bluuebunny/crossref_metadata_2025 huggingface dataset:
A Multiple Chamber, Semicontinuous, Crop Carbon Dioxide Exchange System: Design, Calibration, and Data Interpretation
Authors: van Iersel M.W. , Bugbee B.
Published: January 2019

Long-term, whole-crop CO2 exchange measurements can be used to study factors affecting crop growth. These factors include daily carbon gain, cumulative carbon gain, and carbon use efficiency, which cannot be determined from short-term measurements. We describe a system that measures semicontinuously crop CO2 exchange in 10 chambers over a period of weeks or months. Exchange of CO2 in every chamber can be measured at 5 min intervals. The system was designed to be placed inside a growth chamber, with additional environmental control provided by the individual gas exchange chambers. The system was calibrated by generating CO2 from NaHCO3 inside the chambers, which indicated that accuracy of the measurements was good (102% and 98% recovery for two separate photosynthesis systems). Since the systems measure net photosynthesis (Pnet, positive) and dark respiration (Rdark, negative), the data can be used to estimate gross photosynthesis, daily carbon gain, cumulative carbon gain, and carbon use efficiency. Continuous whole-crop measurements are a valuable tool that complements leaf photosynthesis measurements. Multiple chambers allow for replication and comparison among several environmental or cultural treatments that may affect crop growth. Example data from a 2 week study with petunia (Petunia ×hybrida Hort. Vilm.-Andr.) are presented to illustrate some of the capabilities of this system.
Characterization of Aspergillus niger B-1 RNase and Its Inhibitory Effect on Pollen Germination and Pollen Tube Growth in Selected Tree Fruit
Authors: Roiz Levava , Ozeri Uzi , Goren Raphael , Shoseyov Oded
Published: January 2019

Aspergillus niger B-1 (CMI CC 324626) extracellular RNase (RNase B1) was purified to homogeneity. It was found to contain two isoforms of 32- and 40-kDa glycoproteins, sharing a 29-kDa protein moiety. Optimal RNase activity was observed at 60 °C and pH 3.5. In `Almog' peach [Prunus persica (L.) Batsch (Peach Group) `Almog'] and `Murcott' tangerine (Citrus reticulata Blanco `Murcott') the enzyme inhibited pollen germination and pollen tube growth in vitro as well as in vivo. In field experiments, spray application of the RNase caused a reduction in `Fantasia' nectarine [Prunus persica (L.) Batsch (Nectarine Group) `Fantasia'] fruit set and interfered with embryo development. The biological effect of the RNase may be of horticultural value, due to its potential to control fertilization.
Omega-3-Fatty Acid Concentration in Portulaca oleracea is Altered by Nitrogen Source in Hydroponic Solution
Authors: Palaniswamy Usha Rani , McAvoy Richard J. , Bible Bernard B.
Published: January 2019

Purslane (Portulaca oleracea L.) has been identified as an exceptionally rich source of α-linolenic acid (LNA), an essential fatty acid that is beneficial in reducing the incidence of coronary heart disease and certain cancers. In general, about two thirds of the LNA in terrestrial plants is associated with chloroplasts. A green-leafed unnamed cultivar of purslane and a golden-leafed cultivar `Goldberg' were grown hydroponically in a complete nutrient solution with 14.3 mm nitrogen provided as nitrate (NO3-) and ammonium (NH4+) forms to yield NO3--N: NH4+-N ratios of 1:0, 0.75:0.25, 0.5:0.5, and 0.25:0.75. Young leaves, harvested 18 days after treatment initiation, were analyzed to determine the fatty acid composition and concentrations, and thylakoid protein and chlorophyll concentrations. Although the leaves of plants grown with a NO3--N: NH4+-N ratio of 0.5:0.5 contained 239% and 114% more LNA than plants grown with ratios 1:0 and 0.75:0.25, respectively, they contained only 41% and 26% more chlorophyll. The green-leafed cultivar had higher (39%) chlorophyll concentrations than `Goldberg', but both cultivars had similar LNA concentrations [per g dry weight (DW)]. These results suggest that the LNA concentration in the fatty acid-rich species P. oleracea may not be as closely associated with chlorophyll concentration as reported earlier for other plants. Leaves of plants grown in solutions with 0.25:0.75 NO3--N: NH4+-N ratio contained 35% less LNA per g leaf DW than the leaves of plants grown in nutrient solutions with a 0.5:0.5 ratio. Although total DW production was not affected by the NO3--N: NH 4+-N ratios in the nutrient solutions, the green-leafed cultivar produced higher fresh weight, leaf area, total DW, and number of shoots than `Goldberg'.
Spray Application Factors and Plant Growth Regulator Performance: IV. Dose Response Relationships
Authors: Knoche Moritz , Lownds Norman K. , Bukovac Martin J.
Published: January 2019

Effect of carrier volume (range 119 to 668 L·ha-1) on dose response relationships of daminozide and GA3 was investigated using bean (Phaseolus vulgaris L.) seedlings as a model system. Carrier volume was varied by altering nozzle travel speed thereby maintaining constant flow rate and droplet size. Response was indexed by inhibition (daminozide) or stimulation (GA3) of elongation of first plus second internodes above primary leaves 14 days after spray application. Increasing dose by increasing concentration and/or increasing carrier volume at constant concentration increased response. For a given dose retained, response to daminozide was related positively to carrier volume, while GA3 response was not affected. Chemical names used: butanedioic acid mono(2,2-dimethylhydrazide) (daminozide); gibberellic acid (GA3).
Limitations on Growth and Net Gas Exchange of Diploid and Tetraploid Citrus Rootstock Cultivars Grown at Elevated CO2
Authors: Syvertsen J.P. , Lee L.S. , Grosser J.W
Published: January 2019

Diploid (2x) and autotetraploid (4x) Citrus L. rootstock cultivars were grown at elevated CO2 to obtain insights into limitations on growth and net gas exchange that have been associated with tetraploidy. Well-nourished 2x and 4x seedlings of `Volkamer' lemon (Volk, C. volkameriana Ten & Pasq.), `Troyer' citrange [Troy, C. sinensis (L.) Osbeck × Poncirus trifoliata (L.) Raf.] and `Cleopatra' mandarin (Cleo, C. reticulata Blanco.), were grown in greenhouses at either ambient or twice ambient CO2 for 4 months. Plant growth, water relations, mineral nutrition, and net gas exchange characteristics of leaves were measured. Most 4x plants were smaller and had lower rates of whole plant transpiration but shorter fibrous roots than 2x plants. Fibrous roots of 4x were thicker than 2x roots as indicated by a lower specific root length (SRL) in 4x than in 2x roots. Root hydraulic conductivity was correlated to total plant growth but there were no effects of CO2 or ploidy on root conductivity. Tetraploid leaves had lower N concentrations than 2x leaves when expressed on a dry weight basis but these differences disappeared when N concentration was expressed on an leaf area basis because 4x leaves had more leaf dry weight per area (LDW/a) than 2x leaves. Plant growth was greater and SRL was lower at elevated CO2 than at ambient CO2. LDW concentrations of N, P, and K were lower at elevated CO2 than at ambient apparently due to a growth dilution effect. LDW/a, net CO2 assimilation (ACO2), and leaf water use efficiency were greater at elevated CO2 than at ambient. Overall, there was no effect of ploidy on ACO2 but 4x Volk and Troy had lower rates of ACO2 than their 2x at elevated CO2. Net gas exchange of tetraploid leaves was less responsive to elevated CO2 than 2x leaves. The low SRL of tetraploids was correlated with low whole plant transpiration rates and low leaf area-based N concentrations, which may be operative in determining the growth characteristics associated with tetraploidy.
Surface Energy Balance Affects Gas Exchange and Growth of Two Irrigated Landscape Tree Species in an Arid Climate
Authors: Montague Thayne , Kjelgren Roger , Rupp Larry
Published: January 2019

Research was conducted to investigate how energy balance of bark mulch and turf surfaces influence gas exchange and growth of recently transplanted trees. On several occasions over a 3-year period, stomatal conductance and leaf temperature were measured throughout the day on `Emerald Queen' Norway maple (Acer platanoides L.) and `Greenspire' littleleaf linden (Tilia cordata Mill.) trees growing over each surface. Tree water loss was estimated using a general transport flux equation applied to the tree crown apportioned between sunlit and shade layers. Microclimate variables were measured over each surface with a permanent weather station. Tree growth data were collected at the end of each growing season. Soil heat flux data revealed that a greater portion of incoming radiation was prevented from entering the soil below mulch than below turf. Due to this insulating effect, and consequent lack of evaporative cooling, mulch surface temperature was greater, and emitted more longwave radiation, than turf. Leaves over mulch intercepted more longwave radiation, had greater leaf temperature, and greater leaf-to-air vapor pressure difference than leaves over turf. As a result, leaves over mulch had greater stomatal closure than leaves over turf. Estimated tree water loss varied between surface treatments and with climatic conditions. Trees over turf had greater shoot elongation and leaf area than trees over mulch. These data suggest that gas exchange and growth of recently transplanted trees in an arid climate may be reduced if planted over nonvegetative, urban surfaces.
Calcium and Magnesium Concentration of Inbred and Hybrid Broccoli Heads
Authors: Farnham Mark W. , Grusak Michael A. , Wang Min
Published: January 2019

Broccoli (Brassica oleracea L., Italica Group) is a good vegetable source of Ca and Mg, two critical minerals in human nutrition. Studies have shown that bioavailability of Ca from broccoli is comparable to that from milk. Thus, broccoli is an important alternative source of Ca in segments of the population that consume limited amounts of dairy products. Essentially nothing is known about the genetic influence on variation in Ca or Mg concentration of broccoli heads. Thus, the goal of this research was to examine variation in Ca, and also Mg concentrations, in a collection of USDA inbreds and commercial F1 hybrids. In 1996 and 1997 field studies, significant differences among inbred entries and among hybrid entries were observed for Ca and Mg concentrations of broccoli heads. With hybrids and inbreds, mean head Ca concentrations were ≈3.0 mg·g-1 dry weight (DW), and entries with lowest and highest Ca concentrations differed >2-fold. Mean Mg concentrations of hybrid heads was 2.3 mg·g-1 DW (range 1.8 to 2.6) and 2.8 mg·g-1 DW (range 2.2 to 3.7) in 1996 and 1997, respectively. Inbred lines had mean head Mg concentrations of 2.0 and 2.6 mg·g-1 DW in the two respective years and ranges in concentration were similar as for hybrids. Analysis of variance indicated significant environment and entry by environment effects for Ca and Mg concentrations of hybrids. With inbreds, a significant entry by environment effect for Ca concentration and environment effect for Mg concentration was also observed. Significant environment and entry by environment effects indicate that the environmental influence on phenotypic expression of Ca and Mg concentrations may complicate genetic improvement of head mineral concentration.
Canopy Position and Heat Treatments Influence Gamma-irradiation-induced Changes in Phenylpropanoid Metabolism in Grapefruit
Authors: McDonald R.E. , Miller W.R. , McCollum T.G.
Published: January 2019

Irradiation is being evaluated as a quarantine treatment of grapefruit (Citrus paradisi Macf. `Marsh'), but it can cause damage to the fruit. Research was conducted to determine if preirradiation heat treatments would improve fruit tolerance to irradiation as they improve tolerance to low temperature injury and to determine if canopy position influenced fruit tolerance to irradiation. Initially, grapefruit were irradiated at 0 or 2.0 kGy at a dose rate of 0.14 kGy·min-1 and selected biochemical changes were monitored over time. There was a marked increase in phenylalanine ammonia-lyase (PAL) activity following irradiation. Maximum activity (≈18-fold increase) was attained 24 hours after irradiation. Subsequently, grapefruit were harvested from interior and exterior canopy positions and irradiated at 0 or 1.0 kGy at a dose rate of 0.15 kGy·min-1 before storage for 4 weeks at 10 °C. Following storage, pitting of flavedo was the most evident condition defect noted as a result of irradiation. Pitting was observed on 27% and 15% of irradiated exterior and interior canopy fruit, respectively, whereas there was no pitting on nonirradiated fruit. Heat treatment before irradiation decreased susceptibility of fruit to damage. Pitting was 26%, 19%, and 17% when fruit were held 2 hours at 20 (ambient), 38 or 42 °C, respectively. Irradiation-induced PAL activity was reduced by temperature conditioning at 38 or 42 °C. Exterior canopy fruit flavedo contained higher levels of total phenols, including flavanols and coumarins compared with interior canopy fruit. Deposition of lignin was not related to canopy position. Neither irradiation nor heat treatment had an effect on total phenols or lignin deposition. Generally, cholesterol, campesterol, stigmasterol, β-sitosterol, and isofucosterol were found to be higher in four steryl lipid fractions in exterior canopy fruit compared with interior canopy fruit. Irradiation increased campesterol in the free sterol and steryl glycoside fractions and decreased isofucosterol in the free sterol fraction. Heat treatments had no effect on individual sterol levels. It seems that irradiation causes a stress condition in the fruit, which leads to pitting of peel tissue. Heat treatment before irradiation reduced damaging effects of irradiation.
Heat Shocks Reduce Chilling Sensitivity of Cotton, Kenaf, Okra, and Rice Seedling Radicles
Authors: Mangrich Mary E. , Saltveit Mikal E.
Published: January 2019

Seeds of cotton (Gossypium hirsutum L.), kenaf (Hibiscus cannabinus L.), okra [Abelmoschus esculentus (L.) Moench. `Clemson Spineless' (syn. Hibiscus esculentus L.)], rice (Oryza sativa L.), and wheat (Triticum sativum (L.) Lam.) were germinated and grown at 25 °C until their radicles reached 10 mm in length. They were then exposed to chilling temperatures for 0 to 5 days followed by 3 days at 25 °C. Radicle length was measured periodically and inhibition of elongation was used as an indicator of the severity of chilling injury. Exposure to chilling reduced radicle elongation in all species except chilling insensitive wheat. When seedlings were heat-shocked at 45 °C for 1 to 12 min before being chilled, radicles of the chilling sensitive okra, kenaf, cotton, and rice seedlings elongated more than seedlings not heat-shocked before chilling. The method of heat-shock application and the stringency (i.e., time× temperature) of the heat-shock and chilling treatments all affected the response of the tissue. In comparison to nonheat-shocked wheat seedlings, the radicles of chilling insensitive wheat seedlings did not elongate more than seedlings in which the heat shocks were applied before chilling. A brief heat shock ameliorates chilling injury in these chilling sensitive species.
Expression Pattern of Homologues of Floral Meristem Identity Genes LFY and AP1 during Flower Development in Apple
Authors: Kotoda Nobuhiro , Wada Masato , Komori Sadao , Kidou Shin-ichiro , Abe Kazuyuki , Masuda Tetsuo , Soejima Junichi
Published: January 2019

Two apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] homologous fragments of FLO/LFY and SQUA/AP1 (AFL and MdAP1, respectively) were analyzed to determine the relationship between floral bud formation and floral gene expression in `Jonathan' apple. The AFL gene was expressed in reproductive and vegetative organs. By contrast, the MdAP1 gene, identified as MdMADS5, which is classified into the AP1 group, was expressed specifically in sepals concurrent with sepal formation. Based on these results, AFL may be involved in floral induction to a greater degree than MdAP1 since AFL transcription increased ≈2 months earlier than MdAP1. Characterization of AFL and MdAP1 should advance the understanding of the processes of floral initiation and flower development in woody plants, especially in fruit trees like apple.
Relating Freeze-induced Electrolyte Leakage Measurements to Lethal Temperature in Red Raspberry
Authors: Lindén Leena , Palonen Pauliina , Lindén Mikael
Published: January 2019

Seasonal cold hardiness of red raspberry (Rubus idaeus L.) canes was measured by freeze-induced electrolyte leakage test and visual rating of injury. Leakage data were transformed to percentage-adjusted injury values and related to lethal temperature by graphical interpolation and by the midpoint (T50) and inflection point (Tmax) estimates derived from three sigmoid (the logistic, Richards, and Gompertz) functions. Tmax estimates produced by Richards and Gompertz functions were corrected further using two different procedures. The 10 leakage-based hardiness indices, thus derived, were compared to lethal-temperature estimates based on visual rating. Graphical interpolation and Tmax of the logistic or T50 of the Gompertz function yielded lethal-temperature estimates closest to those obtained visually. Also, Tmax values of the Gompertz function were well correlated with visual hardiness indices. The Richards function yielded hardiness estimates deviating largely from visual rating. In addition, the Richards function displayed a considerable lack of fit in several data sets. The Gompertz function was preferred to the logistic one as it allows for asymmetry in leakage response. Percentage-adjusted injury data transformation facilitated curve-fitting and enabled calculation of T50 estimates.
Day and Night Temperatures, Daily Light Integral, and CO2 Enrichment Affect Growth and Flower Development of Pansy (Viola ×wittrockiana)
Authors: Niu Genhua , Heins Royal D. , Cameron Arthur C. , Carlson William H.
Published: January 2019

Pansy [Viola ×wittrockiana Gams. `Delta Yellow Blotch' (Yellow) and `Delta Primrose Blotch' (Primrose)] plants were grown in a greenhouse under two CO2 concentrations [ambient (≈400 μmol·mol-1) and enriched (≈600 μmol·mol-1)], three daily light integrals (DLI; 4.1, 10.6, and 15.6 mol·m-2·d-1), and nine combinations of day and night temperatures created by moving plants every 12 h among three temperatures (15, 20, and 25 °C). Time to flower decreased and rate of flower development increased as plant average daily temperature (ADT) increased at all DLIs for Yellow or at high and medium DLIs for Primrose. Increasing the DLI from 4.1 to 10.6 mol·m-2·d-1 also decreased time to flower by 4 and 12 days for Yellow and Primrose, respectively. Both cultivars' flower size and Yellow's dry weight [(DW); shoot, flower bud, and total] decreased linearly as plant ADT increased at high and medium DLIs, regardless of how temperature was delivered during day and night. DW in Yellow increased 50% to 100% when DLI increased from 4.1 to 10.6 mol·m-2·d-1 under both CO2 concentrations. Flower size in Yellow and Primrose increased 25% under both CO2 conditions as DLI increased from 4.1 to 10.6 mol·m-2·d-1, but there was no increase between 10.6 and 15.6 mol·m-2·d-1, regardless of CO2 concentration. Plant height and flower peduncle length in Yellow increased linearly as the difference between day and night temperatures (DIF) increased; the increase was larger under lower than higher DLIs. The ratio of leaf length to width (LL/LW) and petiole length in Yellow increased as DIF increased at medium and low DLIs. Carbon dioxide enrichment increased flower size by 4% to 10% and DW by 10% to 30% except for that of the shoot at medium DLI, but did not affect flower developmental rate or morphology. DW of vegetative and reproductive parts of the plant was correlated closely with photothermal ratio, a parameter that describes the combined effect of temperature and light.
Water Stress Affects Rhizosphere Respiration Rates and Root Morphology of Young `Mutsu' Apple Trees on M.9 and MM.111 Rootstocks
Authors: Psarras Georgios , Merwin Ian A.
Published: January 2019

One-year-old potted `Mutsu' apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] trees on scion invigorating Malling-Merton 111 (MM.111) and scion dwarfing Malling 9 (M.9) rootstocks were grown outdoors in containers under three levels of water availability (irrigated at -20, -80, and -200 kPa) to investigate the effects of soil water availability on combined soil/root (rhizosphere) respiration rates, and developmental morphology of root systems. Rhizosphere respiration was measured with a portable infrared gas analyzer, and root biomass was estimated by electrical capacitance. These nondestructive measurements were compared with final root dry weights of harvested trees, to determine their reliability for estimating relative differences in root biomass. Water stress reduced final biomass similarly for both rootstocks, but the relative reduction in shoot growth was greater for MM.111. Root to shoot ratios were higher and average specific root respiration was lower for M.9 rootstock compared with MM.111. M.9 appeared to be more tolerant of water stress then MM.111, due to reduced canopy transpiration relative to root system mass. Water stress increased root to shoot ratios, specific root length, and the carbohydrate costs of root maintenance as indicated by specific respiration rates. Root dry weight (DW) was better correlated to rhizosphere respiration than to root electric capacitance. The observed r2 values between root capacitance and root DW were as high as 0.73, but capacitance measurements were also influenced by soil water content and rootstock type. Electrical capacitance estimated total root biomass more accurately for M.9 than for MM.111.
Root Growth Phenology, Root Longevity, and Rhizosphere Respiration of Field Grown `Mutsu' Apple Trees on `Malling 9' Rootstock
Authors: Psarras Georgios , Merwin Ian A. , Lakso Alan N. , Ray John A.
Published: January 2019

A 2-year field study of `Mutsu' apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] on `Malling 9' (M.9) rootstock was conducted to observe root growth in situ, and compare patterns of root growth, root maturation and turnover rates, and soil-root respiration. Rhizosphere respiration was monitored with a portable chamber connected to an infrared gas analyzer; root emergence, browning, and turnover rates were measured by direct observation through minirhizotron tubes inserted in the root zone. Negligible root growth was observed before the onset of shoot growth in mid-May. In both years, a main peak of new root emergence in late June and early July coincided partially with major phases of shoot and fruit growth. A smaller peak of root emergence during August to September 1997 consisted primarily of new roots at 20 to 45 cm soil depths. Most roots remained <1 mm in diameter and developed in the upper 25 cm soil profile; no roots were observed at any time below 50 cm, due to a compacted soil layer at that depth. The cumulative survivorship of new roots was 38% in 1996 and 64% in 1997, and 50% of emergent white roots turned brown or senesced within 26 days in 1996 and 19 days in 1997. Root turnover rates were highest in mid-August both years. Rhizosphere respiration was correlated (r2 = 0.36 and 0.59, P = 0.01 and 0.004) with soil temperatures in 1996 and 1997, with Q10 values of 2.3 in both years. The Q10 for root-dependent respiration (the difference between soil only and combined soil-root respiration) in 1997 was 3.1, indicating that roots were more sensitive than soil microflora to soil temperature. The temporal overlap of high rates of shoot, root and fruit growth from late May to mid-July suggests this is a critical period for resource allocations and competition in temperate zone apple trees.
Cell Wall Enzymes and Cell Wall Changes in `Flavortop' Nectarines: mRNA Abundance, Enzyme Activity, and Changes in Pectic and Neutral Polymers during Ripening and in Woolly Fruit
Authors: Zhou Hong-Wei , Sonego Lilian , Khalchitski Andrai , Ben-Arie Ruth , Lers Amnon , Lurie Susan
Published: January 2019

Most `Flavortop' nectarines [Prunus persica (L.) Batsch (Nectarine Group)] that were placed directly into 0 °C storage developed chilling injury after removal, while preconditioning fruit for 2 days at 20 °C (delayed storage) reduced chilling injury substantially. Chilling injury was expressed as the development of a dry, woolly flesh texture during ripening. Delayed-storage fruit were as firm as control fruit when placed in storage, but softened more during storage. Analysis of cell wall components showed that in woolly fruit a higher percentage of pectin was retained in the sodium carbonate fraction, although during ripening polymers in this fraction decreased in molecular mass (Mr). In the guanidine thiocyanate hemicellulose fraction of woolly fruit, the associated pectin and hemicellulose remained as large polymers, while in delayed-storage fruit they decreased in Mr during ripening. Endo-polygalacturonase (PG), pectin esterase (PE), and endo-glucanase (EGase) activities of delayed-storage fruit were the same as control fruit at the beginning of storage, although exo-PG was higher. However, differences were observed at the end of storage. Endo-PG activity was lower in control than delayed-storage fruit at the end of storage while PE activity was higher, and exo-PG and EGase activities were similar. These differences in activity were not reflected in the mRNA abundance of the respective enzymes. Endo-PG and PE message was similar in all fruit at the end of storage and increased during ripening, while EGase message was low at all times except in control fruit after storage and development of woolliness. Prevention of chilling injury by delayed storage appears to be due to the ability of the fruit to continue a progressive, slow cell wall degradation in storage which allows normal ripening to proceed when the fruit are rewarmed. Regulation of the softening process did not appear to be by enzyme synthesis, since mRNA levels of the enzymes did not correspond with enzyme activity.
Defoliation and Fruit Removal Effects on Papaya Fruit Production, Sugar Accumulation, and Sucrose Metabolism
Authors: Zhou Lili , Christopher David A. , Paull Robert E.
Published: January 2019

Papaya (Carica papaya L.) source size and sink strength were modified by a single defoliation or continual defoliation and fruit thinning. Fruit set, development, weight, total sugar (sum of sucrose, fructose, and glucose), sucrose phosphate synthase (SPS), sucrose synthase (SS), and acid invertase (AI) enzyme activities in response to defoliation and fruit thinning were determined. The effects of defoliation and fruit thinning varied with weather conditions, plant growth conditions, and cultivar. Removal of 75% of the leaves significantly reduced new flower production and fruit set, and decreased ripe fruit total soluble solids (TSS), while 50% defoliation did not reduce new fruit set or ripe fruit TSS. When every third leaf from the oldest leaf was not removed, the number of new flowers was reduced by 47% more than when the same number of leaves was removed from the oldest to younger leaves. Continual removal of old leaves reduced new fruit set, fruit weight, and TSS in the 168 day experimental period. Fruit thinning increased new fruit set and ripe fruit TSS. Larger fruit size, faster fruit development, lower respiration rate, and higher sugar contents and AI activity were observed in immature (young) fruit when old fruit were removed. AI activity was reduced during early fruit development and increased again in mature fruit in plants subjected to defoliation, and suggested a role for AI in mature fruit sugar accumulation, while SS activity declined significantly in fruit 154 and 175 days after anthesis and in mature fruit when plants were subjected to continual defoliation. SPS activity was not affected significantly by defoliation or fruit thinning. Source-sink balance was critical for papaya fruit set, development, and sugar accumulation and each mature leaf was able to provide photoassimilate for about three fruit.
Evaluation of Glyphosate Resistance in Transgenic Lettuce
Authors: Nagata Russell T. , Dusky Joan A. , Ferl Robert J. , Torres Antonio C. , Cantliffe Daniel J.
Published: January 2019

Six transgenic `South Bay' lettuce lines (Lactuca sativa L.) with elevated levels of 5-enolpyruvyl shikimate-3-phosphate synthase (EPSPS) were evaluated for tolerance to the herbicide glyphosate. The six lines were selected from ≈150 independent transformation events using an Agrobacterium tumefaciens system. Three assay methods were used to identify gene expression with regard to glyphosate resistance. Leaf disks of the transgenic lines were cultured on media containing 0 to 1280 μm glyphosate. Leaf disks of the control had lower dry weight (DW) at 40 μm and greater glyphosate than all the transgenic lines. The transgenic lines continued to grow even at 1280 μm. Plants 21 days old were sprayed in the greenhouse with rates of glyphosate at 0 to 35.84 kg·ha-1. DW of all the lines were similar to the control, with a few exceptions, at glyphosate concentrations from 0 to 0.56 kg·ha-1. At 2.24 to 8.96 kg·ha-1 all of the transgenic lines had DW greater than the control, while at 17.92 and 35.84 kg·ha-1 only B-32, B-33, C-3, and C-14 had DW greater than the control. The resistant line from the greenhouse experiment, B-32, grew normally in field trials at the highest glyphosate rate, 17.92 kg·ha-1, while control plants died at 0.56 kg·ha-1 glyphosate. Lines A-11 and C-3 had lower DW than B-32 at 2.24 kg·ha-1 glyphosate and greater. While leaf disk assays can identify potential transformed lines expressing the EPSPS and glyphosate oxidase (GOX) gene, and greenhouse screening can evaluate seedling vigor after glyphosate application, field trials are necessary to evaluate plant growth and yield through the growing season. Chemical name used: N-(phosphono-methyl) glycine (glyphosate).
Relationship between Cold Tolerance during Seed Germination and Vegetative Growth in Tomato: Germplasm Evaluation
Authors: Foolad M.R. , Lin G.Y.
Published: January 2019

Cold tolerance (CT) of 31 tomato accessions (cultivars, breeding lines, and plant introductions) representing six Lycopersicon L. sp. was evaluated during seed germination and vegetative growth. Seed germination was evaluated under temperature regimes of 11 ± 0.5 °C (cold stress) and 20 ± 0.5 °C (control) in petri plates containing 0.8% agar medium and maintained in darkness. Cold tolerance during seed germination was defined as the inverse of the ratio of germination time under cold stress to germination time under control conditions and referred to as germination tolerance index (TIG). Across accessions, TIG ranged from 0.15 to 0.48 indicating the presence of genotypic variation for CT during germination. Vegetative growth was evaluated in growth chambers with 12 h days/12 h nights of 12/5 °C (cold stress) and 25/18 °C (control) with a 12 h photoperiod of 350 mmol.m-2.s-1 (photosynthetic photon flux). Cold tolerance during vegetative growth was defined as the ratio of shoot dry weight (DW) under cold stress (DWS) to shoot DW under control (DWC) conditions and referred to as vegetative growth tolerance index (TIVG). Across accessions, TIVG ranged from 0.12 to 0.39 indicating the presence of genotypic variation for CT during vegetative growth. Cold tolerance during vegetative growth was independent of plant vigor, as judged by the absence of a significant correlation (r = 0.14, P > 0.05) between TIVG and DWC. Furthermore, CT during vegetative growth was independent of CT during seed germination, as judged by the absence of a significant rank correlation (rR = 0.14, P > 0.05) between TIVG and TIG. A few accessions, however, were identified with CT during both seed germination and vegetative growth. Results indicate that for CT breeding in tomato, each stage of plant development may have to be evaluated and selected for separately.
Leptine Glycoalkaloids Reduce Feeding by Colorado Potato Beetle in Diploid Solanum sp. Hybrids
Authors: Rangarajan Anusuya , Miller A. Raymond , Veilleux Richard E.
Published: January 2019

Leptine glycoalkaloids in leaves of the weedy diploid potato, Solanum chacoense Bitt., have been shown to reduce feeding by Colorado potato beetle (CPB; Leptinotarsa decemlineata Say). Development of cultivated potatoes with natural resistance to CPB has the potential to reduce costs and environmental impacts of production by reducing pesticide use. Through efforts to move the genes controlling leptine biosynthesis into cultivated potato, a series of hybrids was generated between the high leptine producing S. chacoense and a cultivated type, S. phureja Juz. and Buk. These hybrids were evaluated for solanine (+chaconine), leptinins, leptines, and total steroidal glycoalkaloid content. All hybrids contained leptines, but at different levels (ranging from 117 to 802 mg·g-1 dry weight of leptine aglycon). Some hybrids appeared to convert solanine (+chaconine) to leptinine and leptine efficiently and had no detectable solanine in sampled leaves. To verify the biological significance of these glycoalkaloids, leaf tissue was subjected to feeding assays with second instar CPB. CPB feeding rate ranged from 38 to 87 mm2·d-1 and was most closely correlated with leptine concentration. A minimum leptine level of 300 mg/100 g fresh leaves suppressed feeding by 50%, and levels below this had no effect on CPB feeding.
Mango Tolerance to Reduced Oxygen Levels in Controlled Atmosphere Storage
Authors: Bender Renar J. , Brecht Jeffrey K. , Sargent Steven A. , Huber Donald J.
Published: January 2019

`Haden' and `Tommy Atkins' mangoes (Mangifera indica L.) were stored in air, 2, 3, 4 or 5 kPa O2 plus N2, or 25 kPa CO2 plus air for 14 days at 15 °C or 21 days at 12 °C, respectively, then in air for 5 days at 20 °C to determine their tolerance to reduced O2 levels for storage times encountered in typical marine shipments. All low O2 treatments reduced mature green mango respiration (CO2 production), however, elevated ethanol production occurred in 2 and 3 kPa O2 storage, with the levels two to three times higher in `Tommy Atkins' than `Haden'. In contrast, `Haden' fruit at the onset of the climacteric also accumulated ethanol in 4 kPa O2 and produced 10 to 20-fold more ethanol in 2 and 3 kPa O2 than preclimacteric fruit. While there were no visible injury symptoms, off flavor developed in mature green fruit at 2 kPa O2 and in ripening initiated fruit at 2 and 3 kPa O2. Ethanol production was not affected by storage in 25 kPa CO2. Ethylene production was reduced slightly by low O2, however, `Haden' fruit also showed a residual inhibitory effect on ethylene production after 2 or 3 kPa O2 storage, while `Tommy Atkins' fruit stored in 2 kPa O2 produced a burst of ethylene upon transfer to air at 20 °C. Fruit firmness, total sugars, and starch levels did not differ among the treatments, but 2, 3 or 4 kPa O2 and 25 kPa CO2 maintained significantly higher acidity than 5 kPa O2 or air. The epidermal ground color responded differently to low O2 and high CO2 in the two mango cultivars. Only 2 kPa O2 maintained `Haden' color better than air, while all low O2 levels maintained `Tommy Atkins' color equally well and better than air. High CO2 was more effective than low O2 in maintaining `Haden' color, but had about the same effect as low O2 on `Tommy Atkins'. Results indicate that preclimacteric `Haden' and `Tommy Atkins' mango fruit are able to tolerate 3 kPa O2 for 2 or 3 weeks at 12 to 15 °C and that tolerance to low O2 decreases as mangoes ripen. Results also show that low O2 and high CO2 affect mango ripening differentially.
Tomato Cultivation Systems Affect Subsequent Quality of Fresh-cut Fruit Slices
Authors: Hong Ji Heun , Mills Douglas J. , Coffman C. Benjamin , Anderson James D. , Camp Mary J. , Gross Kenneth C.
Published: January 2019

Experiments were conducted to compare changes in quality of slices of red tomato (Lycopersicon esculentum Mill. `Sunbeam') fruit from plants grown using black polyethylene or hairy vetch mulches under various foliar disease management systems including: no fungicide applications (NF), a disease forecasting model (Tom-Cast), and weekly fungicide applications (WF), during storage at 5 °C under a modified atmosphere. Slices were analyzed for firmness, soluble solids content (SSC), titratable acidity (TA), pH, electrolyte leakage, fungi, yeasts, and chilling injury. With both NF and Tom-Cast fungicide treatments, slices from tomatoes grown with hairy vetch (Vicia villosa Roth) mulch were firmer than those from tomatoes grown with black polyethylene mulch after 12 days storage. Ethylene production of slices from fruit grown using hairy vetch mulch under Tom-Cast was ≈1.5- and 5-fold higher than that of slices from WF and NF fungicide treatments after 12 days, respectively. The percentage of water-soaked areas (chilling injury) for slices from tomatoes grown using black polyethylene mulch under NF was over 7-fold that of slices from tomatoes grown using hairy vetch under Tom-Cast. When stored at 20 °C, slices from light-red tomatoes grown with black polyethylene or hairy vetch mulches both showed a rapid increase in electrolyte leakage beginning 6 hours after slicing. However, slices from tomatoes grown using the hairy vetch mulch tended to have lower electrolyte leakage than those grown with black polyethylene mulch. These results suggest that tomatoes from plants grown using hairy vetch mulch may be more suitable for fresh-cut slices than those grown using black polyethylene mulch. Also, use of the disease forecasting model Tom-Cast, which can result in lower fungicide application than is currently used commercially, resulted in high quality fruit for fresh-cut processing.
Involvement of Ethylene in Development of Chilling Injury in Fresh-cut Tomato Slices during Cold Storage
Authors: Hong Ji Heun , Gross Kenneth C.
Published: January 2019

Experiments were conducted to determine if ethylene influences chilling injury, as measured by percentage of slices exhibiting water-soaked areas in fresh-cut tomato slices of `Mountain Pride' and `Sunbeam' tomato (Lycopersicon esculentum Mill.). Ethylene concentration in containers without ventilation significantly increased during storage at 5 °C, whereas little or no accumulation of ethylene occurred in containers with one or six perforations. Chilling injury was greatest for slices in containers with six perforations, compared to slices in containers with one perforation, and was over 13-fold greater than that of slices in control containers with no perforations. An experiment was also performed to investigate the effectiveness of including an ethylene absorbent pad in containers on subsequent ethylene accumulation and chilling injury. While ethylene in the no-pad controls increased continually during storage of both `Mountain Pride' and `Sunbeam' tomatoes at 5 °C under modified atmosphere conditions, no increase in accumulation of ethylene was observed in containers containing ethylene absorbent pads throughout storage. The ethylene absorbent pad treatment resulted in a significantly higher percentage of chilling injury compared with the no-pad control. In studies aimed at inhibiting ethylene production using AVG during storage of slices, the concentration of ethylene in control containers (no AVG) remained at elevated levels throughout storage, compared to containers with slices treated with AVG. Chilling injury in slices treated with AVG was 5-fold greater than that of controls. Further, we tested the effect of ethylene pretreatment of slices on subsequent slice shelf life and quality. In slices treated with ethylene (0, 0.1, 1, or 10 μL·L-1) immediately after slicing, ethylene production in nontreated controls was greater than that of all other ethylene pretreatments. However, pretreatment of slices 3 days after slicing resulted in a different pattern of ethylene production during storage. The rate of ethylene production by slices treated with 1 μL·L-1 ethylene 3 days after slicing was greater during storage than any of the other ethylene treatments. With slices pretreated with ethylene, both immediately and 3 days after slicing, the rate of ethylene production tended to show a negative correlation with chilling injury. Chemical name used: 1-aminoethoxyvinylglycine (AVG).
Phosphate and Potassium Retention and Release during Chrysanthemum Production from Precharged Materials: II. Calcined Clays and Brick Chips
Authors: Williams Kimberly A. , Nelson Paul V.
Published: January 2019

Soilless container media have almost no capacity to retain PO4 or K. The nutrient retention of two calcined clays, attapulgite and arcillite, and brick chips, precharged with PO4 and K, was investigated. These could serve as an alternative slow-release fertilizer when incorporated into a soilless medium as a component of the mix. Sorption curves were developed at 25 °C for attapulgite of two particle sizes (0.8 to 1.6 mm and 1.6 to 3.2 mm), arcillite (1.1 to 3.2 mm), screened pieces of brick (1.0 to 3.6 mm), and a medium of 7 sphagnum peat: 3 perlite (v/v) using solutions of KH2PO4 (P at 0 to 20,000 mg.L-1). Curves indicated that PO4 and K sorption were similar for both particle sizes of attapulgite, so only the larger size [1.6 to 3.2 mm (8 to 16 mesh)] was used in greenhouse studies. Materials were evaluated in greenhouse studies by growing 'Sunny Mandalay' chrysanthemum [Dendranthema ×grandiflora Kitam. (syn. Chrysanthemum morifolium Ramat.)]. The precharged materials were tested at 10%, 20%, and 30% by volume of a peat: perlite root medium. Phosphate, K, and pH were determined on unaltered medium solutions collected throughout the cropping cycle and foliar analyses were determined on tissue collected at midcrop and end of the crop. Data indicated that precharged calcined clays retained and released PO4, and to some degree K, over time. Precharged clays did not provide K at levels which met plant needs during the latter half of the cropping cycle, but it was released and used at appreciable levels during the first month of crop production. Growth of plants receiving PO4 solely from precharged attapulgite and arcillite at 20% of the medium volume was not significantly different from that of a commercial control when the leaching fraction was maintained at 0.2. However, release of PO4 from the brick chips was not enough to match plant demand. Phosphate lost through leaching from the precharged clays was reduced by about two-thirds compared to control plants fertilized with P at 46.5 mg.L-1 from water-soluble fertilizer at each watering.
Characterization of Topiary (top) an Architectural Mutant of Common Bean
Authors: Guner N. , Myers J.R.
Published: January 2019

Plant breeders are interested in developing upright common beans (Phaseolus vulgaris L.) to reduce diseases and permit mechanical harvest, and improve seed quality. Morphological and genetic characteristics of an architectural mutant in common beans were studied. The mutant had shiny, dark green leaves, overlapping leaflets, and short petioles. Branching was nearly absent, resulting in single stemmed plants. Although mutant plants carried Fin for indeterminacy, and plants progressed in flowering from lower to higher nodes, the terminal node was reproductive. This represents a new form of determinacy in common bean. Inheritance studies demonstrated that the mutant syndrome was controlled by a single recessive gene. Allelism tests between the mutant and overlapping leaflets (ol), and dark green savoy leaf (dgs) showed that the mutant was not allelic to either locus. The trait was designated as Topiary with the gene symbol top, describing its compact and neat appearance. Linkage was tested between top and growth habit (fin), shiny leaves, cross-sectional shape of pods, striped pod (C prpst), and pod suture strings. All genes segregated independently. The genetic merit of the Topiary mutant for improving common beans needs to be investigated, especially the value of single stem growth habit combined with an upright plant habit.
Stomatal Density and Calcium Concentration of Six Snap Bean Cultivars
Authors: Quintana J.M. , Harrison H.C. , Palta J.P. , Nienhuis J. , Kmiecik K. , Miglioranza E.
Published: January 2019

Stomatal density of pods and leaves were determined for six commercial snap bean cultivars (Phaseolus vulgaris L. `Evergreen', `Hystyle', Labrador', `Tenderlake', `Top Crop', and `Venture') grown at three planting dates, in an attempt to find morphological traits that could be related to cultivar differences in pod Ca concentration. Snap beans were planted three times at ≈1-week intervals beginning 15 June 1995, and harvested 59 to 62 days after planting. Stomatal counts were performed using a microscope linked to a video camera, and Ca concentration determinations were made using atomic absorption spectrophotometry. Calcium concentration and stomatal density of leaf tissue was higher than that of pods. Cultivar differences for pod Ca concentration (P = 0.001) and stomatal density (P = 0.001) were observed although cultivars with higher pod stomatal density did not necessarily result in higher pod Ca concentration. Calcium concentration and stomatal density for leaves did not differ among cultivars. Stomatal density and Ca concentration of pods were positively correlated (R2 = 0.37), while pod maturity was negatively associated to both pod Ca concentration (R2 = 0.93), and pod stomatal density (R2 = 0.99). The effect of planting dates was absent in pod Ca concentration and significant in pod stomatal density.
Chilling Temperature Storage Changes the Inorganic Phosphate Pool Distribution in Cherimoya (Annona cherimola) Fruit
Authors: Muñoz Teresa , Ruiz-Cabello Jesús , Molina-García Antonio D. , Escribano María I. , Merodio Carmen
Published: January 2019

Phophorous nuclear magnetic resonance (31P-NMR) spectroscopy was used to study the vacuolar and cytoplasmic pH and the inorganic phosphate (Pi) pool distribution in `Fino de Jete' cherimoya (Annona cherimola Mill.) fruit stored at a chilling temperature (6 °C). Fruit stored at the ripening temperature (20 °C) for 3 days were used as a control. 31P-NMR results confirmed that 6 °C storage caused cytoplasmic acidosis (a decrease of 0.72 ± 0.08 pH units) and a notable increase in the amount of Pi in the cytoplasm. Spectra of perchloric acid extracts also revealed that storage at 6 °C was associated with an increase in the total amount of Pi and phosphorylated metabolites. Moreover, perfusion experiments with a phosphate medium confirmed the preferential accumulation of Pi in the cytoplasm in chilled tissues. Specific activation of phosphoenolpyruvate carboxylase (PEPC) (32.1 ± 1.7 μmol·min-1·mg-1) was observed in those fruit. In chilled fruit the amount of ADP was held at steady-state levels and ATP levels increased, contrary to observations for ripe fruit, where the pool of total nucleotides decreased beyond the point of NMR detection. Fruit stored at 6 °C exhibited a low respiration rate, but metabolism was not arrested and an increase in total soluble solid contents was also observed.