bluuebunny/crossref_metadata_2025 huggingface dataset:
Shoot Regeneration from Rhododendron Leaf Explants and Callus
Authors: Crist Sarah S. , Preece John E.
Published: February 2019

Shoots were regenerated adventitiously from leaf explants and from callus to determine if there is any effect on somaclonal variation and tissue proliferation of the three rhododendron cultivars, Arctic Pearl, P.J.M. Elite, and Purple Gem. The focus of this paper is regeneration. Leaves from shoot cultures were placed on a pre-conditioning medium for 2 weeks containing 10 μM indolebutyric acid (IBA) and 50 μM isopentenyladenine (2iP) and then transferred to treatment media. The six media tested were 0.1, 1.0, or 10.0 μM thidiazuron (TDZ) or 25.0, 50.0, or 75.0 μM 2iP. All treatment media contained 10 μM IBA. Data were collected on shoot regeneration after 24 weeks. Shoot number increased with increasing levels of TDZ for `P.J.M. Elite', but decreased with increasing concentrations of TDZ for `Arctic Pearl'. Shoot number for `Purple Gem' leaf explants was greatest when there was 1.0 μM TDZ in the medium. In another experiment, leaf explants were placed on the same preconditioning medium for 2 weeks as above and then transferred to three treatment media containing 0.1, 1.0, or 10.0 μM TDZ and 100 μM IBA. Callus was produced on leaf explants after 4 weeks, regardless of cultivar or level of TDZ. After 11 weeks, adventitious shoots regenerated from `Purple Gem' callus regardless of level of TDZ and from `Arctic Pearl' callus when the medium contained 0.1 or 10.0 μM TDZ. After 11 weeks, there were no visible shoots on `P.J.M. Elite' callus.
Tumor Incidence and Shoot Morphology Differences in Rooted Cuttings from Rhododendron With and Without “Tissue Proliferation”
Authors: Brand Mark H. , Kiyomoto Richard
Published: February 2019

Tissue proliferation (TP) occurs in Rhododendron and is characterized by basal tumors that often develop numerous dwarf shoots. Growers need to know if the TP condition will persist in plants grown from normal-appearing cuttings collected from plants with TP tumors. Cuttings of seven cultivars were collected from plants with TP [TP(+)] and without TP [TP(-)] and rooted. Plants were grown in containers outdoors for a minimum of 2 years. For all cultivars, plants grown from TP(+) cuttings had more leaves per growth flush than plants grown from TP(-) cuttings. Shoots of TP(+) plants were either similar in length to shoots of TP(-) plants, or were shorter, as was the case for `Boule de Neige', `Catawbiense Album', and `Montego'. `Montego' and `Scintillation' TP(+) leaves were shorter, narrower, had smaller leaf areas and larger length to width rations than leaves from TP(-) shoots. No difference in leaf size and shape were detected for other cultivars. TP tumors were not observed on any plants. Another study examined the effect of stock plant age from tissue culture on development of TP symptoms in rooted cuttings. `Montego' plants grown from cuttings collected from microplants, 3-year-old TP(+) plants, 6-year-old TP(+) plants and TP(-) plants were compared. Plants grown from 6-year-old TP(+) and TP(-) cuttings did not develop tumors. 83% of plants from microplant cuttings and 74% of plants from 3-year-old TP(+) cuttings formed tumors. Plants from microplant cuttings were more likely to develop large tumors that surround half or more of the stem than plants from 3-year-old TP(+) cuttings.
Mitotic Activity Dynamics in Recalcitrant Seeds Acer sachharinum during Maturation and Germination
Authors: Kozeko L. , Troyan V. , Musatenko L.
Published: February 2019

In orthodox seeds the cell division within the embryo meristems arrests during maturation at embryo moisture content (MC) 65% to 47%, and the maturation completion and transition of seeds to quiescent state occurs at MC about 10%. The arrest of cycling happens asynchronously in different meristematic tissues during desiccation: first in shoot and then in root. The aim of this work was to define a mitotic activity dynamics in recalcitrant seeds with the high MC at maturation end and the absence of quiescent state characteristic of it. The object was seeds of Acer saccharinum, using widely for planting of greenery in Kiev city. The mitotic activity was determined in 0.5 mm of the embryo root pole (RP) and 0.5 mm of the shoot pole with embryo leaves (SP). The A. sachharinum seeds completed them maturation at MC 53% (FW basis). During maturation the mitotic index (MI) in RP decreased from 3.2% in immature seeds (at embryos MC 80%) to 0 in mature seeds and in SP–from 5.4% to 3.3%, respectively. Cell division in SP arrested by dehydration of mature embryos to MC 46% by PEG 6000 (30%). The seeds lost viability by desiccation to MC 34%. The mature seeds were able to germinate immediately after abscission. During seed germination the cell division reactived in RP and increased in SP already before root protrusion. In plantlets 10–15 mm long the MI increased to 8% in RP and 12% in SP. Thus, the strategy of immediate germination of recalcitrant A. sachharinum seeds includes a preservation of cell division in SP of mature embryos, in contrast with orthodox seeds, and high mitotic activity levels in meristems of germinating embryos before and after root protrusion.
Growth of Ornamental Plants in Compacted Soils in Relation to Root Growth under Low Oxygen and High Atmospheric Pressure
Authors: Knee Michael , Brake Ruth
Published: February 2019

In urban situations, particularly after construction, herbaceous ornamentals may be planted into soils that are compacted or have poor structure so that plant roots may encounter poor aeration or physical resistance. Low oxygen concentrations may be the most important aspect of poor aeration and are readily reproduced in the laboratory. High atmospheric pressure might be used to screen for the ability to grow against physical resistance. We tested the suggestion that “native” plants would grow better in compacted soils than typical bedding plants and for differences in tolerance to low oxygen or high pressure. Plants were grown from seed in the greenhouse at four levels of compaction in peat-based medium and in field soil. Shoot dry weights of the native plants Asclepias tuberosa, Echinacea purpurea, and Schizachyrium scoparius, were less affected by growth in compacted soil or peat medium than those of the bedding plants, Antirrhinum majus, Gypsophila elegans, Impatiens balsamina, Tagetes patula and Zinnia elegans. The oxygen content of media declined with compaction to a minimum of 10 kPa. Half maximal root elongation was observed at 1 to 3 kPa oxygen for most species without any separation between the groups. A presure of 1100 kPa reduced root elongation of the bedding plants by 50 to 70% but only 5 to 20% for the native plants.
Sensitivity of Selected Vegetable and Weed Seedlings to Ultraviolet-B Radiation
Authors: Furness Nancy H. , Upadhyaya Mahesh K. , Ormrod Douglas P.
Published: February 2019

Relative sensitivity of selected vegetable and weed seedlings to ultraviolet-B (UV-B) radiation (280–320 nm) was investigated. Seedlings were grown for 4 weeks in a greenhouse, in chambers equipped with UV-B-emitting fluorescent tubes and Mylar (control) and cellulose acetate (UV-B) filters. UV-B radiation reduced seedling height, leaf area, and leaf fresh weight in tomato (Lycopersicon esculentum `Cour Di Bue'), broccoli (Brassica oleracea var. Italica `Purple Sprouting'), cabbage (Brassica oleracea var. Capitata `Red Drumhead'), and cucumber (Cucumis sativus `Straight Eight'), leaf area and leaf fresh weight in beet (Beta vulgaris `Cylindra' and `Early Wonder'), seedling height and leaf area in spinach (Spinacia oleracea `Long Standing Bloomsdale'), lettuce (Lactuca sativa ``Red Salad Bowl Everest') and `Savoy' cabbage, and seedling height in `Chinese Tip Top' cabbage and lettuce (`Saladin'). `Winterton' cabbage was not affected. UV-B radiation decreased leaf area and leaf fresh weight in common chickweed (Stellaria media) and corn spurry (Spergula arvensis) and seedling height in green foxtail (Setaria viridis) and redroot pigweed (Amaranthus retroflexus). Tillering was stimulated in response to UV-B in green foxtail. There was no effect of UV-B on lady's-thumb (Polygonum persicaria) growth. Leaf number was not affected by exposure to UV-B in any species. The differential morphological sensitivity of vegetable and weed seedlings may result in altered competitive relationships under enhanced UV-B levels expected with the depletion of the earth's ozone layer.
Effect of Preemergent Herbicides on Growth of Dwarf Nandina, Eleagnus, Asiatic Jasmine, Bradford Pear, and Arizona Ash
Authors: Pemberton H. Brent , Roberson William E. , McDonald Garry V.
Published: February 2019

The list of species that are known to tolerate the use of Factor® (prodiamine), a preemergent herbicide, in a containerized production system is limited. Plants of swarf nandina (Nandina domestica `Firepower'), eleagnus (Eleagnus × eggingei), and Asiatic jasmine (Trachelospermum asiaticum) growing in 3.8-L containers were obtained from a local nursery and treated with herbicide treatments to determine effects on growth. Plants were treated with one or two applications of Factor® 65WG at either 0, 1.4, 2.8, or 5.5 kg·ha–1 (0.9, 1.8, or 3.6 kg·ha–1 active ingredient, respectively). The first application was made on 10 Aug. 1995 and the second application was made on 19 Oct. 1995. Plants were grown under 30% Saran shade and watered and fertilized as needed. Plants of Arizona ash (Fraxinus sp.) and Bradford Pear (Pyrus calleryana `Bradford') ptted in 19-L containers were treated with herbicide treatments on 25 Oct. 1995 for fall weed control at a local nursery. Treatments included a single application of Factor® 65WG at either 0, 1.4, 1.8, or 2.8 kg·ha–1 (0.9, 1.2, or 1.8 kg·ha–1 active ingredient, respectively) with or without Gallery® (isoxaben) at 1.2 kg·ha–1 (0.9 kg·ha–1 active ingredient). There was no effect of the herbicide treatments on growth of eleagnus. Herbicide treatments did not affect shoot dry weight and did not have a deleterious effect on shoot length and root dry weight of Asiatic jasmine or affect trunk caliper growth of the two tree species. Factor® did affect the growth of dwarf nandina. Plant height and shoot and root dry weight were not affected. However, plant width was decreased by all Factor® treatments when compared to untreated plants.
Suppression of Liverwort Growth in Containers Using Irrigation, Mulches, Fertilizers, and Herbicides
Authors: Svenson Sven E.
Published: February 2019

Liverwort (Marchantia sp.) is often a serious weed in many nursery and greenhouse operations. Combinations of irrigation frequencies, surface mulches, surface fertilizers and herbicides were applied to the surface of the growing medium in 10-cm square pots planted with Rhododendron or Picea. Liverwort infestations were evaluated as the percentage of media surface covered. Mulches were placed at least 1/2-inch thick on the surface of the growing media. Five blocks of two pots per treatment were used in a completely randomized design. Oyster shell, hazelnut shell, and copper-treated geotextile mulches provided good suppression (less than 10% surface coverage) of liverwort for up to 6 weeks, while rockwool, peatmoss, coarse sand, perlite and pumice mulches required low-frequency irrigation to provide fair suppression (less than 40% surface coverage). Surface applications of oxadiazon (Ronstar), oryzalin (Surflan), iron oxide, copper sulfate, and manganese sulfate provided good suppression of liverwort for up to 4 weeks using low-frequency irrigation, but suppression was nearly eliminated if high-frequency irrigation was applied. Some combination applications of mulches and herbicides or fertilizers provided good suppression for 8 weeks (high-frequency irrigation) or 12 weeks (low-frequency irrigation). Liverwort suppression was fair when untreated geotextile mulches were used, but suppression was good (even under high-frequency irrigation) when copper-treated geotextile mulches were used.
Early Onset of Poinsettia Bract Necrosis is Associated with Condensed Tannin Accumulation
Authors: McAvoy R.J. , Bible B.B. , Evans M.R.
Published: February 2019

The early onset of bract necrosis in poinsettia (Euphorbia pulcherrima Willd. ex. Klotzch) is characterized by small dark-stained spots that precede the development of enlarged necrotic lesions. Electron micrographs of adaxial epidermal and subepidermal tissues with early symptoms of necrosis revealed large, electron dense deposits in cell vacuoles. These spherical bodies resembled condensed tannins observed in the epidermal tissues of peach and apple fruit. Chemical analysis of bract tissues showed higher condensed tannin concentrations in bract samples with 2 mm diameter lesions than in samples with lesions less than 0.5 mm (equivalent to catechin concentrations of 59 and 13 mg·g–1 fresh mass, respectively). Tannin bodies were not observed in micrographs from parallel samples of healthy appearing bracts, and chemical analysis revealed only trace concentrations of condensed tannins in these tissues (0.2 mg·g–1 fresh mass). The evidence suggests that condensed tannins accumulate in affected cells at the earliest observable stages of bract necrosis.
Vase Life of Cut Rose Flowers Harvested at Different Months and Treated with Poly(2-Hydroxypropyldimethylammonium Chloride)
Authors: Izumi Hidemi , Fujii Atsuo
Published: February 2019

Flowering rose (cv. Rote Rose) stems, harvested at different months of the year, were placed in 250 ppm poly(2-hydroxypropyl-dimethylammonium chloride)(PHPAC) solution or in water as the control at 4 °C for 24 h. They were then transferred to water and held at 20 °C for 6 or 7 days. Bent-neck of control roses was the greatest with those harvested in July, least with December or May harvest, and intermediate with October harvest, and occurred after day 2, 4, 4, and 3 at 20 °C, respectively. PHPAC reduced the occurrence and degree of bent-neck of all roses and had the greatest inhibitory effect on roses harvested in July. PHPAC accelerated flower opening of roses harvested in July and December. Rates of water uptake and transpiration decreased during the holding period, and PHPAC retarded the decrease after day 3-4 of all roses. Hydraulic conductance in the basal 3 cm segment of all rose stems decreased during holding and PHPAC retarded the decrease. Electrolyte leakage from the basal 3 cm of the stem was greater with the PHPAC-treated stems than that of the control of all roses. These results indicate that PHPAC suppressed bent-neck probably by reducing the rate of decrease in water uptake and transpiration, which related to the hydraulic conductance and electrolyte leakage in the basal 3 cm of the stems.
Genotypic Influences on Fatty Acid Profiles and Germinability of Pecan Pollen
Authors: Nail William R. , Storey J. Benton , Grauke L.J.
Published: February 2019

Pollen of pecan [Carya illinoinensis (Wangenh.) K. Koch] from five protandrous and five protogynous genotypes was analyzed for germinability and fatty acid profile. Fatty acid profiles as a function of genotype were distinctive in all selections, but only three of the genotypes had fatty acid profiles that were easily distinguishable from others by canonical discriminant analysis. Specific fatty acid percentages influenced germination in some genotypes. Total saturated and unsaturated fatty acids influenced pollen germination to a greater degree than individual fatty acids. The effects of fatty acids on pollen germination of protandrous genotypes were opposite those on `Stuart', the only protogynous genotype to be influenced by fatty acid percentages.
Effect of Harvest Maturity and Ethylene Gassing on Tomato Flavor Volatile Concentrations
Authors: Baldwin E.A. , Scott J.W. , Maul F.
Published: February 2019

Tomato fruit (Lycopersicon esculentum Mill.) cvs. Solar Set and Olympic were harvested at three maturity stages: green (stage 1, USDA color classification) gassed with 100 ppm ethylene, green not gassed, turning (stage 4), and red-ripe (stage 6). After ripening at 21 °C, the fruit were homogenized with CaCl2 and analyzed for important flavor volatile compounds. For `Solar Set', acetone, ethanol, 1-penten-3-one, hexanal, and trans-2-heptenal were significantly higher in red-harvested fruit, while 2+3-methylbutanol, and trans-2-hexenal were higher in green-harvested fruit. trans-2-Hexenal was at higher levels in green-harvested fruit not gassed compared to those that were gassed for `Solar Set'. `Olympic' fruit followed similar trends for harvest maturity and gassing, but there were fewer significant differences in volatile levels. Using a multivariate discriminant pattern recognition procedure, red fruit were separated from turning and green-harvested fruit, while green-gassed separated from non-gassed based on the aroma volatile profile within each cultivar.
Relationship Between Cover Crop Growth, Weed Suppression, and Yield of No-tillage Broccoli (Brassica oleraceae L. var. italica)
Authors: Morse Ronald D. , Abdul-Baki Aref
Published: February 2019

In 1997, no-till fall broccoli was grown at the Kentland Agricultural Research Farm (KARF), Blacksburg, Va., and the Beltsville Agricultural Research Center (BARC), Md., to determine supplemental N requirements above the nitrogen contribution from legume in situ mulches. Treatments were tillage systems [CT = conventional tillage, bare soil, tilled prior to transplanting; NT-BS = untilled bare soil; NT-SB = soybean (Glycine max L.) cover crop; and NT-CP = cowpea (Vigna sinensis Endl.) cover crop; and nitrogen fertilizer rates (0, 84, and 168 at KARF, and 0, 56, 112, and 168 kg·ha–1 at BARC). All plots at both sites were treated with recommended herbicides and drip irrigated as needed to supplement rainfall. Dry weight soybean and cowpea biomass was 6.1 and 4.3 at KARF and 4.8 and 3.5 t·ha–1 at BARC. In N-unfertilized plots at both sites, average broccoli yield was higher in NT-SB and NT-CP than CT and NT-BS. The N contribution from the legume mulches was inadequate to meet total crop demand, since N fertilizer applications increased broccoli yield in all tillage treatments, including the legume cover crops (soybean and cowpea). In N-fertilized plots, broccoli yield was similar among tillage treatments at KARF where weed problems were not severe; however, at BARC, yield in CT was higher than in all no-till treatments. Weed pressure was considerably lower in CT than in no-till plots at BARC. Based on these data and other related no-till studies, two conclusions can be drawn: a) no-till systems are a viable option for production of broccoli when weeds are adequately controlled; and b) uniformly distributed, high-residue levels are required for weed suppression when weed pressure is high and herbicides are either ineffective or not applied.
Evaluation of Endothall and Ammonium Thiosulfate as Potential Bloom Thinning Compounds for `Delicious' and `Fuji' Apples
Authors: Williams Kathleen M.
Published: February 2019

Consistent cropping of apple under Pacific Northwest growing conditions depends on a reliable bloom-thinning compound. Although there are two commercially available bloom-thinning chemicals, performance of these chemicals is not always consistent. Research on two unregistered bloom thinning compounds, Endothall and ATS, has been ongoing for several years in commercial orchard blocks. In 1997, multiple applications of Endothall and ATS were tested on `Delicious' and `Fuji'. Endothall was applied at 1.0, 1.5 or 2.0 pints/100 gal per acre rates at 40% and 80% full bloom. Endothall averaged 19 to 23% thinning in comparison to the water control on `Delicious'. With `Fuji', Endothall averaged 55% to 83% thinning. ATS was applied at 1.0% (v/v) on `Delicious' and 1.5% (v/v) on `Fuji' at 40% and 80% full bloom. ATS thinned `Delicious' an average of 30% compared to the water control. In `Fuji', ATS thinned an average of 20% to 42%. Another experiment involved the combination of ATS or Endothall with standard postbloom thinning regimes. Fruit quality data were collected on both bloom and postbloom thinned blocks. Differences in fruit size and shape were significantly correlated with NAA applications. No significant differences in soluble solids, titratable acidity, skin color, or flesh firmness were related to thinning treatments.
Ethephon Alters the Physiology of Young Apple Fruits
Authors: Ward Daniel , Marini Richard
Published: February 2019

Methods are needed to quickly assess the efficacy of chemical thinning treatments, so, if needed, additional treatments can be applied. When fruit diameter averaged 19 mm, `Smoothee' trees were sprayed with Ethrel at the rate of 3.7 ml formulation/L to induce abscission of most fruits on the tree. The diameter of 10 fruit/tree were measured daily and fruits were sampled 2, 4, and 6 days after treatment (DAT) to evaluate fruit development. Fruit on nontreated trees increased in diameter at the rate of about 0.7 to 0.9 mm/day. Fruit growth on treated trees was normal for 1 day, slowed to 0.5 mm for 2 days, and grew <0.1 mm/day thereafter. Fruit water potential was less negative for treated trees 2 DAT. Fresh and dry mass of treated fruit ceased increasing after 4 DAT. Percent dry mass of control fruit declined on each sampling date, but did not decline for treated fruit after 4 DAT. Cellulase was active in the abscission zone 4 DAT for treated fruit, but not control fruit. Compared to control fruit 6 DAT, treated fruit had elevated respiration and less starch accumulation. Fruits began to abscise 6 DAT. Following Ethrel application. The first indication that a fruit is destined to abscise are reduced fruit growth and changes in water potential 2 DAT.
Effects of Fruit Bagging on Accumulation of Anthocyanin, Flavonoid, and Simple Phenols at Harvest and on Anthocyanin Synthesis Potential During Storage in `Delicious' Apples
Authors: Ju Zhiguo
Published: February 2019

`Delicious' fruit were covered with paper bags from the early development stage until harvest at the Horticultural Center, Univ. of Massachusetts. Bagging did not affect fruit maturity, but significantly affected phenolic composition in fruit peel. Compared with the control, bagged fruit did not accumulate anthocyanin, but contained low levels of procyanidin and quercetin glycosides and relatively large amounts of simple phenolic acids. When bagged, fruit were re-exposed to light; they started to accumulate anthocyanin quickly and anthocyanin accumulation reached maximum after 3 days of light exposure. The potential of anthocyanin synthesis in bagged fruit remained constant during 5 months of cold storage. Results indicate that accumulation of anthocyanin, procyanidin, quercetin glycosides, and simple phenolic acids has different light requirement and these fruit could be a useful model in the research on anthocyanin synthesis and gene expression in apples.
Effect of a Single Defoliation and Fruit Thinning on Papaya Fruit Production and Quality
Authors: Zhou Lili , Christopher David , Paull Robert E.
Published: February 2019

The effect of defoliation and fruit thinning on papaya fruit set, growth, and ripe fruit quality was determined. Three defoliation levels (0%, 50%, 75%) and two defoliation methods (75% leaf cut off from the oldest to the youngest vs. 75% leaves removed in a spiral from the oldest) was compared with fruit thinning experiment on `Sunset' papaya during the warm season. Removal of 75% of the leaves significantly reduced new flower and fruit set, and decreased TSS level in ripe fruit. There was no significant difference between 0% and 50% defoliation in new fruit set, or ripe fruit TSS levels. Removal of leaves in a spiral reduced the number of new flower and fruit set more than the defoliation from the bottom to top. Defoliation of the `Kapoho' variety increased ripe fruit number and significantly reduced ripe fruit TSS and sugar level, dry mass persentage 2 weeks after defoliation. There was no significant difference between defoliated and non-defoliated treatment in fruit production, average fruit mass, and percentage of fruit flesh and seed, seed mass ratio, and seed dry mass during the test period. Fruit thinning increased new fruit set and increased ripe fruit TSS level in Line-8 and `Sunset', but not in `Kapoho'. However, average ripe fruit mass increased in fruit thinning experiment in `Kapoho' but not `Sunset' and Line-8 varieties. Fruit thinning also increased remaining young fruit TSS and sugar levels on the remaining fruit on plants compared to same-aged fruit on control and defoliated plants in Line-8. There was no effect on `Kapoho' young fruit TSS and sugar levels of defoliation. Ripe fruit TSS varied with weather conditions, plant growth conditions, and cultivars. These results indicated that although different cultivars had different responses to artificial defoliation and fruit thinning, source–sink balance and the ratio of fruit to leaf was an important factor in controlling potential fruit production and final fruit quality.
Crease (Albedo Breakdown) can be Predicted by Peel Thickness and Peel Nutrient Status as Early as the End of the Cell Division Stage of Fruit Development
Authors: Ali Anwar , Summers Leslie , Klein Grant , Lovatt Carol
Published: February 2019

Crease is a rind disorder of economic consequence to the citrus industry. The literature suggests crease is related to the thickness of the peel at maturity and nutrient status of the tree, especially N, P, and K, which are known to influence peel thickness. Our objective was to quantify the interrelationship between the degree of crease in an orchard at harvest and September leaf nutrient concentrations, as well as peel nutrient concentrations at maximum peel thickness. The 2-year experiment was conducted at seven California `Valencia' and navel orange (Citrus sinensis L. Osbeck) orchards with known differences in the incidence of crease. Maximum peel thickness, which occurs at the end of cell division during fruit development, was significantly negatively correlated with percent crease at harvest for all sites in both years. There was no significant correlation between leaf N, P, or K concentrations and maximum peel thickness or crease. There was a significant negative correlation between peel K concentration and percent crease for all sites in both years. There was a weak correlation between the incidence of crease and peel nitrogen content in both cultivars. Peel P concentration was not correlated to the incidence of crease in either cultivar. These data identified threshold values for maximum peel thickness and peel K concentration at maximum peel thickness below which the incidence of crease would be greater than 10% for both cultivars.
Impact of Nitrogen Management Practices on Total Nitrogen in the Fruits of High Productive Hamlin Orange Trees
Authors: Paramasivam S. , Alva A.K.
Published: February 2019

For perennial crop production conditions, major portion of nutrient removal from the soil-tree system is that in harvested fruits. Nitrogen in the fruits was calculated for 22-year-old `Hamlin' orange (Citrus sinensis) trees on Cleopatra mandarin (Citrus reticulata) rootstock, grown in a Tavares fine sand (hyperthermic, uncoated, Typic Quartzipsamments) that received various N rates (112, 168, 224, and 280 kg N/ha per year) as either i) broadcast of dry granular form (DGF; four applications/year), or ii) fertigation (FRT; 15 applications/year). Total N in the fruits (mean across 4 years) varied from 82 to 110 and 89 to 111 kg N/ha per year for the DGF and FRT sources, respectively. Proportion of N in the fruits in relation to N applied decreased from 74% to 39% for the DGF and from 80% to 40% for the FRT treatments. High percentage of N removal in the fruits in relation to total N applied at low N rates indicate that trees may be depleting the tree reserve for maintaining fruit production. This was evident, to some extent, by the low leaf N concentration at the low N treatments. Furthermore, canopy density was also lower in the low N trees compared to those that received higher N rates.
Substrate pH and Papaya Seedling Growth
Authors: Marler Thomas E.
Published: February 2019

Two studies were conducted to determine the influence of pH on `Waimanalo' papaya seedling growth and morphology. The seedlings were grown in clear, plastic tubes with diameter of 7 cm and length of 21 cm, and substrate was silica sand. The substrate was drenched daily with complete nutrient solution. The solution was adjusted to pH of 3, 4, 5, 6, 7, 8, or 9. We used direct-seeded plants in the first study, and plants were harvested following 9.5 weeks of growth. We used transplants in the second study, and plants were harvested following 4 weeks of growth. Dry mass of plants was relatively unaffected by substrate pH within the range of 4 to 9. In both studies; however, dry mass of plants receiving solution with a pH of 3 was reduced. The response pattern was similar for canopy:root ratio, total root length, root growth rate, lateral root thickness, and root tip density. Unit leaf area per unit root length was greatly increased for plants receiving pH of 3, indicating increased susceptibility to drought conditions.
A New Virus-tolerant Southernpea
Authors: Morelock T.E. , Anderson E.J. , Gonzalez A.R. , Motes D.R.
Published: February 2019

Southernpea (cowpea), Vigna unguiculata L. Walp, is an important processing and fresh-market vegetable in the southern United States. Several varieties are available for growers, but there are very limited numbers that combine bush plant type, earliness, good processing quality and virus resistance. A single plant selection from the variety `Excel' offers this combination of traits. The breeding lines 87-435-68 is a singe plant selection from the variety `Excel' that was made on the basis of its reaction to blackeye cowpea mosaic virus (BLCMV). The resistance mechanism is somewhat different than the traditional varieties with single gene resistance to BLCMV. The reaction to BLCMV is manifested as tolerance rather than classical single gene immunity.
Effect of Mycorrhizal Fungi on Gas Exchange of Micropropagated Guava Plantlets (Psidium guajava L.) during Acclimatization and Plant Establishment
Authors: Estrada-Luna Andrés A. , Egilla Jonathan N. , Davies Fred T.
Published: February 2019

The effect of mycorrhizal fungi on gas exchange of micropropagated guava plantlets (Psidium guajava L.) during acclimatization and plant establishment was determined. Guava plantlets (Psidium guajava L. cv. `Media China') were asexually propagated through tissue culture and acclimatized in a glasshouse for eighteen weeks. Half of the plantlets were inoculated with ZAC-19, which is a mixed isolate containing Glomus etunicatum and an unknown Glomus spp. Plantlets were fertilized with modified Long Ashton nutrient solution containing 11 (g P/ml. Gas exchange measurements included photosynthetic rate (A), stomatal conductance (gs), internal CO2 concentration (Ci), transpiration rate (E), water use efficiency (WUE), and vapor pressure deficit (VPD). Measurements were taken at 2, 4, 8 and 18 weeks after inoculation using a LI-6200 portable photosynthesis system (LI-COR Inc. Lincoln, Neb., USA). Two weeks after inoculation, noninoculated plantlets had greater A compared to mycorrhizal plantlets. However, 4 and 8 weeks after inoculation, mycorrhizal plantlets had greater A, gs, Ci and WUE. At the end of the experiment gas exchange was comparable between noninoculated and mycorrhizal plantlets.
Analysis of Residential Horticultural Questions Answered by Master Gardeners
Authors: Sinnott Larkin , Relf Paula Diane
Published: February 2019

An analysis of commonly asked horticultural questions is being conducted by the Office of Environmental Horticulture at Virginia Tech in order to improve the question and answer process between Master Gardeners and the public. Records of questions received by Master Gardeners from a sampling of Extension offices representing all growing areas of the state are being sorted and categorized to identify the most frequently asked questions and develop a electronic resource to assist in answering those questions quickly and with consistent IPM based information. More than 4000 questions have been analyzed and organized in to the following categories: Plant Questions (specific type or species of plant), General Gardening Questions (composting and fertilizing, herbicides and pesticides, soil testing etc.), Program Questions (Extension programs, Master Gardener program), and Animal and Insect Questions. The plants questions have been further divided into the sub-categories. The animal and insect questions have been sorted by species type with the percentage asked of each calculated. This information is posted on a web site and is linked to additional resources for answers. The address is www.hort.vt.edu/mastergardener/Q&A.html. The site contains useful information, links, and opportunities for feedback via e-mail.
Volunteer Management Reference for Local VCE Master Gardener Coordinators
Authors: Dorn Sheri T. , Relf Paula Diane
Published: February 2019

Virginia Cooperative Extension's (VCE) Master Gardener volunteer program is available in 72 unit offices. The unit programs are managed by MG coordinators who currently include 10 locally funded agents, eight locally funded technicians, and 28 volunteers. The VCE Master Gardener Coordinator Manual, a 12-unit resource book, was developed cooperatively with teams of MGs, coordinators, and agents to enhance coordinators' skills for managing the local VCE MG program. The manual includes chapters on VCE MG components such as risk management; job descriptions; recruitment and screening; and volunteer review, recognition, and retention. Additional resources within the manual include a synopsis of educational program planning, implementation, and evaluation, as well as a copy of the current VCE Master Gardener Program Policies and the volunteer section of the Virginia Master Gardener Handbook, which serves as program orientation for new or prospective trainees. The VCE Master Gardener Coordinator Manual is the basis of three local MG coordinator training sessions in 1998. Additional resources available to coordinators for enhancing the local MG program include a MG newsletter focused on the role of Master Gardeners as community leaders and educators; program policies and guidelines for the management of MG training and operation; VCE publication 426-699 Welcome to Virginia Master Gardenering! Guide to Educational Programming and Resource and Reference Guide; and the VCE Master Gardener Internet website at http://www.ext.vt.edu/vce/specialty/envirohort/mastergard/master.html.
Human Stress Recovery during Exposure to Geranium Visual Stimuli
Authors: Kim Eunhee , Mattson Richard H.
Published: February 2019

Evaluating human psychophysiological responses to plant visual stimuli provides a clearer understanding of factors within plant environments that enhance or maximize recovery from stress. Advances in physiological monitoring technology allow continuous recording and more-refined data collection of human responses to environmental stimuli. The objective of this study was to compare effects on stress recovery by exposures to geranium visual stimuli following an induced stressor, by measuring changes in physiological indicators and emotional states. One-hundred-fifty college students were randomly assigned to one of three treatment groups: red-flowering geraniums, non-flowering geraniums, or no geraniums. Each student viewed a 10-min film of a stressful human situation following a 5-min baseline, then was exposed to an assigned treatment setting during a 5-min recovery period. Continuous physiological measurements were taken of brainwave activities (EEG), skin conductance (EDR), and finger skin temperature. Self-rating scores of subjects' feelings were taken using the Zuckerman Inventory of Personal Reactions. Comparisons among treatment groups will be discussed based on gender and other demographic factors.
Aggie Horticulture on Disk
Authors: Lineberger R. Daniel
Published: February 2019

The Aggie Horticulture Web site was written to CD-ROM using readily available, inexpensive equipment, supplies, and software. The CD-ROM version is accessed using the “load from file” option of the commonly used Web browsers and is cross-platform compatible. Writing to CD does not allow “server-side” functions such as cgi-based searching and forms posting and the content of the site is fixed at the time the CD is written. However, in situations where Web connectivity is limited in speed or where phone connections are unavailable, the CD represents a low-cost alternative for accessing large volumes of information. Aggie Horticulture on Disk will be demonstrated, and several precautions to be followed to ensure an error-free transition from Web site to CD will be described.
Cold Treatments Alter the Photoperiodic Flowering Response of Some Herbaceous Perennial Species
Authors: Runkle Erik S. , Heins Royal D. , Cameron Arthur C. , Carlson William H.
Published: February 2019

Many species of herbaceous perennials either require a cold treatment for flowering or exhibit enhanced and more desirable flowering characteristics following a cold period. For some species, the photoperiodic induction of flowering can change following cold treatments, the parameters generally becoming less strict as plants receive longer durations of cold until a saturation duration is reached. To quantify the minimum and saturation durations of cold for flowering under short days (SD) and long days (LD), five species were selected and cooled for 0, 3, 6, 9, 12, or 15 weeks at 5 °C, then forced at 20 °C under 9-h photoperiods without (SD) or with a 4-h night interruption (LD). The effects of cold and photoperiod on flowering varied by species. For example, under SD, 0%, 80%, or 100% of Leucanthemum xsuperbum `Snowcap' flowered after 0, 3, or ≥6 weeks at 5 °C, respectively, and time to flower decreased from 103 to 57 days as the duration of cold increased from 3 to 12 weeks. `Snowcap' cooled for ≥3 weeks, then forced under LD, flowered completely in 45 to 55 days. Flowering percentage of Lavandula angustifolia `Hidcote' reached 100 under LD or SD only when plants were cooled for ≥6 or 15 weeks, respectively. Under LD, flowering percentage of Astilbe chinensis pumila progressively increased from 0 to 100 as cold treatment increased from 0 to 15 weeks; flowering percentage under SD was low regardless of cold treatment. Additional species and flowering characteristics will be discussed.
Media Temperature in Above-ground and In-ground Pot-in-Pot Container Systems
Authors: London Jason B. , Fernandez R.T. , Young Roy E. , Christenbury Jerry D.
Published: February 2019

In-ground, pot-in-pot (PNP) systems control container blow-over and buffer media temperatures. At least two nursery container manufacturers have recently introduced above-ground, PNP systems to reduce installation cost, overcome land use inflexibility, and eliminate root growth into drainage systems. Above-ground, PNP systems eliminate some of the problems associated with an in-ground PNP system, but little is known about how it compares with in-ground PNP's attributes; specifically media temperaturee buffering. Fifteen-gallon containers of Ligustrum japonicum var. `Repandens' were installed in May 1997 at a nursery in Moncks Corner, S.C. In-ground PNP; conventional pot placement; and two, commercial, above-ground PNP systems were used as treatments with 12 replications. Four of the replications contained six thermocouples in each treatment. Thermocouples were placed in the top and middle of the container media at three orientations: East–northeast, south, and center. During hot weather studies the two above-ground PNP configurations buffered media temperature deviation ranges slightly when compared to conventional pot production, but not nearly as much as the in-ground PNP configuration. Media temperatures rose more slowly during the daylight hours in the above-ground PNP systems than in conventional pots, but eventually approached similar temperature peaks. Neither above-ground PNP treatment cooled to the low temperature levels of the conventional treatment overnight. The in-ground PNP treatment experienced less temperature deviations than the other three treatments and rarely exceeded 32 °C (90 °F). Measurements of biomass and growth were not different among the above-ground pot-in-pot and the conventional pots, yet the in-ground treatments had a larger growth index and biomass weight. Data for cold weather is currently being collected and will be available for this presentation.
Critical Heat Thresholds for Root Tissue of Two Golden Barberry Cultivars
Authors: Murphree B.H. , Sibley J.L. , Eakes D.J. , Ruter J.M.
Published: February 2019

Limited information exists for container production of golden barberry cultivars. The objective of this study was to evaluate root thermostability of container-grown Berberis thunbergii `Monlers' (Gold Nugget™) and Berberis sp. `Bailsel' (Golden Carousel™). Bare root cuttings were planted in 2.7-L containers in an amended 6 pinebark: 1 sand (v/v) substrate in Apr. 1997. Plants were grown under overhead irrigation for 6 months in a completely randomized block design. Young, unsuberized root tips (1.0–2.5 cm), were subjected to temperature treatments from 20 to 63 °C in a thermostatically controlled water bath prior to electrolyte leakage determinations. `Golden Carousel' was more heat-tolerant (critical temperature midpoint = 49.4 ± 0.3 °C) than `Monlers' (critical temperature midpoint = 48.0 ± 0.4 °C). Implications of these differences for container production will be discussed.
Membrane Thermostability for Root Tissue of Red and Freeman Maple Cultivars
Authors: Sibley J.L. , Ruter J.M. , Eakes D.J.
Published: February 2019

Six red (Acer rubrum `Autumn Flame', `Fairview Flame', `Franksred', `Landsburg', `Northwood', and `October Glory') and three Freeman (A. × freemanii `Armstrong', `Celzam', and `Jeffersred') maple cultivars originating in different parts of the United States were grown in containers in 1995 and 1996 prior to laboratory procedures to determine root cell membrane thermostability. Electrolyte leakage from excised root tissue exposed for 30 min to temperatures ranging from 20 to 63 °C, was used to assess cellular injury of unsuberized, current season, fine roots. The critical killing temperatures of root tissue of cultivars evaluated ranged from 52.0 ± 0.8 °C to 53.3 ± 0.5 °C, indicating minimal differences in root membrane thermostability among the selections evaluated. Critical temperatures for cultivars selected from the northern part of the native range did not differ from cultivars originating elsewhere. Implications of these differences for container production will be discussed.
Interaction Between CPPU and NAA on Fruit Thinning and Fruit Development in Selected Apple Cultivars
Authors: Bukovac Martin J. , Hull Jerome , Neilsen John C. , Schroeder Michael , Noga Georg
Published: February 2019

NAA is used extensively for fruit thinning of apples to increase fruit size and to promote return bloom. In some cultivars, even if thinning is achieved, fruit size at harvest may be less than expected based on crop load. CPPU, N-(2-chloro-4-pyridinyl)-N.-phenylurea, has been shown to increase fruit growth in apples, grapes, and kiwi. We evaluated combinations of NAA and CPPU on thinning, fruit growth and return bloom in Redchief `Delicious', `Elstar', and `Gloster'. CPPU was applied at 5 mgμL–1 (based on 0 to 10 mgμL–1 response curve) in combination with 15 mgμL–1 NAA as high-volume sprays at 7 to 10 mm KFD. Yield and fruit size distribution (on total yield) were used as index of response. In `Delicious', CPPU (3-year study) increased % large (70 mm+) fruit, but in the presence of NAA % large fruit was reduced 2 of the 3 years. CPPU did not induce significant thinning. There were no significant effects on color or soluble solids; firmness was increased slightly and seed number reduced. The L/D ratio was increased and uneven lobe and carpel development was common. CPPU had no significant effect on return bloom in presence or absence of NAA, but NAA increased bloom in both the presence and absence of CPPU. With `Elstar' (2-year study) there was no significant thinning with either chemical, but CPPU increased mean fruit size and % large (70–80 mm) fruit over nonthinned, but not significantly greater than NAA alone. There were no significant differences in firmness, color, soluble solids or seed number. NAA + CPPU did not inhibit fruit growth or cause excessive uneven carpel development. Frost damage reduced crop load in `Gloster' where results were similar to `Elstar' except seed number was reduced by the NAA + CPPU combination.
Thinning Peaches by Heat
Authors: Erez A. , Korcinski R. , Yablowitz Z.
Published: February 2019

Flower buds in their last stages prior to opening, open flowers and small fruitlets are the most sensitive organs to frost damage. Such effect of low temperature is well-known as it poses an economical hazard in growing stone fruits in many countries. Heat effect on flower buds and flowers is less known simply because it is not common at time of bloom in most locations where such species are grown. Many of the low-chill early maturing peaches and nectarines set very heavily in subtropical climate and require a major input of manual thinning in order to obtain marketable fruit. As the level of fruitset is usually very high, thinning is been carried out during full bloom. With increase in costs of manual labor, this element becomes the critical one in producing such fruits economically. Up till now, no chemical or physical mean can replace hand-thinning in these early cultivars effectively. During our work with greenhouse-grown stone fruits we came across the enormous sensitivity of non-dormant flower buds as well as flowers to high temperatures. Avoiding excessive heat close to, and during bloom, became number one concern in the practice of growing stone fruits in greenhouses. By using container-grown peaches and temperature-controlled chambers in a phytotron, we were able to quantify the effect of heat on flower buds with the potential of obtaining controlled damage leading to the required level of thinning. Trials with potted and with orchard grown trees will be reported.
Intersubgeneric Hybridization between Muscadinia and Euvitis Species
Authors: Lu Jiang , Schell Lloyd
Published: February 2019

The genus Vitis contains two subgenera: Euvitis Planch. (with the common name bunch grapes) and Muscadinia Planch. (with the common name muscadine grapes). The muscadine grapes (V. rotundifolia) are originated and limited to the southeastern United States and are distinguished from the Euvitis species morphologically and cytologically. They are characterized by high disease and pest resistance, and unique muscat flavor. Bunch grapes, with a total of 60-plus species, are grown world-wide and can be grouped into the American species, the Asiatic species and the European grape (V. vinifera) according to their geographical origination. V. vinifera, which is known for good fruit quality, is the predominant commercial species. Attempts to produce rotundifolia–vinifera hybrids to combine good fruit quality and disease resistance of both into F1 hybrids have been made by grape breeders for many years. Limited success was only reported when the V. vinifera was used as seed parents and it failed vice versa. This study extended the crosses between the V. rotundifolia and other Euvitis species originated from North America and East Asia to see if hybrids could be produced from any of these crosses. Results indicated that a limited success were achieved in a few crosses [muscadine (female) × Euvitis species] while failure occurred in most others. These hybrids may be used as bridges to carry the viticulturally important genes over to the muscadine grapes from V. vinifera. Microscopic study also revealed that the difficulty of hybridization between Muscadinia × Euvitis is due to the pre-fertilization barriers.