bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphorus Requirements for Lettuce Transplant Growth Using a Flotation Irrigation System
Authors: Soundy Puffy , Cantliffe Daniel J. , Hochmuth George J.
Published: February 2019

Phosphorus applied at frequent rates via the flotation irrigation system affected growth of both roots and shoots of lettuce transplants grown with a flotation irrigation system. After an initial P addition of 15 mg·L–1, further P additions up to 90 mg·L–1 P resulted in a minimal growth response. Transplants produced with 0 P had similar poor growth, regardless of the amount of N applied. Nitrogen at 100 mg·L–1 improved the response of shoot growth to any level of P, but adversely affected root growth compared to N at 60 mg·L–1. Quality transplants had a root to shoot ratio of ≈0.25, total root lengths between 276 and 306 cm, and total root area between 26 and 30 cm2 in a 10.9-cm3 cell volume. Only 30% of the plants produced with 0 P could be pulled from the transplant flats, compared to ≈90% pulling success with added P. All pretransplant P treatments had a similar effect of increasing head mass at harvest time, and in reducing time to maturity regardless of production season. At transplanting, plants produced with transplant P were larger than those produced with no transplant P. Thus, at least 15 mg·L–1, supplied every 2 days via flotation irrigation, is recommended for production of high quality lettuce transplants in a peat+vermiculite media containing low concentrations of water extractable P.
Hydroponic Greenhouse Production of Fresh-market Basil in Colorado
Authors: Succop C. Elizabeth , Newman Steven E.
Published: February 2019

Fresh-market basil is becoming a viable greenhouse commodity in Colorado. Marketing pressures and profit advantages also encourage the production of certified organic produce. The research objectives were to determine the length of time basil plants were productive in the greenhouse and to compare the production of fresh-market basil grown with three root zone systems and two fertilizer treatments. The three systems were hydroponic rockwool slab culture, hydroponic perlite raised bed culture, and hydroponic peat/perlite/compost bag culture. The two types of hydroponic fertilizer treatments were an inorganically formulated nutrient solution and an organic solution consisting of fermented poultry compost, hydrolized fish emulsion, and soluble kelp. The plants were harvested once per week and fresh weight was determined. During the 2nd and 3rd months of harvest, productivity from the plants treated with the organic fertilizer was greatest in the perlite system. However, productivity from the plants treated with the traditional fertilizer was greatest in the bag mix and rockwool systems.
Effect of Sampling Date and Production Zone on the Predictive Capacity of Bitter Pit through Magnesium Infiltration in `Granny Smith' and `Braeburn' Apples
Authors: Retamales Jorge B. , Valdes Claudio
Published: February 2019

Bitter pit is the most important physiological disorders for apples in Chile. During the 1995–96 season, the predictive capacity of bitter pit through magnesium infiltration of the fruit in commercial orchards of three locations in South Central Chile: San Fernando (SF), Curico (CU), and San Javier (SJ) was established. Three orchards were chosen in each location and for each cultivar; fruit were collected 60, 40, and 20 days before commercial harvest. Fruit were infiltrated for 2 min with magnesium chloride at 0.05 M using vacuum levels of 500 or 100 mm Hg for `Granny Smith' and `Braeburn', respectively. The predictive capacity (correlation between predicted and effective bitter pit—after 90 days at 2°C + 10 days at 18°C) increased closer to harvest; with regards to location: SF > CU > SJ. Bitter pit-like symptoms, caused by Mg infiltration stabilized 16 days after infiltration. Bitter pit incidence was better predicted than severity. Bitter pit was better predicted for `Granny Smith' than for `Braeburn'.
The Response of `Tifway' Bermudagrass to Growth Retardants as Charged-hydrophilic Polymers or Foliar Spray under Two Irrigation Systems
Authors: Al-mana Fahed A. , Beattie David J.
Published: February 2019

A study of applying growth retardants under overhead and subsurface irrigation systems was conducted on bermudagrass (Cynodon dactylon L. cv. Tifway) grown from rhizomes in 15-cm pots containing sand medium. Paclobutrazol (50%) at 2 mg/pot was used as foliar spray or charged-hydrophilic polymers (Super Sorb C) and either incorporated or put below medium surface. Mefluidide (28%) at 0.01% ml/pot was used only as foliar spray. Before spray treatments, grasses were cut at 2 cm from medium surface, and the second cut was made at the 6th week from treatment. All growth retardant treatments reduced grass height compared to non-treated plants. The lowest grass height was produced by paclobutrazol as foliar spray under overhead irrigation in the 6th and 9th week. By the 9th week, all hormonal treatments under the two irrigation systems had no effect on grass quality, color, and establishment rate. Both paclobutrazol foliar spray and below medium surface charged-polymer treatments under subsurface irrigation had the lowest water loss and dry weight by the 6th and 9th week. The paclobutrazol charged-polymer treatment under subsurface irrigation had also the the lowest root dry weight among all treatments. Although mefluidide foliar spray was less effective on grass height than paclobutrazol, they had similar effect on water loss and shoot dry weight.
In Vitro Regeneration of Buffalograss [Buchloe dactyloides (Nutt.) Engelm] through Immature Inflorescence Culture
Authors: Fei Shuizhang , Read Paul E. , Riordan Terrance P.
Published: February 2019

Buffalograss is native to the Great Plains of North America. Its excellent drought resistance and low growth habit make it a good choice for a low-maintenance turf. A reproducible and efficient regeneration protocol of buffalograss is critical for further genetic transformation. By using immature inflorescences as explants, we have achieved the regeneration of buffalograss of two female clones, `315' and `609', a male clone, NE 84-45-3, and a synthetic cultivar, `Texoka'. Somatic embryogenesis was observed. The medium used for callus initiation was MS basal medium supplemented with various concentrations of 2,4-D and BA. After 4 weeks of dark culture, calli with nodular structures were transferred to the same basal medium supplemented with BA and either a reduced rate of 2,4-D or no 2,4-D. It was demonstrated that 2,4-D at 2 or 3 mg/L is optimal for embryogenic callus production. The presence of BA from 0.1 mg/L to 0.5 mg/L was required for the regeneration of `315', `609', and NE 84-45-3. For `Texoka', 2,4-D at 0.5 mg/L with BA at 0.3 mg/L in the regeneration medium favored normal development of somatic embryos that were capable of germination. A genotypic effect was observed with regard to embryogenic callus production; explants of the male genotype NE 84-45-3 exhibited a higher percentage of embryogenic callus formation than was found for the two female genotypes. A significant seasonal effect was also observed with inflorescences collected in early May exhibiting a higher percentage of callus formation than those collected in the summer and fall.
Rapid Detection of Senescence-related Volatiles of Fruits and Vegetables
Authors: Perez Rufino , Beaudry Randolph M.
Published: February 2019

Volatile production is known to change with stages of plant organ development. Research has primarily focused on ripening-related volatiles; however, the potential exists to use volatiles as markers of organ damage and senescence. We have employed gas chromatography/mass spectrometry to establish stages of senescence based on volatile profiles of whole and lightly processed broccoli and carrot. An air-tight chopping apparatus was used as a flow-through chamber system and the exit gas stream analyzed for each commodity with and without tissue disruption. For carrot, isoprenoid pathway volatiles, such as 3-carene, caryophellene, α-caryophellene, and β-pinene, increase with damage and tissue senescence. Similar trends were obtained for broccoli with volatiles characteristic of β-oxidation and shikimic acid pathways. Time and condition-related volatile profile changes will be presented for carrot, broccoli, and strawberry.
Sensory Evaluation Correlates with Flavor Volatile Profiles of Ripe Tomato Fruits
Authors: Maul Fernando , Sargent Steven A. , Baldwin Elizabeth A. , Sims Charles
Published: February 2019

`Agriset-761' and `CPT-5' tomato fruits were harvested at green stage and subsequently exposed to a postharvest exogenous ethylene-air mixture (100 ppm C2H4 at 20°C). Tomatoes with visual symptoms of ripening (breaker stage = <10% red coloration) were removed from ethylene treatment after 1, 3, and 5 days and were transferred to 20°C and 85% RH. At “table-ripe” stage (full red coloration and 4-mm fruit deformation after 5 sec@9.8N), whole fruit samples were analyzed for difference/discrimination sensory evaluations, aroma volatile profiles, and chemical composition. Flavor of fruits gassed for 1 day was rated significantly different than that of fruits gassed for 3 or 5 days (n = 25 panelists) for both cultivars. Several panelists noted the perception of “rancid” and “metallic” tastes, and “lingering” aftertaste in fruits gassed for 5 days. Chemical composition assays showed that flavor differences could be partially due to a significant increase in pH values between fruits gassed for 1 and 5 days (4.23 and 4.34, respectively for `Agriset-761') and a significant decrease in titratable acidity (0.91% and 0.73%, respectively, for `Agriset-761'; 1.04% and 0.86%, respectively, for `CPT-5'). No significant differences in soluble solids content or total sugars were found in any treatments for either cultivar. `Agriset-761' showed significant increases in the concentrations of acetone, hexanal, 2+3 methylbutanol, and a decrease in 2-isobutylthiazole, whereas, `CPT-5' fruits showed significant increases in hexanal, 2+3 methylbutanol, trans-2-heptenal, 6-methyl-5-hepten-2-one, 2-isobutylthiazole, β-ionone, geranylacetone, and a decrease is ethanol concentration. In both cultivars, these significant differences in important aroma volatile compounds could be of enormous relevance in the perception of off-flavor/off-odors.
Molecular Mass Changes in Cell Wall Pectins of Tomato Fruit Locule Tissue in Response to Deesterification
Authors: Cheng Guiwen W. , Huber Donald J.
Published: February 2019

Changes in the gel filtration behavior (apparent mol mass) of cell wall pectic polymers have been observed in a number of ripening fruits, including some that express little or no detectable polygalacturonase (PG). Pectins from tomato (Lycopersicon esculentum, Mill. v. Solar Set) fruit locule tissue show limited depolymerization during ripening, although alkali-soluble polymers are of reduced mol mass relative to water- and chelator-soluble polymers (Plant Physiol. 111:447). This study addressed whether the lower mol mass of alkali-soluble polymers was a consequence of extraction or specific metabolism of these wall polymers. Pectins from sequential water and chelator extractions of ethanol-insoluble solids from mature green tomato locule tissue were subjected to alkaline conditions. The size distribution of both water- and CDTA-soluble pectins treated with weak alkali were downshifted and similar to those extracted directly by weak alkali, indicating structural similarities of the three pectin fractions. Spectrophotometric analysis showed no involvement of β-elimination hydrolysis in the apparent mol mass reduction. The alkali-treated polymers were of greatly enhanced susceptibility to PG-mediated degradation. The alkali-associated changes also occurred in response to pectinmethylesterase hydrolysis. The results indicate that deesterification can strongly influence gel filtration behavior of pectins and may explain the apparent mol mass decreases of pectins in fruits not containing PG.
Reducing Bell Pepper Bruising during Postharvest Handling
Authors: Marshall Dale E. , Brook Roger C.
Published: February 2019

Green bell pepper is a popular vegetable in the United States. Michigan is the 5th-leading production area, producing 480,000 cwt of green bell peppers in 1994. The tender skin of the green bell pepper covers a crisp, fragile flesh that is easily bruised, cracked, or crushed. During commercial harvest and postharvest handling operations, bell peppers undergo several transfers, each of which has the potential for causing mechanical injury to the pepper fruit. These mechanical injuries include abrasions, cuts, punctures, and bruises. Mechanical injuries and bruises are defects that affect the market grade of the peppers, and may reduce pepper quality and subsequent shipping life. The impacts occurring in a pepper field and on a Michigan packing line were measured using an Instrumented Sphere. Field tests attempted to duplicate how pickers harvest bell peppers into 5-gal pails and empty them into empty wooden tote boxes. Other tests were on an entire packing line. Most bruising on packing lines occurred at the transfers between different pieces of equipment when the peppers fell or were propelled from conveyors onto uncushioned metal plates or rollers. Several transfer points were identified as areas where much of the mechanical damage occurred and improvements were suggested to the packer. Bell peppers were found to bruise on their shoulders; therefore, shoulder bruises may be used as an indicator of injury. The major problems with packing lines were excessive height differences between line components, lack of control of rolling velocity, and lack of cushioning on hard surfaces.
Advances in Plant Nutrition: Re-evaluating Hoagland's Hydroponic Recipe after a Half Century
Authors: Bugbee Bruce
Published: February 2019

Although the principle of mass balance is well-understood, few people understand how Hoagland and Arnon used it to develop their famous nutrient solution recipes. Here I review: 1) the application of mass balance in deriving unique hydroponic solution recipes, 2) the dangers of dumping and replacing hydroponic solutions, 3) the need to alter the silicon and chloride concentrations in Hoagland's solution based on recent advances in our understanding of plant nutrient requirements.
N and K Requirements of Carrot on Sandy Soils in Florida
Authors: Hochmuth George , Brecht Jeff , Bassett Mark
Published: February 2019

Carrot production in Florida has been centered in two major organic-soil vegetable production areas. These areas are the Everglades Agricultural Area near Belle Glade, in southern Florida, and the Zellwood vegetable area in central Florida. The state of Florida is currently in the process of purchasing most of the organic soils used for vegetable production near Zellwood, leading to a movement of vegetable production to the surrounding sandy soil or to other vegetable production regions in the state. The move to sandy soils has lead to questions by growers about fertilization of vegetables such as carrot. We conducted a series of fertilization experiments with `Nantes' and `Imperator' carrot to evaluate yields and carrot quality responses to N and K. Carrot yield was maximized with 170 kg·ha–1 N, confirming current extension recommendations for carrot on sandy soils in Florida. The soil used for the K study tested medium (50 mg·kg–1) in K (Mehlich-1 extracted). Carrot yield responded positively to K up to 50 kg·ha–1 K, near the amount predicted for soils testing N medium in K.
An Evaluation for Pod Calcium Concentration between Eight Commercial Cultivars of Snap Beans and Eight of Dry Beans (Phaseolus vulgaris L.)
Authors: Quintana Juan M. , Harrison Helen C. , Nienhuis James , Palta Jiwan P.
Published: February 2019

We have previously observed significant variation for pod Ca concentration among snap bean genotypes. In the present experiment, we compare pod Ca concentration between snap bean and dry bean genotypes. Eight snap bean cultivars and eight dry bean cultivars were chosen to be evaluated for pod Ca concentration in summers of 1995 and 1996 at Hancock, Wis. The experimental design consisted in randomized complete blocks with three replications in 1995 and six in 1996. Snap and dry beans were planted in June and hand-harvested in August for both experiments. Soil analysis showed 430 ppm of Ca in soil at time of planting. No additional Ca was applied. Plots consisted of 10 plants each. Harvesting was made by collecting a pooled sample of medium size pods from the 10 plants. Ca determinations were made using an atomic absorption spectrophotometer. Data was presented as mg of Ca per gram of dry weight, pooled from both years, and analyzed using SAS. Results reflected significant differences between genotypes. Checkmate (5.5) showed the highest pod calcium concentrations and Labrador (3.9) the lowest among snap beans. G0122 (5.1) resulted in the highest and Porrillo (3.6) the lowest within dry beans Results were consistent across years. Snap beans (4.6) presented significantly higher pod calcium concentration than dry beans (4.2). Apparently, snap bean genotypes have the ability to absorb calcium from the soil more efficiently than dry bean genotypes, and this phenomenon is not significantly influenced by environmental factors.
The Effects of Nitrogen on the Growth, Development, and Medicinal Compound Yield of the Sundew Drosera adelae
Authors: Owen Josee , Stewart K.A.
Published: February 2019

Drosera spp. are used in alternative medicine as sources of the beneficial naphthoquinone compounds plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone) and 7-methyljuglone. Presently, Drosera are harvested from the wild with great detriment to bog habitats. This study focused on the development of a hydroponic rockwool culture of the sundew D. adelae. Tissue-cultured plantlets were raised as transplants in peatmoss. The transplants were planted directly into rockwool slabs primed to pH 6. Three levels of ammonium nitrate fertilizer were applied, the highest level of which approximated natural peat bog levels. Growth and development of the plants was monitored. Plants from each nitrogen treatment were harvested and subjected to extraction with toluene. Subsequently, high-performance gas chromatography was used to separate and quantify the naphthoquinones present in the extract. This method was used for three harvests: harvest of transplants, harvest after 2 months, and after 4 months of active growth.
The Gradient Concept: A Potential Nutritional Paradigm Shift
Authors: Geraldson C.M.
Published: February 2019

The conventional nutritional paradigm has been described as an empirical evaluation of how yield varies with nutrient application and is considered as a trial-and-error procedure. The gradient concept shifts the emphasis from variations in fertilizer application to one specific procedure designed to stabilize the ionic composition of the soil solution; thus providing the potential to enhance productivity beyond the limits of the trial-and-error procedure. By maximizing nutrient movement by diffusion and minimizing movement by mass flow (with the water), movement of nutrients and water to the root can by synchronized with removal by the root. A surface source of soluble nutrients (primarily N–K) in conjunction with a constant water table are the basic parameters. With the shift to a gradient-oriented procedure, commercial tomato yields in Florida (1970s) more than doubled. The Earth Box™, made of recycled plastic (manufactured by Laminations, Inc., Scranton, Pa.) is designed to maintain the parameters for a containerized gradient concept. Tomato yields have averaged 6 to 8 kg/plant (two plants/box). With the addition of side air spaces to the original air space between the media and the water table, the average yield increased by 20% to 30% with a maximum of 11.3 kg/plant (Fall 1996). With minimal water (for transpiration only), minimal management (maintaining the water table), minimal pollution (no leaching), and the associated nutritional stability, the containerized gradient concept has the potential to become a universal sustainable production system for the commercial grower as well as the home gardener.
Cropping and Fruit Growth in Redchief `Delicious': An Analysis of the Effect of NAA and Cytokinins
Authors: Bukovac Martin J. , Neilsen John C. , Hull Jerome
Published: February 2019

Generally, NAA is effective in inducing fruit thinning in `Delicious'. Although significant thinning may be induced, fruit size at harvest may not be closely related to crop load. Further, the magnitude of response to NAA may vary markedly between seasons. Herein, we present an analysis of response of `Redchief Delicious' over several years (tree age 11–14 years old) to high-volume sprays of NAA (15 mg·L–1), BA (25-50 mg·L–1), and CPPU (5 mg·L–1) at KFD of 8–12 mm. A single tree was used for each treatment replicated four to six times and response was measured by yield and fruit size distribution for each tree. In eight experiments over 4 years, NAA resulted in an average 22% reduction in yield, a 5.1% reduction in large fruit (70 mm+) and 2% reduction in small (<64 mm) fruit compared to NTC. There was a marked variation in response among years. Over 4 years, BA averaged a 5% decrease in yield, a 15% increase in large fruit and a 21% decrease in small fruit. In contrast, when NAA was combined with BA at 25-50 mg·L–1, yield decreased an average of 30%, large fruit decreased by 68%, and small fruit increased 8-fold (2.54 vs 20.6 kg/tree). CPPU alone (2-year study) had no significant effect on yield, but increased large fruit by 60% and significantly reduced production of small fruit. When CPPU was combined with NAA, yield was reduced in both years and the amount of large fruit was increased in 1995, but decreased in 1996. NAA had a very inhibitory effect on fruit size in 1996. One explanation may be that the crop was produced by lateral fruit (king flowers were lost to frost), and NAA has a greater inhibitory effect on lateral than king fruit. Results will be discussed in relation to studies with `Jonathan' and `Empire'.
Chemical Thinning of `Gala' Apples in California
Authors: Micke Warren C. , Grant Joseph A. , Yeager James T.
Published: February 2019

`Gala', the third most widely planted apple cultivar in California, requires early and precise thinning to produce good fruit size. Thus, chemical thinning would be ideally suited for this cultivar. However, the normally prolonged bloom for apples in California makes timing of chemical thinning applications difficult. In 1995 and 1996 trials, several chemical thinning treatments provided significantly reduced fruit set on `Gala' compared to the untreated control. Three treatments showed promise for commercial use: 1) carbaryl, two applications at petal fall and again at 10-15 mm diameter of the king fruit; 2) carbaryl plus NAD at petal fall; and 3) carbaryl plus 6-benzyladenine and GA4+7 (Accel®), two applications at petal fall and at ≈10 mm diameter of the king fruit. These treatments generally gave reduced fruit set per 100 flower clusters, fruit set per fruiting cluster and/or numbers of fruit removed by follow-up hand-thinning. None of these treatments showed evidence of phytotoxicity, and some increased fruit size over the untreated control.
Differential Fruit Load in Melon (Cucumis melo L.) Affects Shoot and Root Growth, and Vine Decline Symptoms
Authors: Wolff David W. , Leskovar Daniel I. , Black Mark C. , Miller Marvin E.
Published: February 2019

The effect of zero, one, and two fruits per vine on plant growth and reaction to Monosporascus root rot/vine decline were investigated. In the first study, four cultivars with differing levels of tolerance were evaluated (`Primo', `Deltex', `Caravelle', `Magnum 45'). Vine decline ratings were taken weekly during the harvest period for 4 weeks. Treatments with no fruit showed delayed and less-severe vine decline symptoms. Temperature also effected vine decline symptom expression. In a Fall test, with lower temperatures during fruit maturity, symptoms were delayed in all treatments and often absent in treatments with no fruit load. Vine decline symptom expression is greatly effected by physiological (fruit load) and temperature stress. A subsequent study was conducted to more precisely quantify the effect of various fruit loads on shoot/root partitioning and vine decline symptoms. In addition to growth parameters root disease ratings were taken. `Caravelle', the most-susceptible genotype, was grown under differing fruit loads as mentioned above in Weslaco and Uvalde, Texas. As fruit load increased, root size decreased. Increased vine decline symptoms were observed under higher fruit loads. The implications on germplasm screening and breeding for resistance will be discussed.
Using Seed Volatiles as a Possible Indicator for Seed Deterioration during Storage
Authors: Zhang Ming , Roos Eric E.
Published: February 2019

All kinds of plant seeds evolve volatile compounds during storage. However, a reliable deterioration forecast method is still not established using volatile evolution, even though some preliminary work indicated a relationship between volatile evolution and seed deterioration (Fielding and Goldsworthy, 1982; Hailstones and Smith, 1989; Zhang et al., 1993). Here we review some of the previous work concerning seed volatiles and present some more recent research on the effects of seed moisture content on deterioration. We found that volatile evolution from seeds was controlled by seed moisture level. Generally, seeds tended to evolve more hexanal and pentanal under extremely dry conditions (below 25% equilibrium RH). The production of hexanal and pentanal decreased with increasing seed moisture level. On the other hand, methanol and ethanol increased with increasing seed moisture. All of the volatile compounds accumulated in the headspace of the seed storage container during storage. Therefore, it should be possible to use different volatiles to indicate the deterioration of seeds stored under different moisture levels. We suggest that hexanal may be used for seed assessing deterioration under dry storage conditions (below 25% equilibrium RH), while ethanol may be used for seeds stored under higher moisture conditions (above 25% equilibrium RH). [References: Fielding, J.L. and Goldsworthy, A. (1982) Seed Sci. Technol. 10: 277–282. Hailstones, M.D. and Smith, M.T. (1989) Seed Sci. Technol. 17: 649–658. Zhang et al. (1993) Seed Sci. Technol. 21:359–373.]
Structural Changes in Lettuce Seed during Germination Altered by Genotype, Seed Maturation Temperature, and Priming
Authors: Sung Yu , Cantliffe Daniel J. , Nagata Russell T.
Published: February 2019

Thermotolerance in lettuce seed at high temperature was investigated using primed and nonprimed seed or seeds matured at 20/10°C and 30/20°C. During seed germination at 36°C, the structural changes of the seed coverings in front of the radicle tip were observed in an anatomical study. In all seeds during imbibition, regardless of seed maturation temperature or priming, a crack appeared on one side of the cap tissue and the endosperm separated from the integument in front of the radicle tip. Additional changes took place during imbibition: the protein bodies in the vacuoles enlarged and were gradually depleted, large empty vacuoles formed, the cytoplasm condensed, the endosperm shrank, the endosperm cell wall dissolved and ruptured, then the radicle elongated toward this ruptured area. The findings suggested that the papery endosperm layer presented mechanical resistance to lettuce seed germination and the weakening of this layer was a prerequisite to radicle protrusion at high temperature. Seeds of `Dark Green Boston', `Everglades', and PI 251245 matured at 30/20°C had greater thermotolerance than those matured at 20/10°C. Results of the anatomical study indicated that the endosperm cell walls in front of the radicle of seeds matured at 30/20°C were more easily disrupted and ruptured during early imbibition than seeds matured at 20/10°C, suggesting that these seeds could germinate quickly at supra-optimal temperatures. From anatomical studies conducted to identify and characterize thermotolerance in lettuce seed germination, it was observed that genotype thermotolerance had the ability to reduce physical resistance of the endosperm by weakening the cell wall and by depleting stored reserves.
Enhancement of Student Learning through Newsletter Assignments and Peer Review
Authors: Nonnecke Gail R. , Kastman Lee-Ann M. , Russell David R.
Published: February 2019

A 200-level course at Iowa State Univ., Principles of Horticulture, has included a communication across the curriculum assignment for the past seven semesters involving ≈425 students. Each undergraduate student develops and writes an individual student newsletter on topics and for an audience of the student's choice. The semester-long project motivates students to practice a professional communication task, and teaches technical horticultural material and writing skills. The newsletters contain at least two separate articles for an intended audience, providing the students with an opportunity to learn technical information in subjects in which they are intensely interested, but may not be taught in a principles course. Drafts of the articles and newsletter project are peer-reviewed by the students to model the professional review process, provoke critical thinking, and provide students with more feedback than they would otherwise receive from the instructor alone. Additionally, peer-review facilitates writing intensive courses for the instructor who wishes to focus course activities on writing, but has limited time or resources for reviewing writing assignments. Student newsletter articles are selected to be included in quarterly department and extension newsletters, providing students with a real-world use of a communication across the curriculum assignment.
Leadership Perspectives in Horticulture: Meeting the Needs of Horticulture Students Through Interdisciplinary Education
Authors: Zajicek Jayne M. , Townsend Christine D.
Published: February 2019

Placing the horticulture student on a path of professional development as a society-ready graduate for the 21st century takes more than technical knowledge. New types of team-oriented organizations are being created that were not even imagined a few years ago. To help empower students to survive in these organizations, the course “Leadership Perspectives in Horticulture” was created. This interdisciplinary course serves as a model for leadership skill instruction by incorporating the component of leadership development into a technical horticulture course. The objectives of this course are to provide academic and historical perspectives in technical horticulture issues, develop skills in leadership, problem solving, and team building, complete a theoretical study of specific leadership models, and blend theoretical leadership models with horticulture issues by completing a problem solving experience. An overview of the course in addition to changes in leadership behavior of students will be discussed.
Development of a Hypertext, Graphics-rich Glossary for Use in Teaching Undergraduate Plant Propagation
Authors: Durham Richard
Published: February 2019

Computer-aided instruction is becoming ever-more popular in higher education. The visual nature of horticultural instruction makes it particularly amenable to teaching with computer-based graphic and hypertext formats. The Texas Tech Horticulture Faculty is interested in developing multimedia materials for instruction. Thus far, attention has been directed mainly at courses in introductory horticulture and plant propagation. For the plant propagation course, one activity is the construction of a hypertext glossary in the area of asexual propagation. Topics included in the glossary include propagation by cutting, layering, budding, grafting, and micropropagation. Multiple-choice exams are also available in the module so that students can assess their understanding of the subject matter presented. The glossary is not meant to replace lecture attendance, rather students will be encouraged to access the material outside of class to supplement lecture material. The student is presented a narrative with hot-text links that when activated, pull up additional information with a combination of text and graphics. Alternatively, students can access the same information from a hierarchical topic menu. Plant propagation instructors may also benefit from the glossary's ready supply of visuals that can be down-loaded and used in a traditional classroom format.
Could Irrigation Increase Irish Potato Yields in the Southeast?
Authors: Simonne Eric H. , Kemble Joseph M. , Caylor Arnold W.
Published: February 2019

Most potato (Solanum tuberosum L.) is produced as a non-irrigated crop in the southeastern United States. This practice makes potato yields dependent on rainfall pattern and amount. An irrigation scheduling method based on a water balance and class A pan evaporation data (Ep) was evaluated in Spring 1996 on a fine sandy loam soil with `LaSoda' potatoes. Planting date was 9 Apr. and standard production practices were followed. The model was (12.7 DAH + 191) * 0.5 ASW = D(DAH-1) + [Ep (0.12 + 0.023 DAH - 0.00019 DAH*DAH) - R(DAH) - I(DAH)], where DAH is days after hilling (DAH = 0 on 14 May), ASW is available soil water (0.13 mm/mm), D is soil water deficit (mm), R is rainfall (mm) and I is irrigation (mm). Root depth expanded at a rate of 13 mm/day to a maximum depth of 305 mm. Root depth at hilling was 191 mm. Controlled levels of water application ranging between 0% and 161% of the model rate were created with drip tapes. The model scheduled irrigations on 35, 39, 43 and 49 DAH. On 85 DAH, potatoes were harvested and graded. Irrigation influenced total yield, marketable yield, and combined US #1 grades (P < 0.01; R2 > 0.85). Mean marketable yields were 19, 28, and 21 t/ha for the 0%, 100%, and 160% irrigation rates, respectively. These results suggest that supplementing rainfall with irrigation and controlling the amount of water applied by adjusting irrigation to actual weather conditions could increase potato yields. Excessive water, as well as limiting water, reduced potato yields.
Incremental Effects of Plasticulture System Components on the Growth and Yield of Three Echinacea Species
Authors: Bowen Pat A.
Published: February 2019

The incremental effects of adding plasticulture system components in Echinacea production were determined after one growing season. E. purpurea, E. angustifolia, and E. pallida, were grown in four cultural systems: flat ground, raised bed, raised bed with plastic mulch, and raised bed with plastic mulch and a polyethylene mini-tunnel. Trickle irrigation was used in all systems, with fertilizers injected monthly into the irrigation water. Plant spacing was 0.22 m in rows spaced 0.25 m apart, with 1.30 m between each set of three rows, giving a density of 75,758 plants/ha. In all systems, root dry weight was highest for E. pallida, followed by E. purpurea, then E. angustifolia. Each system component increased the root dry weight, but the percent increase differed among species. The mean root dry weights from the flat ground system were 35.8, 17.1, and 12.0 g/plant for E. pallida, E. purpurea, and E. angustifolia, respectively; whereas from the system including all components they were 51.1, 27.2 and 21.7 g/plant, respectively. The leaf dry weight of E. purpurea also increased with each system component added, but the stem dry weight was reduced by the mini-tunnel. All species produced more flowers when grown on raised beds than when grown on flat ground. The effects of the plastic mulch and mini-tunnel on flower production differed among species.
Compost and Plastic Mulch Sustain Melon Growth over Three Years
Authors: Wells Otho S. , Mitchell James R.
Published: February 2019

For 2 successive years, compost at rates of 0, 12, 24, and 48 t/acre were applied to a previously highly infertile field. Timothy was grown and harvested for these 2 years. Subsequently, for 3 consecutive years, through 1996, `Earliqueen' muskmelons were grown in the same plots without any additional compost being added. Subplots consisted of plastic and paper mulch and bare soil. Yields increased with increasing rates of compost for each of the 3 years, although yields for all treatments declined in the 3rd year. Highest yields were with the higher rates of compost coupled with IRT mulches and red mulch. Generally, organic matter and pH increased with increasing compost rates. Foliar diseases were suppressed with compost; however, there was an interaction of suppression with plastic mulches.
Use of 13CO2 as a Tool to Investigate Carbon Partitioning in Field and Greenhouse-grown Apple Trees
Authors: Lombardini Leonardo , Toselli Moreno , Flore James A.
Published: February 2019

Instrumentation to measure soil respiration is currently readily available. However, the relationship between soil respiration and root activity or root mass is not known. Herein we report on preliminary result using a 13CO2 pulse to the foliage to determine if 13C respiration can be related to either root activity or root mass. An experiment was performed in the field on a 5-year-old apple tree (cv. Jonagold on M7). The tree canopy was enclosed in a Mylar® balloon and 2.1 g 13CO2 were pulsed in the balloon for 1 hr. After the pulse, air emitted by the soil and selected roots was collected every 6 hr for 8 days, by bubbling it in 2 M NaOH. 13C/12C ratios were measured with the mass spectrometer. The emission of 13CO2 from the roots gradually increased after the pulse reaching a peak after 100 hr. The emission trend was not linear, but it seemed related to soil temperature. Leaves and fruit were also collected daily. 13C content in leaves was 1.15% right after the pulse, but it progressively decreased to 1.09% at the end of the experiment. The experiment was then repeated on 12 potted apple trees (cv. Redcort on M7) in greenhouse conditions. Six of them were maintained well-watered, whereas six plants were subjected to a mild water stress, by watering them with half of the volume of water used for well-watered plants. After the two soil moisture levels were achieved, the tree canopies of all the 12 trees were pulsed. Leaves, stems, and roots were ground and run in the mass spectrometer. The results of root emission rate were found to be similar to the field experiment. Results also indicated that, in our experiment, stress did not affect root respiration rate. Specific details of the physiology data will be presented.
The Relationship between Rubisco Activity and Photosynthesis in Apple Leaves with Different Nitrogen Content
Authors: Cheng Lailiang , Fuchigami Leslie H.
Published: February 2019

Based on the curvilinear relationship between carboxylation efficiency and leaf N in apple leaves, we hypothesized that deactivation of Rubisco accounts for the lack of response of photosynthesis to increasing leaf N under high N supply. A wide range of leaf N content (from 1.0 to 5.0 g·m–2) was achieved by fertigating bench-grafted Fuji/M26 apple trees for 6 weeks with different N concentrations using a modified Hoagland solution. Analysis of photosynthesis in response to intercellular CO2 under both 21% and 2% O2 indicated that photosynthesis at ambient CO2 was mainly determined by the activity of Rubisco. Measurements of Rubisco activity revealed that initial Rubisco activity increased with leaf N up to 3.0 g·m–2, then leveled off with further rise in leaf N, whereas total Rubisco activity increased linearly with increasing leaf N throughout the leaf N range. As a result, Rubisco activation state decreased with increasing leaf N. Photosynthesis at ambient CO2 and carboxylation efficiency were both linearly correlated with initial Rubisco activity, but showed curvilinear relationships with total Rubisco activity and leaf N. As leaf N increased, photosynthetic nitrogen use efficiency declined with decreasing Rubisco activation state.
Photometric Measurements of Rubisco Activity in Leaves of Deciduous Fruit Crops
Authors: Cheng Lailiang , Fuchigami Leslie H.
Published: February 2019

Ribulose bisphosphate carboxylase/oxygenase (Rubisco) initiates the photosynthetic carbon metabolism;therefore, its activity has been measured in many physiological studies. However, information on in vitro Rubisco activity from leaves of deciduous fruit crops is very limited and the reported activities are suspiciously low. We measured Rubisco activity in crude extracts of leaves of apple, pear, peach, cherry, and grape by using a photometric method in which RuBP carboxylation was enzymically coupled to NADH oxidation. Replacing polyvinylpyrrolidone with polyvinylpolypyrrolidone in the extraction solution significantly increased extractable Rubisco activity. Depending on species, freezing leaf discs in liquid nitrogen followed by storage at –80°C for only 24 hr reduced both initial and total Rubisco activity to 5% to 50% of that obtained from fresh leaves. Initial Rubisco activity from fresh leaf tissues of all species was well correlated with maximum Rubisco activity (Vcmax) estimated from gas exchange; an exception was pear, where initial Rubisco activity was higher than Vcmax. In most cases, initial Rubisco activity was approximately two to three times higher than net photosynthesis.
Elevated CO2 Increases Growth and Photosynthetic Efficiency of Citrus Rootstock Seedlings
Authors: Syvertsen J.P.
Published: February 2019

The objectives of these greenhouse experiments were to determine the effects of elevated CO2 on growth, mineral nutrition, and gas exchange physiology of seedlings of four commercial Citrus rootstocks. We grew well-watered and fertilized seedlings of `Volkamer' lemon (VL), `Cleopatra' mandarin (CL), `Swingle' citrumelo (SW), and `Troyer' citrange (TC) cultivars (in decreasing order of vigor) in unshaded, air-conditioned greenhouses at ambient CO2 (350 μmol/mol) or 2x ambient CO2 for 5 months. CL was the smallest cultivar, had the lowest root/shoot (r/s) ratio,and lowest rates of CO2 assimilation (A) of leaves, transpiration (E), and water-use efficiency, (A/E). Overall, daily whole-plant water use was correlated with single-leaf E. Elevated CO2 increased both shoot and root growth similarly; therefore, r/s was not affected. Elevated CO2 increased A, leaf dry wt/area, and leaf C, but decreased transpiration and leaf N so that leaf C/N, A/N, and A/E all increased. Although plant size of the four cultivars ranked similarly at both ambient and high CO2, the more-vigorous cultivars grew proportionately more at high CO2 than the less-vigorous cultivars. Growing cultivars at elevated CO2 can yield insights into mechanisms determining vigor and relationships between A and plant growth.
Epicormic Sprouts from Branch Segments of Mature Juglans nigra L. as an Explant Source for in Vitro Culture
Authors: Van Sambeek J. W. , Lambus Lisa J. , Preece John E.
Published: February 2019

At monthly intervals for 1 year, one branch was removed from the lower crown of three 30-year-old trees of black walnut (Juglans nigra L.). The basal 1.3 m of each branch was cut into four 32-cm-long segments that were placed horizontally in shallow plastic trays filled with perlite and watered daily with tap water. Branch segments cut early in the dormant season (29 Sept., 31 Oct., or 1 Dec.) or shortly after flushing (6 June) produced few, if any, epicormic sprouts. Approximately half the branch segments cut on 3 Jan. or 3 Feb. produced one sprout that elongated slowly. Most branch segments cut in the late dormant season (2 Mar., 30 Mar., 3 May) or growing season (5 July, 4 Aug., 6 Sept.) produced one or two sprouts >20 mm long. To prepare explants for in vitro culture, the terminal 2.5 cm was harvested when sprouts exceeded 3.0 cm, trimmed of all leaves, and disinfested. Explants were placed vertically in liquid Long & Preece (LP) medium supplemented with 3% sucrose, 0.3 μM TDZ, 0.05 μM IBA, and 1 μM BA. When shoots began to elongate (4 to 6 weeks), they were then placed horizontally on agar-solidified LP medium with liquid LP overlays to induce axillary shoot proliferation. Advantages of forcing epicormic sprouts on large branch segments are: 1) they can be a source of in vitro explant material for 6 to 7 months a year, 2) aseptic cultures can be easily obtained, 3) shoots from the base of branches may show more juvenility than shoots forced from branch tips, 4) softwood shoot wilting is not a problem as with forcing shoots from branch tips, 5) the procedure does not require preparing and changing forcing solutions, and 6) branch segments should have more stored food than dormant branch tips for forcing softwood growth.
A Unique Bilayer Method for Rooting of in Vitro-produced Shoots of Chestnuts (Castanea spp.)
Authors: Miller Virginia I. , Read Paul E. , Szendrák Erika
Published: February 2019

The American Chestnut Foundation (ACF) has conducted a breeding program aimed at developing blight-resistant chestnut trees exhibiting the phenotype of American Chestnut [Castanea dentata (Marsh) Borkh]. Because such plants are difficult to propagate, we developed a protocol for in vitro multiplication of candidate blight-resistant plants resulting from the ACF breeding programs. Dormant shoots were taken from 5- to 8-year-old trees and forced, producing softwood growth for use as a source of explants for shoot multiplication. Best shoot proliferation took place on WPM containing 0.2 mg BA/L. Explant material for the rooting experiments was taken from 6- to 12-month-old proliferating cultures. The basal rooting medium consisted of WPM containing 0.01 mg IBA/L and was overlaid with a thin opaque layer. Rooting was enhanced overall with this bilayer approach. A “D/W” medium (DKW and WPM) was also used as a rooting medium containing 0.01 mg IBA/L and 0.2 mg BA/L, which further enhanced leaf quality and rooting for some genotypes. After several transfers on the bilayer system, explant growth appeared to become less juvenile in stem and leaf development and more analogous to mature later-season growth. The rooting responses and the time for rooting to be induced were highly variable among the different genotypes.
Rooting Ability of Microcuttings of Desert Almond (Amygdalus arabica Oliv.)
Authors: Qrunfleh Mostafa M. , Al-Eisawi Dawud M. , Hozain Moh'd I.
Published: February 2019

Three experiments were performed to establish rooting procedure of Amygdalus arabica Oliv. Two-centimeter shoots grown in vitro on MS medium supplemented with IBA at 0.01 mg/L, BA 0.2 mg /L, sucrose 30.0 g/L, and agar 6.0 g/L were used in rooting microcuttings using three experiments: 1) IAA, IBA, and NAA at concentrations of 0.5, 1.0, and 1.5 mg/L during the whole experiment with 4 days of dark period; 2) effect of dark and light conditions and IBA and NAA treatments during root induction period (4 days), then shoots were transferred onto free plant bioregulators (PBR), MS medium until end of the experiment; 3) Rooting microcuttings after quick dipping in different NAA concentrations (0.0, 250, 500 ppm) or induced for 6 days in root induction medium (MS) with 3.0 mg/L NAA, then shoots were transferred onto containers containing 200 ml of peatmoss, perlite, or peatmoss: perlite mixture (1:1, v/v). Results of the first experiment showed that best rooting was obtained with NAA, followed by IBA. In the second experiment, dark treatments improved rooting percentage and root length. NAA was superior to IBA in root number. Higher IBA and NAA (3.0 mg/L) concentrations gave the best rooting. In the third experiment, induced shoots transferred to perlite gave better root number and rooting percentage followed by peatmoss: perlite mixture. Regardless of rooting medium, insignificant differences between 250 and 500 ppm NAA in root number and rooting percentage were obtained. In the quick dip method, NAA was superior to the in vitro root induction method. The highest rooting percentage (86.7%) was obtained with perlite at either 250 or 500 ppm, replacing by that the traditional in vitro rooting and obtaining plantlets that are more ready to grow under in vivo conditions.