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  • Author or Editor: Dewayne Ingram x
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Respiration of excised Ilex crenata `Rotundifolia' roots as influenced by root-zone growth temperature and buffer solution temperature was measured in the presence and absence of SHAM and KCN. Respiration rates of roots excised from plants grown for three weeks at root-zone temperatures of 30, 34, 38, and 42 C decreased linearly as root-zone temperature increased when the buffer solution was maintained at 25 C. When the buffer solution temperature was the same as the root growth temperature, no differences in respiration rate were found. When plants were grown at a root-zone temperature of 30 C, respiration was maximal at 34 C and decreased to a minimum at 46 C. Above 46 C, stimulation of O2 consumption occurred which was presumed to be extra-mitochondrial. CN-resistant pathway activity decreased at a buffer solution temperature of 46 C which was similar to the critical threshold temperature (48±1.5 C) for `Rotundifolia' holly roots.

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High root-zone temperatures have been shown to affect photosynthate partitioning, respiration, nitrogen nutrition and growth of `Rotundifolia' holly. The loss of chlorophyll and protein in shoots of other plants in response to high root-zone temperatures has been documented. Therefore, the objectives of this research were to look at the effects of supraoptimal root-zone temperatures on RUBISCO activity, leaf protein and photosynthetic pigment levels.

Soluble protein levels in leaves increased linearly as root-zone temperature increased from 30 to 42 C. RUBISCO activity per unit protein and per unit chlorophyll responded quadratically to root-zone temperatures. Total chlorophyll, chlorophyll a & b, and carotenoid levels decreased linearly with increasing root-zone temperature. It is possible that `Rotundifolia' holly was capable of redistributing nitrogen to maintain RUBISCO activity for photosynthesis.

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Respiration of excised Ilex crenata (Thunb.) `Rotundifolia' roots as influenced by root-zone growth temperature and buffer solution temperature was measured in the presence and absence of salicylhydroxamic acid (SHAM) and potassium cyanide (KCN). Respiration rates of roots excised from plants grown for 3 weeks with root-zones at 30, 34, 38, or 42C decreased linearly with increased root-zone growth temperatures when the buffer solution was maintained at 25C. When the buffer solution was the same temperature as the root growth temperature, respiration rates were similar. Respiration in roots from plants grown with the root zone at 30C was maximal with the buffer solution at 34C and decreased to a minimum at 46C. Above 46C, a presumably extra-mitochondrial stimulation of O2 consumption occurred. The activity of the CN-resistant pathway was fully engaged (P' = 0.99) when roots were grown at 30C and buffer solution was at 25C (30-25). CN-resistant pathway activity decreased with `the buffer solution at 46C.

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University researchers have recently quantified the value of carbon sequestration provided by landscape trees (Ingram, 2012, 2013). However, no study to date has captured the economic costs of component horticultural systems while conducting a life cycle assessment of any green industry product. This study attempts to fill that void. The nursery production system modeled in this study was a field-grown, 5-cm (2-in) caliper Cercis canadensis ‘Forest Pansy’ in the Lower Midwest. Partial budgeting modeling procedures were also used to measure the sensitivity of related costs and potential benefits associated with short-run changes in cultural practices in the production systems analyzed (e.g., transport distance, post-harvest activities, fertilization rates, and plant mortality). Total variable costs for the seedling and liner stages combined amounted to $2.93 per liner, including $1.92 per liner for labor, $0.73 for materials, and $0.27 per liner for equipment use. The global warming potential (GWP) associated with the seedling and liner stages combined included 0.3123 kg of carbon dioxide equivalents (CO2e) for materials and 0.2228 kg CO2e for equipment use. Total farm-gate variable costs (the seedling, liner, and field production phases combined) amounted to $37.74 per marketable tree, comprised of $9.90 for labor, $21.11 for materials, and $6.73 for equipment use, respectively. However, post-harvest costs (e.g., transportation, transplanting, take-down, and disposal costs) added another $33.78 in labor costs and $27.08 in equipment costs to the farm-gate cost, yielding a total cost from seedling to end of tree life of $98.60. Of this, $43.68 was spent on labor, $21.11 spent on materials, and $33.81 spent on equipment use during the life cycle of each marketable tree. As per an earlier study, the life cycle GWP of the described redbud tree, including greenhouse gas emissions during production, transport, transplanting, take-down, and disposal, would be a negative 63 kg CO2e (Ingram et al., 2013). These combined data can be used to communicate to the consuming public the true (positive) value of trees in the landscape.

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Abstract

The addition of peat-perlite to backfill soil increased the initial root movement through the backfill of transplanted holly (Ilex crenata Thunb. cv. Green Luster) grown in a peat-perlite medium. Backfill composition had no effect on the initial movement of roots of plants grown in a soil-peat-sand or pine bark-sand medium.

Open Access

Abstract

Direct heat injury to plant parts may occur in areas of high insolation and high humidity where transpiration is low. Using electrolyte leakage procedures, critical high temperatures of detached leaves of ‘Glen’ citrange [Citrus sinensis L. (Osbk.) × Poncirus trifoliata L. (Raf.)], ‘Swingle’ citrumelo [C. paradisi Macf. × P. trifoliata L. (Raf.)], and ‘Hamlin’ orange [C. sinensis L. (Osbk.)] were determined by exposure to temperatures between 25° and 65°C. Lethal temperatures for a 20 min exposure ranged from 54.3° ± 0.5° for ‘Glen’ citrange to 56.1° ± 0.4° for ‘Swingle’ citrumelo. Maximum canopy temperatures of 36.6° were recorded. Therefore, it appears that under field conditions in Florida, these cultivars are normally not subjected to temperatures that would cause direct heat injury.

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Abstract

Stem caliper and sum of lateral branch lengths of container-grown Quercus shumardii seedlings increased more in 13 months when fertilized with 75:25, 50:50, 25:75 and 100:0 (NH4:NO3) ratios than with 100% NO3-N, regardless of fertilization rate. Stem caliper increased as fertilization rate increased from 5.7 to 11.4 g N/container yr. Height was unaffected by NH4:NO3 ratio or fertilization rate. Chlorosis was evident on plants that received 50% or more NO3-N. Media pH decreased with increasing NH4- N, and leaf N concentration increased from 1.16% with 100% NO3-N to 1.57% with 100% NH4-N.

Open Access

Abstract

Roots of sour orange (Citrus aurantium L.), ‘Carrizo’ citrange [C. sinensis L. (Osbeck.) × Poncirus trifoliata L. (Raf.)] and ‘Swingle’ citrumelo [C. paradisi Macf. × P. trifoliata L. (Raf.)] seedlings were exposed to various high temperatures for 20 minutes and heat injury was determined by electrolyte leakage procedures, microscopic examination, and visual observations. Temperatures at the midpoint of sigmoidal curves fitted through electrolyte leakage data for excised roots were 51.6° ± 0.5°C, 52.5° ± 0.7°, and 53.5° ± 0.5° for ‘Carrizo’ citrange, sour orange, and ‘Swingle’ citrumelo rootstocks, respectively. Electrolyte leakage results with excised roots were supported by microscopic examination and visual observations of whole plants.

Open Access

Abstract

Juniperus horizontalis ‘Andorra Compacta’ and Rhododendron simsii ‘Redwing’ were grown for 6 months in 3 media to evaluate selected nutrient sources at 2 lime levels. Sulfur-coated urea (SCU) induced the lowest final medium pH, and isobutylidene diurea (IBDU) induced the highest. Lime application to the 2 Canadian peat : 1 calcined clay medium (v/v) was detrimental to ‘Redwing’ azalea shoot growth. Nutrient source did not affect shoot or root growth of azaleas growing in the 2 pine bark : 1 sand medium (v/v). In general, SCU produced more azalea shoot and root growth than the other nutrient sources. Liming decreased juniper shoot growth in the 1 pine bark : 1 Canadian peat : 1 sand medium (by volume). Oxamide and Osmocote produced significantly more juniper shoot growth in the pine bark : sand and pine bark : Canadian peat : sand media than other nutrient sources. After 6 months, plants fertilized with either IBDU or SCU had a higher concentration of leaf N than did those fertilized with Osmocote (18N–2.6P–10K).

Open Access

Stage 2 micropropagules were transferred into woody plant medium supplemented with either 0, 0.1, 1, 10, 100 mg/L ABA (Abscisic acid) and with or without 1 mg/L IBA (Indole-3-butyric acid), Significant decreases in total dry weight and shoot length were observed at 1, 10 and 100 mg/L of ABA regardless of IBA concentration, Leaf area was significantly reduced in all treatments by increasing ABA levels. In the absence of IBA no callus formed but lateral roots developed. Another experiment using ABA levels of 0, 0.1, 0.5 and 0, 1 mg/L IBA was conducted. Total number of roots decreased with increasing ABA levels. Adventitious roots which formed on the stem and roots originating from root primordia were observed in all ABA levels with IBA, Callus did not form in the treatments lacking IBA. Scanning electron microscopy was used to document morphological differences due to ABA, Abscisic acid levels in leaf tissue were assayed using immunological techniques.

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