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Raul I. Cabrera*

Rooted liners of the crape myrtle cultivars `Pink Lace', `Natchez' and `Basham's Party Pink' (`BPP') were grown in 20-L containers filled with a 2 peat: 1 pine bark: 1 sand (v/v) medium and irrigated for 15 weeks with irrigation water containing 0, 3, 6, 12, and 24 mm NaCl. Cultivar selection and salinity significantly affected plant growth and quality. Regardless of salinity level, `Natchez' plants had higher leaf area, total and shoot (top) dry weights and growth indices, whereas `Pink Lace' had the lowest. `BPP' had the highest average root dry weights across salt treatments. The vigorous shoot (top) growth of `Natchez' was also evident with an average shoot to root ratio of 4.1, compared to 2.7 and 2.4 for `BPP' and Pink Lace', respectively. Salinity significantly decreased plant growth and quality in the three cultivars, but the rate at which these parameters were reduced with increases in salinity differed among the cultivars. The rate of reduction in plant growth parameters was lower in `Pink Lace' plants compared to `Natchez' and `BPP'. However, foliage burn symptoms due to salt stress increased at significantly higher rate for `Pink Lace' plants compared to the other two cultivars. `BPP' plants had in general the lowest salt burn ratings at each salinity level. Leaf concentrations of Na and Cl increased with salt stress in all cultivars, but significantly lower concentrations were found in `BPP' plants. `Pink Lace' plants had better correlations with the recorded salt burn symptoms as compared to the other two cultivars.

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Sloane M. Scheiber and Richard C. Beeson

Previous research indicated that bedding plants can be maintained in landscape soils allowed to dry to substantially less than field capacity before irrigation; however, canopy size and aesthetic quality were compromised. Continuing this research, Solenostemon scutellarioides (coleus) were grown in drainage lysimeters in an open-sided clear polyethylene-covered shelter to assess growth characteristics and landscape quality when irrigated at various managed allowable deficits. Using tensiometers, plants were irrigated back to field capacity when 30%, 40%, or 50% of plant available water within a soil was depleted. Deficits were evaluated against a control treatment of 1.25 cm daily irrigation. Additional plants were grown in a companion open field plot. Growth indices, biomass, irrigation volumes, and landscape quality ratings were recorded. No differences in final height, growth index, shoot or root dry weights, total biomass, or shoot-to-root ratios were found among treatments for either lysimeter or companion field plots. Landscape quality was comparable among treatments. However, total irrigation volume applied was significantly greater for the control treatments than deficit irrigation treatments. On average, irrigation volumes were 4.75-fold greater for daily irrigation in comparison to other treatments.

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S.M. Scheiber and Richard C. Beeson Jr.

Petunia ×hybrida Vilm. `Midnight' plants were grown in drainage lysimeters to evaluate growth in response to alternative irrigation strategies. Irrigation treatments were tensiometer-regulated automatic irrigation systems, regularly scheduled irrigation using an automated controller, and human perception of plant irrigation need (manual watering). Mean irrigation volumes were reduced by manual watering and tensiometer-regulated treatments, compared to the automated controller. Total mean irrigation volume applied by the automated controller (460 L) was significantly greater than received by the manually watered (293 L) or tensiometer-regulated (286 L) treatments. Regularly scheduled irrigation using an automated controller resulted in higher assimilation rates, final shoot dry mass, final biomass, shoot to root ratios, and growth indices compared to other irrigation methods tested. Assimilation rates were significantly higher for tensiometer-controlled irrigation than the manually watered treatment, but no differences were reported between these two treatments for growth parameters. Visual observations indicated aesthetic quality was compromised among tensiometer-regulated and manually watered treatments relative to the automated controller treatment.

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Kuo-Tan Li and Jim Syvertsen

Young citrus trees and seedlings in Florida's commercial nurseries are often grown under shade cloth netting to avoid high light and temperature. To investigate the potential benefit of altering radiation by colored shade nets, `Cleopatra' mandarin (Cleo, C. reticulata Blanco) seedlings and potted `Valencia' trees [Citrus sinensis (L.) Osbeck] on Cleo or Carrizo [Carr, C. sinensis × Poncirus trifoliate (L.) Raf.] rootstocks were grown in full sun or under 50% shade from blue, black, silver, grey, and red colored shade nets. Changes in photosynthetically active radiation (PAR) and temperatures under the shade were monitored. Leaf function and leaf chlorophyll contents were measured, and plants were harvested by the end of the experiment for shoot and root growth measurements. Plants under the shade received an average of 45% PAR and had lower mid-day leaf temperature than plants in full sun. Plants under blue nets had greatest leaf chlorophyll a, b, and total chlorophyll content, whereas those under red nets had the lowest. However, shading improved photosystem II efficiency from measurements of leaf chlorophyll fluorescence (Fv/Fm) regardless of the color of shade nets. Shading increased shoot growth, shoot to root ratio, and total plant dry weight of Cleo seedlings, especially those under silver nets.

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Haibo Liu

Aluminum toxicity is a major limiting factor for turfgrass establishment and growth when soil pH is <5.0. Limited information on aluminum resistance is available among warm-season turfgrasses and these turfgrasses often grow in the areas with acid soil conditions. The objectives of this study were 1) to evaluate seeded bermudagrass (Cynodon dactylon L.) cultivars for the ability to tolerate a high level of aluminum and 2) to measure the extent of aluminum damage to the root systems. In total, 16 bermudagrass cultivars were evaluated under greenhouse conditions using a solution culture and an acid Tatum soil (Clayey, mixed, thermic, typic, Hapludult). The soil had pH 4.4% and 69% exchangeable aluminum. A concentration of 640 μm aluminum and a pH 4.0 was used for solution culture. The grasses were grown for 28 days in solution culture; 28 days in the acid Tatum soil; and 78 days in the acid Tatum soil before harvesting. Aluminum resistance was determined by measuring the longest root length, the longest shoot length, dry root weight, dry shoot weight, and shoot to root ratio in comparing the control to obtain the relative Al resistance among the cultivars. The results indicate that seeded bermudagrass cultivars differ in their aluminum resistance.

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Bodie V. Pennisi

Geogenanthus Ínca' is a new cultivar introduced the foliage plant industry which shows promise in interior plantscaping. The objectives of this study were twofold; to examine the effects of ancymidol and flurprimidol on G. `Inca' growth and determine if plant growth retardant (PGR) application could improve postharvest performance. Four weeks before attaining marketable sizes, the plants were drenched with ancymidol or flurprimidol at 0.0, 0.5, 1.0, or 1.5 mg (a.i.). Plants were then placed in interior-evaluation rooms under 12 μmol·m–2·s–1. Ancymidol or flurprimidol reduced plant height, width, growth index and total leaf area, total dry weight and shoot to root ratio of Geogenathus `Inca'. Flurprimidol increased the deposition of insoluble carbohydrates (starch) and altered the pattern of starch deposition; higher starch content was found in stem tissue compared to foliage tissue. The effects of ancymidol or flurprimidol persisted in the postharvest environment. After 4 months under low irradiance, PGR-treated plants exhibited higher quality, i.e., compact stature and reduced leaf and shoot necrosis. This research has potential significance for the foliage plant industry and it showed that a single drench application at label recommended rates of ancymidol or flurprimidol late in the production cycle can produce desired growth control of Geogenanthus `Inca' in the postharvest environment. Plants retain aesthetic characteristics for extended period thus necessitating lower replacement rate.

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Davide Neri, Gianpaolo Mascanzoni, Paolo Sabbatini, Franco Zucconi, and James Flore

To simulate soil sickness, 1-year-old trees of `Golden Delicious' (grafted on M9 and M106) were grown in rhizotrons (1 × 1-m and 0.5-m depth) with different plant residues content, at Ravenna, Italy. Sandy loam soil was used as a substrate. Fine-grounded wood from apple and peach residues (6 kg per rhizotron) was mixed to the substrate and considered as main treatment. Mature compost (1% and 2.5% in volume) was added or not to the substrate with the organic residues and considered as subtreatment. The application of residues was localized either near the soil surface (0–25 cm) or deeper in the soil profile (25–50 cm). In each rhizotron, four trees on the same rootstock were planted and each soil treatment was replicated twice. After 2 years, the roots were accurately excavated (washing off the soil with water), and growth was measured. The presence of apple residues near the soil surface induced a 5% to 20% reduction of shoot growth. The reduction per plant dry weight was higher when trees were grafted on M106. At root level, the presence of residues increased the root migration in the search for fresh niches, enhancing root crossing and anastomosis. Both these shoot and root conditions are typical of replant diseases symptoms. The localization of apple residues in the lower part of the profile reduced the symptoms and so did the addition of compost. The peach residues did not affect shoot growth when compared to the control, but the shoot-to-root ratio was reduced, indicating a tendency to increase root migration.

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David R. Sandrock, Anita N. Azarenko, and Timothy L. Righetti

Nitrogen accumulation patterns were established for Weigela florida (Bunge.) A. DC. `Red Prince' (fast growth rate) and Euonymus alatus (Thunb.) Sieb. `Compactus' (slow growth rate). From these, daily and biweekly N delivery schedules were designed to match N supply with N accumulation patterns of each taxon. Delivery schedules were sliding scales in that total N applied was controlled by independent increases (or decreases) of N concentration and solution volume. Daily and biweekly N delivery schedules were tested against a constant N rate (200 mg·L-1) and Osmocote 18N-2.6P-9.9K (The Scotts Co., Marysville, Ohio). Plants were grown in 3.8-L containers in 7 douglas fir bark: 2 sphagnum peatmoss: 1 silica sand (0.65 mm; by volume) outdoors in full sun on a gravel pad for 142 d. Within each taxon, Weigela and Euonymus grown with sliding-scale N fertilization schedules had similar total dry weights, leaf areas, and total plant N contents to plants grown with a constant N rate (200 mg·L-1) or Osmocote 18N-2.6P-9.9K. Sliding-scale liquid fertilization based on plant N requirements introduced less total N to the production cycle and resulted in higher N uptake efficiency than fertilization with a constant N rate of 200 mg·L-1. In general, liquid N fertilizer treatments resulted in plants with higher shoot to root ratios than plants treated with Osmocote 18N-2.6P-9.9K. Weigela and Euonymus treated with biweekly schedules were similar to plants treated with daily schedules (same total amount of N delivered with each treatment).

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Julián Miralles, Raquel Valdes, Juan J. Martínez-Sánchez, and Sebastián Bañón

The appropriate management of crop conditions can reduce the salt damage suffered by ornamental species and produce high-quality plants even when saline irrigation water is used. The aim of this study was to determine whether the pot-in-pot (PIP) cultivation system can improve the saline irrigation tolerance of Euonymus japonicus compared with aboveground potting (AGP) in terms of growth and development, aesthetic quality, ion accumulation, and leaf potentials. A 5-month experiment started on 6 Mar., and the interaction between the cultivation system (PIP or AGP) and water quality (fresh water and saline water, with 1.76 and 9.04 dS·m−1, respectively) was assessed. The substrate used was a mixture of white peat, coconut fiber, and perlite (40/40/20, v/v/v). A soil moisture sensor-controlled system was used to irrigate all the treatments when the AGP treatment irrigated with fresh water reached a volume water content (θ) of 0.33–0.35 m3·m−3. An interaction effect reduced the salinity effects in PIP and saline irrigation (PIP-s) compared with AGP and saline irrigation (AGP-s) in terms of damaged leaf area, plant dry weight (DW), and the compactness index. The PIP-s plants showed a survival rate of 93% compared with 57% in AGP-s. The substrate temperatures were milder in PIP regardless of the irrigation water, and the pore water electrical conductivity (EC) was 36% lower in PIP-s than in AGP-s. PIP reduced the Cl accumulated in leaves but did not influence Na+, Ca2+, Mg2+, or the K+/Na+ ratio. The lower amount of Cl accumulated increased leaf water potential (Ψo) in PIP. Saline irrigation produced a general accumulation of Cl and Na+ in leaves and decreased Ca2+, Mg2+, the K+/Na+ ratio, Ψo, the shoot to root ratio, and height. In general, PIP reduced the salinity damage to Euonymus japonicus, the main effect being the lower Cl ion uptake, which improved its aesthetic value (less damage and greater compactness and growth).

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Kathryn M. Santos, Paul R. Fisher, Thomas Yeager, Eric H. Simonne, Hannah S. Carter, and William R. Argo

The objective was to quantify the effect of the timing of macronutrient applications on nutrient uptake, growth, and development of Petunia ×hybrida Hort. Vilm.-Andr. ‘Supertunia Royal Velvet’ during vegetative propagation. Starting with unrooted cuttings (Day 0), fertigation was applied continuously at three time intervals (Day 0 to 7, Day 8 to 14, or Day 15 to 21) using either a “complete” (C) water-soluble fertilizer containing (in mg·L−1) 75 NO3-N, 25 NH4-N, 12 phosphorus (P), 83 potassium (K), 20 calcium (Ca), 10 magnesium (Mg), 1.4 sulfur (S), 2 iron (Fe), 1 manganese (Mn), 1 zinc (Zn), 0.5 copper (Cu), 0.5 boron (B), and 0.2 molybdenum (Mo) or a micronutrient fertilizer (M) containing (in mg·L−1) 1.4 S, 2 Fe, 1 Mn, 1 Zn, 0.5 Cu, 0.5 B, and 0.2 Mo in a complete factorial arrangement. With constant fertigation using the C fertilizer, plant dry weight (DW) doubled from Day 0 (sticking of unrooted cuttings) to Day 7 (0.020 g to 0.047 g), root emergence was observed by Day 4, and by Day 7, the average length of primary roots was 2.6 cm. During any week that the M fertilizer was substituted for the C fertilizer, tissue N–P–K concentrations decreased compared with plants receiving the C fertilizer. For example, plants receiving the M fertilizer between Day 0 and 7 had 20% lower tissue-N concentration at Day 7 compared with those receiving the C fertilizer. Although both shoot DW and leaf count increased once macronutrient fertilization was resumed after Day 7, final shoot DW and leaf count were lower than plants receiving C fertilizer from Day 0 to 21. Time to first root emergence was unaffected by fertigation. Constant application of C resulted in a higher shoot-to-root ratio at Day 21 than all other treatments. Results emphasize the importance of early fertigation on petunia, a fast-rooting species, to maintain tissue nutrient levels within recommended ranges.