growth and coverage at a substrate depth of 7.0 cm and 10.0 cm relative to 4.0 cm. For the species evaluated, substrate depths of at least 7.0 cm are highly recommended. AC of Sedum was significantly greater at this substrate depth than at 4.0 cm. Mean volumetric moisture content of the three substrate depths followed the same pattern as AC. When averaged over time, the 4.0-cm substrate depth held less moisture than depths of 7.0 or 10.0 cm, whereas the 7.0- and 10.0-cm substrate depths were statistically the same. Species exhibiting the greatest AC at all substrate depths were S. floriferum, S. sexangulare, S. spurium ‘John Creech’, and S. stefco. In general, species that are less suitable at these substrate depths are S. ‘Angelina’, S. cauticola ‘Lidakense’, S. ewersii, S. ochroleucum, and S. reflexum ‘Blue Spruce’.