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J. W. Van Sambeek, Lisa J. Lambus, and John E. Preece

At monthly intervals for 1 year, one branch was removed from the lower crown of three 30-year-old trees of black walnut (Juglans nigra L.). The basal 1.3 m of each branch was cut into four 32-cm-long segments that were placed horizontally in shallow plastic trays filled with perlite and watered daily with tap water. Branch segments cut early in the dormant season (29 Sept., 31 Oct., or 1 Dec.) or shortly after flushing (6 June) produced few, if any, epicormic sprouts. Approximately half the branch segments cut on 3 Jan. or 3 Feb. produced one sprout that elongated slowly. Most branch segments cut in the late dormant season (2 Mar., 30 Mar., 3 May) or growing season (5 July, 4 Aug., 6 Sept.) produced one or two sprouts >20 mm long. To prepare explants for in vitro culture, the terminal 2.5 cm was harvested when sprouts exceeded 3.0 cm, trimmed of all leaves, and disinfested. Explants were placed vertically in liquid Long & Preece (LP) medium supplemented with 3% sucrose, 0.3 μM TDZ, 0.05 μM IBA, and 1 μM BA. When shoots began to elongate (4 to 6 weeks), they were then placed horizontally on agar-solidified LP medium with liquid LP overlays to induce axillary shoot proliferation. Advantages of forcing epicormic sprouts on large branch segments are: 1) they can be a source of in vitro explant material for 6 to 7 months a year, 2) aseptic cultures can be easily obtained, 3) shoots from the base of branches may show more juvenility than shoots forced from branch tips, 4) softwood shoot wilting is not a problem as with forcing shoots from branch tips, 5) the procedure does not require preparing and changing forcing solutions, and 6) branch segments should have more stored food than dormant branch tips for forcing softwood growth.

Open access

H.K. Wutscher and R.E. McDonald

Abstract

Sap extracted by nitrogen gas pressure from branches and lateral roots of healthy and citrus blight-affected ‘Hamlin’ and ‘Valencia’ orange, Citrus sinensis (L.) Osbeck, trees on rough lemon (C. Union Burm. f.) rootstock in 2 commercial groves was analyzed for N, K, Ca, Mg, S, Na, Fe, Mn, Zn, Cu, CI, Si, and organic acids. The branch and root wood (from which the sap was extracted), leaves, and feeder roots were also analyzed. Sap extracted from branches of blight-affected ‘Hamlin’ trees in the spring had higher Zn, Cu, CI, and Si concentrations than sap of healthy trees. Nitrogen was increased twofold and Fe slightly increased with blight in the root sap. Branch sap collected from ‘Valencia’ trees in the fall showed no differences. Branch sap contained more organic acids than root sap and there was no difference between blighted and healthy trees. Citric and malic were the principal acids.

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Laura G. Jull, Stuart L. Warren, and Frank A. Blazich

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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James E. Faust and Royal D. Heins

Dendranthema ×grandiflorm (Ramat.) Kitamura `Powerhouse' plants were pinched to five nodes and grown in growth chambers at 35C day temperature (DT) and 14,17,21,24, or 27C night temperature (NT) to determine if NT influenced lateral shoot development on plants exposed to high DT. Vegetative cuttings were removed from two successive flushes of lateral shoots and evaluated for lateral shoot development after rooting and subsequent apex removal. Lateral shoot development was determined on a third flush of shoots that developed on the stock plants. The percentage of nodes that developed lateral shoots on stock plants or vegetative cuttings was not related to NT. The percentage of first-order, second-order, and third-order axillary nodes that developed a lateral shoot on the stock plants, averaged over all NT, was 76, 65, and 12, respectively. The percentage of nodes that developed lateral shoots on the first-order and second-order cuttings was 29 and 19, respectively. We concluded that cool NT were ineffective in preventing a decrease in lateral branching on plants grown under high (35C) DT conditions.

Open access

Bijan Dehgan and Charles R. Johnson

Abstract

To determine the potential for root branching, the primary root of Zamia floridana L. seedlings was excised near the root–shoot junction and the cut ends were dipped in 2000 ppm IBA, 2000 ppm BA, or combination of the two, each for 5 sec. Whereas excised control plants produced only one root, those treated with IBA, BA, and IBA–BA averaged 2.1, 3.2, and 2.3 roots, respectively. In all instances, the number of secondary roots increased significantly compared with intact seedlings. Since seedling roots are diarch throughout, new primordia must be initiated in the interfascicular parenchyma tissue for more than two roots to be produced. Treatment with IBA probably disrupted apical control of roots by the shoot meristem and stimulated development of the two possible secondary roots associated with xylem poles, while BA caused new primordia to be formed in the interfascicular parenchyma region. Chemical names used: 1H-indole-3-butyric acid (IBA); N-(phenylmethyl)-1H-purin-6-amine (BA).

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Haley Hibbert-Frey, John Frampton, Frank A. Blazich, Doug Hundley, and L. Eric Hinesley

western North Carolina and into eastern Tennessee ( Liu, 1971 ). It is grown commercially as a Christmas tree because of its pleasant fragrance, dark green foliage, natural conical shape, and strong branches ( Frampton, 2001 ). In addition, it has good

Open access

S.P. Monselise, E.E. Goldschmidt, A. Golomb, and R. Rolf

Abstract

Scaffold branches of ‘Michal’ tangerine (a Citrus reticulata hybrid) trees were fall-girdled once. Individual branches were driven into opposite phases of alternate bearing which continued for at least 3 successive years, without an additional stimulus. Bearing and nonbearing branches behaved like whole on- and off-trees, with regard to macronutrient and starch concentration in leaves and twigs, respectively. Off/on ratios for individual factors, however, were closer to unity than those previously found for whole alternating ‘Wilking’ trees, possibly due to the moderating effect of the common root system.

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Paul J.R. Cronjé, Gerard Jacobs, and Nigel C. Cook

Two-year-old apple branches, ≈50 cm long, were selected from a commercial `Royal Gala' orchard in the Ceres (Koue Bokkeveld) region of the Western Cape, South Africa [33 °S, 945 m, 1500 Utah model chilling units (CU)]. In 2000, the branches received either cold storage at 5 to 7 °C or natural chilling in the field. In 2001, the trial was repeated, but only with field chilling. The branches received five dormant pruning treatments: control (not pruned); pruning back to the fourth lateral shoot (heading) before or after chilling; and removal of the second and third lateral shoots (thinning) before or after chilling. After pruning and chilling, the branches were removed from the orchard or cold room every 2 weeks and forced in a growth chamber at 25 °C. The rate of budburst (1/days to budburst) was determined for the terminal buds of the lateral shoots. Lateral shoots on the 2-year-old branches were categorized according to position: the most distal extension shoot, and all other laterals grouped. Removing distal tissue by pruning (heading more than thinning) enhanced the effect of chilling on the terminal buds on the lateral shoots and promoted budburst. Pruning was more effective before than after chilling. Pruning enhanced the growth potential of the terminal buds on proximal shoots on 2-year-old branches.

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Brad G. Howlett, Samantha F.J. Read, Maryam Alavi, Brian T. Cutting, Warrick R. Nelson, Robert M. Goodwin, Sarah Cross, Trevor G. Thorp, and David E. Pattemore

consisted of 20 trees of the same cultivar. For each tree, two fully flowering racemes located in similar positions (height, aspect, branch location) but on separate branches, were marked with tape. Chosen racemes were 120 to 200 cm above ground and

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Tadeusz Jacyna

One-year-old trees of three apple selections [NY73334-35 (A), NY75414-1 (B), and NY75413-30 (C)] from the Geneva Breeding Program were transplanted into an orchard. While at the nursery, the trees were treated with Promalin and Accel, by themselves or in combination, to promote lateral branch formation (feathering). After trees were transplanted, no growth regulators were applied to the trees. One year after transplanting, treated trees of B and C had produced more feathers than the controls. This was particularly pronounced with the very difficult-to-branch selection C. No differences between chemical treatments were found. Regardless of selection, each chemical treatment significantly influenced increase in total extension growth compared to the control and contributed to rapid build up of tree structure. There were no differences between the treatments in tree height, tree caliper, or the number of spurs.