bluuebunny/crossref_metadata_2025 huggingface dataset:
Isotopic and Nonisotopic Estimation of Nitrogen Fertilizer Uptake in Container-grown Woody Ornamentals
Authors: Sandrock* David R. , Righetti Timothy L. , Azarenko Anita N.
Published: February 2019

Accurate methods for determining the fate and recovery of nitrogen (N) fertilizer applied to container-grown nursery crops are essential to comply with regulations and develop innovative fertilizer programs. The objectives of this study were (i) to use 15N techniques to determine the fate of fertilizer N, (ii) to compare nonisotopic and isotopic methods of determining N recovery, and (iii) to determine the relative importance of fertilizer and non-fertilizer N at rates of 25, 50, 100, 200, and 300 mg·L-1 in container-grown Euonymus alatus (Thunb.) Sieb., Cornus sericea L., and Weigela florida (Bunge) A. DC. In all species, root and shoot N increased with N rate, and at each rate more N was stored in the roots than in the shoots. Estimation of N recovery determined by the total N method (Kjeldahl N/applied N) was significantly higher for all species and at each N rate than estimation of N recovery determined by the labeled fertilizer N method (labeled N/total applied N). Increasing fertilizer rates up to 100 mg·L-1 resulted in increased uptake of N derived from other sources (NDFO). NDFO at low N concentrations was a significant portion of the total N in the plant. As a result, the difference in estimation of percent N recovery between each method was larger at lower N concentrations for all species. The nonisotopic total N method produces higher fertilizer N uptake estimates, as much as three to four times the isotopic based estimates, in container-grown plants at N concentrations of 25 mg·L-1. Actual fertilizer N loss increases dramatically from 25 to 300 mg·L-1 (due to dramatic increases in N applied), despite small gains in fertilizer N recovery efficiency.
Growth and Physiological Response of Nursery-grown Landscape Trees to Fertigation
Authors: Schneller* Katrina L. , Cregg Bert , Jones Grant
Published: February 2019

Thirteen species of shade trees including four oak and three maple species were planted from bare root whips in Spring 2001 at the Michigan State Univ. horticulture station near Benton Harbor, Mich. Forty trees of each species were planted and placed under a randomized complete block design consisting of four fertigation treatments in a 2 × 2 factorial (with and without irrigation; with and without nitrogen fertilization). Fertilized trees received 168 kg per hectare of ammonium nitrate annually via the drip system. We measured tree height, stem diameter, and stem volume index (D2 H) at the end of each growing season. We also measured photosynthetic gas exchange with a portable photosynthesis system. After three growing seasons irrigation increased stem volume and height growth. Fertilization has not increased stem volume and height growth, yet there is an interaction between irrigation and fertilization meaning that among irrigated trees fertilizer produced significantly more growth. Species effect on growth was significant (P < 0.001); honey locust trees have grown the most with an average height increase of 1.28 meters in 2003. `Crimson King' Norway maple and goldenchain trees grew the least averaging less than.305 meters of height growth per year. There is no interaction between species and fertigation responses meaning that all species had similar responses to the treatments. From light response curves obtained with a portable photosynthesis system Amax (maximum rate of CO2 assimilation) varied significantly by species and treatment, but showed no interaction between species and treatment effects. Implications for the nursery industry along with further photosynthetic responses will be discussed.
Stand Reduction and Foliage Damage Reduce Yield of Dehydrating Onion
Authors: Clough George H.
Published: February 2019

Field trials were conducted at Hermiston, Ore., from 1995 through 1998, to determine impact of stand loss and plant damage at different growth stages on yield of onions (Allium cepa) grown for dehydration. Stand reduction (0%, 20%, 40%, 60%, 80%) and foliage damage (0%, 25%, 50%, 75%, 100%) treatments were applied at three-, six-, nine-, and twelve-leaf onion growth stages. Although average bulb weight increased as stand was reduced, marketable, cull, and total yields decreased as stand reduction increased (plant population decreased) at all plant growth stages. Bulb weight was not changed by up to 100% foliage removal at the three-leaf stage. At the six- and twelve-leaf stages, weight was reduced when ≥50% of the foliage was removed. The most severe response occurred at the nine-leaf stage. At the three-leaf stage, yield was not affected by foliage damage. At the six-leaf growth stage, yield was reduced by 75% or more foliage loss, but at the nine- and twelve-leaf stages, ≥50% foliage removal reduced expected yields. As with bulb weight, the impact of foliage removal on yield was most severe at the nine-leaf growth stage.
Shearing Date Affects Growth and Quality of Fraser Fir Christmas Trees
Authors: Hinesley L. Eric , Derby Scott A.
Published: February 2019

Fraser fir [Abies fraseri (Pursh) Poir.] Christmas trees were sheared once annually over 4 years on dates ranging from July to March. Shearing reduced total tree growth. Trees sheared in July and August had the highest quality and retail value. Early shearing (July and August) yielded fewer leaders, longer leaders, and 35% to 66% more internodal branches on the leader, compared to later shearing (September through March). Early shearing also yielded more second-order laterals, followed by greater elongation of those laterals. Shearing late into the fall yielded progressively fewer branches, with the minimum in October. Shearing in March gave a little better results than October, but neither date was as good as July or August. In one experiment, two types of residual tip buds (bubble and whisker) were compared as future leaders. Differences in length and straightness of leaders derived from whisker and bubble buds were considered negligible in commercial shearing practice. The ratio of adaxial and abaxial buds on the proximal portion of the leader was about 1:1, and showed little change with shearing date. Distance from the base of the leader to the first abaxial branch also showed little variation among shearing dates.
Effect of Aminoethoxyvinylglycine (AVG) on Preharvest Drop, Fruit Quality, and Maturation of `McIntosh' Apples. I. Concentration and Timing of Dilute Applications of AVG
Authors: Schupp James R. , Greene Duane W.
Published: February 2019

To compare the effects of growth regulators on preharvest fruit drop and fruit maturity, aminoethoxyvinylglycine (AVG) was applied to `McIntosh' apple trees at 75, 150, or 225 mg·L-1, at 8, 4, or 2 weeks before harvest (WBH). These treatments were compared to NAA, daminozide, and to an untreated control. All AVG treatments and timings except 75 mg·L-1 applied 8 WBH delayed preharvest drop and fruit maturity. AVG applied at 225 mg·L-1was more effective in delaying drop and development of maturity than other rates when applied 8 or 2 WBH, but at 4 WBH, 150 mg·L-1 gave equivalent results to 225 mg·L-1. AVG at 150 mg·L-1 was superior to NAA or daminozide as a stop-drop agent. No concentration, or time of application of AVG influenced fruit size at harvest. AVG reduced internal ethylene concentration (IEC) in `McIntosh' apples linearly with increasing AVG concentration. There was a linear relationship between time of AVG application (8, 4, or 2 WBH) and IEC in the fruit after harvest, and the time required for harvested fruit to enter the ethylene climacteric. Development of red color was delayed by AVG. This was attributed to a delay in ripening as determined by a slower increase in IEC and starch hydrolysis. In general, earlier application of AVG resulted in reduced effectiveness of lowering IEC following harvest. Chemical names used: aminoethoxyvinylglycine (AVG), naphthaleneacetic acid (NAA), succinic acid-2,2-dimethylhydrazide (daminozide).
Effect of Aminoethoxyvinylglycine (AVG) on Preharvest Drop, Fruit Quality, and Maturation of `McIntosh' Apples. II. Effect of Timing and Concentration Relationships and Spray Volume
Authors: Greene Duane W. , Schupp James R.
Published: February 2019

AVG was evaluated for its effect on controlling preharvest drop and influencing ripening of `McIntosh' apples in Maine and Massachusetts. AVG consistently and effectively retarded preharvest drop. AVG was superior to NAA and comparable to daminozide in drop control. Dilute or 2× applications were more effective than applications made at lower water volumes. One application of AVG made 4 weeks before anticipated normal harvest was more effective in controlling preharvest drop than split applications of the same amount made earlier or later. In general, AVG delayed ripening as assessed by a retardation in the development of red color, maintenance of flesh firmness, delayed degradation of starch, and a delayed onset of the ethylene climacteric. We conclude that AVG is an effective drop control compound that is also useful as a management tool to extend the harvest window for blocks of `McIntosh' that would otherwise ripen simultaneously. Chemical names used: aminoethoxyvinylglycine (AVG), naphthaleneacetic acid (NAA), succinic acid-2,2-dimethylhydrazide (daminozide, Alar).
Weed Competition in a Mature Matted Row Strawberry Planting
Authors: Pritts Marvin P. , Kelly Mary Jo
Published: February 2019

Various levels of weed competition were implemented in a second-year well-established strawberry (Fragaria ×ananassa `Jewel') planting by cultivating and hand weed removal for defined periods of time over 3 years. The impact of weeds on subsequent productivity was then determined. Sixteen treatments were established where weeds were allowed to grow for defined periods (0, 1, 2, 3, 4, or 5 months) throughout the growing season. Treatments were maintained in the plots for 3 consecutive years. Spring weed biomass in 1997 had no impact on yield that same year. Weed biomass in 1997 was negatively associated with yield in 1998, although the trend was nonsignificant. However, several individual contrasts were significant. For example, the weed-free control treatment had the highest average yield, while season-long weed competition reduced yield by 14%. The inverse relationship between weed biomass and fruit yield became significant in 1999. For every 100 g·m-2 increase in weed biomass in 1998, fruit yield was reduced by 6% in 1999. Season-long uncontrolled weed growth reduced productivity by 51%. However, several plots with a limited amount of weed competition had higher yields than the continuously weeded control. These data indicate that yields from a well-established strawberry planting may not be vulnerable to a limited amount of weed competition for at least 2 years. Furthermore, data suggest that hand weeding and cultivation on a monthly basis for multiple years may be damaging as well. Growers should direct a majority of their efforts and resources toward controlling weeds in the planting year. Once the planting is well-established, growers may limit the number of times they hand weed to two or three per season.
Changes in the Activity and Expression of 1-Aminocyclopropane-1-Carboxylate (ACC) Synthase, ACC Oxidase, and Phenylalanine Ammonia-lyase in Asparagus Spears in Response to Wound-induced Ethylene Synthesis
Authors: Bhowmik Pankaj Kumar , Matsui Toshiyuki
Published: February 2019

The molecular and enzymatic changes that follow harvesting of asparagus are important aspects for postharvest deterioration. To define the factors contributing to postharvest deterioration, the early changes in ethylene production and the activities and expression of 1-aminocyclopropane-1-carboxylate (ACC) synthase, ACC oxidase, and phenylalanine ammonia-lyase (PAL) were studied in whole spears and in excised top and bottom portions. As a result of wounding, ethylene production was found higher in both top and bottom portions compared with whole spears but followed the same trend reaching the peak at 16 hours after harvest. ACC synthase was rapidly induced in excised top portions but no significant ACC synthase activity was observed in excised bottom portions. In top portions, ACC synthase reached a peak 8 hours after harvest and thereafter started to decline. In contrast to ACC synthase, ACC oxidase was induced markedly in both top and bottom portions and remained high until 16 hours after excision. On the other hand, PAL greatly increased in activity in bottom portions but not in excised tops. Northern blot analysis showed that increased mRNA levels coincided well with the excision-promoted increases in enzyme activity and ethylene production.
Random Amplified Polymorphic DNA (RAPD) Analysis of Long-term Cultured Hybrid Hazelnut
Authors: Nas Mehmet Nuri , Mutlu Nedim , Read Paul E.
Published: February 2019

RAPD and phenotypic analysis were conducted to assess clonal stability of hazelnuts generated from axillary buds cultured in vitro for long-term. The nuts produced on in vitro-propagated plants were indistinguishable from those of donor plants. With the exception of rare horizontal (plagiotropic) growth, all in vitro-propagated plants exhibited phenotypes similar to those of donor plants. RAPD analysis did not reveal any somaclonal variation between donor plants from which in vitro cultures were initiated and micropropagated plants (6-year cultures), and no somaclonal variation was detected among in vitro-propagated plants. However, polymorphism (15.6%) was detected between the parent plant and its in vitro-propagated progenies (from seedlings). These results show a good discriminatory power of RAPD to detect polymorphism between samples where it is expected, and it can be effectively used for genetic assessment of micropropagated hazelnut. No evidence of genetic or epigenetic changes was observed in long-term cultured hazelnut, and thus long-term in vitro culture of hazelnut does not seem to limit its clonal propagation.
Comparison of Agar and an Agitated, Thin-film, Liquid System for Micropropagation of Ornamental Elephant Ears
Authors: Adelberg Jeffrey , Toler Joe
Published: February 2019

Micropropagation of black-stemmed elephant ear (C. esculenta (L.) Schott `Fontanesii')' and upright elephant ear (A. macrorrhizos G. Don) were compared in semi-solid agar media and agitated, liquid thin-film bioreactor vessels at four explant densities (33, 100, 165, and 330 explants/L of media) using two growth regulator combinations: 1) 1 μm benzylaminopurine (BA)—growth medium, and 2) 3 μm BA plus 3 μm ancymidol—multiplication medium. The thin-film liquid system outperformed agar culture for most measured responses. Some exceptions were relative dry weights at higher explant densities and multiplication rate of Colocasia. When the thin-film liquid system was compared to agar culture, Alocasia explants produced their greatest biomass and had the least residual sugar at the highest explant density. Alocasia explants multiplied most rapidly and had the greatest relative dry weight on liquid media at the low explant densities. Alocasia plants were larger in growth medium than multiplication medium and larger in liquid medium than agar medium. When compared to agar, Colocasia in the thin-film liquid system produced the greatest biomass at the highest explant density in growth medium, had the greatest relative dry weight at the lowest explant density, and used the most sugar at the highest explant density. Alocasia and Colocasia would likely produce greater fresh and dry weight at the highest explant density if additional sugar were supplied during thin-film culture. Greater growth in thin-film culture of Alocasia and Colocasia is due in part, to greater availability of sugar in liquid compared to agar medium.
Explant Initiation Date and BA Concentration Influence Shoot Proliferation in vitro of Two Liatris Interspecific Hybrids
Authors: Ault James R.
Published: February 2019

Shoot proliferation cultures were established in vitro using flower-stem explants from two different interspecific hybrid plants of Liatris. Explants taken on two dates from field-grown plants were successfully established and axillary shoot growth promoted on a medium consisting of Murashige and Skoog basal salts and vitamins with 30 g·L-1 sucrose, 1.0 μm BA, and 7.0 g·L-1 agar, with a medium pH = 5.7. Initial explant contamination rates were significantly higher among explants collected later in the growing season. Addition of BA (1.0, 2.0, 4.0, 8.0, or 16.0 μm) improved shoot formation compared to the control for both plants. Proliferation rates differed between the dates of establishment, the plants, and the BA treatments. Shoots rooted readily in medium without PGRs or with 1.0, 2.0, 4.0, or 8.0 μm K-IBA. Overall rooting was 88%. About 90% of the plants rooted in the presence of 1.0 μm K-IBA were successfully established in the greenhouse. Chemical names used: 6-benzyl adenine (BA); potassium salt of indole-3-butyric acid (K-IBA).
Abscisic Acid Accumulation in Relation to Drought Tolerance in Kentucky Bluegrass
Authors: Wang Zhaolong , Huang Bingru , Bonos Stacy A. , Meyer William A.
Published: February 2019

Drought is a major factor limiting plant growth, which has been associated with the accumulation of absicsic acid (ABA) in various species. The objective of the study was to determine the relationship between ABA accumulation and drought tolerance for kentucky bluegrass (Poa pratensis L.) during short-term drought stress. Eight kentucky bluegrass cultivars (`Midnight', `A82-204', `RSP', `Alpine', `Moonlight', `Brilliant', `Washington', and `Baruzo') were subjected to drought stress in a growth chamber. Water relations, gas exchange rate, and ABA content of leaves were determined at various times during drought stress. Turf quality decreased with drought duration for all eight cultivars. Leaf ABA content increased linearly with drought stress within 11 days of treatment; the rate of the increase was negatively related to the rate of turf quality decline. The rate of ABA accumulation during drought stress was positively correlated with the rates of decrease in turf quality (r2 = 0.6346), increase in electrolyte leakage (r2 = 0.7128), and decrease in relative water content (r2 = 0.5913). There were highly significant negative correlations between ABA content and leaf water potential (r2 = 0.9074), stomatal conductance (r2 = 0.6088), transpiration rate (r2 = 0.6581), net photosynthesis rate (r2 = 0.6956), and a positive correlation between ABA content and electrolyte leakage (r2 = 0.7287). The results indicate that drought tolerance is negatively related to ABA accumulation during shortterm drought stress. ABA accumulation in response to drought stress could be used as a metabolic factor to select for drought tolerance in kentucky bluegrass.
Genetic Relationships of Spanish Olive Cultivars Using RAPD Markers
Authors: Belaj A. , Satovic Z. , Trujillo I. , Rallo L.
Published: February 2019

Eighty-two Spanish olive cultivars from the World Germplasm Bank of the Centro de Investigación y Formación Agraria (CIFA) Alameda del Obispo in Cordoba (Spain) were analysed by RAPD markers to assess their genetic relatedness and to study patterns of genetic variation. The dendrogram based on unweighted pair group cluster analysis using Jaccard's index included two major groups that consisted mostly of cultivars from the southern and central part of Spain. Clustering together of cultivars from the Levante zone was also observed. The pattern of genetic variation among olive cultivars from three different Spanish zones (Levante, central and Andalusia) was analysed by means of the analysis of molecular variance (AMOVA). Although most of the genetic variability was attributable to differences of cultivars within each zone (95.88%), significant φ-values among zones (φst = 0.041; p < 0.001) suggested the existence of phenotypic differentiation. These results are consistent with the predominantly allogamous nature of Olea europaea L. species. Significant values of φst for the pair Andalusia/Levante indicate the presence of differentiation. The negative value of φst observed in the case of the Andalusia/central pair suggests that some varieties from central Spain are more similar to the Andalusian ones than to the varieties of their own geographic area, and vice versa.
Evaluation of Brassica carinata Accessions for Resistance to Black Rot (Xanthomonas campestris pv. campestris)
Authors: Tonguç Muhammet , Griffiths Phillip D.
Published: February 2019

Black rot, caused by Xanthomonas campestris pv. campestris (Pam.) Dawson (Xcc), is a major bacterial disease of Brassica oleracea L. vegetables. In this study the related species Brassica carinata Braun (ethiopian mustard), which can be used to generate interspecific crosses with B. oleracea was evaluated for resistance to Xcc. Fifty-four accessions and susceptible control plants were wound inoculated with four isolates of Xcc race 4 at the juvenile stage. Of the 54 accessions tested, A 19182 and A 19183 exhibited no symptoms when inoculated with Xcc for all plants tested, and the accessions including PI 199947, PI 199949 and PI 194256 segregated for resistance to Xcc.
Photosynthetic Characteristics of Apple Spur Leaves after Summer Pruning to Improve Exposure to Light
Authors: Li Kuo-Tan , Lakso Alan N.
Published: February 2019

Summer pruning increases canopy light penetration and re-exposes spur leaves of the interior canopy of apple trees (Malus ×domestica Borkh.). However, we hypothesized that leaf photosynthetic ability is determined by the pre-pruning light environment, and the re-exposure intensity after summer pruning is incapable of restoring the photosynthesis efficiency of shaded leaves. To test this hypothesis, a commercial-type thinning-cuts pruning was applied to mature central leader `Empire'/M.26 apple trees. Changes in light availability, leaf net photosynthesis (Pn), photosystem II efficiency, and specific leaf weight (SLW) were recorded periodically before and after pruning. Leaf photosynthesis declined slightly through the growing season and was well correlated with pre-pruning light availability until late September. Although Pn decreased more substantially late in the season on exterior leaves than on interior leaves, Pn of leaves in the inner and middle canopies was lower than exterior leaves until late October. Maximum efficiency of photosystem II of dark-adapted leaves, measured by chlorophyll fluorescence (Fv/Fm), was not related to prior exposure or re-exposure. Specific leaf weight was well correlated with pre-pruning light availability and with leaf Pn in August but not in October. Results suggested that commercial summer pruning significantly increases light environments in the inner and middle canopies. However, light availability at interior and middle canopy sites was still much lower than exterior canopy and, consequently, leaf photosynthetic ability did not increase after summer pruning.
The Inflorescence and Fruit Peduncle as Indicators of Nitrogen Status of the Avocado Tree
Authors: Razeto Bruno , Salgado Jorge
Published: February 2019

A tissue analysis trial for the diagnosis of nitrogen level was performed during the 2001 growing season in Paine County, Metropolitan Region, Chile. Seven-year-old `Hass' avocado (Persea americana Mill.) trees were soil treated with urea at rates of 0, 333, 666, and 999 g N/tree, split in two applications (2 and 4 months after fruit set). Each treatment was applied to three randomly selected trees. Fifty spring flush leaves and fifteen fruit peduncles were taken per tree 4 months after application. Two months later, 70 panicles per tree were taken, and nitrogen concentration in these samples was determined by Kjeldahl digestion. Differences between treatments were better detected in peduncle and inflorescence samples than in leaf samples. The relationship between nitrogen dose and nitrogen concentration in the tissue was R2 = 0.67, 0.65, and 0.56 in peduncle, leaf, and inflorescence, respectively. Consequently, peduncle appears a promising tissue, probably better than leaf, for diagnosing the nitrogen status of avocado trees.
Resistance of Raspberry Cultivars to Fire Blight
Authors: Braun P.G. , Hildebrand P.D. , Jamieson A.R.
Published: February 2019

Twenty-five cultivars of red raspberry (Rubus idaeus L.) and one purple raspberry (R. occidentalis L. × R. idaeus L.) were evaluated for their resistance to fire blight caused by Erwinia amylovora (Burr.) Winslow et al. Actively growing raspberry cane tips were wound inoculated with three isolates of the pathogen and disease development was assessed over 17 days. Three methods of evaluating resistance were used: area under the disease progress curve (AUDPC), a weighted AUDPC called the area under the disease severity curve (AUDSC), and lesion length. A wide range of resistance levels was observed, but no cultivars were symptomless. Primocane-fruiting cultivars tended to be more resistant than floricane-fruiting ones. Of the three E. amylovora isolates used in this study, one was significantly more virulent than the other two, but no cultivar × isolate interaction was detected.
Photosynthesis and Growth of Rhamnus caroliniana during Drought and Flooding: Comparisons to the Invasive Rhamnus cathartica
Authors: Stewart J. Ryan , Graves William R.
Published: February 2019

Rhamnus caroliniana Walt. (carolina buckthorn or indian cherry) is an attractive small tree or shrub found in diverse habitats in the United States. Because the species occurs in both mesic and xeric soils, we questioned whether selections of carolina buckthorn could be marketed as new nursery crops resistant to both drought and flooding. Our first objective was to characterize how soil water affects growth and gas exchange of carolina buckthorn. We studied potted plants subjected to soil moistures that ranged from complete submersion of the root zone to severe drought (7% soil water by volume). The maximal photosynthetic rate occurred at 27% soil water content, and complete submersion killed plants. Our second objective was to compare responses of carolina buckthorn to those of the invasive common buckthorn (Rhamnus cathartica L.) when potted plants were treated with partial flooding of root zones and drought. Carolina buckthorn resisted deleterious effects of partial flooding. In contrast, leaves of common buckthorn became epinastic, and rates of photosynthesis were low (2.14 μmol CO2/m2/s) after 17 days of treatment. Mean photosynthesis of common buckthorn increased to 5.52 μmol CO2/m2/s, a rate similar to that of carolina buckthorn, after 55 days of treatment. Drought reduced net photosynthesis by 52% and 68%, respectively, for carolina buckthorn and common buckthorn relative to rates of plants in the control treatment. We conclude that carolina buckthorn is capable of maintaining carbon fixation and growth over a wide range of soil water contents, and unlike common buckthorn, is not dependent upon morphological, anatomical, or physiological adjustments to optimize growth and net photosynthesis in extremely wet soil. Use of carolina buckthorn as an ornamental is warranted if invasiveness and other potential problems with the species are not identified.
Drought Stress Can Produce Small but not Compact Marigolds
Authors: van Iersel Marc W. , Nemali Krishna S.
Published: February 2019

We examined the effectiveness of an elevated capillary mat system to maintain constant and different moisture levels in the growing medium and verify the potential of drought stress conditioning in producing small and compact bedding plants. To differentiate between plant height and compactness, we determined compactness as the leaf area or dry mass per unit stem length. Marigold `Queen Sophia' (Tagetes erecta L.) seedlings were grown in square, 9-cm-wide, 10-cm-high containers filled with a soilless growing medium. A capillary mat was laid on top of a greenhouse bench which was raised by 15 cm on one side compared to the other side to create an elevation effect. Seedlings were subirrigated by immersing the low end of the capillary mat in a reservoir of water. The amount of water moving to the higher end of the mat progressively decreased with elevation. The moisture content in the growing medium averaged from 26 to 294 mL/pot at different elevations. Regression analysis indicated that growth parameters including, shoot dry mass, leaf area, leaf number, and plant height decreased linearly with decreasing soil moisture content in the growing medium. Of all the measured growth parameters, plant height was found to be least sensitive to decreasing moisture content in the growing medium. Plants in high moisture treatments had more dry mass and leaf area per unit length of the stem compared to those in low moisture treatments. Our results indicate that drought stress can produce small, but not truly compact bedding plants.
Greenhouse Screening of Capsicum Accessions for Resistance to Green Peach Aphid (Myzus persicae)
Authors: Frantz James D. , Gardner Jeffrey , Hoffmann Michael P. , Jahn Molly M.
Published: February 2019

A greenhouse screen for resistance to green peach aphid (GPA) [Myzus persicae (Sulzer)] was done using 50 pepper (Capsicum spp.) accessions. There were significant differences among accessions for damage rating, number of aphids per plant and number of aphids per leaf. Leaf pubescence, the basis of a reported nonpreference resistance mechanism to green peach aphid infestation, failed to protect pepper accessions from GPA colonization and damage. Sources of resistance and tolerance to cotton aphid [Aphis gossypi (Glover)] supported high levels of green peach aphid infestation and exhibited considerable damage. Although no accessions provided strong resistance to aphid colonization evident by significantly reduced numbers of aphids, several commercial varieties and sources of virus resistance exhibited strong tolerance to GPA, evident as reduced damage. Tolerant varieties could be an important component in integrated pest management of green peach aphid.
Greenhouse Evaluation of Capsicum Accessions for Resistance to European Corn Borer (Ostrinia nubilalis)
Authors: Frantz James D. , Gardner Jeffrey , Hoffmann Michael P. , Jahn Molly M.
Published: February 2019

A replicated greenhouse evaluation of a range of commercial and noncommercial (Capsicum spp.) accessions for resistance to european corn borer (ECB) [Ostrinia nubilalis (Hubner)] was conducted. Percentage of fruit damaged was observed among 29 accessions four weeks after plants were artificially infested with ECB egg masses. Small-fruited peppers generally showed lower levels of damage, while large-fruited peppers were the most susceptible. Genotypes with elongate fruit were less damaged than those with bell-shaped fruit. Resistance to fruit damage was also associated with increasing pungency level, with two notable exceptions. The pungent genotype `Large Red Thick Cayenne' was significantly more susceptible than many of the other pungent accessions tested. The relative susceptibility of this accession may be related to large fruit size. The nonpungent pepper `Corno di Toro' showed significantly lower percent fruit damage than other nonpungent peppers including `Banana Supreme' with roughly similar fruit size, ranking amidst highly pungent peppers such as `Red Scotch Bonnet'. These results confirm that resistance to ECB can be identified in nonpungent Capsicum genotypes and demonstrate that pungency is not always correlated with ECB damage. Reported sources of aphid resistance or tolerance showed good levels of ECB resistance, but interpretation of these results was confounded by the presence of pungency.
Shoot Regeneration Rates of Perennial Phlox are Dependant on Cultivar and Explant Type
Authors: Fraga Margarita , Alonso Mertxe , Borja Marisé
Published: February 2019

Meristem culture and/or thermotherapy were used for virus elimination from ornamental Phlox paniculata L. (`Blue Boy', `Orange perfection' and `Starfire') mother plants. Shoot tip, leaf, node and flower ovary explants collected from greenhouse-maintained virus free plants were cultured in vitro for shoot initiation. Adventitious shoot initiation was observed on Murashige and Skoog (MS) medium containing the cytokinin BA with or without the auxin NAA. The addition of 0.4 mg·L-1 thiamine, 0.4 mg·L-1 folic acid, and 40 mg·L-1 adenine sulfate to the MS medium did not improve the regeneration rate. Multiplication and rooting were genotype dependent. Blue Boy and Orange Perfection cultivars regenerated the maximum number of shoots from leaf explants. `Blue Boy' leaf explants from in vitro plants had a lower regeneration rate than explants from greenhouse plants. Cultivar `Starfire' had the highest shoot formation with open flower ovary explants and failed to regenerate from leaf explants. In vitro rooting of adventitious shoots in the presence of auxins (IAA, NAA, or IBA) with or without BA was less effective than ex vitro rooting. Chemical names used: 6-benzyladenine (BA); indole-acetic acid (IAA); indole-3-butyric acid (IBA); α-naphthaleneacetic acid (NAA).
Growth and Pigment Content of Container-grown Impatiens and Petunia in Relation to Root Substrate pH and Applied Micronutrient Concentration
Authors: Smith Brandon R. , Fisher Paul. R. , Argo William R.
Published: February 2019

The objective was to quantify the effect of substrate pH and micronutrient concentration on growth and pigment content for two floricultural crop species, Petunia ×hybrida `Priscilla' and Impatiens wallerana `Rosebud Purple Magic'. A 70% peat: 30% perlite medium was amended with dolomitic hydrated lime to achieve five substrate pH's ranging from pH 4.4 to 7.0. Plants were grown in 10-cm-diameter pots in a greenhouse for 4 weeks, and irrigated with a fertilizer containing (in mg·L-1) 210N-31P-235K-200Ca-49Mg. Micronutrients were applied using an EDTA (ethylenedinitrilotetraacetic acid) chelated micronutrient blend (C111), at 1×, 2×, and 4× concentrations (in mg·L-1) of 0.50Fe-0.25Mn-0.025Zn-0.04Cu-0.075B-0.01Mo. Petunia shoot dry mass and stem caliper decreased as substrate pH increased, whereas leaf length and width remained unchanged. The highest level of C111 resulted in higher dry mass and smaller leaf area compared with other C111 levels. Overall, substrate pH and C111 had little effect on plant size or mass for impatiens. For both species, increasing substrate pH above 5.3 resulted in a decline in chlorophyll, carotenoids, and the SPAD chlorophyll index (measured with a Minolta-502 SPAD meter) compared with the lowest three pH levels. Chlorosis was observed at pH 7 after 2 weeks of growth. Increasing C111 concentration had no effect on pigment content below pH 5.3, but increased pigment content at higher pH levels. The SPAD index was highly correlated with chlorophyll content. This research emphasizes that an acceptable range in substrate pH can vary depending on fertilizer practices, with higher micronutrient concentration compensating for lower solubility at high substrate pH.
Nutrient Uptake in Container-grown Impatiens and Petunia in Response to Root Substrate pH and Applied Micronutrient Concentration
Authors: Smith Brandon R. , Fisher Paul. R. , Argo William R.
Published: February 2019

The objective was to quantify the effect of substrate pH and micronutrient concentration on tissue nutrient levels in Petunia ×hybrida Hort. Vilm.-Andr. and Impatiens wallerana Hook. F. Plants were grown in 10-cm-diameter pots for 4 weeks in a 70% peat: 30% perlite medium amended with five lime rates to achieve substrate pH values ranging from pH 4.4 to 7.0. Plants were irrigated with (in mg·L-1) 210N-31P-235K-200Ca-49Mg. Micronutrients were applied as an EDTA (ethylenedinitrilotetraacetic acid) chelated micronutrient blend (C111), at 1×, 2×, and 4× concentrations of 0.50Fe-0.25Mn-0.025Zn-0.04Cu-0.075B-0.01Mo. Patterns of tissue concentrations across substrate pH differed from nutrient solubility in the medium, particularly with regard to Mn. Foliar N content decreased slightly as substrate pH increased, whereas foliar Ca, Mg, and S increased. Although foliar P and K varied with pH, there was no consistent trend between species. Foliar total Fe, ferrous Fe, and Cu decreased as substrate pH increased, whereas foliar Zn increased. Foliar Mn content decreased for both species as pH rose to 6.0, and then increased from pH 6.0 to 7.0. In contrast, Mn level in the substrate, measured in a saturated medium extract using deionized water as the extractant, decreased as pH increased from pH 4.4 to 7.0. Chlorophyll content decreased when the ratio of tissue Fe to Mn was <0.57 (impatiens) or <0.71 (petunia), or Fe was <106 (impatiens) or 112 (petunia) μg·g-1. SPAD chlorophyll index also declined in petunia with foliar Mn >42 μg·g-1. Increasing C111 increased foliar Cu, total Fe and ferrous Fe in both species, and B for impatiens, and partly compensated for reduced nutrient solubility at high pH.
Ultraviolet-B Radiation Damage on Kentucky Bluegrass. III. Cultivar Effects
Authors: Ervin Erik H. , Zhang Xunzhong , Fike John H.
Published: February 2019

Plants possess various constitutive and inducible defense mechanisms such as pigment and antioxidant systems for protection against stresses such as ultraviolet-B (UV-B; 290 to 320 nm) radiation. Our previous research has indicated that higher chlorophyll, carotenoid, and anthocyanin concentrations were associated with greater tolerance of UV-B stress by `Georgetown' kentucky bluegrass (Poa pratensis L.). The objectives of this study were to determine if kentucky bluegrass cultivars with darker leaf color possessed greater pigment and antioxidant defense systems and if such increases were associated with greater resistance to UV-B. Eight cultivars exhibiting a range of green color intensity (`Apollo', `Brilliant', `Julius', Limerick', `Midnight', `Moonlight', `Nuglade', and `Total Eclipse') were selected and subjected to continuous, artificial UV-B radiation (70 μmol·m-2·s-1). UV-B irradiation reduced turf quality (55% to 62%) and photochemical efficiency (37% to 70%) when measured 5 days after initiation of UV-B exposure. Significant differences in turf color, photochemical efficiency, chlorophyll a, chlorophyll b, chlorophyll a+b, and carotenoids were found among the cultivars. `Moonlight' had greatest photochemical efficiency, chlorophyll, carotenoids, and turf quality. Positive correlations of pigment concentration with photochemical efficiency and turf color were observed under UV-B radiation stress, with correlation coefficients ranging from 0.49 to 0.62. The results of this study suggests that selecting cultivars with higher concentrations of chlorophyll and carotenoids and photochemical efficiency may be an effective way for turfgrass managers and sod producers to improve sod establishment and quality in environments with higher UV-B radiation.
Green-light Supplementation for Enhanced Lettuce Growth under Red- and Blue-light-emitting Diodes
Authors: Kim Hyeon-Hye , Goins Gregory D. , Wheeler Raymond M. , Sager John C.
Published: February 2019

Plants will be an important component of future long-term space missions. Lighting systems for growing plants will need to be lightweight, reliable, and durable, and light-emitting diodes (LEDs) have these characteristics. Previous studies demonstrated that the combination of red and blue light was an effective light source for several crops. Yet the appearance of plants under red and blue lighting is purplish gray making visual assessment of any problems difficult. The addition of green light would make the plant leave appear green and normal similar to a natural setting under white light and may also offer a psychological benefit to the crew. Green supplemental lighting could also offer benefits, since green light can better penetrate the plant canopy and potentially increase plant growth by increasing photosynthesis from the leaves in the lower canopy. In this study, four light sources were tested: 1) red and blue LEDs (RB), 2) red and blue LEDs with green fluorescent lamps (RGB), 3) green fluorescent lamps (GF), and 4) cool-white fluorescent lamps (CWF), that provided 0%, 24%, 86%, and 51% of the total PPF in the green region of the spectrum, respectively. The addition of 24% green light (500 to 600 nm) to red and blue LEDs (RGB treatment) enhanced plant growth. The RGB treatment plants produced more biomass than the plants grown under the cool-white fluorescent lamps (CWF treatment), a commonly tested light source used as a broad-spectrum control.
Establishment of Calibration Curves for Comparing Pour-through and Saturated Media Extract Nutrient Values
Authors: Cavins Todd J. , Whipker Brian E. , Fonteno William C.
Published: February 2019

Most commercial and university substrate testing laboratories' recommended floriculture nutritional values are based on the saturated media extract (SME) method. With the recent gain in popularity of pour-through nutritional monitoring, alternative recommended values are needed for nutrient analyses based on pour-through extracts. Pour-through nutritional values were compared to the SME values to develop calibration curves and recommended nutritional values. Euphorbia pulcherrima `Freedom Red' Willd. ex Klotzch. were grown for two consecutive growing seasons in 16.5 cm plastic pots with Fafard 4 P root substrate and fertigated with 200, 300, or 400 mg·L-1 N from a 13N-0.88P-10.8K fertilizer. Linear relationships existed and inverse calibration curves for pour-through and SME comparisons were developed for (r2): EC (0.98), NO3- (0.98), P (0.97 to 0.99), K (0.99), Ca (0.94 to 0.97), and Mg (0.91). In addition, recommended pour-through substrate value ranges were developed for comparison with SME values. The established calibration curves and pour-through substrate value ranges will allow substrate-testing laboratories to make nutritional recommendations based on pour-through extractions.
Postharvest Characteristics of Canaan Fir and Fraser Fir Christmas Trees
Authors: Bates Ricky M. , Sellmer James C. , Despot David A.
Published: February 2019

Needle retention, xylem pressure potential and overall quality of canaan fir (Abies balsamea var. phanerolepis (L.) Mill.) and fraser fir (Abies fraseri (Pursh) Poir.) Christmas trees were evaluated over a 40-day display period. Cut trees were stored outdoors for 24, 48, or 96 hours, and half the trees had a 2.5-cm section trimmed from the basal portion of the stem, before placement in water at an indoor display room. Controls were placed in water immediately after harvest. Xylem pressure potentials and overall quality were similar for both species except for trees stored 96 hours. Untrimmed canaan fir dried to -2.4 MPa and was rated below average by the end of the display period compared to -1.3 MPa and a good quality rating for fraser fir. Needle retention and color characteristics were excellent across all treatments for fraser fir during the entire display period. Needle loss for canaan fir began relatively soon during display, generally increased across all treatments, and was highly variable. In addition, quality of some canaan fir trees decreased as needles turned brown, but did not shed during the display period. Tree water status alone did not completely account for loss of needles and quality in canaan fir; the need exists to identify seed sources with better postharvest characteristics.
Cutting Production Is Affected by Pinch Number during Scaffold Development of Stock Plants
Authors: Faust James E. , Grimes Larry W.
Published: February 2019

Stock plants of four vegetatively propagated annual species (Argyranthemum frutescens `Comet Pink', Nemesia fruticans `Plum Sachet' Venten., Osteospermum fruticosum `Zulu' L., and Verbena ×hybrida `Lanai Bright Pink' L.) were grown with one (P), two (PP), or three (PPP) pinches during the scaffold development phase. The number of pinches applied to all four species affected the yield and distribution of cuttings produced over time. P began to produce cuttings first; however, the rate (number of cuttings per week) of cutting production was relatively low resulting in the fewest total cuttings produced by the end of the experiment. Cutting harvest from PPP started 3 to 6 weeks after cuttings were initially harvested from P. However, the rate of increase in cutting production was greater in PPP than P for all species, except Osteospermum, so the total cutting yield of PPP equaled P after 3 to 5 weeks of cutting production. The final cutting yield for PPP was 38%, 38%, 20%, and 8% higher than P for Argyranthemum, Nemesia, Osteospermum, and Verbena, respectively. PP produced 24%, 17%, and 21% more total cuttings than P for Argyranthemum, Nemesia, and Osteospermum, respectively, while Verbena displayed no significant difference. At the termination of the experiment, the weekly rate of cutting production increased 66.3%, 84.0%, and 30.5% as pinch number increased from P to PPP for Argyranthemum, Nemesia, and Verbena, respectively. This study demonstrates that the number of pinches performed on stock plants during scaffold development can have a significant impact on the timing, the weekly production rate, and cumulative yield of cuttings harvested.
(169) Root Formation on Stem Cuttings of Yellow-flowered Cultivars of Magnolia Is Influenced by Time-after-budbreak and IBA
Authors: Sharma Jyotsna , Knox Gary , Ishida Maria
Published: February 2019

We propagatedsixyellow-flowered cultivars of Magnolia vegetatively by applying 0, 8, 16, or 30 g·kg-1 indole-3-butyric acid (IBA) in talc to bases of terminal stem cuttings collected 5, 7, 9, or 11 weeks after budbreak. Mean rooting percentage increased from 12% (in the absence of IBA) to 34% (after applying 30 g·kg-1 IBA). Rooting percentage also increased with increasing basal caliper (r2 = 0.25; P< 0.0001) of a cutting. For each collection date, more cuttings of `Ivory Chalice' and `Yellow Lantern' developed roots than did other cultivars. When data were analyzed separately for selected cultivars, 63% rooting was observed among cuttings of `Ivory Chalice' collected 7 weeks after budbreak. Rooting percentage was higher (22%) among cuttings of `Hot Flash' collected 5 or 7 weeks after budbreak in comparison to later collection dates, but harvest date did not influence rooting, which ranged from 44% to 59%, among cuttings of `Yellow Lantern'. Collection of stem cuttings early in the growing season (5 weeks after budbreak) was beneficial (31% rooting) for inducing root formation among cuttings of `Golden Sun'. We conclude that `Ivory Chalice' and `Yellow Lantern' are promising choices for growers interested in clonal propagation of yellow-flowered cultivars of Magnolia. To maximize rooting, terminal cuttings should be collected within 5 to 11 weeks after budbreak and should be treated with 16 or 30 g·kg-1 IBA in talc. Early collection dates improved rooting frequencies among cuttings of other cultivars but these, particularly `Butterflies', remain variably recalcitrant and merit further study.