bluuebunny/crossref_metadata_2025 huggingface dataset:
Spiny Amaranth (Amaranthus spinosus L.), A Serious Competitor to Crisphead Lettuce (Lactuca sativa L.)
Authors: Shrefler James W. , Stall William M. , Dusky Joan A.
Published: February 2019

Three field studies on high-organic-matter soils were conducted to determine the zone of influence of spiny amaranth on lettuce head quality. Spiny amaranth reduced lettuce head firmness at all distances from the weed, ≤105 cm. Lettuce ribbiness increased at 15 and 45 cm compared with the weed-free control. Untrimmed lettuce head weight was not affected by spiny amaranth presence beyond 45 cm. Trimmed lettuce head weight was reduced at all distances compared with the control. Stem diameter and core length were not affected by spiny amaranth competition. The presence of a single spiny amaranth plant significantly influenced some lettuce quality traits at ≤105 cm.
Environmental Control of Flowering and Growth of Achillea millefolium L. `Summer Pastels'
Authors: Zhang D. , Armitage A.M. , Affolter J.M. , Dirr M.A.
Published: February 2019

Achillea millefolium `Summer Pastels' is a qualitative long-day plant with a critical photoperiod between 12 and 16 hours at 18C. Plants grown under a 16-hour photoperiod flowered after 27 days, while those under 8 hours remained vegetative. Shoot dry weight was not affected by photoperiod. Low temperature (10C) delayed the time of flower bud formation and anthesis by ≈20 days. Low irradiance (100 μmol·m–2·s–1) delayed flowering and resulted in lower shoot dry weight, while moderate shading (200 μmol·m–2·s–1) did not significantly affect flowering time and growth compared with high irradiance levels (300 μmol·m–2·s–1).
Isolation and Screening of Mycorrhizal Fungi from Citrus Nurseries and Orchards and Inoculation Studies
Authors: Camprubí Amelia , Calvet Cinta
Published: February 2019

The selection of the most effective arbuscular mycorrhizal (AM) fungi for growth enhancement of citrus cultivars used as rootstocks was the first step toward development of an AM inoculation system in citrus nurseries in Spain. AM fungi were isolated from citrus nurseries and orchards in the major citrus-growing areas of eastern Spain. The most common AM fungi found in citrus soils belonged to Glomus species, and G. mosseae (Nicol. & Gerd.) Gerdemann & Trappe and G. intraradices Schenck & Smith were the AM fungi most frequently associated with citrus roots. The most effective fungus for growth enhancement of citrus rootstocks was G. intraradices. Significant differences in mycorrhizal dependency among rootstocks were confirmed. Sour orange (Citrus aurantium L.) and Cleopatra mandarin (C. reshni L.) were more dependent than Troyer citrange [C. sinensis (L.) Obs. × Poncirus trifoliata (L.) Raf.] and Swingle citrumelo (C. paradisi Macf. × P. trifoliata). Moreover, several inoculation systems for plant production were evaluated for their effectiveness in promoting root colonization of the rootstock cultivars.
Irrigation and Fertilizer Application Methods Affect Performance of High-density Peach Orchards
Authors: Layne Richard E.C. , Tan Chin S. , Hunter David M. , Cline Robert A.
Published: February 2019

Seven treatment combinations of irrigation and fertilizer were compared in a high-density (606 trees/ha) management system for peach [Prunus persica (L.) Batsch cv. Harrow Beauty/Bailey] on Fox sand in southwestern Ontario. Each treatment combination had an irrigation component (N = nonirrigated, D = drip irrigated, or M = microsprinkler irrigated) and a fertilizer placement component (B = banded fertilizer, L = low fertigation, or H = high fertigation). NB and DB are commonly used systems in Ontario, while the other five treatment combinations were experimental. Total soil water in the top 110 cm of soil was lowest under NB but was never at the permanent wilting point. Trunk cross-sectional area was largest under DH and DB, smallest under ML and NB, and intermediate for the other three treatment combinations. No symptoms of N or K deficiency or toxicity were noted for any of the fertilizer treatments. Leaf analyses in July and September indicated that most major and minor elements were in the adequate to slightly excess range. However, there were no significant treatment effects on leaf nutrient concentrations in July or September when averaged over the five years, except for Mg in July. There were large and significant year effects on leaf nutrient concentrations but no significant treatment × year interactions. During the first four cropping years, there were no significant treatment effects, averaged over years, for total yield, marketable yield, or cumulative yield efficiency; however, there were large year effects but no treatment × year interactions for these factors. There was no detectable yield advantage for D vs. M irrigation. B application of N and K promoted no higher yields than fertigation equivalent to the B rate or 50% of this rate. Fertigation of N and K during the first 4 years of this experiment did not provide a detectable yield advantage to warrant the added cost and labor associated with this system compared with the B applications of N and K.
Mefluidide Does Not Consistently Enhance the Freezing Tolerance of Cabbage
Authors: Manley Reeser C. , Hummel Rita L.
Published: February 2019

Mefluidide, a synthetic plant growth regulator, has been reported to protect chilling-sensitive plants from chilling damage and enhance the freezing tolerance of certain winter-hardy herbaceous plants. The potential of mefluidide to enhance the freezing tolerance of nonhardened and dehardening cabbage (Brassica oleracea L. Capitata Group) leaf tissue was investigated. Mefluidide at 0 to 60 mg·L–1 was tested on `Brunswick' and `Golden Acre' cabbage in five experiments. Leaf tissue freezing tolerance was measured 3 to 9 days postapplication by electrolyte leakage assay. The interval between application and freeze testing had no effect on leaf freeze tolerance. The effect of mefluidide at low rates on leaf freeze tolerance was small and inconsistent. At 30 and 60 mg·L–1, leaf freeze tolerance was decreased consistently. Chemical name used: N-{2,4-dimethyl-5-[[trifluromethyl)sulfonyl]amino]phenyl}acetamide (mefluidide).
Linkage Relationships of Isozymes and Morphological Traits in Interspecific Chestnut Crosses
Authors: Huang H. , Dane F. , Norton J.D. , Weaver D.B. , Hebard F.V.
Published: February 2019

Linkage relationships among eight isozyme genes (Acp-3, Est-1, Est-5, Prx-1, Prx-2, Prx-3, Me, and Adh) and two morphological markers (Inh and Twh) were investigated in one F2 and two BC1 families of interspecific crosses between the American chestnut (Castanea dentata Borkh.) and the Chinese chestnut (C. mollissima Blume). Inh was consistently linked with Prx-1 and Est-5 in all families. In addition, four other gene pairs, Acp-3–Inh, Acp-3–Prx-1, Me–Inh, and Twh–Inh, were linked in one of the three families investigated. The two isozyme genes and two morphological marker genes were tentatively integrated into one linkage group with the gene order Twh–Inh–Prx-1–Est-5.
Cryogenic Storage of Tomato Pollen: Effect on Fecundity
Authors: Sacks Erik J. , St. Clair Dina A.
Published: February 2019

The influence of cryogenic pollen storage on fruit set and seed production in tomato (Lycopersicon esculentum Mill.) was investigated. Flowers pollinated with pollen samples stored for 5 weeks at –80C, with or without 20 h precooling at 4C, had similar fruit set and number of viable seed per fruit as those pollinated with fresh pollen. Pollen samples, which were repeatedly cooled (–80C) and warmed (to 22 to 24C) for up to six cycles, continuously maintained the same viability as the fresh pollen. When cryogenically stored pollen of L. esculentum 2-837, LA359, LA3198, and LA3199 were used to pollinate LA359, the number of viable seed formed per fruit differed significantly. Results of this study suggest that pollen cryopreservation can be used successfully for tomato breeding and germplasm storage.
Establishment of a Collection of Rosa Species through in Vitro Embryo Culture
Authors: Lauzer Denis , Laberge Claire
Published: February 2019

To update and complete a collection of wild roses in the Montreal Botanical Garden, Canada, in vitro embryo culture was used to propagate several Rosa species that are only available as seeds and difficult to germinate conventionally. Using embryo culture, it was possible to overcome seed dormancy and to rapidly increase the number of species in the collection, and this from a very limited number of seeds obtained from botanical institutions located around the world.
Florida Red Ruffles and Florida Irish Lace: Two New Lance-leaf Caladium Cultivars
Authors: Wilfret Gary J.
Published: February 2019

Two lance-leaf caladium cultivars are to be released from the ornamental breeding program at the University of Florida. `Red Ruffles', whose pedigree is Red Frill × (`Red Frill' × `Candidum Jr.'), has elongated medium red leaves with ruffled green margins. Plants are upright with strong petioles, have leaf blades 25 cm long and 14 cm wide, and attain a height of 61 cm when grown in full sun in the field. Plants have more leaves and are more cold tolerant than `Red Frill', the major red lance-leaf cultivar of commerce. Tuber yields of `Red Ruffles' are similar to `Red Frill' but less than `Rosalie', with production indices of 95.0, 97.8, and 121.0, respectively. Foliage of `Red Ruffles' is more upright and less likely to elongate under reduced light than the other cultivars. `Irish Lace', an F2 selection from a cross of “Candidum Jr.' × “Red Frill', has elongated dark green leaves with heavily ruffled margins, which are etched with a thin red border. Leaf blades are 26 cm long and 8 cm wide and have heavy substance. Plant height is 65 cm in the field. Tuber yields of `Irish Lace' are greater than `White Wing', a major green/white cultivar. Use of a green caladium would be as a border or a mixture with red or white lance-leaf cultivars.
Isozyme Characterization in Alstroemeria Species
Authors: Stephens Janice L. , Hughes Harrison G.
Published: February 2019

Isozyme analysis was used to characterize and identify 24 species, hybrids, and color variants of Alstroemeria, two plants of Leontochir ovallei, and one plant of Bomarea. A single technique was developed for the extraction of seven enzyme systems (PGM, PGI, 6-PGD, EST, ME, AAT, and LAP) that exhibited a high level of polymorphism. Between 11 and 18 of the species and hybrids could be identified uniquely for each of the first six enzyme systems. The final system, LAP, was tested on only 11 species and hybrids, and nine different patterns were identified. Using only three of the seven enzyme systems, it was possible to uniquely identify all of the species and hybrids investigated.
Fumigant Alternatives to Methyl Bromide for Polyethylenemulched Tomato
Authors: Locascio S.J. , Gilreath J.P. , Dickson D.W. , Kucharek T.A. , Jones J.P. , Noling J.W.
Published: February 2019

Tomato (Lycopersicon esculentum Mill.) was grown to evaluate various chemicals as possible alternatives to methyl bromide as a soil fumigant. Due to pest pressures from weeds, nematodes, and soil fungi, the use of a broad-spectrum fumigant is essential for economical tomato production. Methyl bromide (MBr) is the fumigant of choice for most growers using polyethylene mulch culture. In 1991, MBr was identified to be in a group of chemicals allegedly responsible for depletion of the stratospheric ozone layer. The U.S. Environmental Protection Agency (EPA) has since called for a phaseout of MBr by the year 2001. At several locations in Florida, alternative soil fumigants were evaluated including 98% MBr-2% chloropicrin (Pic) at 450 kg·ha–1, 67% MBr 33% –Pic (392 kg·ha–1), Pic (390 kg·ha–1), 1,3-dichloropropene + 17% Pic (1,3-D+C17) at 327 L·ha–1, and metham sodium (935 L·ha–1). Metham sodium was also applied by drip irrigation as well as enzone (1870 L·ha–1). Dazomet (448 kg·ha–1) was surface applied and incorporated. Pebulate (4.5 kg·ha–1) was incorporated with some treatments. Pic and 1,3-D+C17 treatments provided control of nematodes and soil fungi. With the addition of pebulate, some nutsedge control also was obtained. Tomato fruit yields with 1,3-D+C17 + pebulate and with Pic + pebulate ranged from 86% to 100% of that obtained with MBr treatments. Pest control and crop production were lower with the other treatments than with the above combinations and with MBr. These studies indicate that no one pesticide can provide the broad spectrum control provided by MBr.
Repellency of n-Alkanes and Relationship of Structure and Repellency of Trichome Secretions from Lycopersicon hirsutum
Authors: Snyder John C. , Antonious George , Thacker Richard
Published: February 2019

Many accessions of Lycopersicon hirsutum are highly resistant to insects. Trichomes and their secretions have been extensively indicated as factors of resistance. One mechanism of resistance mediated by secretions is repellency, a mechanism that is consistent with the observation that few insects visit plants of L. hirsutum. Trichome secretions from certain accessions of L. hirsutum f. typicum are repellent to spider mites. However, the composition of secretions from different accessions of f. typicum are chemically diverse. Sesquiterpene hydrocarbons are prevalent in secretions, but are structurally diverse. How structure may relate to repellency is of interest but difficult to address because isolation of pure sesquiterpene hydrocarbons from hydrocarbon mixtures is difficult. To begin examining relationships between structure and activity we determined how chain length of n-alkanes related to repellency of spider mites. n-Alkanes having chain lengths from 8 to 22 carbon atoms were assayed for repellency. The C16-C18 alkanes were most repellent. Smaller and larger hydrocarbons were less repellent. The EC50 for n-hexadecane was equal to that of the most repellent natural products we have isolated from trichome secretions of L. hirsutum.
Physiological Differences between Zinc-efficient and Zinc-inefficient Genotypes of Interspecific Exacum
Authors: Riseman Andrew , Craig Richard
Published: February 2019

Research in Penn State's Exacum breeding program has revealed genotypic variation for the development of zinc deficiency, which may indicate the presence of zinc efficiency factors. Through preliminary experiments, we have identified both genetic families and individual genotypes that can be classified as either zinc-efficient or zinc-inefficient. Chi-square contingency analyses indicate significant differences (P < 0.001) in segregation patterns for zinc deficiency among hybrid families. Segregation patterns within families ranged from 100% of the progeny developing zinc deficiency to 100% of the progeny remaining healthy. Two genotypes contrasting in zinc efficiency have been identified and used in experiments designed to investigate physiological factors related to zinc efficiency. The zinc-efficient genotype has a significantly higher ability to decrease solution pH (P < 0.01), significantly higher root cation exchange capacity (P < 0.007), significantly lower root/shoot ratio (P < 0.001), significantly lower water loss/cm2 leaf (P < 0.03), and significantly higher fresh weight/dry weight ratio (P < 0.001). Research on zinc uptake rates is currently being conducted utilizing the efficient and inefficient genotypes. Based on all of our research, we conclude that 1) a strong genetic effect is involved in the zinc nutritional status of interspecific Exacum hybrids and 2) a number of physiological traits differ between zinc-efficient and zinc-inefficient genotypes.
Postharvest Behavior of Transgenic Cantaloupe Melons with Suppressed ACC Oxidase Activity
Authors: Pech Jean-Claude
Published: February 2019

We have generated transgenic Cantaloupe Charentais melons expressing an ACC oxidase antisense gene in which ethylene production was reduced to less than 1% as compared to control untransformed fruits. As a consequence, some aspects of the ripening process were strongly inhibited (aroma volatiles production, chlorophyll and cell wall degradation, pigmentation of the rind, activation of peduncular abscission zone) while others remained unchanged (coloration of the flesh), allowing us to distinguish between ethylene-dependent and ethylene-independent pathways. Some postharvest characteristics of the transgenic fruit are described in terms of expression of ripening-related genes, respiratory behavior, and biochemical composition. Data also are presented showing that exogenous ethylene treatments could reverse the antisense phenotype.
Establishment of a Plant Regeneration and Genetic Transformation System of Panax ginseng C.A. Meyer
Authors: Lim Hak-Tae , Lee Haeng-Soon , Eriksson Tage
Published: February 2019

Plant regeneration of ginseng has been known to be difficult, and there are a few reports on plant regeneration of ginseng via somatic embryogenesis. In vitro flowering has, however, been one of the major drawbacks in these regeneration systems in which BA and GA3 were included in germination and shoot multiplication media. Multiplication of adventitious shoots from a single somatic embryo, abnormal morphology, and vitrified shoots were also observed. All these facts have made successful acclimatization of ginseng plantlets difficult. The purposes of this study were 1) to establish the plant regeneration system via organogenesis, 2) to improve normal plant regeneration via somatic embryogenesis, 3) to improve the efficiency of plant regeneration from protoplast culture, 4) to understand the acclimatization process, 5) to develop effective genetic transformation protocol. Data in relation with all these studies are presented in detail.
Interaction of In-row Spacing and Degree of Pruning on Yield of `Agriset 761' Tomato
Authors: Olson S.M.
Published: February 2019

Three in-row spacings of 46, 61, and 76 cm were combined with three pruning methods [none, light (half the suckers removed from the ground to the fork), and heavy (all suckers removed from the ground to the fork] in a complete factorial design. Three harvests were made and responses differed among harvests. At first harvest yields decreased as in-row spacing increased and yields increased as degree of pruning increased. No interactions occurred. At second harvest yields again decreased as in-row spacing increased but only heavy pruning decreased yields. A interaction occurred where the closest in-row spacing pruned lightly did not follow the same pattern as the other two row spacings pruned the same. At third harvest yields increased as in-row spacing increased but pruning method had little effect. With seasonal total yield, in-row spacing had little effect but heavy pruning reduced seasonal total yield over none or light pruning.
Adaptation of the CROPGRO Model to Simulate Yield of Fresh-market Tomato
Authors: Scholberg J.M.S. , McNeal B.L. , Jones J.W. , Locascio S.J. , Olsen S.R. , Stanley C.D.
Published: February 2019

Modeling the growth of field-grown tomato (Lycopersicon esculentum Mill.) should assist researchers and commercial growers to outline optimal crop management strategies for specific locations and production systems. A generic crop-growth model (CROPGRO) was previously adapted to simulate the growth of fresh-market tomato under field conditions. Plant growth and development of field-grown tomato, and fruit yields, will be outlined and compared to model predictions for a number of locations in Florida, nitrogen fertilizer rates, and irrigation management practices. Possible application of the model to quantify effects of crop management on crop production will be discussed using simulated yield values for a wide range of environmental conditions.
Spatial Arrangement for Daikon Seed Production
Authors: Leskovar Daniel I. , Boales A. Kipp
Published: February 2019

Seed production systems for daikon or Chinese winter radish (Raphanus sativus L., Longipinnatus Group) were investigated in the Winter Garden of southwest Texas in 1992 and 1993. Planting dates ranged from October through March. Bed configurations (number of rows × bed spacings) were 2 × 0.96 m, 2 × 1.93 m, 3 × 1.93 m, and 4 × 1.93 m. Within-row spacings were 5, 10, and 15 cm. Crops were grown using minimum fungicide and insecticide amounts, while no attempt was made to control weeds chemically. Seed was harvested between May and June. Seed yields (kg·ha–1) increased for planting dates of October to November. Lower seed yields from the January or later plantings appear to be related to increased disease and insect pressures. Total and medium class size (≥3 and ≤4 mm in diameter) seed yields were highest at 40 rows × 1.93 m bed spacings and 10 cm within-row plant spacings. Germination and percent coatless seeds were unaffected by bed configuration and within-row plant spacings. The closest within-row spacings (5 cm) increased the risk of plant lodging and delayed plant maturity.
Adjustments of Irrigation Scheduling Model for Bell Pepper
Authors: Drouot Vanessa , Simonne Eric H. , Witt James B.
Published: February 2019

An irrigation scheduling model represented by 12.7 DAT * 0.5 * ASW = D(DAT – 1) + [Ep(DAT) * CF(DAT) – R – I] was tested in central Alabama for Spring-grown bell pepper (Capsicum annuum L.). In the model, DAT (days after transplanting) is crop age; effective root depth is 12.7 DAT with a maximum of 250 mm; usable water (mm3·mm–3) is 0.5 ASW; deficit on the previous day is D(DAT–1); evapotranspiration is pan evaporation [Ep(DAT)] times a crop factor value [CF(DAT) = 0.15 + 0.018 DAT – 0.0001 DAT * DAT]; rainfall (R) and irrigation (I) are in mm. The model called for 13 irrigations between 17 and 85 DAT. Under the current N recommendation rate for bell pepper (112 kg/ha), marketable yield increased quadratically from 36% to 148% of the model rate. Highest marketable yields occurred near the model rate. Under a N rate of 170 kg/ha, yields increased linearly. These results suggests that the model provided adequate moisture to maximize bell pepper marketable yields under the recommended N rate.
Fifty-year History of Harvesting Pickling Cucumbers Mechanically
Authors: Marshall Dale E.
Published: February 2019

For 50 years, engineers, producers, processors, and manufacturers have been working on new and improved ways for mechanization of the harvest of pickling cucumbers, Cucumis sativus L. In 1957, processors investigated multiple-pick concepts. Multiple-pick harvesters were commercially manufactured in the early 1960s (Chisholm–Ryder). In the late 1950s, Stout and Ries evaluated the known multiple-pick harvesting concepts. In the early 1960s, once-over harvesting concepts were considered and evaluated by Ries and Stout. By significantly increasing the plant population and other horticultural practice and variety improvements, once-over harvest became the main thrust of mechanization from 1965 on. By 1970, at least major five commercial manufacturers sold harvesters (Blackwelder, FMC Corp., Hart Carter [later sold out to Cuke, Inc.], Porter-Way, and Wilde). In 1996 there are four commercial manufacturers (Cuke, FMC Corp., Jerry's Welding, and Pik Rite). Limited multiple-pick research and manufacturers persisted (Aero-Glide, Mac-Weld, and Powell). By 1975 over 85% of Michigan's pickling cucumbers were mechanically harvested, leading all other states. Today, about 60% of Michigan's production is harvested with machines. The information presented will be informative and an historical aid for engineers, manufacturers, horticulturists, processors, and historians, etc. to ensure that the worldwide research is known by scientists endeavoring to accomplish harvest mechanization.
Plant Population and Spacing Effects on Processing Tomato Growth and Yield
Authors: Bennett Mark A. , Grassbaugh Elaine M.
Published: February 2019

Processing tomato (Lycopersicon esculentum Mill.) producers in the Great Lakes region have expressed interest in cutting crop establishment costs and improving profitability by reducing plant populations. This study compared plant development, fruit set, fruit size and yields using a range of single and twin-row plant populations (14,800 to 44,500 plants/ha) and four commercially important processing tomato cultivars (`OH8245', `H9036', `PS696', and `H7135') with differing vine types and maturities. The 3-year study was conducted at Fremont, Ohio, on a Colwood fine sandy loam, using raised beds and other standard cultural practices. Six- to seven-week-old transplants (288 cell size) were mechanically planted in middle to late May. Once-over harvest was timed to achieve 80%–90% red fruit, using a Johnson tomato harvester. Plant population had a significant effect on 1995 fruit yields for all cultivars tested. Optimum red fruit yields were observed at 37,100 plants/ha in twin-rows for `OH8245', which was similar to 1994 results. Optimum fruit yields for `PS696' were obtained at twin-row populations of 29,600-44,500 plants/ha in 1995. Three year results for `OH8245' (medium-sized vine) indicate no significant differences due to plant population or arrangement. Mean red fruit yields varied considerably by year in this field research (62.7, 95.2, and 44.8 MT/ha in 1993, 1994, 1995 respectively), but twin-row spacing of `OH8245' provided significant yield gains in 2 of 3 years for populations of 29,600 plants/ha or greater.
Seed Leakage Does Not Contribute to Thermoinhibition in Jalapeno and Cayenne Cultivars
Authors: Carter A.K. , Vavrina C.S.
Published: February 2019

Chile (Capsicum annuum L.) seeds sown in July for fall transplants in the greenhouse often yield poor stands due to thermoinhibition. To determine cultivar response to high temperature, five jalapeno cultivars and one cayenne cultivar used commercially in Florida and New Mexico were tested. Two seedlots of `Cayenne, Large Red Thick', `Ole', `Jalapeno M', `Mitla', and `Tam Veracruz', and one seedlot of `Ebano' were evaluated on a thermogradient table at a temperature range of 20, 25, 30, 35, and 40°C. Percent germination, mean daily germination, and germination performance index were calculated. Additional seeds were soaked for 24 hours at 25, 30, 35, and 40°C. The exudate was then measured for electrical conductivity and glucose equivalents as an indication of seed leakage. All cultivars exhibited thermoinhibition, but the critical temperature of onset varied among cultivars. `Ebano' had the highest germination performance index across all temperatures among the six cultivars. At 40°C, however, no cultivar exceeded 4.0% germination. There was significant variation in germination performance between seedlots of some cultivars. The electrical conductivity and the number of glucose equivalents leached from the seed varied among cultivars, but did not correlate with decreased germination. Thermoinhibition in chile is probably due to factors other than those associated with membrane leakage.
Salvaging a Rabbiteye Blueberry Crop with GA3 following Sub-freezing Temperatures
Authors: NeSmith D. Scott , Krewer Gerard , Lindstrom Orville
Published: February 2019

Recent research in Georgia indicated gibberellic acid (GA3) could possibly be used to induce fruit set of freeze damaged rabbiteye blueberry (Vaccinium ashei) blooms. This research was conducted to determine the subfreezing temperature limit at which GA3 could be expected to be of use in salvaging a crop with freeze-damaged flowers. Rabbiteye blueberries with flower buds at stages 5 to 6 of development (fully elongated corollas and open blooms) were exposed to temperatures of 0, –1, –3, and –4.5°C in growth chambers to simulate overnight freezing events. After cold exposure, plants were placed in a greenhouse with a hive of bumblebees. Half of the plants were treated with GA3 and half were not. The number of flowers and subsequent fruit were recorded in order to calculate fruit set. Temperatures of –1°C and below caused fruit set resulting from pollination by bees to decline compared to control plants; whereas, flowers treated with GA3 had fruit set comparable to control plants down to –3°C. Plants exposed to –3°C had 50% to 80% fruit set when treated with GA3 compared to 5% to 19% fruit set for untreated plants. Temperatures of –4.5°C caused severe flower damage, and fruit set by pollination or GA3 was very poor (<2%). These results indicate that GA3 should be useful in salvaging a blueberry crop exposed to temperatures of – 1 to –3.5°C during bloom.
The Effects of an Experimental Antitranspirant on Whole-plant Transpiration of Ornamental Landscape Shrubs
Authors: Kindred Christopher B. , Zajicek J.M.
Published: February 2019

Survivability of ornamental landscape plants during transport and the early stages of transplanting is a concern of the nursery and landscape industries. An effective antitranspirant may help avoid unnecessary plant losses during these periods of plant stress. The objective of this study was to evaluate the effects of a new experimental antitranspirant on whole-plant transpiration of two ornamental landscape shrubs. Plants of Hibiscus rosa-sinensis and Photinia ×fraseri were treated with the experimental antitranspirant N2001. Treatment rates included: 0% (as a control), 10%, 12.5%, or 15%. All treatments were mixed as a percentage of N2001 in a given volume of reverse osmosis water and applied to the roots as a drench. Whole-plant transpiration was determined gravimetrically by weighing the plants daily. Stem-flow gauges further monitored daily water use on an hourly basis. At the termination of the experiment, leaf areas and leaf dry weights were determined. Application of the antitranspirant reduced whole-plant transpiration immediately for all treated plants compared to that of control plants. On day 1, the 10%, 12.5%, and 15% treatments significantly reduced whole-plant transpiration levels by 41%, 50%, and 62%, respectively, compared to untreated plants. On day 3 and 4, the antitranspirant was still effective, reducing whole-plant transpiration by 47% and 24% on average, respectively, compared to untreated plants. By day five there were no significant differences in whole-plant transpiration between any treatment. Differences in whole plant transpiration can be attributed to antitranspirant application due to lack of differences in leaf area, dry weight or leaf area ratio between any treatment.
Water Loss, Embolism, and Post-transplant Growth of Acer rubrum and Crataegus phaenopyrum as Influenced by Length of Storage
Authors: Knight P.R. , Harris J.R. , Fanelli J.K.
Published: February 2019

Year-old seedlings of Acer rubrum L. and Crataegus phaenopyrum (L.f.) Medic. were grown for 1 year in a Groseclose silty clay loam. Seventy-two plant per species were harvested on 15 Dec. 1995 and weighed. Plants were stored at 4°C for 0, 1, 3, 5, 10, or 15 weeks. At the end of each storage period, 12 plants were weighed to determine water loss. Six plants were then sacrificed to determine percent embolism, and six plants were planted in a pine bark media and grown in a glasshouse for 15 weeks to determine the influence of storage on post-transplant growth and embolism recovery. Length of storage had no influence on embolism of Crataegus. Embolism of Acer increased linearly with increasing length of storage. Embolism was greater for Crataegus compared to Acer at each harvest. Water loss for both species increased linearly as time of storage increased.
Responses of the Fine Roots of Citrus to Dry Surface Soil
Authors: Eissenstat David M. , Espeleta Javier F. , Whaley Eric L.
Published: February 2019

Despite the frequent occurrence of hot, dry surface soil, little is known about the fate of roots in this soil layer during and following periods of surface drought. Phosphorus uptake kinetics were examined in surface roots of citrus seedlings exposed to different periods of drought. Exposure to dry soil for up to 43 days had no effect on phosphate uptake of excised roots measured at solution concentrations of 50, 750, and 1500 μm phosphate. Effects of surface drought on fine root behavior of seedlings and bearing trees were examined in the field using a split-pot arrangement. At the end of 5 weeks of drought, only about 1% of the roots in the top pot of either the seedling or tree had died. By 8 to 9 weeks of drought, about 26% of the fine laterals of the adult citrus had died, but only 6% had died in the seedling. After 15 weeks of drought, 33% of the mature tree fine roots had died but only 8% had died in the seedling. Root-soil respiration per gram root at this time was at least twice as high in the seedling as in the mature tree. Fine roots of citrus are remarkably tolerant to dry surface soils of about 5 weeks duration, both in terms of root survival and resumption of physiological activity after rewetting.
Municipal Solid Waste (MSW) Compost Maturity Influence on Weed Seed Germination
Authors: Ozores-Hampton Monica , Bewick Thomas A. , Stoffella Peter , Cantliffe Daniel J. , Obreza Thomas A.
Published: February 2019

The influence of compost (derived from MSW and biosolids) maturity on seed germination of several weed species was evaluated. A bioassay was developed by extracting 20 g of compost of different maturities with various volumes of water, then measuring germination percentage of ivyleaf morningglory (Ipomoea hederacea) seeds placed on extract-saturated filter paper in a petri dish. A 20 g (dry weight) compost: 50 mL of water generated an extract that produced the widest percentage seed germination variation in response to composts of different maturity. Ivyleaf morningglory, barnyardgrass (Echinochloa crus-galli L.), purslane (Potulaca oleracea L.), and corn (Zea mays L) were selected as plant indicators to determine the compost maturity stage with maximum germination inhibition. Compost 8-week-old decreased percent germination, root growth, and germination index (combines germination rate and root growth), and increased mean days to germination (MDG) of each plant indicator. Immature 8 week-old compost extract effect on MDG and germination percent of 15 weed species was evaluated. Extract from 8-week-old compost inhibited germination in most weed species, except yellow nutsedge (Cyperus esculentus). Compost extracts derided from immature (3-day, 4-, and 8-week-old) compost resulted in delayed and reduced germination percent of important economic weed species.
Dynamic Optimization of Photosynthetic Photon Flux for Efficient Photosynthesis and Growth of Leaf Lettuce Canopies
Authors: Chun Changhoo , Mitchell Cary A.
Published: February 2019

`Waldmann's Green' leaf lettuce (Lactuca sativa L.) is being used as a model leafy vegetable crop to develop a protocol for variable control of photosynthetic photon flux (PPF) during crop production. Feedback from real-time photosynthetic gas exchange rates by lettuce canopies is used to modulate electronic dimming ballasts of lamp banks. Algorithms within process-control software are being fine tuned to maximize increments of photosynthetic output relative to increments of photon input. Dynamic optimization of PPF was 21% more efficient than constant high PPF saturating photosynthesis with respect to biomass accumulated per photons absorbed. Dynamic optimization also is being combined with principles of phasic control, in which environmental resources such as photosynthetically active radiation (PAR) and carbon dioxide (CO2) are deliberatively limited in input during specific phases of crop development when plants are less sensitive to inputs (e.g., lag, plateau, and senescence phases) but optimized for the responsive exponential phase. Preliminary results indicate that leaf lettuce growth benefits from optimizing environments for no more than 4 or 5 days during a 20-day production cycle. Dynamic optimization of CO2 level is achieved by controlling the injection of CO2 into the inlet air stream of Minitron II crop canopy cuvette/growth chambers. Algorithms are being modified to simultaneously vary PPF and CO2 for optimum photosynthesis.
Seasonal Change in Cold Hardiness of Field-grown Ash Trees
Authors: Hummel Rita L. , Regan Richard
Published: February 2019

Cold hardiness of Fraxinus americana `Autumn Purple', Fraxinus oxycarpa `Raywood' and Fraxinus pennsylvanica `Summit' was measured in laboratory tests. Current season stem growth was collected from trees in Willamette Valley nurseries at 3 to 6 week intervals from November 1994 to February 1995 and from October 1995 to March 1996. Replicated 9-cm stem samples with two buds each were placed in tubes and immersed in an ethylene glycol bath. Samples were nucleated with crushed ice, held overnight at –2°C and then frozen at 3°C/hour. After freezing, samples were thawed overnight, incubated at room temperature and 100% relative humidity for 10 to 14 days, then sample viability was determined by visual browning. A Tk50, the temperature at which 50% tissue injury occurred, was calculated for buds and stems. Buds were generally less hardy than stems. `Raywood' was slower to cold acclimate in the fall and did not become as cold hardy in midwinter as `Summit' and `Autumn Purple'. Cold acclimation and midwinter hardiness of `Summit' and `Autumn Purple' was similar; however, `Summit' deacclimated more rapidly. Between the 11 Dec. 1995 and 9 Jan. 1996 freeze tests, `Summit' stems lost about 9 °C of freeze tolerance. In both the 1995 and 1996 February freeze tests, `Summit' stems were less hardy than `Raywood' stems.
Variability in the Speed of Cold Deacclimation among Tuber-bearing Wild Potato Species
Authors: Vega Sandra E , Palta Jiwan P. , Bamberg John B.
Published: February 2019

Frost injury limits the cultivation of potatoes in many regions around the world. We are currently studying the factors that contribute to frost survival in potato in an attempt to improve its frost tolerance. Wild potato species have been distinguished for their high degree of non-acclimated frost tolerance (growing under normal conditions) and their high cold acclimation capacity (able to increase frost tolerance upon exposure to cold). Cold acclimation can be reversed upon exposure to warm temperatures (deacclimation). The ability to gain freezing tolerance rapidly in response to low temperatures as well as not being able to deacclimate rapidly in response to warm daytime temperatures would be advantageous for a plant against spring or fall freezes. Last year we presented evidence for the variability in the speed of cold acclimation among 7 wild tuber-bearing potato species (S. acaule, S. commersonii, S. megistacrolobum, S. multidissectum, S. polytrichon, S. sanctae-rosae and S. toralapanum). The same set of species was used for the present study to find out if there is also variability for the speed of deacclimation. Relative freezing tolerance of these species was measured before and after cold acclimation as well as after one day of deacclimation (exposure to warm temperatures). Our results suggest that there are differences in the speed of deacclimation among these species. We found that while some species lost near a half of their hardiness, others lost only a third or less of their hardiness after one day of deacclimation.
Ta Tao Peach Interstems Influence Cultivar Phenology, Vigor, and Fruiting in South Carolina
Authors: Reighard Gregory L. , Ouellette David R.
Published: February 2019

Twenty-six peach and six plum cultivars budded to 20–50 cm Ta Tao five or twenty-four interstems on Lovell rootstock were observed in four trials at two locations in South Carolina. The locations were in the Piedmont near Clemson and the Sandhills near Pontiac, S.C. The objective of growing peach cultivars on interstems was to delay scion phenology to reduce risk from late spring freezes. Data from these trials were collected from 1989 to 1996. Average bloom delay for peach cultivars on interstems was significant each year from 1991 through 1996 and ranged from 5 to 9 days later than the noninterstem controls. Bloom of plum cultivars on interstems was not significantly affected. Interstem peach trees had significantly smaller trunk cross-sectional areas and averaged from 32% smaller in 3-year-old trees to 35% in 7-year-old trees. Interstem trees also had fewer lateral vegetative budbreaks (i.e., blind wood). Fruit maturity was significantly delayed on most peach cultivars on interstems. Fruit of early cultivars (90 days past bloom) ripened 2–4 days later on interstems. Likewise, mid-season cultivars ripened 5–6 days later and late season cultivars (>130 days past bloom) 3-4 days later. Fruit size was smaller on interstem trees when trees were either inadequately thinned or drought-stressed.
Molecular Responses of Plants to Phosphate Starvation
Authors: Raghothma K.G. , Muchhal Umesh , Liu Chunming , Mukatira U.
Published: February 2019

Phosphate deficiency is wide spread in the nature. The deficiency results in several morphological and biochemical changes in plants. Some of these changes have been shown to involve altered gene expression. We have isolated two full--length cDNAs (AtPT1 and AtPT2), showing significant amino acid sequence similarity with the high-affinity phosphate transporters of yeast, Neurospora and the mycorrhizal fungi Glomus versiforme, from a phosphate-starved Arabidopsis root library. The transcripts of both genes are highly induced under Pi starvation and they are expressed in roots. Using Arabidopsis cDNAs as probes, we have isolated several tomato root cDNA clones representing the two different genes. The expression characteristics of the tomato isoforms of the putative high affinity phosphate transporter genes will be discussed. The northern blots of RNA isolated from phosphate-deficient and phosphate-sufficient roots of tomato indicated that both genes are strongly induced in response to Pi starvation in roots. Furthermore, by the method of differential display of mRNA, we have cloned and characterized a full-length cDNA representing a Pi starvation induced gene (TPSI1) from tomato. The gene is expressed as a specific response to Pi starvation in roots and leaves. The TPSI1 is an intron-less gene represented by a single copy in the tomato genome. The structure, expression, and functional significance of these genes will be discussed. This research has been supported, in part, by USDA grant 94-37100-0834 to KGR.
Asparagus Yield Cycles and Heat Unit Correlations
Authors: Dean Bill B.
Published: February 2019

Asparagus is a unique crop in that the yield of the crop is entirely dependent on the storage of carbohydrates from the previous season. The number of spears produced is determined by the number of buds on underground rhizomes and the size of each spear is related to the size of the bud from which it originates. Growth of spears begins in the spring when some minimal temperature is reached in the soil. We have determined that the minimum temperature for spear growth is 10°C (50°F) and that temperatures in excess of 35°C (95°F) inhibit growth. Using data from growth response to temperature experiments, we have compared the accumulative effects of hourly temperatures preceding harvest to subsequent yields. There was a significant effect of the number of hours above 10°C for the 24 hours preceding harvest and the yield obtained. Yield of spears cycled over an 11-day period which correlated to an eleven day weather cycle determined from the heat unit accumulations. Heat unit and yield cycles for seven cultivars over a 4-year period will be discussed.
Remote Sensing Imagery on the Web and Its Potential for Use in Horticulture Classes
Authors: Harp Derald A. , McWilliams Edward L.
Published: February 2019

As the World Wide Web (WWW) expands, information is rapidly becoming more accessible. Using satellite data previously required high-end computers running complex imaging software, sophisticated downloading equipment, and high monetary support. Satellite data is now available on the internet for little or no cost and can be handled on standard desktop computers using common software programs. The purpose of our project was to determine the availability and cost of different types of data and how this data may benefit horticultural instruction. Satellite data currently is archived at NASA, NOAA, the Department of Defense, the US Geological Survey, and various meteorological departments throughout the world. Satellite data such as large-scale thermal imagery can be used to determine microclimate effects within urban areas, including the cooling effects of urban plants. Natural Density Vegetation Index (NDVI) imagery can indicate changes in vegetational cover or give general indications of plant health in large areas. NASA photographic imagery can show the effects of erosion on a large scale. Higher resolution imagery can give indications of plant stresses in large plantings such as orchards or vegetable plots.
Development of a National, On-line, Interactive Database of Internship Opportunities for Students of Horticultural Science
Authors: Lyons Robert E. , Rhodus Timothy W.
Published: February 2019

Internships are becoming an increasingly used mechanism of providing undergraduates with experience in their chosen profession before job placement, and potential employers view internships favorably in making hiring decisions. Many horticulture programs require internships as part of their curricula, while others are considering the option. Because internship opportunities in horticulture have been compiled in a wide variety of discipline-specific resources with no central, inclusive “clearinghouse,” students often overlook potential opportunities, particularly those outside of their home state, leaving some industry members without interns. The internet-based database of internships developed jointly by Virginia Tech and Ohio State will be discussed within the context of being a resource for all horticulture programs. Other schools will be shown how to contribute to and to use the database so its national scope can be fully used and expanded.
Effect of Carbon Dioxide on Stability of Anthocyanins and Other Phenolic Compounds during Storage of Fresh Strawberries
Authors: Holcroft D.M. , Gil M.I. , Kader A.A.
Published: February 2019

Carbon dioxide-enriched atmospheres are used to reduce decay incidence and severity and extend the postharvest life of strawberries. However, depending on the cultivar, carbon dioxide concentrations of ≥20% can be detrimental to color (change from red to purple) and flavor (development of off-flavors). Our objective was to determine the effect of elevated carbon dioxide levels on the stability of the anthocyanins and other phenolic compounds to examine their role in color changes of strawberries. Freshly harvested strawberries were placed in jars ventilated continuously with air or air enriched with 10%, 20% or 40% carbon dioxide at 5°C for 10 days. Anthocyanins and other phenolics were extracted at 0, 5, and 10 days from homogenized samples. The samples were purified using Sep-pac C18 cartridges. The purified methanolic extract was injected directly into HPLC coupled to a photodiode array detector. Cyanidin-3-glucoside, pelargonidin-3-glucoside, and pelargonidin-3-rutinoside were identified as the major anthocyanins. After 5 and 10 days in storage there was a reduction in the total amount of anthocyanins. This degradation was lower in air than in carbon dioxide-treated strawberries, but the anthocyanin profile remained the same. Flavonols (e.g., quercetin and kaempferol derivatives) and phenolic acids (e.g., ellagic acid) decreased during storage, and this decrease was exacerbated by elevated carbon dioxide atmospheres. Carbon dioxide-induced changes in the quantities of the previously listed anthocyanins and phenolic compounds may be the cause of color changes from red to purple in strawberries.