bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Root Zone Calcium on Shoot Tip Necrosis and Apical Dominance of Potato Shoot: Simulation of This Disorder by Ethylene Glycol Tetra Acetic Acid and Prevention by Strontium
Authors: Ozgen Senay , Busse James S. , Palta Jiwan P.
Published: February 2019

The important roles of calcium on plant growth and development including cell division and cell elongation is well documented. The purpose of the present study was to determine the impact of root zone calcium on the growth and health of potato apical meristem and on the maintenance of apical dominance. For this purpose, single-node potato cuttings (Solanum tuberosum L. cv. Dark Red Norland) were grown in sterilized modified Murashige and Skoog (MS) media containing varying concentrations of calcium (1 to 3000 μM). After 13 to 30 d of growth, plantlets were harvested and data for height of the main shoot and for the number of axillary shoots produced were recorded. Plantlets were ashed and tissue calcium concentration was determined. Shoot height was retarded with decreasing concentration of calcium in the media. Calcium deficiency induced shoot tip injury and loss of apical dominance. Tip injury was followed by the development of axillary shoots. The number of axillary shoots increased from one to 21 as calcium concentration in the media decreased from 3000 to 1 μM. At calcium concentration of 1500 μM or higher, there was a single main shoot with no axillary shoots. Addition of ethylene glycol tetra acetic acid (EGTA), a calcium chelator, to the media with 2720 μM calcium (sufficient calcium) resulted in the development of shoot injury and in the formation of axillary shoots. Calcium deficiency injury symptoms were prevented by the addition of a calcium analog, strontium, to MS media deficient in calcium. Strontium has been reported to strongly bind to plant cell walls and the inclusion of strontium prevented injury in shoots of plants grown on calcium-deficient media. These results suggest that strontium is able to mimic the role of calcium in the maintenance of cell wall integrity and supports previous studies that showed that calcium deficiency results from cell wall collapse of the subapical cells.
Rotation with Cover Crops Suppresses Weeds and Increases Plant Density and Yield of Strawberry
Authors: Portz Dennis N. , Nonnecke Gail R.
Published: February 2019

Yield of strawberry grown continuously on the same site often declines over time as a result of proliferation of weed seeds and pathogenic organisms in the soil. Plots were established and maintained in seven different cover crops and as continuous strawberry or continuous tillage for 10 years (1996 to 2005) in a site that was previously in strawberry production for 10 years (1986 to 1995). Cover crops included blackeyed Susan (Rudbeckia hirta L.), sorghum Sudangrass [Sorghum bicolor (L.) Moench], marigold (Tagetes erecta L.), big bluestem (Andropogon gerardii Vitman), perennial ryegrass (Lolium perenne L.), switchgrass (Panicum virgatum L.), and Indiangrass [Sorghastrum nutans (L.) Nash]. Treatments were ended in 2005 and plots were planted with ‘Honeoye’ strawberry in a matted row. Effectiveness of soil pretreatments in reducing weed populations and enhancing strawberry production was evaluated for four growing seasons by quantifying weed growth by type and biomass and strawberry plant density and yield. The results indicate that matted-row strawberry production plots that were either in continuous tillage or established in S. bicolor, P. virgatum, or A. gerardii before planting strawberry had lower weed biomass and greater strawberry plant establishment and yield than plots established in L. perenne or R. hirta or that had supported continuous strawberry production.
Apple Fruitlet Ethylene Evolution and MdACO1, MdACS5A, and MdACS5B Expression after Application of Naphthaleneacetic Acid, 6-Benzyladenine, Ethephon, or Shading
Authors: Kolarič Jure , Mavrič Pleško Irena , Tojnko Stanislav , Stopar Matej
Published: February 2019

Abscission of apple (Malus ×domestica Borkh.) fruitlets is associated with increased ethylene evolution, although the role of ethylene is not clear. Fruitlet ethylene evolution and expression of ethylene-related MdACO1, MdACS5A, and MdACS5B genes were followed in the abscission zone (AZ) and fruit cortex (FC) of king and lateral fruitlets of ‘Golden Delicious’/M.9 after spraying with 15 mg·L−1 naphthaleneacetic acid (NAA), 150 mg·L−1 6-benzyladenine (BA), 500 mg·L−1 ethephon, and after 3 days 96% shading, all applied at a mean 10 mm fruitlet diameter. Lateral fruitlets (LF) were more susceptible to abscission after treatment with chemical thinners or shading compared with king fruitlets (KF) in which only ethephon-treated KF abscised later. On KF, only ethephon increased fruitlet ethylene evolution, MdACO1 expression in FC and AZ 8 days after treatment (DAT), and abscission of KF 10 DAT, but the other treatments did not. Although ethephon increased MdACO1 expression in FC of KF 8 DAT, the expression of MdACS5A and MdACS5B remained unchanged. On LF, all treatments at 8 DAT increased ethylene evolution and MdACO1 expression in FC and enhanced abscission 10 to 22 DAT. Expression of MdACS5A and MdACS5B in FC of LF 8 DAT was expressed at a lower level compared with MdACO1. In the AZ of both KF and LF, only ethephon increased expression of MdACO1, MdACS5A, and MdACS5B.
Stolon Growth and Tillering of Experimental Zoysiagrasses in Shade
Authors: Okeyo David O. , Fry Jack D. , Bremer Dale J. , Chandra Ambika , Genovesi A. Dennis , Engelke Milton C.
Published: February 2019

Zoysiagrass (Zoysia spp.) grown under shade on golf courses and in home lawns is slow to recover from damage and declines in quality over time. We evaluated stolon growth and tillering of ‘Meyer’ and Chinese Common (both Z. japonica Steud.); ‘Zorro’, ‘Diamond’, and ‘Cavalier’ [all Z. matrella L. (Merr.)]; ‘Emerald’ (Z. matrella × Z. pacifica Goudsw.); and six experimental progeny from ‘Emerald’ × Z. japonica and reciprocal crosses of Z. japonica × Z. matrella under silver maple (Acer saccharinum L.) shade and in full sun in 2008 and 2009 in Manhattan, KS. A single 6-cm diameter plug was planted in the center of 1.2 m × 1.2-m plots, and data were collected weekly on the number of stolons, stolon elongation, and number of stolon branches. Tiller number was collected at the start and end of each study period, and biomass (excluding roots) was determined at the end of each season. Zoysiagrasses under an average of 76% tree shade exhibited reductions of 38% to 95% in stolon number; 9% to 70% in stolon length; 10% to 93% in stolon branching; and 56% to 98% in biomass. Seven of the 10 grasses exhibited a decline in tiller number in each experiment; none of the grasses differed from ‘Meyer’ in percentage change in tiller number under shade. ‘Emerald’, ‘Cavalier’, ‘Zorro’, and several progeny from crosses between ‘Emerald’ × Z. japonica or reciprocal crosses of Z. matrella × Z. japonica produced more, longer, or more highly branched stolons than ‘Meyer’, suggesting they may have improved recovery potential in shade.
Screening and Characterization of 11 Novel Microsatellite Markers from Viburnum dilatatum
Authors: Dean Deborah , Wadl Phillip A. , Wang Xinwang , Klingeman William E. , Ownley Bonnie H. , Rinehart Timothy A. , Scheffler Brian E. , Trigiano Robert N.
Published: February 2019

Viburnum dilatatum is a popular and economically important ornamental shrub. The wide range of desirable horticultural traits, paired with a propensity for seedlings to become invasive, has created interest in the genetics and breeding of this species. To investigate the genetic diversity of V. dilatatum, microsatellite loci were identified from a GT-enriched genomic library constructed from V. dilatatum ‘Asian Beauty’. Eleven microsatellite loci have been characterized on a group of 16 different related V. dilatatum cultivars and hybrids. Two to 12 alleles were identified per locus, and the polymorphism information content (PIC) values ranged from 0.36 to 0.87. Expected heterozygosity (He) ranged from 0.48 to 0.88 and observed heterozygosity (Ho) ranged from 0 to 0.73. This set of molecular markers also exhibited expected transferability between various V. dilatatum cultivars and two hybrids with V. japonicum. As a consequence, these markers will aid in breeding for new cultivar development, assist with early detection and screening of plants that have escaped cultivation, and are expected to help in refining the phylogenetic relationship of V. dilatatum to other species and genera within the Adoxaceae.
Phenology, Canopy Composition, and Fruit Quality of Yellow Pitaya in Tropical Taiwan
Authors: Jiang Yi-Lu , Lin Tzong-Shyan , Lee Ching-Lung , Yen Chung-Ruey , Yang Wen-Ju
Published: February 2019

Yellow pitaya, Selenicereus megalanthus (Schum. ex. Vaupel) Moran, is a potential new fruit in Taiwan. It sprouts mostly in winter and flowers in late spring and fall. In this study, an average of 60% shoots within canopies flowered. Shoots sprouted in the current winter flowered in fall and produced winter fruits, and shoots sprouted earlier than the current winter flowered in late spring and produced summer fruits. Floral buds on most shoots appeared at the distal end. The weight, pulp percentage, and total soluble solids of winter fruits were significantly higher than those of summer fruits. The number of black seeds was positively correlated with pulp weight (R2 = 0.87). The total soluble solids in the core region of winter fruits reached 22.7 °Brix, higher than that in other regions. Future efforts to improve yellow pitaya production in Taiwan include increasing winter fruit production by enhancing growth of the current year's new shoots through proper canopy management and increasing the size of summer fruit by artificial pollination, fruit thinning, and other means.
The Role of Temperature in the Late-season Decline in Soluble Solids Content of Strawberry Fruit in a Subtropical Production System
Authors: MacKenzie Steven J. , Chandler Craig K. , Hasing Tomas , Whitaker Vance M.
Published: February 2019

In west–central Florida, strawberries (Fragaria ×ananassa Duch.) are harvested from early December to late March. The peak harvest occurs at the end of the season and lasts ≈1 month, usually from late February to mid-March. As the peak harvest progresses and temperatures increase, fruit become smaller and the soluble solids content (SSC) of fruit declines. The main objective of this study was to determine whether the progression of peak harvest results in a decline in SSC independent of temperature. In 2007 and 2008, recently opened flowers were tagged in the field on the first week into the peak bloom (WPB) and for 3 additional weeks thereafter. Three days after tagging, plants were transplanted to one of two constant temperature environments (15 or 22 °C). At maturity, the weight, SSC, and fruit development period (FDP) of tagged fruit were recorded. Fruit SSC was lower at the higher temperature (5.2% at 22 °C versus 6.5% at 15 °C) in both years. In 2007, SSC was not correlated with WPB, and in 2008, SSC was positively correlated with WPB at constant temperatures. In addition, the coefficient of determination (r2) for a regression of SSC on mean temperature over the period 8 days before harvest was 0.73 for fruit harvested from fields between 2003 and 2009. These results indicate that rising temperature is a major factor responsible for the late-season decline of SSC in strawberry fruit in a subtropical production system.
L-Citrulline Levels in Watermelon Cultigens Tested in Two Environments
Authors: Davis Angela R. , Webber Charles L. , Fish Wayne W. , Wehner Todd C. , King Stephen , Perkins-Veazie Penelope
Published: February 2019

Producers of fresh fruits and vegetables face increasing production costs and international market competition. Growers who can offer high-quality watermelons [Citrullus lanatus (Thumb.) Matsum. & Nakai] that are also highly nutritious will have better market opportunities. To accomplish that, germplasm must be identified that has enhanced phytonutrient levels. Surprisingly, there is little information on the genetics of nutritional quality in watermelon. The present study was performed on 56 watermelon cultivars, breeding lines, and PI accessions (hereafter collectively referred to as cultigens) to determine the importance of genotype and environmental effects on L-citrulline concentration in fruit, an amino acid that helps regulate blood pressure. Our results demonstrated that L-citrulline concentration was affected by environment and the amount of environmental effect varies among cultigens. The mean of fruit tested in Lane, OK, was 3.10 mg·g−1 fresh weight and in College Station, TX, it was 1.67 mg·g−1 fresh weight. All cultigens had a higher mean L-citrulline concentration when grown in Lane, OK, instead of College Station, TX. Additionally, the L-citrulline concentration varied considerably within cultigens; i.e., ‘Congo’ had a 1.26 to 7.21 mg·g−1 fresh sample deviation. The cultigen ‘AU-Jubilant’ had the most stable L-citrulline concentration (2.23 to 4.03 mg·g−1 fresh deviation) when tested from one location. Environment did not significantly increase within-genotype variation (average se of 10 cultigens tested at each location was ± 35.3% for College Station, TX, and ± 32.9% for Lane, OK). L-citrulline concentration did not correlate with watermelon type (open-pollinated or F1 hybrid) or flesh color (red, orange, salmon yellow, or white). Differences among cultigens for L-citrulline were large (1.09 to 4.52 mg·g−1 fresh sample). The cultigens with the highest L-citrulline concentration were ‘Tom Watson’, PI 306364, and ‘Jubilee’. These could be used to develop cultivars having a high concentration of L-citrulline.
Impact of Environments on the Accumulation of Capsaicinoids in Capsicum spp.
Authors: Gurung Tulsi , Techawongstien Suchila , Suriharn Bhalang , Techawongstien Sungcom
Published: February 2019

The use of a chili fruit is distinguished by its capsaicinoid content, which shows many beneficial effects in food and pharmaceutical applications. However, chilies exhibit wide variations in the accumulation of capsaicinoids depending on their genotype and environmental interaction. Therefore, we conducted experiments to evaluate the capsaicinoid responses of 14 cultivars of chili across four different elevations. Experiments were conducted during the rainy season from June to Oct. 2009 at elevations of 200 m asl (Khon Kaen) and 680 m asl (Chiang Mai) in Thailand and from Apr. to Sept. 2010 at elevations of 1400 m asl (Lobesa) and 1630 m asl (Kabesa) in Bhutan. A high-performance liquid chromatography technique was used to determine capsaicin and dihydrocapsaicin. Significant differences were observed among the cultivars, the locations, and the cultivar-by-location interactions. Large variations of cultivar effects indicate that it is possible to select cultivars for capsaicinoid concentration that are adapted over a wide range of environments. Average capsaicin, dihydrocapsaicin, and total capsaicinoids were greater at higher elevations in a particular year. There was significant correlation between capsaicin and total capsaicinoid contents with elevations, but capsaicinoid yield showed negative correlation. Small-fruited cultivars with high pungency showed consistent capsaicinoid production over different environments. Dallay khorsaney, KKU-P-22006, KKU-P-31141, and KKU-P-21041 cultivars showed high stability for pungency, producing high capsaicinoids at all four locations.
Effect of Plant Species and Benomyl on Lead Concentration and Removal from Lead-enriched Soil
Authors: Zheljazkov Valtcho D. , Astatkie Tess
Published: February 2019

Some agricultural soils in North America are lead (Pb)-enriched as a result of the application of lead arsenate (PbHAsO4) insecticide. A controlled-environment experiment was conducted with Pb-enriched Canning soil series in Nova Scotia, Canada, to evaluate the remediation potential of 10 plant species in combination with the fungicide benomyl applied as a soil drench to suppress mycorrhizae. Overall, the highest biomass was provided by yellow poppy followed by Indian mustard and thorn apple. The application of benomyl increased Pb concentration in thorn apple tissue but not in the other crops. The phytoremediation potential (Pb removal with the harvested biomass) was higher with clary sage, alyssum, garden sage, and Indian mustard with benomyl treatments and lower in the Swiss chard, thorn apple without benomyl, and in the geranium with benomyl treatments. The results suggest that some plants can be used for phytoremediation of mildly Pb-contaminated soils.
Seasonal Variation in Glucosinolate Accumulation in Turnip Cultivars Grown with Colored Plastic Mulches
Authors: Justen Veronica L. , Cohen Jerry D. , Gardner Gary , Fritz Vincent A.
Published: February 2019

Glucosinolates (GSLs) are thioglucosides with important properties for plant defense and human health. The objective of this study was to quantify yield and GSL concentration in turnip (Brassica rapa subsp. rapa) roots and shoots as influenced by colored plastic mulches. Four turnip cultivars (‘Just Right’, ‘Purple Top’, ‘Royal Crown’, and ‘Scarlet Queen’) were grown over five mulch treatments: white, yellow, silver, red, blue, and a bare soil control in both a May and an August planting in 2006 and 2007. Yield varied by variety; however, there was no consistent relationship between mulch treatment and yield. Glucosinolate concentrations and profiles varied with tissue type, genotype, and environmental factors, including temperature and planting date. Mulch-dependent increases in GSL concentrations were not consistent across tissue types, cultivars, planting dates, and years of the study, possibly as a result of differences in climatic factors and mulch-dependent changes in soil temperature between planting dates and years of the study.
The Effect of Growth Medium Temperature on Corn Salad [Valerianella locusta (L.) Laterr] Baby Leaf Yield and Quality
Authors: Costa Luisa Dalla , Tomasi Nicola , Gottardi Stefano , Iacuzzo Francesco , Cortella Giovanni , Manzocco Lara , Pinton Roberto , Mimmo Tanja , Cesco Stefano
Published: February 2019

Soil temperature has a crucial impact on physiological processes and growth of plants with important consequences for plant productivity and food safety including nitrate accumulation in leaf blades of leaf vegetables. Consumer demand for high-quality, fresh-cut vegetables has increased rapidly in the last decades, and temperature modulation can help control nitrate concentration in fresh vegetables, an important trait of product safety. Corn salad plants [Valerianella locusta (L.) Laterr., cultivar Gala] were grown at three root temperatures (15, 20, and 25 °C) in a floating system. This experimental setup allowed to directly evaluate the effect of root temperature on yield and plant quality excluding the effect on soil processes and properties. Nutrient solution was renewed weekly and kept aerated while air temperature was maintained constant at 20 °C for all treatments during the entire time of experiments. At harvest, plants were collected, the shelf life evaluated, and the nutrient uptake [NO3−, iron (Fe) from 59Fe-o,oEDDHA, and 35SO42−] and mineral content were determined. Results showed that growing conditions at 20 °C of the nutrient solution led to the best plant performance in terms of yield, nitrate content at leaf level, root biomass, leaf area, and greenness with positive effects on postharvest quality, i.e., less rapid leaf loss of greenness and leaf fresh weight (FW) loss during conservation at 4 °C. At this temperature condition of the nutrient solution, it has also been observed an enhanced functionality of mechanisms involved in the acquisition of nutrients like NO3−, Fe, and SO42−, which are known to play an important role in nitrate level in leaf tissues of crops. Plants grown at 15 °C showed minor growth, whereas the nutrient solution at 25 °C caused stress for the plants affecting negatively the quality and yield. Overall, the results obtained showed that root temperature plays a fundamental role in several plant processes that affect yield and its quality; for hydroponic system cultivations, a level of growing-medium temperature close to that of the surrounding air seems suitable.
Changes in the Phytoremediation Potential of Indoor Plants with Exposure to Toluene
Authors: Kim Kwang Jin , Yoo Eun Ha , Jeong Myeong Il , Song Jeong Seob , Lee Seung Youn , Kays Stanley J.
Published: February 2019

Changes in phytoremediation efficiency after repeated exposures (three) to toluene (1.3 ppm) were assessed in 26 species and two additional cultivars of indoor plants. There was a rapid increase in toluene removal efficiency in 27 of the 28 crops with the greatest increase between the first and second exposure (i.e., after 3 days). The increase in efficiency between the first and third exposure ranged from 378 μg·m−3·h−1·m−2 leaf area in Pinus densiflora to –16.6 in Salvia elegans with a mean of 156 for all crops. Percent change ranged from 614 (Pittosporum tobira) to –8 (Salvia elegans) but was not necessarily indicative of phytoremediation value of a species. Rapid changes in phytoremediation efficiency in response to exposure to toluene appear to be widespread in plants and may be the result of an effect on gene expression in the plant and/or certain soil microbes or changes in the population density of toluene-metabolizing microbes. Increasing toluene removal efficiency is advantageous and as a consequence, a better understanding of the mechanism(s) operative may improve use of the response for practical applications.
Overcoming Dormancy and Enhancing Germination of Sphaeralcea munroana Seeds
Authors: Kildisheva Olga A. , Dumroese R. Kasten , Davis Anthony S.
Published: February 2019

The results of a series of experiments involving a variety of dormancy-breaking treatments indicate that Munro's globemallow [Sphaeralcea munroana (Douglas) Spach] seeds are physically dormant, possess a cap-like structure in the occlusion of the water gap, which inhibits imbibition, and can be artificially dislodged through boiling water scarification. The highest germination capacity (93%) was achieved by mechanical scarification of previously stored seeds. Exogenous application of a gibberellin solution and cold stratification failed to enhance germination compared with scarification alone, indicating an absence of additional dormancy types. These results should improve the usefulness of this drought-tolerant perennial for landscaping and restoration given its effectiveness in soil stabilization, tolerance to a variety of soil types, extreme temperatures, and ecological importance.
A Review of Elevated Atmospheric CO2 Effects on Plant Growth and Water Relations: Implications for Horticulture
Authors: Prior Stephen A. , Runion G. Brett , Marble S. Christopher , Rogers Hugo H. , Gilliam Charles H. , Torbert H. Allen
Published: February 2019

Empirical records provide incontestable evidence for the global rise in carbon dioxide (CO2) concentration in the earth's atmosphere. Plant growth can be stimulated by elevation of CO2; photosynthesis increases and economic yield is often enhanced. The application of more CO2 can increase plant water use efficiency and result in less water use. After reviewing the available CO2 literature, we offer a series of priority targets for future research, including: 1) a need to breed or screen varieties and species of horticultural plants for increased drought tolerance; 2) determining the amount of carbon sequestered in soil from horticulture production practices for improved soil water-holding capacity and to aid in mitigating projected global climate change; 3) determining the contribution of the horticulture industry to these projected changes through flux of CO2 and other trace gases (i.e., nitrous oxide from fertilizer application and methane under anaerobic conditions) to the atmosphere; and 4) determining how CO2-induced changes in plant growth and water relations will impact the complex interactions with pests (weeds, insects, and diseases). Such data are required to develop best management strategies for the horticulture industry to adapt to future environmental conditions.
Predicting Transpiration Response to Climate Change: Insights on Physiological and Morphological Interactions that Modulate Water Exchange from Leaves to Canopies
Authors: Bauerle William L. , Bowden Joseph D.
Published: February 2019

Leaves are key factors in the global water exchange cycle. As the primary control interface involved in regulating water loss, understanding the relative influence of leaf morphological and physiological transpiration factors is critical to accurate evapotranspiration predictions. We parameterized a three-dimensional array model, MAESTRA, to establish a link from the leaf to canopy scale and attempted to isolate and understand the interplay among variation in morphological and physiological variables affecting transpiration. When physiological differences were accounted for, differences in leaf width (Lw) among Acer rubrum L. genotypes significantly affected leaf temperature and transpiration under slow to moderate wind velocities. In instances, Lw variation among genotypes resulted in a 25% difference in transpiration. This study demonstrates how simple morphological traits like Lw can provide useful selection criteria for plant breeders to consider in a changing climate.
Tropical Street Trees and Climate Uncertainty in Southeast Asia
Authors: Kjelgren Roger , Trisurat Yongyut , Puangchit Ladawan , Baguinon Nestor , Yok Puay Tan
Published: February 2019

Urban trees are a critical quality of life element in rapidly growing cities in tropical climates. Tropical trees are found in a wide variety of habitats governed largely by the presence and duration of monsoonal dry periods. Tropical cities can serve as a proxy for climate change impacts of elevated carbon dioxide (CO2), urban heat island, and drought-prone root zones on successful urban trees. Understanding the native habitats of species successful as tropical urban trees can yield insights into the potential climate impact on those habitats. Species from equatorial and montane wet forests where drought stress is not a limiting factor are not used as urban trees in cities with monsoonal dry climates such as Bangkok and Bangalore. Absence of trees from a wet habitat in tropical cities in monsoonal climates is consistent with model and empirical studies suggesting wet evergreen species are vulnerable to projected climates changes such as lower rainfall and increased temperatures. However, monsoonal dry forest species appear to have wider environmental tolerances and are successful urban trees in cities with equatorial wet climates such as Singapore as well as cities with monsoonal climates such as Bangkok and Bangalore. In cities with monsoonal dry climates, deciduous tree species are more common than dry evergreen species. Although dry deciduous species generally have better floral displays, their prevalence may in part be the result of greater tolerance of urban heat islands and drought in cities; this would be consistent with modeled habitat gains at the expense of dry evergreen species in native forest stands under projected higher temperatures from climate change. Ecological models may also point to selection of more heat- and drought-tolerant species for tropical cities under projected climate change.
Comparisons of Scion/rootstock Growth Rates among U.S. Pistachio Cultivars
Authors: Kallsen Craig E. , Parfitt Dan E.
Published: February 2019

Scion and rootstock circumferences of seven male and 26 female cultivars or potential cultivars of pistachio trees (Pistacia vera L.) were measured at 16 locations in the San Joaquin Valley of California. The trees were of variable age and on Pistacia integerrima-type or UCB1 (a P. atlantica Desf. × P. integerrima Stewart hybrid) rootstock. Differences were found in the ratio of scion to rootstock circumference (SRR) between the standard industry female cultivar Kerman and the other cultivars collectively. ‘Kerman’ produced a smoother trunk with a SRR closer to one than other cultivars. The SRR was also affected by rootstock with values closer to one for UCB1 as compared with higher values for P. integerrima rootstocks. The relationship between SRR and tree age demonstrated here can be a tool for comparing, evaluating, and selecting new rootstocks with growth rates to match those of newly developed or introduced scion cultivars.
Growth, Partitioning, and Nutrient and Carbohydrate Concentration of Petunia ×hybrida Vilm. Are Influenced by Altering Light, CO2, and Fertility
Authors: Frantz Jonathan M. , Ling Peter
Published: February 2019

Fuel prices have fluctuated wildly in the last several years, and faced with unpredictable or rising fuel costs, growers often lower temperature set points to decrease fuel use. However, plant growth and development are influenced by lower temperatures and may actually cause increases in fuel use as a result of longer production times. Alternative strategies to efficient crop production are needed. Fertility, light, and CO2 are other environmental factors that can be manipulated within a greenhouse but how all three interact together on growth and development are surprisingly not well known. Petunia ×hybrida Vilm. were grown in controlled environments in a 2 × 2 × 2 factorial study investigating how light, fertility, and CO2 influence growth and development, including shoot partitioning, nutrient uptake, and carbohydrate concentration. Generally, light enhanced flowering, both mass and fraction of total biomass, whereas increased fertility was detrimental to the proportion of biomass allocated to flowers. The influence of CO2 was complex with high CO2 suppressing flowering and enhancing leaf growth, but only midway through the 7-week experiment. Carbohydrate concentration remained high in elevated CO2, even when light and fertility were not limiting. This suggests a sink limitation, so even in high light and fertility, crop response to enhanced CO2 was low. Although CO2 had no size effect late in growth, CO2 suppressed nutrient concentrations. Together, these data suggest strategies that growers may have in controlling their crop growth and development and indicate that enhanced growth (leaf and steam mass) may be at the detriment of development (flowering mass and allocation).
Antioxidant and Phenolic Changes Across One Harvest Season and Two Storage Conditions in Primocane Raspberries (Rubus idaeus L.) Grown in a Hot, Dry Climate
Authors: Freeman Brenner L. , Stocks Janet C. , Eggett Dennis L. , Parker Tory L.
Published: February 2019

Antioxidant phytochemical differences among cultivars and changes after storage have not been explored in primocane raspberries grown in a hot, dry climate. It was hypothesized that significant differences would be detected in total phenolics and antioxidant capacity [oxygen radical absorbance capacity (ORAC)] between cultivars and over time. ‘Autumn Bliss’ had the highest ORAC and phenolic content, whereas ‘Caroline’ had the lowest ORAC and phenolic content when fresh. Averaging all cultivars and pickings, refrigerated berries had a significantly higher total phenolic content than fresh or frozen berries, although some moisture loss occurred during standard refrigeration. Antioxidant capacity and total phenolic content of primocane raspberries grown in hot, dry conditions vary between cultivars, on average do not change significantly after storage, are higher later in the season, and are higher than supermarket cultivars.
Increasing Chilling Reduces Heat Requirement for Floral Budbreak in Peach
Authors: Okie William R. , Blackburn Bryan
Published: February 2019

Response to chilling temperatures is a critical factor in the suitability of peach [Prunus persica (L.) Batsch] cultivars to moderate climates such as in the southeastern United States. Time of bloom depends on the innate chilling requirement of the cultivar as well as the timing and duration of cold and warm temperatures experienced by the buds. Most current chilling models have considered dormancy break a sequential process: after appropriate chilling is received, a fixed amount of heat accumulation will produce bloom. This research shows that as chilling exposure increases, the time and heat accumulation required for peach floral budbreak decreases in an exponential relationship. When chilling is ample, a sequential, two-part dormancy model is adequate to describe budbreak, and increased chilling has little effect on heat requirement. In lower-chilling situations relative to a particular cultivar, the curvilinear relationship between chilling and heat requirement results in more heat being required for budbreak. This relationship, in conjunction with the range of chilling requirement found among the buds on a tree, results in an extended, asymmetrical budbreak.
Alfalfa-based Organic Amendment in Peat-compost Growing Medium for Organic Tomato Transplant Production
Authors: Nair Ajay , Ngouajio Mathieu , Biernbaum John
Published: February 2019

In the last decade, organic production has been the fastest growing segment in U.S. agriculture. With increase in organic acreages there is a strong and growing demand for organically grown transplants. As a result of limited commercial availability of certified vegetable transplants, growers often produce their transplants on-farm. Commercial organic mixes for organic transplant production may not be locally available and are usually expensive. Growers often design their own mixes using compost and other organic amendments. The purpose of this study was to evaluate the incorporation of alfalfa-based amendment in a peat-compost medium for organic tomato transplant production. Growing medium of 2 peat:1 vermiculite:1 compost (by volume) was amended with 0%, 0.6%, 1.2%, 1.8%, or 2.4% weight by weight of alfalfa-based organic amendment and incubated for 0, 1, 2, 3, or 4 weeks. Medium pH and electrical conductivity (EC), seed germination (untreated Solanum Lycopersicon L. ‘Mountain Fresh’ seed), transplant dry weight, height, stem diameter, and SPAD values were measured. Medium pH increased with addition of alfalfa-based amendment but remained within the range of 5.5 to 7.0. Germination percentages were less than 50% in amended medium that was either not incubated or incubated for 4 weeks. Germination was greater than 75% if amended media were incubated for 1, 2, or 3 weeks. Seeds grown in peat-compost without any amendments had the highest germination rates; however, severe nutrient deficiency suppressed seedling growth. Relative to growth in medium with no amendments, plants growing in the amended medium had increased stem diameter, height, leaf chlorophyll content, and plant dry weight (90% to 160% more), provided the amended medium was incubated for at least 1 week. Application rate of 0.6% or 1.2% of alfalfa-based amendment produced transplants with suitable growth characteristics and met commercially acceptable standards for transplanting and handling at a reasonable estimated cost.
Ethylene Exposure Duration Affects Postharvest Needle Abscission in Balsam Fir (Abies balsamea L.)
Authors: MacDonald Mason T. , Lada Rajasekaran R. , Martynenko Alex I. , Dorais Martine , Pepin Steeve , Desjardins Yves
Published: February 2019

Needle loss after harvest is a major problem for Atlantic Canada's Christmas tree and greenery industry. Ethylene is a signal for abscission in balsam fir, but preliminary studies have suggested that the role of ethylene may be influenced by length of exposure. Short-term and long-term ethylene exposure experiments were conducted. Branches were exposed to ethylene for 24 h (short-term) or continuously (long-term) at concentrations of 0 to 1000 ppm. The response variables measured were needle retention duration (NRD), average water use (AWU), and xylem pressure potential (XPP). Short-term exposure to any concentration of ethylene delayed needle abscission by 30 to 40 days. In contrast, long-term exposure to all concentrations of ethylene accelerated abscission, most evident by a 21-day decrease in NRD at 1000 ppm ethylene. There was a 60% decrease in NRD, 160% decrease (more negative) in XPP, and 80% increase in AWU as a result of long-term exposure to ethylene. Overall, our results demonstrate an opposite effect of short-term and long-term ethylene exposure, which suggests that short-term exposure to ethylene might help to precondition balsam fir and delay needle abscission during postharvest handling.
Detection of Pigments and Natural Colorants from Thai Herbal Plants for Possible Use as Coloring Dyes
Authors: Boonsong Panthip , Laohakunjit Natta , Kerdchoechuen Orapin , Matta Frank B.
Published: February 2019

Fourteen Thai herbal plants were extracted using methanol, ethanol, and acetone. Comparison of the various extraction methods for pigments and polyphenols (colorants) showed that methanol provided a more complete extraction than ethanol and acetone. Percentage yield ranged from 1.7 to 40.7 and was dependent on the plant extracted and solubility of pigments and polyphenols (colorants) extracted by the various solvents. The absorption spectra of pigments and polyphenols (colorants) in the plant extract were present in the visible region (351 to 665 nm) and the absorption spectra of polyphenols were present in the ultraviolet region (200 to 349 nm). Color of plant extracts varied and included violet–blue, yellow–green, red, orange–red, gray–purple, blue–green, gray–orange, gray–yellow, and black. High-performance liquid chromatography (HPLC) was used to separate and identify compounds of plant pigments and polyphenols (colorants). Ya-nang had the greatest number of peaks and chlorophyll A and chlorophyll B were found only in Ya-nang. Numerous pigments and polyphenols were detected. Such compounds have the potential to be used as coloring dyes.
Effects of Gamma Irradiation, Modified Atmosphere Packaging, and Delay of Irradiation on Quality of Fresh-cut Iceberg Lettuce
Authors: Fan Xuetong , Sokorai Kimberly J.B.
Published: February 2019

This study was conducted to investigate the effect of modified atmosphere packaging (MAP) and delay of irradiation application on the quality of cut Iceberg lettuce. Overall visual quality and tissue browning of cut lettuce were evaluated using a scale of 9 to 1, whereas texture was analyzed instrumentally during 14 days of storage at 4 °C. Results showed that irradiation (0.5 and 1.0 kGy) of cut lettuce induced tissue browning when stored in air; however, when cut lettuce was stored in MAP, irradiated lettuce had better appearance than the non-irradiated ones as a result of lower O2 levels in the packages of irradiated samples compared with the levels in control packages. In general, irradiation at doses of 0.5 and 1.0 kGy did not affect firmness of the lettuce. After 14 days of MAP storage, overall visual quality of non-irradiated samples had a score of ≈4, a score below the limit of sales appeal, whereas the two irradiated samples had scores of 6.5 to 7.9, indicating the irradiated samples had a fair to good quality. Delaying irradiation by 1 day after preparation of cut lettuce did not significantly (P > 0.05) affect cut edge browning, surface browning, or overall visual quality compared with lettuce irradiated immediately after preparation. Our results suggest that MAP is essential to minimize quality deterioration caused by irradiation.
Enhanced Seed Germination of Ilex dumosa R. (Aquifoliaceae) through In Vitro Culture of Cut Pyrenes
Authors: Dolce Natalia R. , Mroginski Luis A. , Rey Hebe Y.
Published: February 2019

An in vitro culture protocol was developed that increased the germination percentage and decreased the lag time to germination for Ilex dumosa R. pyrenes as a tool for replacing the laborious task of embryo rescue technique. This method involves transversely cutting surface-sterilized pyrenes with a scalpel blade, then placing the micropylar one-third end with the rudimentary embryo (≈0.25 mm long) on solidified (agar 0.65%) quarter-strength salts and vitamins of Murashige and Skoog, 1962 medium with 3% sucrose, and incubating in a growth room at 27 ± 2 °C with a 14-h photoperiod (116 μmol·m−2·s−1). Most of the cut pyrenes (greater than 50%) germinated within the first month after inoculation and achieved maximum germination (≈70%) in 2 months compared with whole pyrenes, which began to germinate 3 months after sowing and required more than 8 months for maximum germination (37%). Moreover, the germination percentage of cut pyrenes was significantly higher than the germination of isolated embryos (34%). Thus, the cut pyrenes culture is a simpler and more effective technique than embryo rescue. Easily, on average, a trained operator is able to culture ≈1000 cut pyrenes per day instead of ≈100 isolated embryos.
Nutrient Uptake and Loss by Container-grown Deciduous and Evergreen Rhododendron Nursery Plants
Authors: Scagel Carolyn F. , Bi Guihong , Fuchigami Leslie H. , Regan Richard P.
Published: February 2019

The influence of nitrogen (N) fertilizer application on plant allocation, uptake, and demand for other essential nutrients was evaluated from May 2005 to Feb. 2006 in evergreen Rhododendron ‘P.J.M. Compact’ (PJM) and ‘English Roseum’ (ER) and deciduous Rhododendron ‘Gibraltar’ (AZ) grown in containers filled with soilless substrate. Net nutrient uptake and losses were calculated using piecewise regression and uptake efficiency, root absorption capacity, aboveground demand, nutrient use efficiency, and uptake ratios between N and other nutrients (N ratios) were calculated using net uptake between harvest dates. Nitrogen application increased uptake rate of all nutrients, enhanced late-season uptake of many nutrients, and increased the rate of nutrient loss during the winter. Nutrient uptake often occurred as late as November in plants grown with N but was usually undetectable after September in plants grown without additional N fertilizer. Nutrient losses during the winter were not always associated with biomass loss and were related to differences in preferential nutrient allocation to different structures and the plant's ability to export nutrients before biomass loss. Plants with a greater potential for rapid growth were more capable of later-season nutrient uptake than plants with slower growth rates. Nitrogen availability altered N ratios indicating that when adding N to container-grown Rhododendron, fertilizers with higher ratios of N/phosphorus (PJM, AZ), N/calcium (PJM, ER), N/boron (PJM AZ), N/copper (PJM, ER), and N/iron (PJM, ER) and lower ratios of N/potassium (PJM, ER, AZ), N/sodium (PJM, ER, AZ), N/calcium (AZ), N/boron (ER), N/manganese (AZ), and N/zinc (ER) may be needed to optimize growth and minimize nutrient inputs. Increasing N availability altered uptake efficiency, root absorption capacity, aboveground demand, and nutrient use efficiency for several nutrients, indicating that changes in N management practices need to consider how altering N application rates may influence the plant's ability to take up and use other nutrients. This information can be used to develop fertilizer formulations to minimize excess application of nutrients and to evaluate the potential effects of altering N management practices on use of production resources. Our results indicate that nutrient management strategies for perennial crops such as Rhododendron need to take into consideration not only the nutrient demand for current growth, but also how to optimize nutrient availability for uptake that contributes to future growth potential and end-product quality.
Response of Pecan Orchard Soil Chemical and Biological Quality Indicators to Poultry Litter Application and Clover Cover Crops
Authors: Wells M. Lenny
Published: February 2019

Little information is available regarding the activity of soil quality biological indicators in southeastern U.S. pecan [Carya illinoinensis (Wangenh.) K. Koch] orchards. The objectives of this study were to examine the effect of poultry litter application and the use of crimson clover (Trifolium incarnatum L.) as a cool-season cover crop on soil chemistry and soil quality biological indicators, including mycorrhizal inoculum potential (MIP), microbial biomass carbon (MBC), and phosphatase activity in a southeastern U.S. Coastal Plain pecan orchard system. The use of clover as a cool-season cover crop between tree rows provided multiple benefits for pecan orchard soil quality, including increased MIP and MBC. Soil phosphatase activity was also enhanced by clover during two of the three years of study. Soil elemental properties, including total nitrogen (N), and soil organic matter (SOM) were also enhanced by clover and/or poultry litter, although there was an obvious time lag in the response of soil N to the treatments. Poultry litter application increased soil phosphorus (P) but did not consistently enhance soil biological activity parameters. At times, poultry litter appeared to neutralize or minimize the positive effects of clover on MIP.
Differential Photosynthetic Responses to Salinity Stress between Two Perennial Grass Species Contrasting in Salinity Tolerance
Authors: Liu Yiming , Du Hongmei , Wang Kai , Huang Bingru , Wang Zhaolong
Published: February 2019

Salinity is a detrimental abiotic stress for plant growth in salt-affected soils. The objective of this study was to examine photosynthetic responses to salinity stress in two warm-season turfgrasses differing in salinity tolerance. Salt-tolerant species seashore paspalum (Paspalum vaginatum) and salt-sensitive species centipedegrass (Eremochloa ophiuroides) were exposed to salinity at three NaCl concentrations (0, 300, and 500 mm) in a growth chamber. Turf quality, relative water content (RWC), and leaf photochemical efficiency (Fv/Fm) declined, whereas electrolyte leakage (EL) increased under the two NaCl regimes for both grass species, and the changes were more dramatic in centipedegrass than that in seashore paspalum as well as in the higher salinity concentration. Two grass species showed different phytosynthetic responses to salinity stress. The earlier inhibition of photosynthesis in seashore paspalum was mainly associated with stomatal closure. As salinity increased and salinity stress prolonged, the inhibition of photosynthesis in seashore paspalum was mainly associated with non-stomatal factors. The inhibition of photosynthesis in centipedegrass was associated with both stomatal closure and non-stomatal factors at both salinity levels. The sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) analysis demonstrated the Rubisco large subunit had no obvious decrease during the whole stress period under the 300-mm and 500-mm treatments in seashore paspalum, whereas it significantly decreased in centipedegrass under both the 300-mm and 500-mm treatments. The results indicated that the superior salinity tolerance in seashore paspalum, compared with centipedegrass, could be attributed to its maintenance of Rubisco stability, chlorophyll content, photochemical efficiency as well as photosynthetic rate (Pn) capacity under salinity stress.