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V.M. Gingas

Partially expanded male catkins at the pre-pollen shedding stage of Quercus rubra L. and Quercus bicolor Willd. were cultured on MS medium supplemented with BA or 2,4D Explants on 2,4D produced a yellow embryogenic callus, seeming to originate from the pedicels. Subsequent transfers to BA and then, MS without growth regulators, resulted in callus proliferation. After ten weeks in culture, white embryoids developed from the callus of Q. bicolor. Separated and individually cultured embryoids underwent direct, repetitive embryogenesis. Upon transfer to ½-strength MS, embryoid germination and plant regeneration occurred, Callus of Q. rubra degenerated after five months in culture, failing to produce embryogenic structures.

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Rico A. González, Daniel K. Struve, and Larry C. Brown

An irrigation control system has been developed and used to estimate evapotranspiration of contamer-grown plants by monitoring randomly selected plants within a container block and watering on an “as needed” basis. Sensor reliability and operational ease allows application of the system in a wide variety of field conditions. First-year tests, using red oak (Quercus rubra L.) seedlings, showed a reduction of 95% or better in both total irrigation and leachate rates with the computer-controlled treatment relative to a manually controlled, drip irrigation treatment without reducing plant growth.

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Cameron Rees and James Robbins

The iron-efficiency of pin oak (Quercus palustris) and red oak (Quercus rubra) grown in a static solution culture system was evaluated. Treatments included nutrient solutions with no iron, an unavailable iron form (Fe2 O3), and an available iron form (FeEDDHA), each adjusted to a starting pH of 5.5 or 7.0. Both oaks grew better when the available form of iron was used than when the solution contained unavailable or no iron. There was no difference in the height or leaf color for plants of either species when grown with unavailable or no iron. Red oak grown with an available iron form significantly lowered the pH of the solution prior to a growth flush. A similar drop in solution pH was not observed for pin oak growing under similar conditions.

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Cameron Rees and James Robbins

The iron-efficiency of pin oak (Quercus palustris) and red oak (Quercus rubra) grown in a static solution culture system was evaluated. Treatments included nutrient solutions with no iron, an unavailable iron form (Fe2 O3), and an available iron form (FeEDDHA), each adjusted to a starting pH of 5.5 or 7.0. Both oaks grew better when the available form of iron was used than when the solution contained unavailable or no iron. There was no difference in the height or leaf color for plants of either species when grown with unavailable or no iron. Red oak grown with an available iron form significantly lowered the pH of the solution prior to a growth flush. A similar drop in solution pH was not observed for pin oak growing under similar conditions.

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Jill C. Larimer and Dan Struve

In the spring of 1993, red oaks (Quercus rubra) and `Red Sunset' red maples (Acer rubrum cv. `Red Sunset') were propagated from seed and microcuttings, respectfully. From June through October, plants were fertilized twice daily with 1.4 liters of fertilizer solution at concentrations of 0, 25, 50, 100, 200, or 400 ppm nitrogen from a 20-10-20 water soluble fertilizer. Destructive harvests were conducted six times at intervals from June through December. Leaf area, stem height, root length, root area, and dry weights of roots, stem, and leaves of harvested plants were measured and tissue nutrient concentration analyzed. Nutrient analyses of roots, stems, and leaves show seasonal distribution patterns of nitrogen. Dose- response patterns of fertilizer rate and growth were identified throughout the growing season.

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Chris Cooper, Daniel Struve, and Mark Bennett

Previous experiments showed that a 10 day aerated water soak (water priming) increased red oak (Quercus rubra) seed vigor. After water priming most seed had split pericarps. Seed with split pericarps were observed to be more visorous than water primed seed without split pericarps. An experiment was conducted to determine if pericarp splitting could be used as an indicator of red oak seed vigor. The following experiment was conducted. Red oak seed from three open pollinated, half-sib families, were water primed for 10 days. Seed were separated into two groups, seed with split pericarps and without split pericarps, and a germination test conducted. Unprimed seed were used as a control. There were significant differences among the families in seed vigor (germination completeness, uniformity and speed). Primed seed with intact pericarps had lower seed vigor than primed seed with split pericarps and unprimed seed. The results suggest that pericarp splitting following water priming is an indicator of high seed vigor.

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Daniel G. Krueger Jr. and Bert T. Swanson

To increase root fibrosity, acorns of northern red oak (Quercus rubra L.) were germinated and subjected to several radicle clipping (+/-) and K-IBA concentration treatments combintations prior to planting. Taproots and laterals ≥ 1 mm in diameter at the point of origin were counted. Low concentrations of K-IBA (0-4000 ppm) resulted in four root morphologies: 1) a single taproot and 3-6 laterals (no clipping/no K-IBA), 2) 4-5 taproots and 1-3 laterals (clipped only), 3) a single taproot and 5-12 laterals (not clipped/K-IBA) and 4) 6-12 taproots and 1-2 laterals. High concentrations of K-IBA (4000-10,000 ppm) `clipped' unclipped radicles resulting in root systems similiar to those clipped by hand. Stem height was unaffected by treatment. Radicle-clipping may increase stem caliper. K-IBA treatments may decrease root dry weight.

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V.M. Gingas

Partially expanded male catkins of swamp white oak (Quercus bicolor Willd.) and red oak (Quercus rubra L.) were cultured on Murashige and Skoog (MS) medium supplemented with BA or 2,4-D. Explants on 2,4-D produced a yellow embryogenic callus originating from the junction of the pedicel and peduncle. Subsequent transfers to MS with BA and then MS without growth regulators resulted in callus proliferation. After 10 to 14 weeks in culture, white embryoids developed from the callus of Q. bicolor. Separated and individually cultured embryoids underwent direct, repetitive embryogenesis. Upon transfer to l/2-strength MS, embryoid germination and plant regeneration occurred. Callus of Q. rubra degenerated after 5 months in culture, failing to yield embryogenic structures. Chemical names used: dichlorophenoxyacetic acid (2,4-D); benzyladenine (BA).

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Petra Sternberg and Daniel K. Struve

In nursery production, increased branching is desirable, especially when growing stock that will be marketed at smaller sizes. Typically, branching is increased by pruning, which reduces growth potential. As an alternative to mechanical pruning, a chemical branching agent, Cyclanilide, has been evaluated for its ability to increase branching in container-grown whip production systems. Cyclanilide sprays of 0, 50, 100, and 200 mg·L-1 were applied to elongating shoots of Acer ×freemanii `Jeffsred', Cercis canadensis, Diospyros virginiana, Eucommia ulmoides, Malus ×`Prairie Fire', Malus ×`Harvest Gold', and Quercus rubra whips. Branching was increased in all taxa except Eucommia at concentrations >100 mg·L-1, without significantly reducing plant dry weight. For Diospyros, branching was increased when combined with pruning before Cyclanilide application.

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A.M. Shirazi and L.H. Fuchigami

Previously, we reported that plant recovery from “near-lethal” (NL) (sublethal) stresses depended on stage of development and poststress environment (PSE). Dormant red-osier dogwood (Cornus sericea) plants exposed to NL heat, freezing, and hydrogen cyanamide either died or were severely injured when stored at 0C or recovered at 23C and nautral condition. Exposure of dormant stem tissues of red oak (Quercus rubra), paper birch (Betula papyrifera) and European mountain ash (Sorbus aucuparia), to heat stress also resulted in higher ion leakage when they were stored at 0C PSE for 3 weeks. Soaking NL-heat-stressed (49C for 1 hour) stem tissue of red-osier dogwood in double distilled water for 48 hours before incubating at 0C PSE for 2 and 12 weeks resulted in lower ion leakage and 80% tissue survival. NL-stressed tissue had higher sodium and similar potassium leakage at 0C PSE. At 23C, PSE NL stress had no effect on leakage of these specific ion.