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Thomas E. Marler and Jonathan H. Crane

Lateral branches arising from the primary bud complex on limbs of containerized `Gefner' atemoya (Annona squamosa L. × A. cherimola Mill.) plants were removed to determine the influence of branch regrowth on the crotch angle. Pruning the lateral branches to a stub (cl cm) was more effective in inducing regrowth and increasing branch angle of the regrowth than stripping lateral branches by hand. Following lateral branch removal, regrowth did not develop from every node along a stem axis. In a second study, the angle of branch regrowth from tagged nodes following pruning of lateral branches was determined. The mean crotch angle of the primary lateral branches was 58°. Regrowth from the second and third supernumerary buds within each node produced branches with an average crotch angle of 72° and 88°, respectively. The largest increase in attachment angle following pruning was obtained at nodes with narrow primary lateral branches and at nodes located closest to the base of a major axis. The increase in branch crotch angle was not correlated with the size of the preceding lateral branch at a node. These results indicate that pruning off lateral branches with narrow crotch angles may be performed during training atemoya plants to produce scaffold limbs from supernumerary buds within the same nodes with desirably wide crotch angles.

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J.E. Preece, C.A. Huetteman, R.G. Adams, W.C. Ashby, and P.L. Roth

Whole-tree branch architecture was quantified by counting and measuring the lengths of main stems, basal branches, and all primary (1°), secondary (2°), and tertiary (3°) branches. Trees were grown in replicated clonal plantations established in 1991 on a southern Illinois lowland and an upland site. Fifty-two clones in each of five complete blocks were measured from each plantation. Number of primary branches that formed in 1991, 1992, and 1993, and the number of nodes in the terminal meter of growth were highly significant for silver maple provenance and for clones (four clones for each of 13 provenances), except that clonal differences were nonsignificant for the number of 1° branches on 1991 wood. There were significant effects of provenance and clone on total number and the various sizes of 2° and 3° branches. Generally, a greater number and longer length of 2° and 3° branches formed on trees from the more rapidly growing southern provenances.

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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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Michelle L. Jones, Kenneth K. Cochran, Gary A. Anderson, and David C. Ferree

Deciduous holly branches were visually rated over a period of 5 weeks to evaluate differences in display life between various cultivars of winterberry (Ilex verticillata) and japanese winterberry (I. serrata) x winterberry. Holly branches were naturally defoliated and the postharvest performance of the cut branches was therefore based on the quality and longevity of the fruit. Chemical treatments including floral preservative, floral preservative plus silver, and anti-transpirant were also evaluated. `Bonfire' and `Sunset' had the highest ratings for marketability based on the longevity and quality of their fruit. `Bonfire' and `Winter Red' had the highest fruit density per stem. Treatment with floral preservatives significantly increased the display life of holly branches. Preservative plus silver delayed deterioration later in the study, presumably by delaying the senescence of the fruit. Anti-transpirant treatment did not decrease solution uptake by the holly stems. Cold storage of dry branches at 0.00 ± 1.11 °C (32.0 ± 2.0 °F) did not significantly reduce branch display life if held for 23 days or less. Cut branches of all cultivars had a longer display life when stuck in sand and left outdoors in a lath house than when rated in vase solutions indoors. This study indicates that deciduous holly branches provide an attractive alternative cut branch for both interior and outdoor holiday displays.

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David R. Ouellette, C.R. Unrath, and Eric Young

One-year-old unbranched `Empire' apple (Malus domestica Borkh.) trees on Malling 26 EMLA and Malling–Merton 111 EMLA rootstocks were planted in Nov. 1991 or Mar. 1992 at an eastern Piedmont or mountain site of North Carolina. In Mar. 1992 and 1993, trees were dormant-headed and then subjected to one of five branch-inducing techniques: 1) control—untouched, 2) notching—removing a thin band of bark above each lateral bud, 3) leaf removal—periodic removal of immature apical leaves, 4) bending—placing at horizontal and setting upright in summer, or 5) renewal—setting a lateral branch upright as the new leader. The second year (1993), half of the trees were periodically sprayed with Promalin (GA4+7 + BA). At the Piedmont site, notching, leaf removal, and bending resulted in more branching than the control after 1 year. At the mountain site, leaf removal was considerably less effective in inducing branches. Bending produced asymmetric trees and, at the mountain site, considerably reduced terminal shoot growth. Planting date had little influence on branching. Two years after planting, notched trees were significantly larger and had twice as many branches as other trees. Promalin increased branching on current-season growth and, when combined with leaf removal, resulted in the most uniform distribution of branches along the length of the central leader. Using notching or Promalin produced a tree structure suitable for high-density plantings. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA), gibberellins A4 + A7 (GA4+7).

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Richard K. Schoellhorn, James E. Barrett, and Terril A. Nell

Effects of photosynthetic photon flux (PPF) and temperature on quantitative axillary budbreak and elongation of pinched chrysanthemum [Dendranthema ×grandiflorum (Ramat.) Kitamura] plants were studied in three experiments. In Expt. 1, 12 commercial cultivars were compared under fall and spring environmental conditions. Spring increases in lateral shoot counts were attributable to increased PPF and air temperature. Cultivars varied from 0 to 12 lateral branches per pinched plant and by as much as 60% between seasons. There was a linear relationship between lateral branches >5 cm at 3 weeks after pinching and final branch count (y = 0.407 + 0.914(x), r 2 = 0.92). In Expt. 2, air was at 20 or 25C and the root zone was maintained at 5, 0, or –5C relative to air temperature. With air at 20C, lateral branch counts (3 weeks after pinch) declined by ≤50% with the medium at 15C relative to 25C. At 25C, lateral branch count was lower with medium at 30C than at 20C. Cultivars differed in their response to the treatments. Experiment 3 compared the interactions among temperature, PPF, and cultivar on lateral branch count. Depending on cultivar, the count increased the higher the PPF between 400 and 1400 μmol·m–2·s–1. Air temperature had no effect on lateral branch count. PPF had a stronger effect on lateral branch count than air temperature, and cultivars differed in their response.

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A. James Downer, Matthew Shaw, and Dennis Pittenser

Coast Live Oak (Quercus agrifolia) and White oak (Q. lobata) are landscape trees which are prone to sudden branch drop. The purpose of this work was to determine the effect of various pruning techniques on growth reduction of one member of a pair of codominant stems. Forty trees of each species were selected with codominant stems. One stem of each pair was pruned by: 1. removing all apical meristems; 2. thinning 50% of branches; 3. heading back to a 10cm stub or, 4. unpruned. Calipers of thinned or headed branches were most retarded while tipped and unpruned branches grew most. Results suggest that pruning by thinning may be an alternative to removal of codominant branches when training young trees.

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Gerardo Martinez-Díaz, J.A. Crisitóbal Navarro-Ainza, and Raúl Grijalva-Contreras

Flower density, number of flowers per inflorescence and fruit set in `Mission' `Barouni' and `Ascolano' olive trees were related to cardinal orientation of branches: branches located at W and N showed higher values than S and E branches. Observations about floral development indicated that floral initiation of cv Mission ocurred earlier on N and W branches (Feb. 26th to March 7th) than on E and S ones (March 7th to April 26th). Defoliation on January 12th decreased number of inflorescences per branch, but such effect. was counteracted if buds up or below the defoliated region were eliminated. Girdling decreased the action of desbudding, mainly if desbudding was performed above the defoliated region.

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Dane K. Fisher, Charles D. Boyer, and Mark Guiltinan

During plant starch biosynthesis, starch branching enzymes (SBE) catalyze a-1,6 branch point formation in starch, and thus are responsible for many properties of the starch polymer. Recently we have cloned cDNAs encoding the two major branching enzymes in developing maize endosperm, SBEI and SBEII. These genes are being used to alter starch biosynthesis via genetic engineering strategies. Transgenic tobacco plants with sense and antisense constructs of SBEI and SBEII have been produced. No major difference in the phenotypes of control and transgenic plants have been observed. Initial experiments demonstrated the transcription of the introduced genes. Enzyme levels and the molecular properties of the starch in the transgenic plants will be determined. These experiments will provide us with information as to the role of starch branching enzymes in starch biosynthesis, the feasibility of creating novel starch, and the effect altered starch has on plastid development and photosynthesis.

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David R. Ouellette and Eric Young

The ability of various leaf removal treatments or shoot tipping to induce lateral shoot development on current-season stoolbed shoots of MM.106 EMLA and M.26 EMLA apple (Malus domestica Borkh.) rootstocks was investigated. Removal of the five uppermost immature leaves or shoot tipping after every 20 to 25 cm of terminal growth produced more lateral budbreak than occurred on nontreated shoots. Shoot tipping resulted in the highest number of branches (≥5 cm) and greatest total branch length. Only tipping consistently induced lateral budbreak higher than 30 cm up the shoot. Removal of the 10 uppermost leaves and tipping resulted in the shortest terminal shoots. MM.106 shoots had more lateral budbreak, branches, and total branch length than did M.26 shoots.