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Carolyn F. Scagel

Using several different ericaceous ornamental species, we compared the growth, mineral nutrition, and composition of plants in response to growing media amended with varying proportions of sphagnum moss peat (peat) or coir dust (coir). Plants were grown for 16 weeks in media consisting of 80% composted Douglas fir bark with 20% peat, 20% coir, or 10% peat and 10% coir. Sixteen weeks after planting, decreases in extractable P were larger in peat-amended medium than the coir-amended medium, while decreases in extractable NH4-N and NO3-N were larger in the coir-amended medium. In general, leaf and stem dry weight, the number of leaves and stems, and total stem length increased with increasing proportion of coir in the medium while root dry weight either increased (Kalmia latifolia), decreased (Rhododendron, Gaultheria), or was not influenced by increasing the proportion of coir in the medium. The composition of the growing medium also influenced aspects of plant marketability and quality including: leaf greenness (SPAD), plant form (e.g., number of leaves per length of stem), and partitioning of biomass (e.g., root to shoot ratio). Nutrient uptake and fertilizer use was significantly different between the media types. Depending on the cultivar, we found that the coir-amended medium resulted in higher uptake or availability of several nutrients than peat-amended medium. Up take or availability of N, P, K, Ca, and S was enhanced for several cultivars, while uptake or availability of Mg, Fe, and B was similar between media types. Most cultivars/species growing in the coir-amended medium had higher production or accumulation of proteins and amino acids in stems than plants growing in peat-amended medium, while the production of proteins and amino acids in roots was lower in plants growing in coir-amended than in peat-amended medium. For the cultivars/species we tested, coir is a suitable media amendment for growing ericaceous plants and may have beneficial effects on plant quality.

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Carolyn F. Scagel

Seven highbush blueberry cultivars were inoculated with one of three different isolates of ericoid mycorrhizal fungi (EMF) and grown in pots for 2 years with either inorganic or organic fertilizer. Root colonization of noninoculated plants was low (<15%) regardless of fertilizer source. Root colonization on inoculated plants was 15-30%. Colonization was typically higher when plants were grown with organic fertilizer. Inoculation generally increased plant growth but decreased root:shoot biomass ratios regardless of the type of fertilizer used. Inoculation also increased nutrient uptake and/or nutrient use efficiency in several cultivars, particularly when plants were fertilizer with organic fertilizer. Without inoculum, however, some cultivars fertilized with organic fertilizer had less growth and lower concentrations of N, K, S, and Cu than those fertilized with inorganic fertilizer. Cultivars that were genetically close in ancestry showed a high degree of variability in response to mycorrhizal fungi, while responses to fertilizer type were similar in closely related cultivars. Results suggest that nutrient availability may influence colonization and growth responses to EMF; however aspects of fungus–host specificity and inoculum availability also play a role in EMF colonization of roots in container production.

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Guihong Bi and Carolyn F. Scagel

Rooted liners of Hydrangea macrophylla (Thunb.) Ser. ‘Berlin’ were fertigated with different rates of nitrogen (N) from July to Sept. 2007 and leaves were sprayed with 15N-labeled urea in late October to evaluate urea uptake and 15N translocation by hydrangea leaves in relation to plant N status. Four plants from each N fertigation rate were harvested before they were sprayed with urea and 2, 5, 10, and 15 days after urea spray. Increasing rate of N fertigation increased plant N content in October before being sprayed with urea. Leaves rapidly absorbed 15N from urea spray. The highest rate of 15N uptake occurred during the first 2 days after urea spray and then decreased. Export of 15N from leaves occurred rapidly after uptake and the highest rate of 15N export occurred during the first 2 days after urea spray and then decreased. During the first 5 days after urea spray, the rate of 15N uptake by leaves and export from leaves decreased with increasing rate of N fertigation. On a whole plant basis, the total amount of 15N from foliar 15N–urea spray increased with increasing rate of N fertigation; however, the percentage of 15N exported from leaves and the percentage of N that derived from foliar 15N–urea spray decreased with increasing rate of N fertigation. Results suggest that hydrangea plants with lower N status in the fall are more efficient in absorbing and translocating N from foliar urea than plants with higher N status.

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Carolyn F. Scagel and Jungmin Lee

Four cultivars of basil (Ocimum basilicum L. ‘Cinnamon’, ‘Siam Queen’, ‘Sweet Dani’, and ‘Red Rubin’) were inoculated or not with the arbuscular mycorrhizal fungus (AMF), Rhizophagus (formerly Glomus) intraradices (Schenck & Smith) Walker & Schüßler and grown with a fertilizer containing either 64 mg·L−1 phosphorus (P) (low P) or 128 mg·L−1 P (high P) to assess whether 1) P availability and inoculation with AMF influences the phenolic composition of basil; and 2) treatment effects on phenolic composition are related to plant nutrient status. Growth, root colonization by AMF, anthocyanins, total phenolics, specific polyphenolics, and mineral nutrients were measured after 16 weeks of growth. Non-inoculated plants were not colonized by AMF. AMF colonization of inoculated plants was not influenced by P rate. Increased P rate and AMF inoculation increased biomass. Increased P rate enhanced (increased concentration and content) P and calcium (Ca) uptake and AMF inoculation enhanced nitrogen (N), potassium (K), sulfur (S), boron (B), iron (Fe), and zinc (Zn) uptake. Increased or decreased uptake (content) of other nutrients between P rates and AMF treatments were related to differences in biomass (e.g., similar or lower concentration). Treatment effects on phenolic accumulation were related to the effects of P rate and AMF on 1) plant growth; 2) nutrient uptake; and 3) other factors not directly related to measured differences in nutrient uptake or plant growth. Differences between treatments in rosmarinic acid, the predominant polyphenolic produced by all cultivars, were related to the effects of P rate and AMF on plant growth. Both increased P rate and AMF inoculation enhanced production (increased concentration and content) of chicoric acid and caffeic acid derivative. Increased P rate and inoculation with AMF differentially enhanced production of several other minor polyphenolics resulting in plants with different polyphenolic profiles. Results indicate that AMF inoculation may be an additional strategy for optimizing basil quality in terms of polyphenolic production and composition beyond benefits obtained from just altering plant nutrient status or selecting specific cultivars.

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Guihong Bi and Carolyn F. Scagel

In two separate experiments, Hydrangea macrophylla (Thunb.) Ser. ‘Merritt's Supreme’ plants were used to study the effects of foliar sprays of Def 6 (tributyl phosphorotrithioate, 2500, 5000, 7500, and 10,000 mg·L−1), gibberellic acid (GA, 50 mg·L−1), copper–EDTA (CuEDTA, 0.5% and 1.0%), Florel (2000 mg·L−1), and urea (3%) on defoliation in the fall and growth and flowering performance during forcing. Compared with controls (plants sprayed with water only), spraying plants with urea or GA alone had no influence on defoliation or plant performance during forcing, and spraying plants with Florel alone had no influence on defoliation but decreased total flower dry weight during forcing. Combining urea with Florel sprays decreased the adverse effects of Florel on plant quality and combining GA with Florel improved defoliation. Increasing concentrations of Def 6 and CuEDTA increased defoliation. Compared with controls, plants sprayed with CuEDTA exhibited more defoliation, showed bud and leaf necrosis, and produced lower flower dry weight during forcing. Combining urea with CuEDTA sprays decreased the adverse effects of CuEDTA on plant quality. Compared with controls, spraying plants with Def 6 increased defoliation, caused no visible damage to plants, and had no adverse effects on plant quality during forcing. Adding urea to sprays containing Def 6 decreased or had no influence on the efficiency of defoliation and increased total flower dry weight during forcing compared with Def 6 alone. Adding GA to sprays containing lower concentrations of Def 6 (2500 and 5000 mg·L−1) increased the efficiency of defoliation without adversely influencing plant quality.

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Guihong Bi, Carolyn F. Scagel and Richard Harkess

Plants of Hydrangea macrophylla ‘Merritt's Supreme’ were fertigated with 0, 70, 140, 210, or 280 mg·L−1 nitrogen (N) from July to Sept. 2005 and sprayed with 0% or 3% urea in late October to evaluate whether plant N status during vegetative growth influences plant performance during forcing. In late November, plants were manually defoliated, moved into a dark cooler (4.4 to 5.5 °C) for 8 weeks, and then placed into a greenhouse for forcing. After budbreak, plants were supplied with either 0 N or 140 mg·L−1 N for 9 weeks. Plant growth and N content were evaluated in Nov. 2005 before cold storage and plant growth, flowering, and leaf quality parameters were measured in late Apr. 2006. Increasing N fertigation rate in 2005 significantly increased plant biomass by ≈14 g (26%) and plant N content by ≈615 mg (67%). Spray applications of urea (urea sprays) in the fall had no influence on plant biomass but significantly increased plant N content by ≈520 mg (54%). In general, plants grown with 210 and 280 mg·L−1 N during 2005 had the greatest growth (total plant biomass, height), flowering (number of flowers, flower size), and leaf quality (leaf area, chlorophyll content) during forcing in 2006. Urea sprays before defoliation increased plant growth, flowering, and leaf quality characteristics during forcing in 2006. Providing plants with N during the forcing period also increased plant growth, flowering, and leaf quality characteristics. Urea sprays in the fall were as effective as N fertilizer in the spring on improving growth and flowering. We conclude that both vegetative growth and flowering during forcing of ‘Merritt's Supreme’ hydrangea are influenced by both the N status before forcing and N supply from fertilizer during forcing. A combination of optimum rates of N fertigation during the vegetative stage of production with urea sprays before defoliation could be a useful management strategy to control excessive vegetative growth, increase N storage, reduce the total N input, and optimize growth and flowering of container-grown florists’ hydrangeas.

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R. Paul Schreiner and Carolyn F. Scagel

An interplay between carbon and phosphorus is known to regulate root colonization by arbuscular mycorrhizal fungi (AMF); however, it is unclear whether plant C or plant P status plays a bigger role in controlling the abundance of arbuscules (the primary site of nutrient exchange in AMF symbiosis) in roots. In this study, ‘Pinot noir’ grapevine (Vitis vinifera) was grown in an unsterilized vineyard soil and colonized by indigenous AMF in two experiments, where photosynthetic capacity (defoliation or shading) and shoot nutrition (foliar fertilizer) were manipulated. Temporal changes in root colonization by AMF and plant growth and nutrition were determined. Foliar fertilizer application increased P and K uptake, but reduced Cu uptake in both experiments. Decreasing the photosynthetic capacity of shoots due to defoliation or shading rapidly reduced arbuscules in fine roots (within 7 to 14 days). In contrast a 3-fold increase in shoot P status from foliar fertilizer only reduced arbuscules after a more prolonged time (28 to 56 days). The combination of shading (15% of full sun) and foliar P application reduced arbuscules more than shading alone within the first month, whereas foliar P use in full sun had no influence on arbuscules within a month. Returning plants to full sun after 28 days in shade resulted in a resurgence of arbuscules in roots regardless of plant P status. Arbuscules in grapevine roots are regulated by the interaction between plant C and P status, such that high shoot P reduces arbuscule formation or maintenance more when combined with reduced plant photosynthesis. This indicates that grapevines do not reduce AMF nutrient transfer as an immediate response to elevated shoot P as long as plants are maintained in a high light environment.

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R. Paul Schreiner and Carolyn F. Scagel

Grape growers rely on tissue tests of leaf blades or petioles for routine monitoring of vine nutritional health and for diagnosing potential nutrient deficiency or toxicity. There has been a long-standing debate as to which tissue better reflects the nutrient status of vines. A comparison of leaf blade and petiole nutrient concentrations was carried out to investigate which tissue better relates to vine growth, yield, and must nutrient responses of ‘Pinot noir’ grapevines to varying levels of nitrogen (N), phosphorus (P), and potassium (K) supply using data from a pot-in-pot vineyard over 4 years. Leaf blades and petioles were collected at 50% bloom and 50% veraison in each year and N, P, and K concentrations were assessed as predictors of leaf area at veraison, pruning mass at dormancy, yield, and must nutrient concentrations at fruit maturity. Data from commercial ‘Pinot noir’ vineyards were also used to investigate the relationship between leaf blade and petiole N concentrations with must N levels. Results indicated that leaf blades were superior to petioles in predicting vine growth, yield, and must yeast assimilable nitrogen (YAN) responses across a wide range of vine N status at both sampling times. Leaf blade N was a better predictor than petiole N in predicting YAN using data sets from both the pot-in-pot vineyard and commercial vineyards. Relationships between leaf blade and petiole concentrations of P and K and vine response variables generally did not differ and both tissues appeared to be equally effective in predicting P and K effects on growth, yield, and must P or K levels. Although petiole P was slightly better than leaf blade P at bloom in predicting must P levels, and models including both leaf and petiole K simultaneously as predictors relied only on leaf K. For all three nutrients, sampling at bloom and veraison had a similar predictive strength for response variables. Based on these findings, we recommend using leaf blades as opposed to petioles for diagnosing the N, P, and K status of ‘Pinot noir’.

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R. Paul Schreiner, Carolyn F. Scagel and John Baham

The nutrient uptake and distribution patterns for N, P, K, Ca, and Mg were determined in mature (23 to 24 year old), field-grown, rainfed grapevines (Vitis vinifera L. `Pinot noir') growing in a red hill soil in Oregon in 2001 and 2002. Biomass, nutrient concentrations, and nutrient contents of all plant organs, including roots, were determined on 14 sampling dates over 2 years. There was no seasonal change in the standing biomass of primary roots (fine feeder roots), small woody (<4 mm diameter) or large woody (>4 mm diameter) roots. Trunk biomass also did not change during the 2 years, but all other vine organs showed significant seasonal changes in biomass. The rate of N uptake was greatest at bloom, when remobilization from reserves was also high. Nitrogen was also taken up after leaf fall in 2001, but not in 2002, when an early frost occurred before soil moisture recovery by fall rains. Uptake of N, K, and Ca from soil was similar between years, even though canopy demand for N and K was greater in 2002 (significantly larger crop). Phosphorus uptake from soil was lower in 2002 than in 2001, which was most likely due to the drier conditions in 2002. A greater quantity of canopy N, K, and especially P was supplied from stored reserves in the drier 2002 growing season. About 50% of canopy requirements for N and P were remobilized from reserves in the trunk and roots by the time of fruit maturity in 2002. Only 15% of canopy K and <5% of canopy Ca or Mg came from stored reserves in 2002. Our findings indicate that nonirrigated grapevines grown in Oregon acquire nutrients from soil earlier in the growing season and have a greater reliance on stored reserves of N and P than reported in previous studies from other growing regions. Replenishment of nutrient reserves occurred to large extent during the postharvest period. Rainfed vineyards in Oregon may require different nutrient management practices than irrigated vineyards, since low soil moisture may limit summer uptake of P.

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Pinghai Ding, Leslie H. Fuchigami and Carolyn F. Scagel

The accuracy of nondestructive optical methods for chlorophyll (Chl) assessment based on leaf spectral characteristics depends on the wavelengths used for Chl assessment. Using spectroscopy, the optimum wavelengths (OW) for Chl assessment were determined by using 1-year-old almond (Prunus dulcis), poplar (Populus trichocarpa × P. deltoides), and apple (Malus ×domestica) trees grown at different rates of nitrogen fertilization to produce leaves with different Chl concentrations. Spectral reflectance of leaf discs was measured using a spectroradiometer (300 to 1100 nm at 1-nm intervals), and total Chl concentration in leaf discs was extracted and determined in 80% acetone. The OW for nondestructive Chl assessment by reflectance spectroscopy was estimated using 1) the coefficient of determination (r 2) from simple linear regression; 2) reflectance sensitivity analysis (a measure for changes of spectral reflectance on unit change in leaf Chl concentration); and 3) the first spectral derivative method. Our results indicated that the first derivative method can be used only to identify OW in the red edge region of the spectrum, whereas r 2 and reflectance sensitivity analysis can be used to identify the OW in both the red edge and green regions. Our results indicate that using simple linear r 2 in combination with reflectance sensitivity and/or the first derivative analyses is a reliable method for determining OW in plant leaves tested. Two optimum wavebands with larger r 2, smaller root mean square error, and higher reflectance sensitivity were found in red edge (700 to 730 nm) and green (550 to 580 nm) regions, respectively, which can be used as common OW for Chl reflectance assessment in poplar, apple, and almond leaves tested. Single-wavelength indices if developed with OW were even more accurate than those more wavelength indices that developed without using OW. The accuracy of indices can be further improved if indices developed by using one OW and one Chl-insensitive wavelength from near infrared (NIR) (750 to 1100 nm) in the form of RNIR/ROW or (RNIR – ROW)/(RNIR + ROW).