Search Results

You are looking at 31 - 40 of 62 items for

  • Author or Editor: Dewayne Ingram x
Clear All Modify Search

Plants of `Rotundifolia' holly (Ilex crenata Thunb.) were grown for 3 weeks with root zones at 30,34,38, or 42C for 6 hours daily to evaluate the effects of supraoptimal root-zone temperatures on various photosynthetic processes. After 3 weeks, photosynthesis of plants grown with root zones at 38 or 42C was below that of plants grown at 30 or 34C. Chlorophyll and carotenoid levels decreased while leaf soluble protein levels increased as root-zone temperature increased. Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) activity per unit protein and per unit chlorophyll responded quadratically, while RuBisCO activity per unit fresh weight increased linearly in response to increasing root-zone temperature. Results of this study suggest that `Rotundifolia' holly was capable of altering metabolism or redistributing available assimilates to maintain CO2 assimilation rates in response to increasing root-zone temperatures.

Free access

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.

Free access

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.

Free access

Previously published life cycle assessment (LCA) studies regarding the global warming potential (GWP) of tree production have shown that the carbon footprint during the cradle-to-grave life cycle of a tree can reduce atmospheric CO2. This study provides another unique contribution to the literature by considering other potential midpoint environmental impacts such as ozone depletion, smog, acidification, eutrophication, carcinogenic or non-carcinogenic human toxicity, respiratory effects, ecotoxicity, and fossil fuel depletion for 5-cm-caliper, field-grown, spade-dug trees. Findings from this study validate using data from various literature sources with a single-impact focus on GWP and compiled and calculated in a spreadsheet or using a LCA software package with embedded databases (SimaPro) to generate comparable GWP estimates. Therefore, it is appropriate to use SimaPro to generate midpoint environmental impact estimates in LCA studies of field-grown trees. The authors also compared the midpoint environmental impacts with other agricultural commodities [corn (Zea mays), soybean (Glycine max), potato (Solanum tuberosum), and wool] and determined that trees compare favorably, with the exception that fossil fuel depletion for the trees was greater than the other products as a result of the high equipment use in harvesting and handling trees. In addition, the water footprint (WF) associated with tree production is also determined through LCA using the Hoekstra water scarcity method in SimaPro. The propagation-to-gate WF for the three tree production systems ranged from 0.09 to 0.64 m3 per tree and was highly influenced by irrigation water, which was the major contributor to WF for each production system. As expected, the propagation stage of each tree represented significantly less WF than the field production phase with larger plants and lower planting densities, even with more frequent irrigation/misting in liner production.

Free access

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.

Open Access

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

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.

Free 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