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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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Diana R. Cochran, Amy Fulcher and Guihong Bi

Pruning is commonly performed during production of nursery crops to produce symmetrical, compact plants that are pleasing to the consumer’s eye. To achieve the desired results, nursery growers hand prune or apply plant growth regulators (PGRs). However, hand pruning is expensive and is not always effective, and efficacy of PGRs can depend on cultural practices, environmental conditions, irrigation, cultivar, and rate. Therefore, the objective of these experiments was to evaluate the effect of dikegulac sodium applied to pruned or unpruned ‘Limelight’ hardy hydrangea (Hydrangea paniculata). Plants were grown at two locations, Tennessee (TN) and Mississippi (MS). The pruned treatment consisted of hand pruning, leaving three nodes followed by applications of dikegulac sodium (400, 800, or 1600 ppm). Applications of dikegulac sodium to pruned or unpruned plants were made the same day using a carbon dioxide backpack sprayer. There were two additional control treatments: hand-pruned untreated (hand-pruned) and unpruned untreated (untreated). Plants were grown outdoors under full sun in TN and under 40% shade in MS. Data were collected at the close of the experiment on the number of branches over 1 inch, final growth index (FGI), floral attributes, branch symmetry, and phytotoxicity. At both locations, pruned and unpruned plants treated with 800 or 1600 ppm dikegulac sodium had more branches than the hand-pruned and unpruned plants. Flower number and size tended to be greater for unpruned plants than pruned plants. Phytotoxicity was observed at 2 and 6 weeks after treatment (WAT). For plants grown in TN, symptoms were more pronounced on plants following treatment with 800 (pruned plants) and 1600 ppm (pruned and unpruned) dikegulac sodium compared with the untreated plants. There were no visible phytotoxicity symptoms at 6 WAT for plants grown in MS, regardless of treatment.

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Diana R. Cochran and Amy Fulcher

The objective of these experiments was to evaluate the response of Little Lime™ hardy hydrangea (Hydrangea paniculata ‘Jane’) across two seasons in response to single foliar applications of three plant growth regulators (PGRs) at two rates: dikegulac sodium at 800 or 1600 ppm, benzyladenine at 300 or 600 ppm, or ethephon at 500 or 1000 ppm. There were two additional treatments: a hand-pruned control leaving three nodes and an unpruned water control (untreated) applied the same day as the PGR applications. To evaluate PGR efficacy, vegetative growth, floral attributes, branch symmetry, and phytotoxicity were assessed. Dikegulac sodium significantly increased branch number (BN) compared with all other treatments. Branch symmetry was greater in dikegulac sodium (800 or 1600 ppm) and hand-pruned treatments compared with the untreated and other PGR treatments (2011 and 2012). Flower number was greater in all PGR treatments compared with hand-pruned plants (2011 and 2012). The only treatment that promoted more symmetrical branching without reducing flower count was dikegulac sodium (800 or 1600 ppm). Phytotoxicity was observed in both seasons; however, no injury symptoms were evident 16 weeks after treatment (WAT), the termination of the experiment.

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Chris A. Martin, Jean C. Stutz, Bruce A. Kimball, Sherwood B. Idso and David H. Akey

Growth and topological indices of `Eureka' lemon were measured after 6 months in well-watered and well-fertilized conditions and factorial combinations of moderate (29/21C day/night) or high (42/32C day/night) temperatures and ambient (350 to 380 μmol·mol) or elevated (constant 680 μmol·mol-1) CO2. In high temperatures, plants were smaller and had higher levels of leaf chlorophyll a than in moderate temperatures. Moreover, plants in high temperatures and elevated CO2 had about 15 % higher levels of leaf chlorophyll a than those in high temperatures and ambient CO2. In high temperatures, plant growth in elevated CO2 was about 87% more than in ambient CO2. Thus, high CO2 reduced the negative effect of high temperature on shoot growth. In moderate temperatures, plant growth in elevated CO2 was only about 21% more than in ambient CO2. Irrespective of temperature treatments, shoot branch architecture in elevated CO2 was more hierarchical than those in ambient CO2. Specific shoot extension, a topological measure of branch frequency, was not affected by elevated CO2 in moderate temperatures, but was increased by elevated CO2 enrichment in high temperatures-an indication of decreased branch frequency and increased apical dominance. In moderate temperatures, plants in elevated CO2 had fibrous root branch patterns that were less hierarchical than at ambient CO2. The lengths of exterior and interior fibrous roots between branch points and the length of second-degree adventitious lateral branches were increased >50% by high temperatures compared with moderate temperatures. Root length between branch points was not affected by CO2 levels.

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Thomas M. Gradziel, Mary Ann Thorpe and Diane M. Barrett

the freestone peach ‘Elberta’ and the clingstone nectarine PI 292557. In long-term commercial evaluations, fruit have demonstrated good firmness, color, shape, and productivity. Tree form is upright-spreading with vigor and branch architecture similar

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Thomas M. Gradziel and Mary Ann Thorpe

in over 10 years of continuous commercial evaluation in environments having 700 h or more of winter chilling. Tree form is semiupright with vigor and branch architecture similar to ‘Andross’. Flowers are pink, non-showy, and medium in size. Leaves are

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Thomas Gradziel and Sabrina Marchand

form is semi-upright, with vigor and branch architecture similar to ‘Andross’. Flowers are pink, showy, and large. Leaves are medium-to-dark green, with globose leaf glands. Origin The University of California at Davis (UCD) has maintained a processing

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Thomas Gradziel and Sabrina Marchand

years of commercial evaluation. Tree form is semi-upright, with vigor and branch architecture similar to those of ‘Andross’. Flowers are pink and nonshowy. Leaves are medium to dark green with globose glands. Origin A main objective of the University of

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Omar Carrillo-Mendoza, Wayne B. Sherman and José X. Chaparro

southeastern United States. In contrast, almond has reduced branching, an open tree canopy, and can produce short branches or spurs. Commercial peach germplasm typically has a branching architecture that is intermediate to the two described previously but

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Claudia Negrón, Loreto Contador, Bruce D. Lampinen, Samuel G. Metcalf, Theodore M. DeJong, Yann Guédon and Evelyne Costes

proleptic spurs and subsequent blooms ( Aldrich, 1984 ). In contrast, ‘Winters’ has an upright and highly branching architecture. Production occurs on spurs, on terminal 1-year-old shoots, and on characteristic, medium-short sylleptic shoots ranging in