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  • Author or Editor: Frank A. Blazich x
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Abstract

Hardwood stem cuttings of Ilex crenata Thunb. ‘Convexa’, treated with and without indolebutyric acid (IBA), were inserted into a perlite rooting medium and misted with deionized water during intermittent mist propagation in a controlled-environment chamber. Initially, and at weekly intervals for 6 weeks, leaves, upper stems (portion of stem above rooting medium), and lower stems (portion of stem in rooting medium) were analyzed for N, P, K, Ca, and Mg. At the conclusion of the study, both nontreated and IBA-treated cuttings showed a slight increase in dry weight with detectable but slight leaching of N and K and no detectable leaching of P, Ca, and Mg. Mineral nutrient mobilization to the lower stem was not detected during root initiation for nontreated and IBA-treated cuttings. Following root initiation and later budbreak on the upper stem, N, P, K, Ca, and Mg were all mobililized from the leaves of nontreated and IBA-treated cuttings to the upper stem, whereas only N, P, and K were mobilized to the lower stem of IBA-treated cuttings. For nontreated cuttings, all nutrients were mobilized from the lower stem to the upper stem, while for IBA-treated cuttings only Ca and Mg were mobilized from the lower stem to the upper stem. Root development as influenced by IBA treatment and budbreak on the upper stem had a strong influence on mineral nutrient mobilization.

Open Access

Abstract

The electrolytic, visual, and electrical impedance methods for estimating freezing injury were highly associated. The electrolytic method was more closely associated with the visual method and better separated the effects of freezing temperatures than did the electrical impedance method. The electrical impedance method yielded results in the shortest time. The electrical impedance and visual methods evaluated freezing injury to woody internodal stem sections without the need for unfrozen controls.

Open Access

Seedlings of flame azalea [Rhododendron calendulaceum (Michx.) Torr] were grown for 12 weeks under long-day conditions with days at 18, 22, 26, or 30C for 9 hours in factorial combination with nights at 14, 18, 22, or 26C for 15 hours. Total plant dry weight, top dry weight, leaf area, and dry weights of leaves, stems, and roots were influenced by day and night temperatures and their interactions. Dry matter production was lowest with nights at 14C. Root, leaf, top, and total dry weights were maximized with days at 26C in combination with nights at 18 to 26C. Stem dry weight was maximized with days at 26 to 30C and nights at 22C. Leaf area was largest with days at 18 and 26C in combination with nights at 18 or 26C. Within the optimal, day/night temperature range of 26 C/18-26C for total plant dry weight, there was no evidence that alternating temperatures enhanced growth. Shoot: root ratios (top dry weight: root dry weight) were highest with days at 18 and 30C. Leaf area ratio (total leaf area: total plant dry weight) was highest and specific leaf area (total leaf area: leaf dry weight) was largest when days and nights were at 18C and were lower at higher temperatures. Regardless of day/night temperature, leaf weight ratio (leaf dry weight: total plant dry weight) was higher than either the stem weight ratio (stem dry weight: total plant dry weight) or root weight ratio (root dry weight: total plant dry weight). Net leaf photosynthetic rate increased with day temperatures up to 30C.

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Seedlings of mountain laurel (Kalmia latifolia L.) were grown for 16 weeks under long-day conditions with days at 18, 22, 26, or 30C for 9 hours in factorial combination with nights at 14, 18, 22, or 26C for 15 hours. Total plant dry weight, top dry weight, and dry weights of leaves, stems, and roots were influenced by day and night temperatures. The night optimum for all dry weight categories was 22C. Dry matter production was lowest with nights at 14C. Total plant dry weight and dry weights of tops, leaves, and stems were maximized with days at 26C, but for roots the optimum was 22C. Dry weight accumulation was lower with days at 18 or 30C. Responses of leaf area were similar to that of total plant dry weight, with optimum days and nights at 26 and 22C, respectively. Within the optimal day/night temperature range of 22-26/22C for dry weights, there was no evidence that alternating temperatures enhanced growth. Shoot: root ratios (top dry weight: root dry weight) increased with day temperatures up to 30C and were highest with nights at 14 or 26C. Leaf weight ratio (leaf dry weight: total plant dry weight) decreased with increasing night temperature, and increased curvilinearly in response to day temperature with the minimum at 26C. Stem weight ratio (stem dry weight: total plant dry weight) increased with increasing day or night temperature. Root weight ratio (root dry weight: total plant dry weight) was highest with nights at 18 or 22C and decreased with days >22C. Net leaf photosynthetic rate was maximized with days at 26C.

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Selected isolates of Hymenoscyphus ericae (Read) Korf and Kernan, Oidiodendron griseum Robak, O. maius Barron, and a second O. Robak species were evaluated as inocula for in vitro establishment of micropropagated plantlets of Pieris floribunda (Pursh ex Sims) Benth. and Hook. Severity of shoot necrosis on microshoots differed for each isolate of Oidiodendron. Inoculation of micropropagated plantlets with isolates of H. ericae benefited initial shoot and root development on agar-solidified Woody Plant Medium (WPM) supplemented with sucrose and covered by a layer of autoclaved 1 peat: 1 vermiculite (v/v). Inoculation of microshoots with H. ericae or isolates of Oidiodendron did not stimulate production of adventitious roots.

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Inoculation of microshoots of Pieris floribunda (Pursh ex Sims) Benth. and Hook. (mountain andromeda) with isolates of Hymenoscyphus ericae (Read) Korf and Kernan ericoid mycorrhizal fungi stimulated growth during 1 month in vitro. However, no benefits were apparent after 3 months in a greenhouse. Acclimatization of plantlets of P. floribunda to greenhouse conditions following in vitro inoculation improved survival (42% vs. 16% for controls). The protocol reported herein is similar to procedures utilized currently for micropropagation of various ericaceous species and has potential to improve plantlet survival during acclimatization.

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Two experiments were conducted during which juvenile hardwood or softwood stem cuttings of loblolly pine (Pinus taeda L.) were rooted under six mist regimes in a polyethylene-covered greenhouse to investigate the effect of mist level on vapor pressure deficit (VPD) and cutting water potential (Ψcut), and to determine the relationships between these variables and rooting percentage. In addition, net photosynthesis at ambient conditions (Aambient) and stomatal conductance (gs) were measured in stem cuttings during adventitious root formation to determine their relationship to rooting percentage. Hardwood stem cuttings rooted ≥80% when mean daily VPD between 1000 and 1800 hr ranged from 0.60 to 0.85 kPa. Although rooting percentage was related to Ψcut, and Aambient was related to Ψcut, rooting percentage of softwood stem cuttings was not related to Aambient of stem cuttings. Using VPD as a control mechanism for mist application during adventitious rooting of stem cuttings of loblolly pine might increase rooting percentages across a variety of rooting environments.

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Two experiments were conducted to develop a protocol for rooting stem cuttings from 3-, 5-, and 7-year-old fraser fir [Abies fraseri (Pursh) Poir.] Christmas trees. The first experiment tested the effect of stumping treatments and tree age on shoot production and subsequent adventitious rooting. One auxin concentration [4 mm indole-3-butyric acid (IBA)] and a nonauxin control were tested. Stock plants were stumped to the first whorl (trees in the field 3 and 5 years) or the first, third, and fifth whorls (trees in the field 7 years). Intact (nonstumped) controls were also included for each age. The second experiment was designed to create a quantitative description of the effects that crown (foliage and above ground branches of a tree) position have on the rooting of stem cuttings collected from stumped and nonstumped trees. The exact position was determined by measuring the distance from the stem, height from the ground, and the degrees from north. Crown positions were recorded as cuttings were collected and then cuttings were tested for rooting response. The rooting traits assessed in both experiments included rooting percentage, percent mortality, number of primary roots, total root length, root symmetry, and root angle. In the first experiment, rooting percentage, primary root production, and total root length increased as the age of the stock plant decreased and the severity of the stumping treatment increased. Auxin treatment significantly increased rooting percentage, root production, root lengths, and root symmetry while decreasing mortality. Overall, the highest rooting percentages (51%) and the greatest number of primary roots (8.1) occurred when 3-year-old stock plants were stumped to the first whorl and treated the cuttings with 4 mm IBA. The greatest total root lengths (335 mm) occurred in cuttings from the 3-year-old stock plants. In the second experiment, rooting percentage was significantly affected by the position from which the cuttings were collected. Cuttings collected lower in the crown and closer to the main stem rooted more frequently than cuttings collected from the outer and upper crown.

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Mahonia ‘Soft Caress’ is a unique new cultivar exhibiting a compact form and delicate evergreen leaves. Protocols for micropropagation of M. ‘Soft Caress’ were developed to expedite multiplication and serve as a foundation for future work with other taxa of Mahonia Nutt. Combinations of sucrose at 30 or 45 g·L−1 in conjunction with Gamborg B5 (B5), Quoirin and Lepoivre (QL), and Murashige and Skoog (MS) basal media as well as other selected growth regulator treatments were evaluated as multiplication media. Rooting of microcuttings was conducted in vitro using combinations of indole-3-butyric acid (IBA) at 0, 2, 4, 8, or 16 μM under either light or dark. Quick dip treatments with aqueous solutions of the potassium (K) salt (K-salt) of IBA at 0, 5.2, 10.4, 20.7, or 41.4 μM were tested in a second experiment for ex vitro rooting. Media containing B5 basal salts and vitamins supplemented with sucrose at 30 g·L−1, 5 μM 6-benzylaminopurine, 5 μM kinetin, 0.5 μM indole-3-acetic acid, and 2.5 μM gibberellic acid yielded 2.80 ± 0.14 microshoots with a mean length of 14.76 ± 0.63 mm over a 6-week culture period and was an optimal multiplication media. Light treatment and IBA concentration had a significant effect on rooting percentages. Microcuttings treated with 8 μM IBA and maintained in the dark resulted in the best rooting (70%) and ex vitro establishment.

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Success and subsequent growth of fraser fir [Abies fraseri (Pursh) Poir.] cleft grafts were studied in relation to origin and type of scion material in the tree crown. First- and second-order shoots (current-year) were collected from five zones in the crown, ranging from top to bottom, and grafted to 5-year-old fraser fir transplants in April. Success rates were similar for first- and second-order scions, whereas budbreak and subsequent growth were best for first-order scions. In general, results were best for first-order scions taken from the upper crown. Plagiotropism of grafts was similar for all crown zones and shoot types.

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