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Container-grown Viburnum plicatum var. tomentosum `Mariesii' were planted in tilled beds and tilled beds amended with aged pine bark. After transplanting, plants were fertilized at three different rates: no fertilizer, 18.4 g of N m-2, and 36.8 g of N m-2. A 31 day drought was begun 73 days after planting. Fertilization of tilled plots induced ammonium toxicity, which caused a linear reduction in leaf area, shoot dry weight, and root dry weight. Fertilization of amended plots had no effect on shoot growth but reduced mot growth by 54%; thus, amendments ameliorated ammonium toxicity. Between 10 and 28 days after beginning the drought, plants in unfertilized-amended plots maintained higher relative leaf water contents (RLWC) and relative leaf expansion rates (RLER) than plants in unfertilized-tilled plots. Amendment induced nitrogen deficiencies contributed to the increased drought tolerance of plants from unfertilized-amended plots. Since fertilized plants developed symptoms of ammonium toxicity, we were unable to determine if increasing fertility would counteract the drought tolerance conferred by pine bark soil amendments.

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Deciduous fruit trees undergo endo-dormancy during fall at which time they also attain maximum cold hardiness (CH). Because these two processes occur simultaneously it is difficult to study them independently. We have been able to overcome this limitation with the use of genetically related (sibling) deciduous and evergreen peach trees. Using this system we conducted a time course study to characterize the seasonal fluctuations in CH and proteins in bark and xylem tissues. Cold hardiness (LT50) was assessed using electrolyte leakage method. Polypeptides were separated using SDS-PAGE. The data indicated that 1) CH of bark increased from -5°C (in August) to -49°C (in January) and from -3°C to -22°C for deciduous and evergreen trees, respectively. In January, under favorable conditions, evergreen trees were actively growing. 2) CH of xylem successively increased from -11°C to -36°C in deciduous trees and from -7°C to -16°C (in November) in evergreen trees and then plateaued. 3) LT50 of xylem in both genotypes closely approximated the mid-point of low temperature exotherms determined by differential thermal analysis. 4) As CH increased several qualitative and quantitative differences in polypeptides were noted between two genotypes. These changes during cold acclimation will be compared with those during de-acclimation.

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Abstract

‘Red Prince Delicious’/East Mailing (EM) VII trees were grown in sand culture and fertilized with a complete nutrient solution containing 0.5, 5.0 or 50.0 ppm Mn. 54Mn was supplied to provide the same specific activity in all treatments. Autoradiographs showed “islands” of radioactivity in bark patches from all treatments 2½ months after initiation of the experiment. These “islands” disappeared after 8 months in the 0.5 ppm treatment, and after 10 months in the 5.0 ppm treatment, but continued to exist in bark patches from the 50.0 ppm treatment through the last sampling at 15½ months. Typical, and some aberrant, symptoms of IBN first appeared after 5½ months in the 50.0 ppm treatment. Pimples occurred at sites where autoradiographs indicated Mn concentrations. As the pimple stage of IBN progressed to necrotic lesions, radioactivity was concentrated around the periphery of the lesions. Data is presented which suggests that, as Mn supply is increased, alteration of mechanisms for regulating uptake and distribution of Mn occurs.

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Seasonal changes in cold tolerance and proteins were studied in the leaves of sibling deciduous and evergreen peach [Prunus persica (L.) Batsch]. Freezing tolerance [defined as the subzero temperature at which 50% injury occurred (LT50)] was assessed using electrolyte leakage. Proteins were separated by sodium dodecyl sulfate polyacrylamide-gel electrophoresis. Electroblots were probed with anti-dehydrin and anti-19-kD peach bark storage protein (BSP) antibodies. Leaf LT50 decreased successively from -5.8 °C on 18 Aug. to -10.3 °C in the evergreen genotype and from -7.0 °C to -15.0 °C in the deciduous genotype by 14 Oct. Protein profiles and immunoblots indicated the accumulation of a 60- and 30-kD protein during cold acclimation in the leaves of deciduous trees; however, levels of these proteins did not change significantly in the evergreen trees. Immunoblots indicate that the 60-kD protein is a dehydrin-like protein. Gel-electrophoresis and immunoblots also indicated that the 19-kD BSP progressively disappeared from summer through fall in leaves of deciduous peach but accumulated to a high level in bark tissues. A similar inverse relationship was not evident in evergreen peach.

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The objective of this study was to determine the influences of 8 commercial media, 4 peat-based and 4 pine bark-based, on the effects of paclobutrazol and uniconazole applied as a media drench to `Gutbier V-14 Glory' poinsettias. The peat-based media were Baccto Grower's Mix, Baccto High Porosity Professional, Baccto High Porosity Professional with Bacctite, and Baccto Rockwool Mix. The pine bark-based media were Metro 360, 366, 700, and 702. Paclobutrazol and uniconazole were each applied to plants grown in each media at 5 rates (0, 0.125, 0.250, 0.375, and 0.500 mg·15 cm pot-1). Paclobutrazol and uniconazole effectively reduced plant height in all media. Plants grown in the Metro products, however, tended to be larger than those grown in the Baccto products. Plants grown in the peatbased media were more sensitive to growth regulator drenches. Plants grown in Metro 360 and 366 were the least sensitive to plant growth regulator drenches compared to the Baccto media.

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Abstract

Equal volumes of peanut hulls, pine bark, and sphagnum peatmoss were combined into 5 media. Particle size distribution, total porosity, air space, easily available water, water buffering capacity, and bulk density were determined for each medium. Top dry weight, root dry weight, and percent growth of Rhododendron indicum (L.) Sweet cv. George L. Taber were measured 14 weeks after potting in 1-liter containers. Peanut hulls increased particle size, total porosity, and air space, and decreased easily available water, water buffering capacity, and bulk density of media. Peatmoss generally reduced total porosity and air space and increased easily available water, water buffering capacity, and bulk density regardless of other component combinations. Top dry weight, root dry weight, and percent growth were greater in peanut hull-containing media. Addition of peatmoss to the container media tended to produce less growth.

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Abstract

The phellogen of cultivated apple, sweet cherry, and peach trees was wounded at regular intervals beginning in early May and ending in late Aug. 1983. Bark tissue supporting the wounds was excised, sectioned, treated with phloroglucinol + HCl, and examined under a bright field to determine the extent of lignification. The same sections were examined under ultraviolet epi-illumination to determine the extent of suberin deposition in the boundary zone tissue formed from cells present at the time of wounding. Mean daily temperature, time post-wounding, and accumulated degree days (base = −5°, 0°, 5°, and 10°C) were used to predict the percentage of wounds lignified and suberized. A segmented quadratic equation incorporating accumulated degree days (base = 0°) was the best model for predicting lignification for the 3 species and for suberin deposition in peach and sweet cherry.

Open Access

A study was conducted to determine the effects of pine bark grind size and pine bark levels on the activity of two growth regulators on poinsettia Two bark grinds (≤ 6 mm and >10 mm) were used with four media combinations within each grind: vermiculite:bark:peat moss at 2:0:3, 2:1:2, 2:2:1, and 2:3:0 (by volume). Two growth regulators, paclobutrazol and uniconazole, were applied at 0, 0.125, and 0.250 mg/15 cm container in 250 ml water. Two poinsettia cultivars, `Freedom' and `Gutbier V-14 Glory', were planted September 2, 1993, pinched September 16, and growth regulators applied September 30. There were five single plant replications for each treatment. Stem length and bract area were effected by bark grind, bark level, growth regulator, and growth regulator rate. Plants treated with uniconazole had the shortest stems and the least bract area. Plants grown in the smaller grind and at higher bark levels were less effected. Plants treated with paclobutrazol had longer stems than those treated with uniconazole.

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Abstract

Volume of loose media was determined accurately by a devised mechanical method and used for bulk density (BD) calculations. BD associated with increasing percentages of pine bark and/or sand potting media were plotted. Linear increase in BD associated with increasing percentage of sand in the medium was used to predict the percentage by volume of sand and/or bark in an unknown mixture of the two components. The technique should be useful in synthesis studies utilizing pine bark and sand as medium components.

Open Access

Rosa × hybrida 'Samantha' plants were planted in pots of three soilless and two soil-containing media. Soilless media consisted of coal bottom ash and composted hardwood bark in 1:1, 2:1, and 3:1 ratios. Soil-containing media were equal parts soil, peat, and coal bottom ash; and a control of equal parts soil, peat, and sand. Half the pots of each media were treated with a cover crop of Hordeum vulgare L. 'Barsoy' to simulate weathering and incorporate additional organic matter prior to planting the roses. Physical and chemical properties of all five original media were examined, and production indices of two harvests were measured; including stem length, flower bud diameter, fresh weight, days to harvest and average number of blooms per plant. Results to date indicate satisfactory growth in all treatments. The three soilless treatments have produced more stems with larger flower bud diameters and shorter days-to-harvest than the soil-containing treatments. However, the fertilization, and electrical conductivity of all treatments remains below normal. Moisture retention data also show the soil-containing treatments to have higher container capacity and easily available water. Cover-cropped plants also had shorter days-to-harvest, but in one of two harvests produced flower buds of smaller diameter.

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