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  • Author or Editor: Frank A. Blazich x
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Abstract

Dormant hardwood stem cuttings of Fraser Fir [Abies fraseri (Pursh) Poir.] were severed from upper and lower tree crowns and artificially chilled at 4°C for 0, 4, or 8 weeks to achieve a partial break in rest. Following chilling, the resulting semi-dormant cuttings were treated with 0, 1500, 3000, or 4500 ppm IBA, and rooted for 135 days using a heated medium in a cool greenhouse. Rooted cuttings were evaluated, potted, and rechilled for 11, 7, or 3 weeks so that all cuttings were chilled a total of 11 weeks. Vegetative growth then was evaluated after a 12-week growing period. Cuttings initially chilled 4 weeks rooted in highest percentages, regardless of crown position, and exhibited little or no bud activity. Subsequent expansion of terminal and subterminal buds was greatest for cuttings initially chilled 0 or 4 weeks. Superior overall responses were achieved with upper-crown cuttings chilled 4 weeks and then treated with 4500 ppm IBA, or lower-crown cuttings dipped in 3000 ppm IBA after 4 weeks of chilling. The separation of rooting and budbreak apparently produced rooted cuttings comparable in size to 2-year-old plants grown from traditional hardwood cuttings. Chemical name used: 1H-indole-3-butanoic acid (IBA).

Open Access

Studies were conducted to investigate the effects of season (timing), IBA application, genotype, crown position, type of cutting (straight vs. heel), cutting length, and stock plant age upon adventitious rooting of stem cuttings of eastern redcedar (Juniperus virginiana L.). Genotype had a strong influence on percent rooting, root count, and root length of 4-year-old trees. With trees of this age, percent rooting was maximized (87%) with hardwood cuttings taken in January and treated with 5000 ppm IBA. Crown position from which cuttings were collected did not influence rooting. Straight cuttings, with or without a light wound, rooted at a significantly higher percentage (78%) than heel cuttings (52%). With 30-year-old trees, cuttings from the lower third of the crown rooted at a significantly higher percentage (67%) than cuttings from the middle third (43%). Better rooting was obtained with straight (68%) than heel (47%) cuttings. Cutting length affected rooting, with root count and length highest in longer cuttings. Increased tree age reduced rooting, although cuttings from 40-year-old trees retained substantial rooting capacity. Chemical name used: 1 H-indole-3-butyric acid (IBA).

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Catawba rhododendron (Rhododendron catawbiense Michx.) seedlings of two provenances, Johnston County, N.C. (35°45′N, 78°12′W, elevation = 67 m), and Yancey County, N.C. (35°45′N, 82°16′W, elevation = 1954 m), were grown in controlled-environment chambers for 18 weeks with days at 18, 22, 26, or 30C in factorial combination with nights at 14, 18, 22, or 26C. Shoot and root dry weights and total leaf areas of seedlings of the Yancey County provenance (high elevation) exceeded (P ≤ 0.05) those of the Johnston County (low elevation) provenance at all temperature combinations. Leaf area was maximal at 22/22C, 18/26C, and 22/26C and minimal at 30/14C (day/night). Shoot dry weight responded similarly. Root dry weight decreased linearly with increasing day temperature, but showed a quadratic response to night temperature. Leaf weight ratio (leaf dry weight: total plant dry weight) increased, while root weight ratio (root dry weight: total plant dry weight) decreased with increasing day temperature. Leaf weight ratio was consistently higher than either stem or root weight ratios. Day/night cycles of 22 to 26/22C appear optimal for seedling growth.

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Stem cuttings of `Yoshino' Japanese cedar [Cryptomeria japonica (L.f.) D. Don `Yoshino'], consisting of tips (terminal 20 cm) of first-order laterals, distal halves (terminal 10 cm) of tips of first-order laterals, and proximal halves (basal 10 cm) of tips of first-order laterals, or tips (terminal 10 cm) of second-order laterals, were taken on four dates that represented four growth stages (softwood, semi-hardwood, hardwood, and pre-budbreak). The cuttings were treated with 0, 3000, 6000, or 9000 mg IBA/liter. Branch order affected all rooting measurements at each growth stage. Regardless of growth stage, tips of and proximal halves of first-order laterals containing lignified wood had the highest percent rooting, root count, total root length, root area, and root dry weight. Hardwood tips of and semi-hardwood proximal halves of first-order laterals exhibited the highest overall rooting (87%), followed by softwood proximal halves of first-order laterals (78%). Rooting of distal halves of first-order laterals and tips of second-order laterals never exceeded 55% and 34%, respectively, at any growth stage. IBA treatment influenced percent rooting, root count, total root length, root area, and root dry weight of semi-hardwood, hardwood, and pre-budbreak cuttings, except for root dry weight of semi-hardwood cuttings. IBA had no affect on softwood cuttings. Chemical name used: 1H-indole-3-butyric acid (IBA).

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Cones of two provenances (Wayne Co., N.C., And Escambia Co., Ala.) of Atlantic white cedar [Chamaecyparis thyoides (L.) B. S. P.], were collected Fall 1994. Cones were dried for 2 months, followed by seed extraction and storage at 4°C for 6 months. Seeds were graded and stratified (moist-prechilled) for 0, 30, 60, or 90 days. Following stratification, seeds were placed at 25°C or 8/16 hour thermoperiods of 25°/15°C or 30°/20°C with daily photoperiods at each temperature of 0, 1/2, 1, 2, 4, 8, 12, or 24 h. At the conclusion of a 30-day germination period, the Alabama provenance exhibited greater germination than the North Carolina provenance for all treatments (74% vs. 46%). There were no significant differences between 25°/15°C and 30°/20°C with regard to total percent germination for both provenances. Germination was lowest at 25°C for each provenance. In some cases, however, there were no significant differences in germination of the North Carolina provenance when stratified for 60 or 90 days and germinated at 30/20°C or 25°C (61% vs. 63%). There was a highly significant quadratic response to stratification for cumulative percent germination for both provenances. The North Carolina provenance required 90 days stratification to maximize germination (66%) in contrast to the Alabama provenance, which only needed 30 days (80%). Seeds of both provenances did not exhibit an obligate light requirement. However, photoperiods ≥1/2 h increased germination greatly over seeds in darkness (29% vs. 62%).

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Hypocotyl cuttings were prepared from Ii-week-old aseptically grown seedlings of Fraser fir [Abies fraseri (Pursh) Poir.] and cultured 18 days on media containing 0 to 40 mg IBA/liter followed by transfer to the same medium without auxin. Greatest rooting (66%) occurred after treatment with 20 mg IBA/liter, whereas the greatest number of roots per rooted cutting (7.4) was noted following treatment with 40 mg·liter-1. Chemical name used: 1H-indole-3-butyric acid (IBA).

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Adventitious shoots developed on cotyledons of Virginia pine (Pinus virginiana Mill.) excised from seeds germinated for 3, 6, or 9 days and cultured on media containing 0.5 to 10 mg/liter benzyladenine (BA). Shoot regeneration was greatest (46 shoots per embryo) on cotyledons from seeds germinated for 6 days and placed on medium containing 10 mg/liter BA. Shoots were excised and elongated on medium lacking BA. Following elongation, shoots were placed on media containing 0 to 40 mg/liter indolebutyric acid (IBA) for 14 days followed by transfer to the same medium lacking auxin. Without IBA treatment, percent rooting was 3% and increased to 50% for concentrations of 5 to 40 mg/liter. Rooted shoots averaged 2.0 roots per shoot without auxin treatment, 3.3 roots when treated with 5 mg/liter IBA and root number increased linearly with increased IBA concentration up to 40 mg/liter (4.5 roots). Plant lets were transferred to growing medium and acclimated successfully to greenhouse conditions.

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Adventitious shoots developed on cotyledons of Virginia pine (Pinus virginiana Mill.) excised from seeds germinated for 3, 6, or 9 days and cultured on media containing 0.5 to 10 mg/liter benzyladenine (BA). Shoot regeneration was greatest (46 shoots per embryo) on cotyledons from seeds germinated for 6 days and placed on medium containing 10 mg/liter BA. Shoots were excised and elongated on medium lacking BA. Following elongation, shoots were placed on media containing 0 to 40 mg/liter indolebutyric acid (IBA) for 14 days followed by transfer to the same medium lacking auxin. Without IBA treatment, percent rooting was 3% and increased to 50% for concentrations of 5 to 40 mg/liter. Rooted shoots averaged 2.0 roots per shoot without auxin treatment, 3.3 roots when treated with 5 mg/liter IBA and root number increased linearly with increased IBA concentration up to 40 mg/liter (4.5 roots). Plant lets were transferred to growing medium and acclimated successfully to greenhouse conditions.

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Hypocotyls of Fraser fir (Abies fraseri (Pursh) Poir.) were excised from seeds germination 9 days and placed on bud induction medium containing 10 mg/liter benzyladenine (BA) and 0.01 mg/liter naphthaleneacetic acid (NAA) or medium without growth regulators. After 3 days on medium containing growth regulators, cell divisions were localized in epidermal and subepidermal layers of the hypocotyl while similar cell divisions were not observed in control-treated hypocotyls. Cell clusters consisting of two to five cells were present after 7 days in hypocotyls placed on bud induction medium. In control-treated hypocotyls, stomata continued to develop and cells within the cortex became vacuolated during the first 2 weeks in culture. All hypocotyls were transferred to secondary medium after 3 weeks. Cell clusters continued to enlarge into meristemoids in hypocotyls initially placed on bud induction medium. Gradually, meristemoids developed into buds and cataphylls were observed covering bud meristems.

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Temperature sensitivity of net photosynthesis (Pn) was evaluated among 4 taxa of rhododendron including Rhododendron hyperythrum, R. russatum, and plants from two populations (northern and southern provenances) of R. catawbiense. Measurements were conducted on individual leaves at temperatures ranging from 15 to 40C. Temperature optima for Pn ranged from a low of ∼21 C for R. russatum to a high of ∼27C for R. hyperythrum. At 40C, Pn rates for R. hyperythrum, R. catawbiense (northern provenance), R. catawbiense (southern provenance), and R. russatum were 7.8, 5.7, 3.5, and 0.2 μmol·m-2·s-1, respectively. R. catawbiense from the southern provenance did not appear to have greater heat tolerance than plants from the northern provenance. There was no difference in temperature sensitivity of dark respiration among the taxa. Variations in heat tolerance among species appeared to result from a combination of stomatal and nonstomatal limitations on Pn at high temperatures.

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