bluuebunny/crossref_metadata_2025 huggingface dataset:
505 Sensitivity of Pear and Apple Plants to Urea Fertilizers
Authors: Dong Shufu , Cheng Lailiang , Bi Guihong , Fuchigami Leslie H.
Published: February 2019

`Gala'/M26 apple and `Bartlett'/OH97 pear trees growing in containers were treated with either 0, 1, 5, 10, 20, or 30g of urea dissolved in 150 mL of distilled water on 7 Sept. 1999. Two weeks after application, a soil sample from each container was analyzed for NH4+ and NO3–. One day after treatment, the leaves of the apple trees treated with either 20 or 30 g urea wilted and curled and none of the other apple treatments were affected. However, 20 days later, new lateral and terminal buds broke to grow from these two treatments. In contrast, the pear trees showed signs of wilting and leaf necrosis in the 5, 10, 20, and 30 g urea treatments about 6 days after application. Twenty days after treatment, the leaves from the two highest treatments were completely necrotic and remained attached to the trees, while the leaves of 5- and 10-g treatments were partially necrotic and began defoliating. None of the pear trees produced any new lateral or terminal growth. Soil test showed that NH4+ contents of the soils were 54.9, 104.2, 356.9, 884.28, 1154.9, and 1225.2 mg/kg for `Bartlett'/OH97, and 30.2, 62.9, 359.0, 235.1, 529.9, and 499.0 mg/kg for `Gala'/M26 and NO3– contents of the soils were 40.5, 62.4, 211.0, 129.8, 54.5, and 39.5 mg/kg for `Bartlett'/OH97, and 37.6, 42.0, 178.7, 138.2, 186.2, and 142.1 mg/kg for `Gala'/M26 treated with 0, 1, 5, 10, 20, and 30 g urea, respectively.
507 Nitrogen Uptake Dynamics of Citrus Seedlings
Authors: Scholberg J.M.S. , Parsons L.R. , Wheaton T.A.
Published: February 2019

Improving our understanding of processes that control and limit nitrogen uptake by citrus can provide a scientific basis for enhancing nitrogen fertilizer use efficiency. Nitrogen uptake dynamics of two rootstock seedlings will be compared to those of young budded trees. Three-month old Swingle citrumelo [Citrus paradisi Macf. × Poncirus trifoliata (L.) Raf.] and Volkamer lemon (C. volkameriana Ten. & Pasq.) trees were planted in PVC columns filled with a Candler fine sand. Field experiments were conducted using 4-year-old `Hamlin' orange trees [Citrus sinensis (L.) Osb.] grafted on `Carrizo' [C. sinensis × Poncirus trifoliata (L.) Raf.] or on Swingle citrumelo. Trees were either grown in solution culture using 120-L PVC containers or in 900-L PVC tubs filled with a Candler fine sand. Additional trees were planted in the field during Spring 1998. Two lateral roots per tree were trained to grow in slanted, partly burried, 20-L PVC columns filled with a Candler fine sand. Nitrogen uptake from the soil was determined by comparing the residual N extracted by intensive leaching from planted units with that of non-planted (reference) units. With the application of dilute N solutions (7 mg N/L), plants reduced N concentrations to near-zero N concentrations within days. Applying N at higher concentrations (70 or 210 mg N/L) resulted in higher initial uptake rates, increased residual soil N levels, and reduced nitrogen uptake efficiency. Contributions of passive uptake to total nitrogen uptake ranged from less than 5% at soil solution concentrations around 3 ppm N to 20% to 30% at concentrations of 60 ppm N.
517 Heat Treatments and Controlled Atmospheres Maintain Quality and Reduce the Inner Leaf Extension or “Telescoping” of Minimally Processed Green Onions
Authors: Hong G. , Cantwell M.I.
Published: February 2019

Minimal processing of green onions (Allium cepa × A. fistulosum) involves trimming and removing damaged leaves, cutting of roots, and removal of the compressed stem. If the stem tissue is completely removed with the roots, the white inner leaf bases may extend, or “telescope,” during storage. Storage at 0 °C greatly retards extension growth, but storage at 5 °C results in unacceptable extension rates. To maintain high quality and to extend the shelf life of intact and minimally processed green onions, the potential benefits of heat treatments and controlled atmosphere storage were evaluated. Atmospheres of 0.1% to 0.2% O2 or 0.1% to 0.2% O2 containing 7.5% to 9.0% CO2 at 5 °C were the CA conditions that best maintained visual appearance and prolonged shelf life to more than 2 weeks in both intact and cut onions. No CA treatment completely controlled “telescoping” at 5 °C. Several heat treatment combinations (52.5 and 55 °C water for 4 and 2 min, respectively) of the white inner leaf bases were effective in controlling “telescoping” of cut green onions stored at 5 °C. The effective heat treatments resulted in higher average respiration rates during 12 days, but did not affect the visual quality or shelf life of the cut green onions. Total soluble sugars decreased in intact or cut green onions, but concentrations were maintained in heat -treated onions. Thiosulfinate concentrations did not vary importantly during 14 days at 5 °C, except for a reduction in heat-treated onions not stored under CA.
518 Heat Shocks Applied Either Before or After Wounding Reduced Browning of Lettuce Leaf Tissue
Authors: Loaiza-Velarde Julio G. , Saltveit Mikal E.
Published: February 2019

The wounds and injuries incurred during minimal processing of lettuce stimulates phenolic metabolism, which leads to tissue browning. Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5.) is the first committed enzyme in the phenylpropanoid pathway and regulates its overall activity. The maximum activity of wound-induced PAL occurs sooner as the temperature increases from 0 to 25 °C, but the maximums are lower. A heat shock at 50 °C for 90 s protects minimally processed lettuce tissue against browning, helps to retain greenness, and decreases the production of phenolics when applied either after or before wounding. Browning is reduced when the heat shock is applied up to 36 h after wounding, while the maximum effect occurs around 6 h before cutting. Like the heat-shock treatment, a number of protein synthesis inhibitors (e.g., chloramphenicol, cycloheximide, emetine, and puromycin) reduced wound-induced PAL activity, but they did not prevent browning itself. These inhibitors seemed to cause chemical damage that promoted tissue browning. When cycloheximide was applied in combination with heat-shock treatments browning did not occur. Heat shocks appear to control tissue browning by more than just interfering with protein synthesis.
524 Vegetable Production in Southeast Virginia
Authors: Bevacqua Robert F.
Published: February 2019

A research and extension program for increasing vegetable production in southeastern Virginia was launched by Virginia Cooperative Extension in 1997. The launch was triggered by the construction of a shipping point market in Southampton County. First, a market window study identified target crops and the harvest period when they could be most profitably marketed. Target crops were watermelon, sweet corn, snap beans, muskmelon, bell pepper, and pumpkin. Second, a technology transfer program was formulated that emphasized demonstrations, field days, classes, and workshops. On-farm demonstrations of intensive vegetable production techniques formed the foundations of the extension effort and focused on drip irrigation, plastic mulch on raised beds, water and nutrient monitoring, honey bee pollination, and integrated pest management (IPM). “Growing Vegetables for the Commercial Market” was the title of a short course offered in partnership with the local community college. Sixty-five graduates completed the course in 1999. Workshops were offered on farm labor, marketing, irrigation, and production techniques. On-farm research was conducted in support of the emerging vegetable industry. The focus was on sweet corn IPM, variety trials for watermelon and pumpkin, and soil and plant analysis. Information was made available to growers through a bimonthly newsletter, an annual bulletin entitled Commercial Production Recommendations, and VCE postings on the World Wide Web.
525 A Walk through the Garden: Can a Visit to a Botanic Garden Reduce Stress?
Authors: Kohlleppel Tammy C. , Bradley Jennifer C. , Jacob Steve
Published: February 2019

Stress has been called the epidemic of the 90s and has been found to play an important role in causing many diseases. To help cope with the stresses of life, people often seek out leisure activities and nature. Botanic gardens provide a place for experiencing recreational activities and the natural environment. Researchers at the Univ. of Florida developed a survey to gain insight into the influence of a botanic garden on visitor stress. Three botanic gardens in Florida participated in the survey of garden visitors; these included Bok Tower Gardens, Fairchild Tropical Garden, and Mounts Botanical Garden. More than 300 surveys were administered to and completed by visitors of these gardens in Apr. 1999. The survey consisted of three main sections: 1) visitor perceptions of botanic gardens, 2) visitor personal perceptions, and 3) demographic variables. A stress process model was developed that incorporated botanic gardens as a coping strategy. The relative importance of a visit to a botanic garden and other stress process factors were examined for their importance in stress reduction. Also, botanic gardens were placed in context of the stress process model with the development of a multivariate framework. The stress process model included individual factors, stressors, stress mediators, and stress outcomes. Findings from this study provided insight into the role of botanic gardens as a method to cope with the effects of stress. Results showed that a visit to a botanic garden is important in the context of the stress process model as a coping strategy. Data also showed that visitors receiving the most benefit of stress reduction were persons most needing a coping strategy, those having higher depression index scores.
527 Improvement of Agricultural Research Components in Urban Landscape and Greenery of Kuwait
Authors: Abdal Mahdi , Sulieman Majda
Published: February 2019

Agricultural development in Kuwait faces many problems and obstacles, such as limitation of water resources for irrigation, soils conditions, climatic extreme (particularly during the summer periods), and trained labor. With these extreme conditions for agricultural development in Kuwait, there is a strong demand from the public and the government for agricultural activities, particularly in urban landscape and greenery. World travel has enhanced the public's desire for the beautification of the urban areas and has emphasized the importance of the urban landscape. Planning urban landscape and greenery for Kuwait depends on various variables and efficient management of limited resources. Irrigation water is limited in Kuwait, and the quality of water is deteriorating from over-pumping of underground water and increased soil salinity by over irrigation and lack of drainage. Efficient irrigation-water management can be improved in Kuwait with enhanced irrigation research and implementation of the recommendations of this research. Research topics can also include water evaporation, which is high in Kuwait, and the introduction of mulching materials to improve water irrigation efficiency. Most of the soils in Kuwait are sandy with limited organic materials and plant nutrients. Research in soil fertility and plant uptake of nutrients is essential for any agricultural activities. Introducing ornamental plants tolerant to drought, salinity, and heat is a continuous research component of urban landscape and greenery in Kuwait. Training local staff in basic agricultural activities and research development should improve resource management and enhance the greenery of Kuwait.
529 Pollen Tube Growth in Stage 2 Pollinated Avocado Flowers
Authors: Davenport Thomas L.
Published: February 2019

Individual avocado (Persea americana Mill.) flowers are perfect, opening two times to display two distinct reproductive stages on consecutive days. Stage 1 focuses on presentation of pistils and Stage 2 on presentation of pollen. The Stage 1 opening offers the greatest opportunity for outcrossing due to the absence of available pollen in that stage. Stage 2 flowers, however, are self-pollinated within flowers in direct proportion to the number of white stigmas present at the time of pollen dispersal. The potential success of these self-pollination events was examined in orchard trees of seven commercial Florida cultivars: Booth 7, Brooks Late, Choquette, Monroe, Simmonds, Tonnage, and Tower 2 and compared with hand-pollinations from complementary cultivars (cross pollination) and from flowers of the same cultivar (close pollination). The furthest advancement of pollen tubes down styles and into the ovaries on their way to the egg apparatus was noted in hundreds of individual flowers 24 and 48 h after pollen deposition on receptive white stigmas of the Stage 2 flowers. Virtually none of the seven cultivars exhibited pollen tubes reaching the egg apparatus by 24 h after deposition. By 48 h, however, pollen tubes had reached the egg apparatus in 25% to 85% of the pollinated flowers, depending upon cultivar. Pollen source was inconsequential. The results demonstrate the success of self-pollination in avocados. It is especially important for cultivars growing in humid climates, which display a high proportion of receptive white stigmas in Stage 2.
530 Graft-transmissible Agents Affect Membrane Fatty Acid Saturation During Chilling Accumulation and Dormancy Release in Peach
Authors: Gibson Philip G. , Reighard Gregory L. , Powell Gary L. , Jenkins Thomas C.
Published: February 2019

Graft-transmissible agents found in `Ta Tao 5' peach have been associated with phenological changes, including delay in bloom, reduced shoot vigor, and early autumn defoliation. Peach Latent Mosaic Viroid (PLMVd) is present as a graft-transmissible agent in `Ta Tao 5'. In order to further characterize the changes occurring in trees exposed to PLMVd from `Ta Tao 5' grafts, total fatty acid content was measured for peach buds during chilling accumulation and release from dormancy in `Coronet' peach trees and `Coronet' trees treated with `Ta Tao 5' bud grafts. Palmitic (16:0), stearic (18:0), oleic (18:1), linoleic (18:2), and linolenic (18:3) acids were the major fatty acids in dormant and releasing peach buds of both the controls and treated trees. The degree of unsaturation increased immediately following completion of chilling requirement in both the untreated controls and in the treated trees. However, the desaturation of linoleic acid to linolenic acid was significantly inhibited in the trees treated with `Ta Tao 5' bud grafts, which was accompanied by a concomitant delay in the resumption of growth. The disparity between the control and treated trees in the trend toward increased fatty acid unsaturation continued through the resumption of growth. The changes in degree of fatty acid saturation correlated with a response to forcing conditions and the release from dormancy. The presence of PLMVd in `Coronet' peach trees affects membrane fatty acid saturation during chilling accumulation and dormancy release. These findings suggest that metabolic pathways involving fatty acid desaturation are linked to the phenotypic variation in trees exposed to PLMVd.
531 CMN-Pyrazole-induced Abscission of Mature `Valencia' Oranges in Relation to Young Fruit, Root, and Shoot Growth
Authors: Yuan Rongcai , Hartmond Ulrich , Kender Walter J.
Published: February 2019

The seasonal abscission response of mature `Valencia' oranges [Citrus sinensis (L.)Osb.] to 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMN-Pyrazole) was examined in relation to young fruit, shoot, and root growth. CMN-Pyrazole dramatically increased ethylene production in fruit and effectively reduced the fruit detachment force (FDF), except in a period of reduced response to CMN-Pyrazole in early May. Root growth was inhibited by trunk girdling, in combination with removal of spring vegetative flushes and flowers, but not by their removal alone. During the responsive period, there was no difference in both ethylene production and FDF of CMN-Pyrazole-treated mature oranges between 1) the unmanipulated trees and those manipulated by either 2) girdling, removal of spring flushes and flowers, or 3) removal of flushes and flowers alone. However, during the less-responsive period, ethylene production in CMN-Pyrazole-treated mature oranges was significantly lower while the FDF was higher from non-manipulated trees than from trees treated by either girdling and removal of flush, or only removal of flush. There was no difference in either ethylene production or FDF of CMN-Pyrazole-treated mature oranges between trees manipulated by girdling and removal of flush, and those by removal of flush alone. Flush growth terminated at least 2 weeks before the onset of the less responsive period. This suggests that the hormones from rapidly growing young fruit may be responsible for the less responsive period.
533 Monitoring Soil Water Content in Tropical Fruit Orchards in Southern Florida with Multi-sensor Capacitance Probes and Tensiometers
Authors: Nuñez-Elisea R. , Schaffer B. , Zekri M. , O'Hair S.K. , Crane J.H.
Published: February 2019

Tropical fruit trees in southern Florida are grown in porous, oolitic limestone soil that has very low organic matter content and water-holding capacity. Thus, trees require frequent irrigation during dry periods. In these soils, a quantitative basis for monitoring soil water content to determine when and how much to irrigate has been lacking. Multi-sensor capacitance probes (EnviroSCAN™, Sentek, Australia) were installed in commercial carambola, lime, and avocado orchards to continuously monitor changes in soil water content at depths of 10, 20, 30, and 50 cm. Eight probes were installed per orchard. Volumetric soil water content was recorded at 15-min intervals with a solar-powered datalogger. Results were downloaded to a laptop computer twice a week. Monitoring the rate of soil water depletion (evapotranspiration) allowed irrigation before the onset of water stress. The time at which soil reached field capacity could be determined after each irrigation (or rain) event. Soil water tension was recorded periodically using low-tension (0–40 cbars) tensiometers placed adjacent to selected capacitance probes at 10- and 30-cm depths. Soil water tension was better correlated with volumetric soil water content at a 10-cm depth than at 30-cm depth. Using multi-sensor capacitance probes is a highly accurate, although relatively expensive, method of monitoring soil water content for scheduling irrigation in tropical fruit orchards. Whereas tensiometers require periodic maintenance, the multi-sensor capacitance probe system has been virtually maintenance free. The correlation between soil water content and soil water tension obtained in situ indicates that tensiometers are a less precise, but considerably cheaper, alternative for scheduling irrigation in tropical fruit orchards in southern Florida.
536 The Gradient—A Nutritional Paradigm Shift
Authors: Geraldson C.M.
Published: February 2019

A gradient concept was initiated and evaluated at the Gulf Coast Research and Education Center, Bradenton, during the 1960s as the nutritional component in a full-bed mulch system of production. Commercial tomato yields in Florida more than doubled with the shift to the gradient-mulch system. Conventionally, nutrients move to the root in the water by mass flow and thus are a function of water requirement. With the soil as the buffer component, nutrient input may or may not be synchronized with root removal. Movement with the gradient is by diffusion and the nutrient/water input is synchronized with rate of removal by the root. The limited buffer potential of the soil is replaced by the gradient with an unlimited buffer potential. Production in the field or a container has a maximum potential with the gradient procedure but can become limited in the field and a failure in the container with conventional procedure. The gradient requires minimal soil (a framework for the gradient) uses minimal water, creates minimal pollution, requires minimal management and provides a nutritional stability that has an unlimited productivity potential. The N–K banded on the soil bed surface in conjunction with a continuing water supply are the basic parameters of the gradient concept.
538 Understanding Why Horticultural Crops in the Desert Rarely Respond to K Fertilization
Authors: Sanchez Charles A. , Galadima Abraham , Silvertooth Jeffrey C.
Published: February 2019

Vegetable and fruit crops produced in the desert southwestern United States generally do not respond to K fertilization. Even when pre-plant soil test K levels are low and crop K accumulations are high, responses are infrequent. We have performed a number of evaluations aimed at understanding why crops produced in this region fail to respond to K fertilization. First, data show the potential for substantial K inputs through irrigation. For example, Colorado River water, which is widely used for irrigation in this region, contains ≈5 ppm K, resulting in potential K inputs of 30 to 60 kg K/ha. Second, many of the soils used for crop production have a clay content and mineralogy making a response to K unlikely. Studies evaluating the kinetics of K release from the mineral fraction of soils in the region has shown that many soils used for crop production have a high capacity to replenish K to the soil solution and exchange sites following crop uptake. Finally, the observation that Na can partially substitute for the K requirement of many fast-growing leafy vegetables may also be a contributing factor for the infrequent K fertilizer responses for these commodities.
539 Assessing Soil and Water Thresholds for Potential Dietary Zinc Toxicity in Selected Vegetable Crops
Authors: Yang X.E. , Long X.X. , Ni W.Z. , Stover E.W.
Published: February 2019

Vegetables play an important role in the human diet, and production in suburban areas has increased as populations have become more urbanized. However, heavy metal pollution of soils has enhanced in such areas, and metal accumulation in vegetables may pose a human health risk when consumed. Zinc is an essential micronutrient for plants and humans, but it is toxic to plants and humans at high levels. Although a maximum Zn tolerance for human health has been established for edible parts of vegetables (20 mg/kg DW), little information is available for predicting vegetable Zn concentration based on soil and water Zn levels. The objectives of this study were to determine the critical Zn concentrations in nutrition solution and soil to reach maximum Zn tolerance concentrations in Chinese cabbage, bok choy, and celery. Five Zn levels were used for both solution and soil culture experiments, with three replicates of each. Shoot growth was significantly inhibited at Zn concentrations above 50 mg/L in nutrition solution and above 180 mg/kg in soil. The sensitivity of crops to zinc toxicity, in term of shoot and root growth, decreased in the order: celery > Chinese cabbage > bok choy. Zinc accumulation in shoots and edible parts varied with Zn supply levels and type of vegetables. A negative correlation was noted between Zn accumulation and dry matter yields, with r-squared values of 0.980** for nutrient solution and 0.960* for soil culture. Zinc concentrations in shoots or edible vegetable parts were below 20 mg/kg (human health threshold) when they were grown at DTPA extractable Zn in the soil less than 75, 100, and 175 mg/kg for bok choy, celery, and Chinese cabbage, respectively.
541 Effect of Supplemental Calcium on Watermelon Yield, Fruit Weight, Soluble Solids, and Calcium Content of Leaves and Fruit
Authors: Olson Stephen M.
Published: February 2019

Inadequate available Ca can cause blossom end rot in watermelons. Many products and materials are marketed to try and help reduce this problem. A 3 X 3 factorial was set up with three soil Ca treatments (none, 1120 kg/ha of dolomite and 1120 kg/ha of qypsum) and three foliar Ca treatments (none, Liqui-Cal at 9.35 L/ha and Foli-Cal at 4.67 L/ha) using both a seeded (2N) and seedless (3N) cultivar. Mehlich-1Ca level prior to planting was 305 ppm. None of the Ca treatments affected leaf or fruit Ca levels. Applied Ca treatments did not affect total yields, fruit weight, or percent soluble solids of the seedless cultivar (Crimson Trio). Yield of `Royal Flush' (2N) was reduced by application of Foli-Cal, but none of the other parameters were affected by the other Ca treatments. Leaf Ca level of `Royal Flush' (3.05%) was almost twice that of `Crimson Trio' (1.59%), while fruit Ca content of `Royal Flush' (0.26%) was lower than that of `Crimson Trio' (0.32%).
544 Using Chlorophyll Fluorescence in Storage and Vegetative Propagation of Taxus
Authors: Bruce Sarah E. , Rowe D. Bradley
Published: February 2019

Propagation failures of Taxus are often attributed to cutting collection from stock plants of poor quality. If a quick, reliable method of determining the potential rooting of cuttings based on the condition of a specific stock plant was available for propagators, rooting success could be predicted before investing time, labor, and resources. Our studies examined chlorophyll fluorescence (Fv/Fm) as a potential tool for stock plant selection, assessment of storage conditions, and measurement of stress over the course of propagation. Ten cultivars of Taxus × media (Taxus baccata L. × T. cuspidata Sieb. & Zucc.) were used: Brownii, Dark Green Pyramidalis, Dark Green Spreader, Densiformis, Densiformis Gem, Hicksii, L.C. Bobbink, Runyan, Tauntoni, and Wardii. Storage condition treatments consisted of desiccation (low, medium, and high), duration (34, 70, and 107 days), and temperature (–30, –2.5, 0, 2.5, 5, 10, and 20 °C). Cultivars differed in Fv/Fm initially as well as over time. Correlations were not found between initial stock plant Fv/Fm and rooting percentage, number of roots, root dry weight, or root length, indicating that Fv/Fm is not a reliable indicator of stock plant propagation potential. Short storage duration at –2.5 to 2.5 °C was found to be ideal. Fv/Fm could detect substandard storage conditions only at temperature and desiccation extremes. Although chlorophyll fluorescence measurements do not appear to be a practical method of predicting adventitious rooting, there is a potential for assessing cutting or plant quality before shipping.
546 Seed Germination of Abelia × grandiflora (Andre) Rehd.
Authors: Scheiber S.M. , Robacker Carol D. , Dirr M.A.
Published: February 2019

Flowering evergreen shrubs that are compact and resistant to pests are in great demand in the nursery and landscape industries. The genus Abelia contains 30 species that vary in many traits including flower color, growth habit, and hardiness. Abelia × grandiflora (Andre) Rehd. and its cultivars are the most widely grown Abelia taxa and are characterized by pest resistance, an abundance of pinkish white flowers, long flowering period, and glossy evergreen foliage. Interspecific hybridization among Abelia × grandiflora, its cultivars, and other species in the genus Abelia offer the potential for new cultivars; however, seed germination within the genus has been described as slow and inconsistent. Experiments were conducted to test procedures to increase germination percentages and rates. Each Abelia seed is enclosed in a leathery achene. The effect of achene removal was examined in combination with cold, moist stratification for 60 days at 4 °C, immersion in 100 ppm gibberellic acid for 24 h, and no treatment. Treatments were replicated five times with 15 seeds per replication. Seeds were sown on sphagnum peat, and grown under mist in the greenhouse. Weekly germination counts were recorded for 8 weeks. Seeds with attached achenes germinated at a significantly higher percentage than those without achenes. Cold, moist stratification and gibberellic acid treatments were not significantly different than the control. No significant differences were found within the achene treatments for relative rate of emergence, but significant differences were found for the time until 90% of final emergence was reached.
553 Genetic Diversity in Papua New Guinea Sweetpotato Germplasm
Authors: Fajardo Diego , La Bonte Don R. , Jarret Robert L.
Published: February 2019

The USDA gene bank currently maintains 668 accessions of cultivated sweetpotato and 219 accessions of related Ipomoea species. Information on the genetic diversity of the collection does not exist due to funding constraints. The development of a core collection would provide a subset of accessions that represent the genetic diversity of the main collection with a minimum of repetitiveness. The small size of the core collection would facilitate the evaluation of the accessions for economically important traits. The objective of this research is to develop a core collection of Papua New Guinea sweetpotato germplasm using the Amplified Fragment Length Polymorphisms (AFLPs) marker system. This approach to quantifying genetic diversity would later serve as a model for the development of a USDA sweetpotato germplasm core collection. The germplasm choosen for this study was collected from this crop's secondary center of genetic diversity based on its potential as a source of new traits. All genotypes were fingerprinted using four primer combinations that generated 224 markers. The molecular data was then analyzed using NTSYSpc 2.0 program to determine the relatedness of the genotypes. The molecular analysis showed a homogeneous genetic constitution. The extent of diversity among accessions was correlated with the geographic origin of the plant material.
559 Preferential Allocation and Inducible Calcium Sinks in Leaf Primordia of Dracaena sanderiana Hort. Sander ex M.T. Mast (Dracaenaceae)
Authors: Pennisi Svoboda V. , McConnell Dennis B. , Kane Michael E.
Published: February 2019

We induced preferential allocation of Ca to two calcium oxalate (CO) sinks in immature leaf tissues of D. sanderiana: subepidermal extracellular deposits and intracellular raphides. Allocation was affected by exogenous Ca levels. Two groups of rooted cuttings were termed Ca-deficient and non-deficient. The first group consisted of cuttings that had been deprived of Ca for 18 months, and, the second, cuttings rooted under standard horticultural conditions. All plants were grown in liquid medium supplemented with 100 ppm of potassium nitrate and subjected to 0, 3, or 7mm Ca from calcium acetate. The most striking feature of Ca-deficient plants grown in 0 mm Ca was the absence of intracellular raphides in the leaf primordia. The largest number of intracellular raphides developed in Ca-deficient plants grown in 7 mm Ca. The number of extracellular crystals in Ca-deficient plants grown in Ca-supplemented solutions versus non-supplemented were similar, but crystals were considerably smaller in non-supplemented plants. Total number of extracellular crystals per epidermal cell did not differ significantly between plants in all treatments. This implies that nucleation sites are pre-determined and finite in number. In contrast, the number of intracellular raphides was highly variable. In terms of Ca prioritization, the extracellular crystals took precedence over intracellular raphides, and this was most obvious in Ca-deficient plants. The significance of this research is that the extracellular crystals represent Ca sinks with limited induction capacity compared to intracellular Ca sinks. Plants with genetic predisposition for intracellular CO crystal formation may be able to respond favorably to root environments with low Ca levels compared to species with limited capacity for intracellular CO deposition. Intracellular CO crystals, therefore, play an integral role in plant nutrition as Ca storage sinks.
561 Reduction of Fertilizer Inputs Using Earthworm Castings as a Substrate Amendment for Poinsettia Production
Authors: Hidalgo Pablo R. , Harkess Richard L. , Matta Frank
Published: February 2019

Earthworm castings were evaluated to determine the effect of earthworm castings on growth of Poinsettia `Freedom Bright Red'. Castings derived from cow (CC), horse (HC), or sheep (SC) manure were combined with peatmoss at 1:0, 1:3, 1:1, 3:1, or 0:1 peat: castings (v/v). One plant was potted per 1.5-L container and were fertilized at 0, 50, 200, or 350 mg/L N in a RCB arrangement. Plant growth index at all fertilizer rates was greatest when grown in SC at 0:1, 1:3, and 1:1 and CC at 0:1 and 1:3 (peat: castings) ratios. For each of the three animal sources, no differences in growth index were observed among fertilizer rates when 100% castings was used as the substrate. Bract area was greatest on plants grown in SC at 1:0, 1:3, and 1:1 (peat: castings) ratios at all four fertilizer rates. Bract area on plants grown in CC at 0:1 and 1:3 (peat: castings) was less than SC, but better than CC at 1:1, 3:1, or 1:0 or any of the HC substrates. Plants grown in substrates with 75% or more castings all had similar bract area regardless of fertilizer rate. As castings in the substrate decreased, bract area increased as fertilizer rate increased. When fertilized at 0, 50, or 200 mg/liter N plant dry weight decreased as castings increased in the substrate. Fertilization at 350 mg/liter did not affect dry weight between substrates.
562 Incorporating Zeolite into Soilless Container Media Reduces Nutrient Leaching in Ornamental Plant Production
Authors: Chen Jianjun , Huang Yingfeng , Yang Zhen , Caldwell Russell D. , Robinson Cynthia A.
Published: February 2019

Containerized ornamental plant production represents extremely intensive agricultural production. An average of 200,000 containers may occupy 1 acre of surface area, to which a large amount of chemical fertilizers will be applied. Because of the use of high-drainage soilless potting mixes coupled with excessive fertigation, a great amount of nutrients, particularly nitrogen and phosphorus, are leached, which increases the potential for ground and surface water contamination. Over the past 2 decades, research has been centered on developing fertigation delivery systems such as nutrient film techniques, ebb-and-flow and capillary mat systems, for reducing leaching. Relatively limited research has been conducted on improving potting medium substrates to minimize nutrient leaching. The objectives of this study were to determine the adsorption isotherm of six different zeolites to ammonium, nitrate and phosphorus, identify and incorporate desired zeolites in a peat/bark-based medium for reducing nutrient leaching in ornamental plant production. Results indicated that the zeolites possess great holding capacities for ammonium, nitrate, and phosphorus. Compared to control, ammonium leaching was reduced 70% to 90%, phosphorus 30% to 80% and nitrate 0% to 60% depending on zeolite species and quantity used per pot. Zeolite amended media caused no adverse effects on plant growth. Conversely, biomass increased significantly when compared to that of the control.
564 Screening Commercial Peat and Peat-based Products for the Presence of Ericoid Mycorrhizae
Authors: Starrett Mark
Published: February 2019

A study was conducted to investigate the presence of ericoid mycorrhizal fungi in select peat and peat-based products. Vaccinium corymbosum, a known host of ericoid fungi, was used as a model plant. Peat and peat-based products were obtained from all major sources that supply the northeastern United States. Seedling roots were examined and average percent colonization was determined for each sample. Results indicate that these fungi are present in the majority of peat and peat-based media tested. Seedlings grown in some of the selected media exhibited an increased percentage of colonized root cells. Mycorrhizal fungi colonizing roots of test plants were isolated. These fungi exhibited typical ericoid fungal growth characteristics.
569 HCC 100: Horticultural Science—A Course Redesigned to Meet the Biological/Physical Sciences Requirement of the All University Core Curriculum
Authors: Hughes Harrison
Published: February 2019

Colorado State Univ. recently underwent the development of a new all university core curriculum. All faculty were encouraged to submit proposals for new courses or revised courses, which would be reviewed for inclusion under specified categories. Basic Horticulture was redesigned te emphasize the scientific method, the understanding between science and society, and the use of handson and inquiry-based instruction in the laboratory. Horticultural Science is now an applied science course that includes the use of hypothesis formulation, experimentation, observation, data collection, summation and presentation in scientific format of reports of at least three laboratory exercises, as well as extensive general observation and presentation in both written and oral format. It teaches science in the context of everyday interaction with the environment in which the student lives, the interior and exterior plants that surrounds the student at CSU, and the controversies as well as the health aspects that surround the production of foods derived from plants that require intensive cultivation. Examples of such issues include sustainability, the organic movement, genetically modified organisms, ground water pollution form overfertilization, and water usage for landscaping and golf courses in a water short region. A review of the revisions as noted above and the use of technology in teaching the course will be presented.
570 Development, Implementation, and Evaluation of a Non-majors Survey Course
Authors: Bradley Jennifer Campbell , McConnell Dennis , Kohlleppel Tammy
Published: February 2019

Attracting new students into traditional agriculture programs has become increasingly difficult. The idea of offering a course as a means for introducing students to agriculture is a concept with popular appeal. As a recruiting effort, and as a method of introducing students to horticulture, the Environmental Horticulture Dept. at the Univ. of Florida designed a one-credit course for non-majors. The course was structured such that a broad understanding of horticulture, including production, landscaping, and floriculture, would be emphasized. The intent was to develop a course somewhat similar to an entry-level course, but incorporating a more enjoyable, practical, hands-on approach. ORH 1030 Plants, Gardens, and You was offered for the first time in summer 1997. It is now offered every semester. The course has one faculty assigned each semester and various other faculty members, including teaching, research, and extension specialists who participate as “guest lecturers”. Student response to ORH 1030 has been favorable, ratings are high and enrollment in the course has continued to rise from 30 to our current cap of 100. As a means of ensuring that we are meeting the needs of our students and to aid in targeting potential students, a survey was administered in Spring 2000. Students enrolled in the course were surveyed at the beginning and the end of the semester to gain insight into student demographics, horticulture background and experience, reasons for enrollment in the class, attitude toward horticulture and overall interest in horticulture. Findings will be discussed in addition to information and suggestions for successfully establishing a similar course in other horticulture departments.
572 Basic Botany On-Line: A Training Tool for the Oregon State Univ. Master Gardener Program
Authors: VanDerZanden Ann Marie , Rost Bob , Eckel Rick
Published: February 2019

At Oregon State Univ. (OSU), a team of educators and web designers developed a noncredit, on-line training module for the OSU Master Gardener program. The on-line module consists of the botany component of the annual Master Gardener training. It is comprised of text from the botany chapter in the Master Gardener handbook, an on-line discussion group, on-line quizzes for each section, a clickable glossary, links to additional educational resources on the web, a few animations, and numerous photographs and line drawings. To evaluate the effectiveness of this learning tool a group of 24 Master Gardeners (all graduates of the Master Gardener training program from previous years) tested the module via their home computers. Additionally usability testing was completed with a group of eight Master Gardener volunteers. These participants navigated through the course in a computer lab setting while they were observed by the development team. Participants from both groups completed an evaluation regarding technical issues, organization and presentation of the module, navigation throughout the module, and content as well as user satisfaction. Overall participants felt this was a useful training tool for the Master Gardener program and that it would be a useful addition to the annual training. They also noted that features such as the on-line discussion group and accessibility of e-mail made them feel connected to the other on-line learners as well as to the course instructor. This module will be used as the primary training tool for the botany component of the annual training for over 75 new trainees in 2000.
573 Enhancing Red Color Development Without Over-ripening Apples by AVG (Aminoethoxyvinylglycine) Followed by Ethephon Treatment
Authors: Wang Zhenyong , Dilley David R.
Published: February 2019

AVG applied alone to `Gala' and `Jonagold' apples delayed maturity and the onset of the ethylene climacteric and delayed red color development. AVG followed by ethephon delayed maturity and the onset of the ethylene climacteric, but promoted red color development of both cultivars. Ethephon applied alone advanced maturity, ethylene production, ripening, and red color development compared to AVG alone. In other studies, the ripening-related effects of these treatments were reflected in the storability of fruit in CA storage. AVG - and AVG + ethephon-treated fruit were still at preclimacteric ethylene levels after 6 months in CA storage, with excellent retention of flesh firmness and shelf-life, while ethephon and control fruits had significantly higher ethylene levels and softened more during storage and shelf-life evaluation. Collectively, our results indicate that an ethephon application following AVG treatment may be useful to overcome the delay of red color development of apples treated with AVG only and that this can be achieved without overly stimulating fruit ripening. Thus, a once-over harvest of `Gala' and `Jonagold' apples may be achieved with a significant reduction in harvest costs. We attribute the promotion of red color development of apples receiving AVG treatment with a follow-up application of ethephon to the action of ethylene temporally-released from ethephon stimulating the development of the anthocyanin biosynthetic pathway, while AVG inhibits the development of the endogenous ethylene climacteric. Inhibiting endogenous ethylene production delays fruit from producing their own ethylene. We attribute maturation uniformity to the action of AVG allowing the less mature fruits to gain maturity while slowing maturity development of the more mature fruits. Improved storability of AVG + ethephon-treated fruit is attributed to the same ethylene-related phenomena.
574 Nitrogen, Trunk Scoring, and AVG Treatments Influence Fruit Color and Quality of `Jonagold' Apple
Authors: Wargo James M. , Merwin Ian , Watkins Christopher
Published: February 2019

`Jonagold' apple often has problems of inadequate red blush development at harvest, and loss of firmness and skin “greasiness” after refrigerated storage. During two growing seasons we tested factorial combinations of three preharvest treatments for managing these problems: 1) N fertilization (no applied N, 34 kg N/ha in May, or 1% (w/w) foliar urea sprays in May and June); 2) mid-summer trunk scoring (girdling); and 3) aminoethoxyvinylglycine (AVG) applications 3 weeks prior to harvest. Fruit were harvested at four weekly intervals each year, and evaluated for size, blush, firmness, soluble solids, ethylene, and starch hydrolysis. Nitrogen delayed blush development in 1998, but not 1999, and there was no difference in fruit surface blush coverage between foliar urea and soil applied N. Nitrogen applications increased fruit size, decreased fruit firmness, and increased post-storage flesh breakdown in 1999. Trunk scoring increased blush coverage and intensity both years, and improved market-grade packouts. Blush increase after trunk scoring was not caused by advanced fruit maturity (based on ethylene and starch indices) in either year, although it did increase skin greasiness slightly. AVG treatments delayed maturity and blush development of `Jonagold' by 7 to 10 days both years, relative to untreated fruit. Flesh firmness increased and greasiness decreased in AVG treated fruit harvested on the same dates as controls. However, in AVG fruit harvested at comparable stages of maturity 7 to 10 days later, firmness and greasiness were equivalent to untreated fruit on the previous harvest date. Trunk scoring and no N fertilizer were effective for improving fruit blush coloration, and AVG for delaying harvest maturity.
575 Effect Of AVG and Dormant Oils on Bloom Delay In `Redhaven' Peach
Authors: Malladi Anish , Hirst Peter M.
Published: February 2019

Peach production is significantly reduced and severely limited by frost injury in regions frequently exposed to late spring freeze conditions. Peach flower buds become increasingly susceptible to low-temperature damage from the period of completion of rest through fruit set. Delaying dehardening and/or flower bud development is an effective way to avoid frost damage. Bio-regulator applications, affecting dormancy or bud development, can delay flowering and dehardening of the buds and can help in avoiding spring freeze injury. Spring applications of AVG and dormant oils on 8-year-old `Redhaven' peach trees were evaluated. AVG applications effectively delayed bloom by 2 to 5 days. The most effective treatment was two applications of 2000 ppm AVG, which delayed bloom by almost 5 days. Repeat applications of AVG were more effective than the single dosage treatments. The 1000 ppm, repeat application delayed bloom by 4 days. A single application of 5000 ppm AVG resulted in severe phytotoxicity. The wetting agent levels were also varied and AVG applications were most effective in combination with 0.2% `Sylgard'. AVG, apparently, delayed bloom by delaying bud development following the completion of rest. The dormant oil sprays were ineffective in achieving bloom delay. The specific leaf weight characteristics of the treated trees were not affected except for the 5000-ppm AVG application, which reduced SLW. Fruit characteristics such as maturity, weight, and soluble sugar concentration were not affected by any of the spring applications (except for the 5000-ppm AVG application, which was phytotoxic). Our studies indicate that AVG is effective in delaying bloom in peaches by up to 5 days. This has the potential to substantially increase peach yields in years with a late spring freeze.