bluuebunny/crossref_metadata_2025 huggingface dataset:
543 Flowering and Growth Response to Photoperiod and Cold Treatment of Arabis sturii Mottet
Authors: Zhang Donglin , Armitage A.M. , Affolter J.M. , Dirr M.A.
Published: February 2019

Arabis sturii Mottet (Brassicaceae) has potential as a new crop for American nurseries and may be used as a perennial pot plant. Cold treatment was required for flowering of Arabis sturii and a 6-week cold treatment resulted in the greatest number of racemes and flowers per plant. Increasing or decreasing length of cold treatment resulted in less flowers per plant. Plant height increased as duration of cold treatment increased. Photoperiod had a significant effect on flowering and growth only after plants received 3 weeks or more cold treatment. All plants given a 16-h photoperiod flowered, while only 50% and 80% flowered under an 8- or 12-h photoperiod, respectively. A 16-h photoperiod shortened the time to production of flower buds and anthesis and the greatest difference occurred after the 9-week cold treatment. At the 6-week cold treatment, number of flowers per plant different significantly between long (145 flowers) and short day (59). The effect of photoperiod on number of flowers per plant became less as cold treatment increased or decreased. Although photoperiod did not induce flower initiation, it had a tremendous effect on flower development. Many more flowers were produced and plants were taller as photoperiod increased. No significant difference was found in plant dry weight.
545 Controlled Flowering of Oenothera fruticosa L. `Youngii-Lapsley' and Stokesia laevis L'Hér `Klaus Jelitto'
Authors: Clough Emily A. , Cameron Arthur C. , Heins Royal D. , Carlson William H.
Published: February 2019

Oenothera fruticosa L.`Youngii-Lapsley' and Stokesia laevis L'Hér. `Klaus Jelitto' are two hardy herbaceous perennials with great potential as pot crops. The vernalization and photoperiod requirements were examined for each species. Plants were cooled for 0, 3, 6, 9, 12, or 15 weeks at 5 °C with a 9-h photoperiod. After cold treatment, plants were forced in greenhouses at 20 °C under a 16-h photoperiod using high-pressure sodium lamps. The photoperiod requirement was determined by forcing plants at 20 °C with and without a 15-week cold treatment at 5 °C under 10-, 12-, 13-, 14-, 16-, 24-h and 4-h night interruption using incandescent lamps. Plants of Oenothera fruticosa `Youngii-Lapsley' cooled for 0 weeks did not flower. All plants cooled for 3 weeks flowered and time to flower decreased from 53 to 43 days as duration of cold increased from 3 to 15 weeks. `Youngii-Lapsley' flowered under every photoperiod, but time to flower and number of flowers decreased from 54 to 40 days as photoperiod increased from 10 to 24 h. Percentage flowering of Stokesia laevis `Klaus Jelitto' increased from 50 to 100, and time to flower decreased from 112 to 74 days as duration of cold increased from 0 to 6 weeks. Without a cold treatment, plants of `Klaus Jelitto' flowered only under daylengths of 12, 13, and 14 h. After cold treatment, plants flowered under every photoperiod except 24 h, and time to flower decreased from 122 to 65 days as photoperiod increased from 10 to 16 h. Additional aspects of flowering and the effect of different forcing temperatures will be discussed.
547 Effects of Media Surfactants on Growth and Postharvest Dessication of Impatiens, Petunia, and Spathiphyllum
Authors: Stamps Robert H.
Published: February 2019

Impatiens `Dazzler Violet', Petunia × hybrida `Carpet Blue', and Spathiphyllum `Ty's Pride' plugs were planted in 10-cm pots containing a commercial peat-based soilless growing medium composed of Canadian 60 peat: 20 vermiculite: 20 perlite (by vol) not treated with surfactant. Growing medium was treated, or not treated, 1) at planting, 2) during production, and/or 3) preshipment with experimental surfactants. The production phase consisted of growing plants on raised benches in a greenhouse until they reached marketable size. Phytotoxicity, plant water use and growth were determined. At the beginning of the postproduction phase, growing medium in all pots was brought to container capacity. Plants were then dried to wilting three times. Water loss and water retained on rewatering and times to wilt and recovery were recorded. Surfactant treatments caused no foliar phytotoxicity and did not delay flowering for petunia or spathiphyllum. However, surfactant treatments delayed flowering for impatiens by ≈4 days. Surfactant treatments increased top growth of petunia but not of the other crops. Postproduction, water retention at rewatering, and times to wilt were increased for petunia and spathiphyllum when they were in surfactant-treated medium. For impatiens, treatments had no effects on water retention or wilting, probably due to the small root systems and limited attendant medium dewatering for this crop. Generally, all three experimental surfactants performed similarly and weekly and preshipment surfactant applications were of no additional benefit compared to a single initial application at planting.
548 Repeated Applications of Growing Medium Surfactants Affect Dianthus barbatus Growth and Development
Authors: Panter Karen L. , Newman Steven E. , Briggs Amy M. , Roll Michael J.
Published: February 2019

Three application rates of two new growing medium surfactants were tested under two different irrigation systems on Dianthus barbatus plants. The objectives of the study were to determine if either of the surfactants influenced plant growth and development and to determine if surfactant applications decreased irrigation frequencies. The three levels of surfactant tested were 0 mg·L–1 (control), 10 mg·L–1 applied at each watering, and 100 mg·L–1 applied once a week. Each surfactant and rate was tested on hand-watered and ebb-and-flood irrigated plants. D. barbatus plants were grown for 8 weeks in 875-ml (12.7 cm) pots. Plants were watered when at least one plant per treatment showed visible wilt. Results showed that phytotoxicity symptoms occurred with repeated applications of both surfactants tested, especially at the 10 mg·L–1 rate at each watering. Application of either surfactant at 10 mg·L–1 at each watering decreased plant heights, dry weights, and plant widths, and increased phytotoxicity symptoms over the controls and the 100 mg·L–1 weekly treatments. Fewer waterings were required in surfactant-treated containers.
551 Evaluation of Vegetable Soybeans for Green Bean Yield and Nutritional Quality
Authors: Rao M.S.S. , Bhagsari Ajmer S. , Mohamed Ali I.
Published: February 2019

In Asian countries and among the oriental populations in the United States, vegetable soybeans are consumed much the same way as green peas are consumed. A need exists for developing soybean cultivars adapted to the U.S. environments to take advantage of the economic potential of vegetable soybeans for both domestic and international markets. During 1997, 12 vegetable soybean genotypes of exotic origin and two local U.S. soybean cultivars were evaluated for their agronomic performance in a randomized complete block, with four replications, at the Agric. Res. Stn. FVSU, Ga. At the R6 stage (when the seeds are of full size and still immature), plants from a half-meter-row length were sampled from each plot to estimate green pod and seed yield, and determine the nutritional quality of green beans. Significant differences were observed among genotypes for the agronomic and biochemical parameters studied. The green seed yield ranged from 7.1 (cv. Ware) to 14.0 Mg·ha–1 (cv. Tanbagura). Three cultivars, Tomahamare, Mian Yan, and Tousan-122, produced green seed yields in excess of 12 Mg·ha–1. The number of green pods varied between 1518 (Tanbagura) and 3526/m2 (cv. Hutcheson). The green bean oil and protein contents, ranged from 53.1 to 105.4 and from 354.2 and 418.3 g·kg–1, respectively. Thus, the green seeds contained only 30% of oil, but 50% to 80% of protein normally found in mature soybean seed. The glucose content was between 4.1% and 7.0%, while the phytate content varied between 0.93% and 1.3%. T he green seed yield was significantly correlated with number of green pods, number of green seeds, and green pod weight. This study showed that some exotic vegetable soybean genotypes may be suitable for production in the southeastern U.S.
552 The Gradient Concept—Replacing the Soil as the Buffer Component
Authors: Geraldson C.M.
Published: February 2019

The gradient concept is designed with a soluble source of N–K banded on the soil bed surface in conjunction with a continuing source of water that synchronizes the nutrient–water input with rate of removal by the root. By placing the N–K on the surface rather than conventionally in the bed, nutrient movement to the root shifts from mass flow to diffusion. Nutrients that move by mass flow are a function of water requirement and potentially a source of nutritional instability. With the shift to movement by diffusion, nutrients move independently of the water to replace those removed from the gradient by the root. The gradient with a continuing nutritional stability replaces the variable and limited stability potential of the soil. Commercial tomato yields in Florida more than doubled with the shift to the gradient-mulch procedure. A containerized version of the concept (The EarthBox™) has been most successful for the home gardener and substantiates the validity of the gradient. Most innovative procedures with the gradient as the buffer component minimize pollution, require minimal management, and use minimal water with microirrigation or an enclosed system. To better understand the gradient concept and utilize the procedure, it may be necessary to consider the procedure as a nutritional paradigm shift.
557 Genetic Diversity in Wild Strawberry (Fragaria virgininia) of the Rocky Mountains
Authors: Horton Grey , Luby Jim
Published: February 2019

This study of genetic diversity in a wild ancestor of the cultivated strawberry was undertaken to describe patterns of variation in nature, assess worth of existing germplasm collections, and identify promising locations for future collection. Previous work reported a similar study of octaploid strawberry ranging east to west across North America. This complementary study focused on variation from north to south in the Rocky Mountains. The morphological diversity of 16 populations of Fragaria virgininia were characterized for morphological and molecular traits. Two clones of each of 133 genotypes from these populations were grown in a common environment in a greenhouse. Eighteen morphological traits, such as leaf area, runner color, and days to flowering, were measured and analyzed with principal components and canonical discriminant analyses. Molecular diversity data were obtained using seven randomly amplified polymorphic DNA primers. Resulting population marker frequencies were also subjected the previously describe anlayses. Differences due to latitude, longitude, and altitude were observed. Implications of the results will be discussed.
558 Evaluation of Sequence-based PCR Markers in an F1 Pseudo-testcross and a BC1 Hybrid Citrus Population
Authors: Weber Courtney A. , Moore Gloria A. , Deng Z. , Gmitter F. , Weber Courtney A.
Published: February 2019

Specific primers were designed for 61 cloned RAPD fragments and from 10 Citrus EST sequences for the production of SCAR, CAPS, and STS markers for a Citrus grandis `DPI 6-4' × Poncirus trifoliata `Rubideaux' F1 pseudo-testcross population. Fifteen SCAR, three CAPS, and one EST/STS markers were developed. An additional 17 SCAR and CAPS primer pairs developed at the Citrus Research and Education Center for a Citrus grandis `Thong Dee' × (Citrus grandis `Thong Dee' × Poncirus trifoliata `Pomeroy') BC1 population were screened in the pseudo-testcross population. A total of 27 markers were identified and scored in the pseudo-testcross population in which 24 were mapped; 13 in the Citrus parental linkage map on seven linkage groups and 11 in the Poncirus parental map on five linkage groups. In the BC1 population, 20 of 27 markers tested were found to be polymorphic and 13 mapped to seven of nine linkage groups. Of these, 11 were mapped in both populations and could be used for aligning presumed homologous regions on the three linkage maps.
562 Plant Regeneration from Embryo and Cotyledons of Laiyang Dwarf Cherry
Authors: Sun Qingrong , Shi Yinping , Wang Qiangsheng , Sun Hongyan
Published: February 2019

Laiyang dwarf cherry (Prunus pseudocerasus Lindl. Var. Laiyang dwary cherry) is an important dwarf type of Chinese cherry. It is both directly used for production and used as rootstock of sweet cherry (P. avium L.). Material used in this study was Laiyang dwarf cherry seed, which is open-pollinated. The fruit surface is sterilized with 70% ethanol on sterile working table, the seed is removed from fruit, and embryo is taken out of cracking seed shell. Explants include whole embryo, embryo without cotyledons, and cotyledons. Basal media are MS and 1/4MS major elements, sugar 30 g·L–1, agar 5.5 g·L–1, adjusted pH 5.8. Hormone used included 6-BA,IBA and 2,4-D for a total eight treatments. Culture temperature was 25° ±2°C, and photoperiod was 14 h. Results show 1) the plant regeneration rate from cotyledons is highest, second is from embryo without cotyledons, lowest is from whole embryo; 2) when BA is in the range of 0.7 to 5 ppm, plant regeneration is higher at a high concentration than that at low concentration; 3) at the same concentration, plant regeneration rate on the medium supplemented with 2,4-D is higher than that on the medium supplemented with IBA; 4) plant regeneration rate is higher on the medium containing cytokinin and auxin is higher than that on the medium only containing cytokinin; and 5) plant regeneration rate of continuous light culture cotyledons is higher than that of first dark culture 2 weeks cotyledons. Effects of light and dark/hormone and explant type on plant regeneration rate is discussed.
565 Evaluation of the Massive Use of Magnesium Infiltration to Predict Bitter Pit in Apples
Authors: Retamales Jorge B. , Valdes Claudio , Donoso Verónica
Published: February 2019

Bitter pit (BP) is the main physiological disorder of apples in Chile. Its incidence affects pre- and postharvest handling of the fruit and the profitability of this species. Since 1991, its control and prediction have been studied by this research team through field and laboratory trials. The BP incidence is linked to the fruit Ca concentration; however, fruit Ca analysis has not adequately predicted BP incidence in postharvest. Several authors have proposed Ca/Mg antagonism, which has been the basis to develop a predictive method through fruit Mg infiltration (IMG) 40 days before harvest. IMG has been massively used for two seasons in Chile, with 375 samples processed in 1997 and 1170 in 1998. The industry has been increasing its proportion of the samples processed, from 22% in 1997 to 71% in 1998. The most prominent varieties are `Granny Smith' (GS) > `Braeburn' (BR) > `Royal Gala' (RG) > `Red King Oregon' (RKO). The massive use of IMG has obtained predictive capacities (r2 between BP predicted and BP after 3 months regular cold storage) of 0.8 for `Fuji'; 0.7 for GS, BR, and RG; and 0.58 for RKO. (This reduction in the predictive capacity with regards to the previous research under controlled conditions would, in part, be due to problems in obtaining fruit samples: non-uniform fruit size, inadequate sampling dates, diverse fruit numbers, etc.) Developments are underway to increase the geographical coverage of the service, the predictive capacity of the method for certain cultivars and productive areas and the number of samples processed.
568 Effect of Twilight and Temperature Difference (DIF) or Temperature Pulse at End-of-day on Height of Easter Lilies
Authors: Blom Theo J. , Kerec David
Published: February 2019

Potted bulbs of Lilium longiflorum Thunb. `Ace', `Nellie White', and `Snow White' were grown under either ambient photo period (APP), 8-h photo period using blackout (no twilight) between 1600 and 0800 HR (8PP) or 8PP extended with 1-h of low-intensity far-red radiation (9PP) at end-of-light period in a greenhouse with either a +5 °C DIF or a –5 °C DIF (= day – night temperature). In a second experiment, Easter lilies were also grown under APP, 8PP, and 9PP regimes with a constant day/night temperature (0 °C DIF) but with either a +5 °C or –5 °C temperature pulse for 3-h during end-of-light period. Each experiment was replicated twice and data was averaged over 2 years. The +5 °C DIF regime produced plants which were 19% taller than under –5 °C DIF. Plants grown under APP were 32% and 25% taller than under 8PP in the +5 °C and –5 °C DIF regimes, respectively. Regardless of the DIF regime, plant height under the 9PP was the same. In the second experiment, there was no significant difference in plant height of plants grown with the –5 °C compared with the +5 °C pulse at end-of-light period.
569 Photoselective Filters Affect Flowering and Stem Extension In Viola ×wittrockiana and Pisum sativum
Authors: Runkle Erik S. , Heins Royal D.
Published: February 2019

For many plants, light quality has a pronounced effect on plant morphology; light with a low red (R, 600 to 700 nm) to far-red (FR, 700 to 800 nm) ratio promotes stem elongation and a high R: FR, or blue light (B, 400 to 500 nm), suppresses it. In addition, FR light is required for rapid flowering in some species, particularly for long-day plants. Our objective was to quantify how flexible spectral filters, which selectively reduce FR, B, or R, influence plant height and flowering of the quantitative long-day plants Pisum sativum L. `Utrillo' and Viola ×wittrockiana Gams. `Crystal Bowl Yellow'. Plants were grown at 20 °C with reduced FR, B, or R environments or with a neutral density control (C) filter. Calculated phytochrome photoequilebria were 0.78, 0.73, 0.71, or 0.46 for the altered FR, B, C, or R environments, respectively. All filter treatments transmitted a similar photosynthetic photon flux. Sixteen-hour photoperiods were created with natural daylight supplemented with high-pressure sodium lamps positioned above filters. Viola grown under the FR filter never reached 100% flowering within 8 weeks, and visible bud appearance was delayed by at least 17 days compared to all other filters. The R and B filters enhanced peduncle length by at least 25% compared to the C or FR filters. In Pisum, average internode length was 2.2, 2.9, 3.4, and 3.7 cm under the FR, C, B, and R filters, respectively, all statistically different. Fresh and dry shoot weights were similar under the C and FR filters but were at least 35% greater under the B filter and 35% lower under the R filter.
574 Capital Investment Analysis of Adopting Zero Runoff Subirrigation Systems in Greenhouse Operations
Authors: Uva Wen-fei L. , Weiler Thomas C. , Milligan Robert A. , Uva Wen-fei L.
Published: February 2019

Adoption of technology to achieve environmental stewardship and remain competitive is a high priority for greenhouse businesses. Zero runoff subirrigation (ZRS) technology offers great promise to manage fertilizer inputs while improving production efficiency. This study applied economic engineering methodology to quantify costs and returns associated with adopting ZRS systems and compare profitability of producing crops using alternative ZRS systems for greenhouse operations in the northeastern and north central United States. The production models showed that using ZRS systems to grow greenhouse crops can be profitable if growers select a system best suitable for their crop choices. Among the four ZRS systems studied (ebb-and-flow rolling benches, Dutch movable trays, flood floors and trough benches), the Dutch movable tray system returned the highest profit per square foot week (SFW) greenhouse area for small potted plant production ($0.244/SFW), and the flood floor system returned the highest profit when producing large potted plants ($0.002/SFW) and bedding crop flats ($0.086/SFW). The trough bench system was least profitable had the lowest profit for the two applicable crop categories—small potted plants ($0.183/SFW) and large potted plants (–$0.006/SFW). Sensitivity analysis showed that changes of cost variables generally did not affect the profitability rankings for alternative ZRS systems. Except for labor costs, as the hourly wage increased, the Dutch movable tray system gained advantages for small potted plant and large potted plant production. Among selected costs variables, changes in labor costs and tax rate had the highest impact on the profitability of small potted plant production, and changes in labor costs and initial investment costs had the highest impact on the profitability of large potted plant and bedding crop flat production.
578 How Much Cover Crop Affects Plant Growth and Yield Components in `Selva' and `Totem' Strawberry (Fragaria × ananassa Duch.) in the Establishment Year
Authors: Datta Braja B. , William Ray D.
Published: February 2019

Field experiment on production systems of `Selva' day-neutral and `Totem' June-bearing strawberry was established in 1995 on the spring-killed cover crop mulched plots using randomized complete-block design. Seven soil cover treatments consisted of `Wheeler' rye (Secale cereale) and `Micah' and `Steptoe' barley (Hordium vulgare), `Micah' residue applied on soil surface, a wedge of perlite (artificial medium) placed next to strawberry row, perlite with `Wheeler' rye, and no treatment were used. During the early summer, cover crops were replanted between strawberry rows and mowed down after 6 weeks. In both cultivars, plant growth doubled during mid-summer, and `Micah'on surface produced better growth than the growth in other treatments. No significant difference was found on CO2 assimilation rate (mmol·m–2·s–1), leaflet length, and number of leaves and runners among treatments (P ≥ 0.1). Yield of `Totem' was ignored during the establishment year. In `Selva', `Micah' residue on surface produced 36% more crowns per plant and the greatest total yield than that of any other treatment. `Micah' on surface produced 50% more shoot biomass and 45% greater yield compared to `Micah' barley planted in the plot. Total `Selva' yield was 61% greater in perlite treatment than the yield in perlite with `Wheeler' rye and 31% greater than the control treatment. Comparison of `Selva' strawberry total yield and average fruit production between cover crops vs. control treatment using non-orthogonal contrast indicated no significant difference might suggests no detrimental interaction between cover crops and strawberry.
579 Effect of Shoot Positioning, Leaf Removal, Cluster Shading, and Curtain Orientation on Fruit Composition and Primary Bud Cold Hardiness in `Norton/Cynthiana' Grapevines (Vitis aestivalis)
Authors: Gu Sanliang , Howard Susanne , Walsh Martin K.
Published: February 2019

The effects of shoot positioning, leaf removal, cluster shading, and curtain orientation on fruit composition and primary bud cold hardiness were investigated in mature `Norton/Cynthiana' grapevines (Vitis aestivalis) trained to Geneva double curtain (GDC) trellis system. For four years (1995–1998) juice soluble solids content, total titratable acidity, and pH were not affected shoot positioning. Cluster shading, curtain orientation, and leaf removal affected fruit composition at harvest. Fruit from the south-facing curtain of the GDC trellis system had higher juice soluble solid content, pH, and skin pigmentation than fruit from the north-facing curtain. Cluster shading decreased skin pigmentation while cluster shading at the highest level only (95%) increased pH and decreased total titratable acidity. Leaf removal, which increases light exposure of the fruit, increased juice pH in the 1997 experiment only. Juice potassium level was decreased by shoot positioning, but not cluster shading or curtain orientation. Cold hardiness of primary buds was affected by these treatments early in the winter, but the differences in primary bud cold hardiness among the treatments diminished toward the end of the dormant season.
587 Study on Adoptability of Pecan, Carya illinoensis L., under Climatic Conditions of the Safiabad Area of Iran
Authors: Talaie A. , Khezrian A.
Published: February 2019

To select proper varieties, several seedlings of Carya illinoensis (pecan) were imported from the United States about 28 years ago and were planted at the Safiabad Research Center, Iran. Because of the existence of docogamy in pecan, protandrous and protoginous cultivars were first determined. Then, qualitative and some quantitative characteristics were studied in a completely random plant test and, with regard to treatments and repetitions, the total yield of trees, weight of kernel, kernel: bark ratio, oil percentage (fat), protein percentage, and the size of fruit were examined. With regard to all circumstances and statistical results, out of 14 examined varieties, varieties 12 (`Wichita') and 1 (`Gratex') were selected on the basis of their high yields, respectively.
595 The Cuticular Membrane: A Critical Factor in Rain-induced Cracking of Sweet Cherry Fruit
Authors: Bukovac Martin J. , Pastor Alicia , Fader Royal G. , Knoche Moritz
Published: February 2019

Morphological and physical characteristics of the cuticular membrane (CM) of selected cultivars of sweet cherry (Prunus avium L.) fruit were studied relative to rain-induced cracking. Two characteristics of the CM may be determinants in rain-induced fruit cracking. The surface morphology and chemistry determine surface wettability and water retention, and the morphology and physicochemical characteristics its water permeability. The fruit epidermis as well as the guard cell walls adjacent to the outer vestibule and stomatal pore are covered by a thin lipoidal CM. Stomata were present at a frequency of 0.1 to 2 per mm2 depending on cultivar and fruit surface position. However, most appeared nonfunctional with many pores partially or completely occluded with wax-like material. There was no evidence of water (containing fluorescein or AgNO3) penetration into stomatal pores following surface application or submerging fruit for short periods. There was stomatal pore penetration when submerged fruit were infiltrated by reduced pressure in the presence of 0.1% L-77. Preferential sorption of AgNO3 and fluorescein by cuticular ledges and guard cells was noted. The epicuticular wax (ECW) had no significant fine-structure. The CM was isolated enzymatically (cellulase/pectinase) and found to be 1 to 2 μm thick with an area weight of 1.2 to 2.3 g·m–2, of which 25% to 40% was chloroform/methanol (1: 1by vol.) soluble. Fractionation of the chloroform/methanol fraction indicated the presence of four groups of nonpolar constituents. The fruit surface was moderately difficult to wet, forming contact angles of 85% to 105%, and with an estimated critical surface tension in the range of 16-24 mN·m–1. Fruit water loss (transpiration) and uptake on submersion was followed and found to be complex. Transpiration increased with an increase in temperature, and both rate of transpiration and water uptake increased after removal of the epicuticular and cuticular waxes. Pathways of water uptake and the significance of our findings to rain-induced fruit cracking will be discussed.
596 Landscape Design and History Affect Urban Plant Gas Exchange Parameters
Authors: McDowell L. Brooke , Martin Chris A.
Published: February 2019

Effects of landscape design and land use history on gas exchange parameters were evaluated for woody plants in a factorial site matrix of formerly desert or agricultural land uses and xeric or mesic residential landscape designs within the metropolitan area of Phoenix, Ariz. Remnant Sonoran Desert sites and an alfalfa agricultural field functioned as controls. Residential landscapes and the alfalfa field were irrigated regularly. Monthly instantaneous measurements of maximum leaf and stem carbon assimilation (A), conductance (gs), and transpiration (E) were made within three replicates of each site type during 1998 and 1999. Measurements were repeated monthly on three woody plant life forms: trees, shrubs, and ground covers. Assimilation fluxes were not related to former land use, but were lower for plants in xeric compared with those in mesic landscapes. Transpiration fluxes were higher for plants in formerly agricultural sites than in formerly desert sites, and were lower in xeric than in mesic landscape design. Compared with plants in residential landscapes, A and E fluxes were generally higher for plants in the agricultural control sites and were lower for plants at the desert control sites. Plant instantaneous transpiration efficiency (ITE = A/E) was higher in formerly agricultural sites than in formerly desert sites but was not affected by landscape design. Patterns of A, gs, and shoot temperature at irrigated sites suggest that maximum plant carbon assimilation was not limited by shoot conductance but was more responsive to shoot temperature. Similarities in patterns of ITE between plants in the different landscape design types suggest that xeric and mesic landscape plants do not differ in terms of water use efficiency.
599 Flooding Effects on Stomatal Conductance and Leaf Color Vary among Genotypes of Red and Freeman Maples
Authors: Zwack James A. , Graves William R. , Townsend Alden M.
Published: February 2019

We compared two putative Freeman maples [`Jeffersred', (Autumn Blaze ®) and `Indian Summer'] and five red maples [`Franksred' (Red Sunset ®), `Autumn Flame', `PNI 0268' (October Glory®), `Fairview Flame', and unnamed selection 59904] for effects of flooding on stomatal conductance. A method for quantifying changes in leaf color that occurred on flooded plants also was developed. Potted plants grown from rooted cuttings in a greenhouse were subjected to 75 days of root-zone inundation (flood treatment) or were irrigated frequently (control treatment). Across genotypes, stomatal conductance of flooded plants initially increased by about 20% and then fell to and was sustained below 50 mmol·s–1·m–2. Stomatal conductance of flooded plants of `Indian Summer' decreased to 20 mmo·s–1·m–2 after 8 days of inundation, and two of three flooded `Indian Summer' plants died during treatment. Other genotypes required at least twice this time to display a similar reduction in stomatal conductance, indicating `Indian Summer' may be particularly flood sensitive. Intensities of red, green, and blue color at a consistent interveinal position were analyzed with Visilog software by using scanned leaf images of the youngest fully expanded leaf of each plant in both treatments. A genotype × irrigation interaction existed for the ratio of green to red intensity. This method provided numerical data that corresponded well to differences among genotypes we observed visually. For example, while flooding did not alter the color of `Autumn Flame' leaves, the ratio of green to red was three times greater for controls of Autumn Blaze® than for the flooded plants of this cultivar.
600 The Effect of Weed Control Methods on Soil Physical Properties and Plant Growth
Authors: O'Leary Amy , Henry Paul , Chong She-Kong
Published: February 2019

There has been recent speculation in trade journals that landscape fabrics, while doing an excellent job of weed control, may have a detrimental effect on ornamental plant growth. A study is in progress to investigate the manner in which hardwood mulch and applied landscape fabric affect soil temperature, soil aeration, and water content over 18 months. Two experiments are in progress, one with compost incorporated at 50% soil volume, the other with no compost incorporation. The experimental design is a randomized complete block with four treatments (mulch, fabric, fabric plus mulch, and control) and four plants per plot. Each plot has been planted with herbaceous perennials so as to allow analysis of treatment effects on plant growth. Soil temperature within plots is monitored on a continual basis. Soil aeration is measured every two weeks using installed oxygen tubes. Water content is measured using time domain reflectometry 24 and 48 h after a significant rainfall event. Preliminary results suggest that hardwood mulch and landscape fabric are similar in their effect on soil water content 0 to 48 h after a significant rainfall event. However, after 48 h, hardwood mulch increases soil water retention compared to landscape fabric.
606 Effects of Compost and Chicken Manure Soil Amendments on Basil Yield
Authors: Radovich T.J. , Valenzuela H.R. , Kratky B. , Hue N.V.
Published: February 2019

To help develop fertilizer recommendations for organic vegetable production in Hawaii, the effects of organic amendments on basil yield were studied in two experiments. The treatments were synthetic nitrogen applied at 100 kg·ha–1 per crop, organic amendments applied at a rate of 8–160 MT·ha–1, and an unammended control. Each treatment was replicated four times in a RCB design. In the first experiment, chicken manure was the organic amendment at 8 MT·ha–1 with a single basil variety grown. In the second experiment, conducted at the same location immediately following the first experiment, the organic amendment was locally produced compost (0.3% N) applied at 40 and 160 MT·ha–1 with three basil varieties grown. Data taken included soil fertility levels before and after experimental completion, marketable yields recorded weekly over 5–10 weeks, and tissue N and nitrate sap analysis measured at two to three different plant growth stages. In the first experiment, treatments receiving chicken manure or synthetic N showed similar yields (256–289 g/plant), which were significantly greater than the control (197 g/plant). Tissue N levels were greatest in the synthetic fertilizer treatment (4.9%) and lowest in the control (4.5%). In the second experiment, there was a differential response by varieties to treatments with respect to yields. Yields from the compost treatments (292–700 g/plant) were equal to or greater than those receiving synthetic fertilizer (320–651 g/plant) and were generally greater than the control (324–532 g/plant). Tissue N levels were greatest in plants receiving synthetic fertilizer (4.6% to 4.7%) and lowest in the control (4.3% to 4.4%). A positive correlation was found between lab tissue N levels and nitrate sap analysis determination.
611 From Weed to Wonder: Taming Bitterweed for the Landscape
Authors: Arnold Michael A.
Published: February 2019

Pilot trials were conducted to explore the potential for use of Helenium amarum (Raf.) H. Rock as a bedding plant in Texas. Bitterweed is an annual wildflower native to the eastern U.S. It occurs on disturbed waste sites, along railroad tracks, roadsides, and in heavily grazed pastures. Bitterweed varies in form from a 15-cm-tall spreading mound to an upright oval crown 60 cm tall. Early growth is in a rosette form. Later foliage is bright green, highly dissected, and attractive. Profusely borne yellow single daisy-like flowers occur from spring to frost, peaking in late summer and fall. The species can survive intense drought and heat. Production responses were tested in 0.06-, 0.13-, 0.16-, and 0.51-L containers in the greenhouse during Summer 1998; then seedlings were transplanted to landscape beds and monitored through fall 1998. Other seedlings from 0.13-L containers were planted to the landscape to determine spacing requirements. Plants were also grown in an outdoor nursery in larger 2.3-L containers to test responses to pine bark- and peat-based media. Seedlings from 0.16- and 0.51-L containers were more effective throughout the growing season in the landscape than seedlings from 0.06- and 0.13-L containers. Seedlings grown in 2.3-L containers in a 4 pine bark: 1 sand media were larger, flowered more rapidly, and reach a marketable size in a shorter time than seedlings grown in a peatmoss-based media.
612 Consumers Knowledge, Practices, and Environmental Attitudes on Lawn Care
Authors: Meyer Mary Hockenberry , Carpenter Perrin
Published: February 2019

Homeowner surveys conducted in Edina, Minn., showed varying levels of horticultural knowledge on lawn care. A majority of consumers, 75%, knew the value of lawn clippings was equivalent to one fertilization treatment, but 72% did not know the amount of fertilizer needed for a medium maintenance lawn. A total of 77% indicated spring as the single best time to control broadleaf weeds, and 39% thought spring was the best time to fertilize, whereas 48% indicating fall as the best time to fertilize. Current practices included the following: leaving clippings on the lawn, 75%; bagged and removed clippings,16%; 83% apply fertilize in the spring; 67% fertilize in the fall; 61% apply herbicides; 74% mow weekly; 51% mow at 2–3″, but 27% mow at 1–2″. Environmental attitudes were rated on a scale of 1 to 4, with 1 being strongly agree and 4 being strongly disagree. Consumers strongly agreed that pesticide (1.5) and fertilizer (1.7) applications should be posted in public areas. The statement “A well kept lawn increases property values” also found strong agreement, (1.6). Consumers disagreed that pesticides are not harmful to the environment (3.3) and public health (3.3); while fertilizers were only slightly less harmful to the environment (3.0) and public health (2.9). A 10% weed population was acceptable (2.2) but 25% was not (3.3). Areas for consumer education exist in the time and amount of fertilizer, timing of weed control, and mowing height. Because of negative attitudes toward pesticides and fertilizers, recommendations for medium to low input grasses should be well received.
619 Temporal and Spatial Weed Control Effects on Tart Cherry Orchards
Authors: Al-Hinai Yahya K. , Roper Teryl R.
Published: February 2019

This experiment was conducted to determine temporal and spatial weed management characteristics for tart cherry orchards. Annual ryegrass and lambsquarter were planted in tree rows of a 14-year-old tart cherry orchard. Vegetation was controlled with nonresidual herbicides (Gramoxone + B-1956) either all season, May, June, July, August, before harvest, after harvest, or not controlled. Shoot growth measurements showed significantly more growth by trees without weed competition during the entire season, May, June, and before harvest compared to the weedy control and postharvest, July, or August treatments. Weedy early season plots reduced the shoot growth by half. All season, before harvest, May, and June weed-free plots showed higher amounts of leaf N compared with weedy controls or late-season treatments. Early season weed control is more important than late season. Vegetation-free areas of 0, 2, 3, and 4 m2 were maintained during 1998 by postemergence herbicides. Tissue analysis showed higher N concentration in leaves with vegetation controlled to 2 m2 or more compared to the weedy control. The critical vegetation free area for young cherry trees is between 0 and 2 m2.
621 Effects of Shading Levels on Seasonal Leaf Color in Fire Power Nandina
Authors: Butler Leiah M. , Hayslett William F. , Harrison Robert
Published: February 2019

A 24-month experiment was conducted to study the effects of shading levels on the foliage color changes in Fire Power Nandinas. This popular ornamental shrub is the dwarf form of the Heavenly Bamboo, Nandina domestica. It originated in New Zealand, and has vivid green leaf color in the spring and summer months that changes to a fluorescent red as winter approaches. In this experiment light was limited by covering the plots with black woven shadecloth of 43% and 78% shade, while allowing the control plots to receive full sunlight. Fifteen shrubs from each plot were randomly selected and 10 leaves per plant in each treatment were taken at 28-day intervals. The leaf color was recorded using a camera attached to a microscope. The results from this study indicate that changes in leaf color may be affected by the change of the seasons. The level of light/shade that the plants receive may also affect leaf color. The control group turned a bright fluorescent red, the 43% shade turned a deep red, and the 78% shade remained a deep green with few leaves turning red. Based on the different hues observed, this research indicates that limiting light has a direct effect on leaf color in this species. The correlation between the amount of sunlight received and the season of the year are the two factors that determine the degree of color change in this ornamental shrub.
628 Influence of Cooling, Long-day Lighting Regime, and Propagule Type on Flowering of Phlox paniculataL. Cultivars
Authors: Garner James M. , Armitage Allan M.
Published: February 2019

Rooted terminal cuttings and dormant 1-year-old transplants of Phlox paniculata L. `Ice Cap' and `Red Eyes' were cooled for 0, 4, 8, 12 or 16 weeks and forced under long-day photoperiod provided by incandescent lights as either a night-interruption (2200–0200 hr) or extended-day (1700–2200 hr). The influence of cooling duration, long-day lighting regime, and propagule type on forcing days to flower, flowering stem counts, and flowering stem length was evaluated in a 3 × 2 × 5 factorial experiment. Cooling accelerated flowering and increased stem yield and length. Days to flower for both cultivars decreased and flowering stems and length increased linearly as cooling increased from 0 to 16 weeks, regardless of lighting or propagule type, but cooling for 8 weeks or more was necessary to produce marketable cut flower stems. Extended-day lighting produced longer stems than night interruption, and stem counts were higher among plants grown from transplants, regardless of cooling duration, lighting regime, or cultivar. Flowering stems from rooted cuttings were generally longer than those from transplants. Cut flower stems of `Ice Cap' were longer than those of `Red Eyes', but days to flower and yields for the two cultivars were similar.
634 Mechanism and Stability of Virus Resistance in Transgenic Papaya
Authors: Manshardt Richard , Gonsalves Dennis
Published: February 2019

Transgenic papaya line 55-1 with resistance to papaya ringspot virus (PRSV) originated in 1989 by particle bombardment of cultivar Sunset with the coat protein gene (cp) of mild mutant Hawaii PRSV strain HA 5-1. Hemizygous (+/cp) R0 clones of 55-1 displayed resistance to the virulent Hawaii HA strain in greenhouse tests in New York in 1991 and to local strains in a field trial in Hawaii from 1992 to 1994. In the R1 generation produced by crossing the pistillate R0 55-1 with `Sunset', up to 50% of the hemizygous transgenic segregants were susceptible to a local Oahu PRSV strain when inoculated as seedlings but not as mature plants. Similar inoculation experiments in New York showed that hemizygous R1 transgenics were susceptible in differing degrees to PRSV strains from regions other than Hawaii. Homozygous (cp/cp) R2, R3, and R4 populations planted in various locations in Hawaii since 1994 have consistently demonstrated high-level resistance to local strains at all stages of development. When inoculated in New York with eight non-Hawaii PRSV strains, homozygous R3 seedlings were resistant to all but a Thai strain. Transgenic resistance is the result of a complex interaction involving the stage of plant development, transgene dosage, the degree of homology between transgene and challenge virus, and environmental variables. Papaya plants transformed with nontranslatable versions of various cp genes are also highly resistant to PRSV, indicating that the resistance mechanism operates at the RNA level. No loss of resistance due to the appearance of resistance-breaking virus strains or to transgene inactivation has been noted thus far.
635 Stability of Herbicide Resistance and GUS Expression in Transgenic Hybrid Poplars during Several Years of Field Trials and Vegetative Propagation
Authors: Meilan Richard , Ma Caiping , Strauss Steven H.
Published: February 2019

We assessed the stability of transgene expression in 79 transgenic lines (i.e., transformation events) of hybrid poplars during several years of field trials. The transgenic lines were comprised of 40 lines of hybrid cottonwoods (P. trichocarpa × P. deltoides) that were grown at three field sites, and 39 lines of hybrid aspens (section Leuce, P. alba × P. tremula) that were grown at a single field site. All the lines were transformed with a binary construct that included two genes that confer tolerance to glyphosate (GOX and CP4), a gene encoding resistance to the antibiotic kanamycin (nptII), and a visible marker gene (GUS). Agrobacterium tumefaciens was used for transformation; callogenesis and organogenesis occurred under kanamycin selection. In addition to repeated applications of herbicide to test stability of transgene expression, for the first time, we challenged ramets of 40 lines that had not previously been tested for herbicide resistance in their fourth season of vegetative growth. We report on the stability of herbicide resistance and GUS expression and evidence for somaclonal variation in growth and leaf morphology.
636 Introduction to the Organic Horticulture Colloquium
Authors: McGiffen Milt
Published: February 2019

Consumption and production of organic food has quadrupled since 1990. Certified organic or pesticide-free produce and other foods are common in most grocery chains. Increased consumer demand and concerns about pesticide use has led to mandates for national standards and local implementation. The Organic Horticulture Colloquium addresses organic certification, production, pest management, consumer demand, education, marketing, and economics. Challenges and results in implementing policy and encouraging change will be related from both national and local perspectives. While the “organic movement” was originally focused on food crops, it has evolved to address issues of pesticide use in non-food horticultural crops as well. This colloquium addresses issues of concern to food and non-food agricultural products.
637 Implementing Government Mandates for Pest Management without Pesticides
Authors: Frieders David C. , Daries Jackie
Published: February 2019

In Oct. 1996, the San Francisco Board of Supervisors passed an ordinance that became Chapter 39 of the Administrative Code, mandating that City departments adopt integrated pest management (IPM) policies that promote nonchemical approaches to pest management and reduce or eliminate the use of pesticides. Eliminated on 1 Jan. 1997 were 1) category I chemicals (listed by EPA—most toxic; these are products marked “DANGER”); 2) cancer- or reproductive-toxicity chemicals (per State of California Safe Drinking Water and Toxic Enforcement Act of 1986); and 3) possible, probable, or definite human carcinogens (per EPA). Eliminated on 1 Jan. 1998 were category II chemicals (listed by EPA—next most toxic; these are products marked “WARNING”). Eliminated on 1 Jan. 2000 will be category III chemicals (listed by EP— relatively less toxic; these are chemicals marked “CAUTION”), except for a list to be developed by 1 Mar. 1999 of low-toxicity chemicals commonly used in IPM programs. To date, 10 exceptions have been approved. Several pesticide-free research projects have been embarked on and on-going IPM training is underway for all city employees, both technical and nontechnical. Challenges remain for pesticide regulators and pest managers in implementing policy and encouraging change.