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Dewayne L. Ingram

The University of Kentucky's Department of Horticulture, led by the extension faculty working with targeted industry associations, facilitated the creation of the Kentucky Horticulture Council to be the voice of a diverse industry. Leadership in industry strategic planning, promoting the opportunities for expansion of the horticulture industry, and educating state agriculture, legislative and university leaders provided a focus of energy and positioned the industry to access emerging resources. Leadership development has been an anticipated byproduct of this process.

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Dewayne L. Ingram

This presentation focuses on driving forces and philosophies in the current Age of Accountability and explores ideas of how to respond. The increased scrutiny faced by all public agencies is requiring that Cooperative Extension approach the issue of accountability a bit differently. We must articulate our objectives and values to specific clientele groups, the general public, and government officials. Hard questions are being asked about past and anticipated return on tax dollars invested in state and federal agencies. The Government Performance and Results Act of 1993 requires “performance based budgeting” for all federal agencies, including the USDA. Each federal agency must develop an action plan with well-defined objectives and anticipated impacts to justify the allocation of federal funds. The overriding theme is not how busy we are and how many activities we can report, but what has been the impact of our efforts.

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Dewayne L. Ingram

The contributions of interrelated production system components of a field-grown, 2-m-tall, 5-cm-caliper Picea pungens (colorado blue spruce) in the upper midwestern (liner) and lower midwestern (finished tree) regions of the United States to its carbon footprint were analyzed using life cycle assessment protocols. The seed-to-landscape carbon footprint was 13.558 kg carbon dioxide equivalent (CO2e), including sequestration of 9.14 kg CO2e during production. The global warming potential (GWP) from equipment use was the dominant contributor to the carbon footprint of production. Seventy-six percent of the GWP investments during field production occurred at harvest. Querying the model, among other things, revealed that adding one year to the field production phase would add less than 3% to the seed-to-landscape GWP of the product. The weighted positive impact of carbon (C) sequestration during a 50-year life was 593 kg CO2e. After its useful life, takedown and disposal would result in emissions of 148 kg CO2e, resulting in a net positive, life cycle impact on atmospheric CO2 of ≈431 kg CO2e.

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Chris A. Martin and Dewayne L. Ingram

Root growth of Magnolia grandiflora Hort. `St. Mary' was studied for 16 wk after an 8-wk exposure period to 30°, 34°, 38°, or 42°±0.8°C root-zone temperature (RZT) treatments applied 6 hr daily, Immediately after the RZT treatment period, total root length was similar for trees exposed to 30°, 34°, and 38°C and was reduced 45% at 42° compared to 38°C. For weeks eight and 18 of the post-treatment period, response of total root length to RZT was linear. Total root length of trees exposed to 28°C was 247% and 225% greater than those exposed to 42°C RZT at week eight and 16, respectively. Root dry weight from the 42°C RZT treatment was 29% and 48% less than 38° and 34°C RZT treatment, respectively, at week eight. By week 16, root dry weight as a function of RZT had changed such that the 42°C RZT was 43% and 47% less than 38° and 34°C RZT, respectively. Differences in root growth patterns between weeks eight and 16 suggest that trees were able to overcome the detrimental effects of the 38°C treatment whereas growth suppression by the 42°C treatment was still evident after 16 wk. Previous exposure of tree roots to supraoptimal RZT regimens may have long-term implications for suppressing growth and lengthening the establishment period of trees in the landscape,

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Chris A. Martin and Dewayne L. Ingram

Leaf photosynthesis of Magnolia grandiflora `St. Mary' (13-month-old rooted cuttings) was studied when tree roots were exposed to 28, 35, or 42 ± 0.8C for 8 weeks. Root-zone temperature (RZT) treatments were sustained for 6 hours per day by an electronically controlled root-heating system. The experiment was conducted in a 3×7.5-m walk-in growth room. Growth room irradiance was supplied by eighteen 1000-W, phosphor-coated metal-arc HID lamps (photosynthetic photon flux = 600 μpmol-2·-1 at canopy height) for 13 hours daily augmented with 3 hours of incandescent light during the dark period. Leaf C assimilation (A) at an RZT of 42C decreased linearly over 8 weeks compared to leaf A at RZTs of 35 and 28C. Leaf A was similar for all trees at week 1; however, leaf A at an RZT of 42C was 30% and 34% less than at RZTs of 3.5 and 28C, respectively, at week 8. Stomatal conductance at RZTs of 28 and 35C increased linearly over 8 weeks compared to conductance at a RZT of 42C. Intercellular CO2 levels were not affected by RZT treatments. This finding suggests that reductions in leaf A were nonstomatal. Photosynthetic inhibition resulted in reduced shoot and root growth. Operators of outdoor container production nurseries should implement cultural practices that minimize exposure of tree roots to RZTs >35C.

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Chris A. Martin and Dewayne L. Ingram

A three-dimensional computer model was developed to simulate numerically the thermal environment of a polyethylene container-root medium system. An energy balance was calculated at the exterior container wall and the root medium top surface. Thermal energy exchanges at the system's boundaries were a function of radiation, convection, evaporation, and conduction energy flaxes. A forward finite difference form of a transient heat. conduction equation was used to calculate rates of temperature changes as a result of thermal energy exchanges at the system's boundaries. The χ2“goodness-to-fit” test was used to validate computer-generated values to actual measured temperature data. Probabilities for the null hypothesis of no association ranged from P = 0.45 (Julian day 271), to P = 0.81 (Julian day 190), with P ≥ 0.70 on nine of 10 validation days in 1989. Relative to net radiation and convection, conduction and evaporation had little effect on thermal energy exchanges at the root medium top surface during sunlight hours. The rate of movement of thermal energy (thermal diffusivity) was slower and generally resulted in lower temperatures in a pine bark medium than in a pine bark medium supplemented with sand when volumetric water content (VMC) ranged from 0.25 to 0.45.

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John M. Ruter and Dewayne L. Ingram

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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John M. Ruter and Dewayne L. Ingram

Ilex crenata Thunb. `Rotundifolia' split-root plants were grown for 3 weeks with root zones at 30/30, 30/34, 30/38, 30/42, 34/34, 38/38, and 42/42C. The 38C root-zone treatment was the upper threshold for several growth and physiological characteristics. A portion of the root system grown at or near the optimum temperature could compensate, in terms of shoot growth, for part of the root system exposed to supraoptimal root-zone temperatures up to 38C. Higher root-zone temperatures did not affect short-term photosynthetic rates or root : shoot ratios, but altered photosynthate partitioning to various stem and root sinks. Although no differences were found for total 14C partitioned to the roots, partitioning of 14C into soluble and insoluble fractions and the magnitude of root respiration and exudation were influenced by treatment. Heating half of a root system at 38C increased the amount of 14C respired from the heated side and increased the total CO2respired from the nonheated (30C) half. Exposure of both root halves to 42C resulted in membrane damage that increased the loss of 14C-labeled photosynthates through leakage into the medium.

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John M. Ruter and Dewayne L. Ingram

Ilex crenata Thunb. `Rotundifolia' split-root plants were grown for 3 weeks at root-zone temperatures of 30/30, 30/34, 30/38, 30/42, 34/34, 38/38 and 42/42. The 38 C root-zone temperature treatment was the upper threshold for a number of growth and physiological parameters. A portion of the root system grown at near optimum temperatures could compensate in terms of shoot growth for part of the root system exposed to supraoptimal root-zone temperatures up to the 38 C critical threshold. Higher root-zone temperatures did not affect photosynthetic rates or root:shoot ratios, but altered photosynthate partitioning to different stem and root sinks. Although no differences were found for total 14C partitioned to the roots, partitioning of the 14C into soluble and insoluble fractions and the magnitude of root respiration and exudation were influenced by treatment. Heating half of a root system at 38 C increased the amount of 14C respired from the heated side and increased the total CO2 respired from the non-heated (30 C) half. Exposure of both root halves to 42 C resulted in membrane damage which increased the leakage of 14C photosynthates into the medium.