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Deborah Dean, Phillip A. Wadl, Denita Hadziabdic, William E. Klingeman, Bonnie H. Ownley, Timothy A. Rinehart, Adam J. Dattilo, Brian Scheffler, and Robert N. Trigiano

Viburnum rufidulum is a member of Adoxaceae, which includes the genera Viburnum , Sambucus , Sinadoxa , and Adoxa . The genus Viburnum is estimated to include ≈170 species with worldwide distribution ( Winkworth and Donoghue, 2004

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Richard C. Beeson Jr

research presented here was to quantify cumulative ET A of Viburnum odoratissimum Ker Gawl (viburnum) to expand the database of woody shrub water requirements during production. The second objective was to analyze the data using the Percent Canopy

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Candice A. Shoemaker and Michael Barnett

Viburnum bracteatum Rehd. is a member of the “dentatum” complex represented by at least three types: V. bracteatum, V. dentatum L., and V. rafinesquianum Schult. V. bracteatum is an endangered species in Georgia and at the federal level is a candidate as an endangered species. Two populations were located in northwestern Georgia; however, there is some concern as to whether they are in fact V. bracteatum. To determine if it is possible to distinguish between the three Viburnum species, cellulose acetate electrophoresis to detect isozyme variation was done. Polymorphic enzymes resolved were alcohol dehydrogenase, malic dehydrogenase, glucose-6-phosphate dehydrogenase, malic enzyme, 6-phosphogluconate dehydrogenase, phosphoglucomutase, and phosphoglucose isomerase. Fresh bud tissue was used, and tissue samples were electrophoresed three times for each enzyme assayed. A review of 100 phylogeny trees created with Dollop analysis was done. V. rafinesquianum, the known sample of V. bracteatum, and the 12 samples of possible V. bracteatum were all equally parsimonious. V. dentatum was consistently an outgroup. In conclusion, isozyme variation can assist in Viburnum species distinction.

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John F. Wachter and Paul E. Cappiello

Stems of 33 varieties of Viburnum were screened for low temperature tolerance on five dates. Terminal stem cuttings were shipped overnight to Orono, Maine, from Oregon, Michigan, and Minnesota. Following a controlled freezing regime, stems were incubated for 7–14 days and evaluated for injury by visual observation. Lowest survival temperatures (LST) were estimated as the lowest temperature at which 100% of stems were uninjured. Varieties of V. dentatum, V. lantana, V. opulus, and V. trilobum were rated as consistently very cold tolerant. Viburnum ×pragense, V. dilatatum, and V. rufidulum were rated as consistently moderately cold tolerant. All V. tomentosum varieties showed inconsistent LST estimates. Varieties from the Oregon source were rated as cold intolerant. Direct comparisons by variety and source will be discussed with emphasis on consistent LST estimates. Rates of deacclimation as they occurred over the five testing dates will also be discussed.

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John F. Wachter and Paul E. Cappiello

Stems of 38 varieties of Kalmia latifolia, 33 varieties of Viburnum, and 45 varieties of Magnolia were screened for low-temperature tolerance on eight dates during the winters of 1995–96 and 1996–97. Terminal 6- to 8-cm stem cuttings were shipped overnight on ice to Orono, Maine, and processed immediately upon arrival. Cuttings were subjected to a controlled freezing regime with a lowest test temperature ranging from –31°C to –42°C. Following freezing, stems were incubated for 5 to 14 days at 21°C and evaluated for injury. Lowest survival temperatures (LST) for each variety were estimated as the lowest temperature at which 100% of stems were undamaged. Varieties of Viburnum dentatum, V. lantana, V. opulus, and V. trilobum were rated as consistently very cold-tolerant, with LSTs of at least –36°C on all test dates. All V. plicatum var. tomentosum varieties showed inconsistent survival and LST estimations. Midwinter LST estimates in Kalmia latifolia showed 40% of the tested varieties remained undamaged at or below –36°C. Ten percent of K. latifolia varieties tested were damaged at –24°C or warmer, with the remaining varieties having LSTs somewhere between –24°C and –40°C. Varieties of Magnolia showed inconsistent survival with LSTs estimated for only 5% of those tested. Direct comparisons by variety, test date and source will be discussed with emphasis on consistent LST estimation. Varieties of K. latifolia, Viburnum, and Magnolia best suited for use in northern landscapes will also be discussed.

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Gisele Schoene, Thomas Yeager, and Joe Ritchie

In crop models, it is important to determine the leaf area, because the amount of light interception by leaves influences two very important processes in the plant: photosynthesis and evaporation. Leaf area is dependent on leaf appearance and expansion rates. Leaf appearance rate is driven mainly by temperature. Although the influence of temperature on leaf area development is well known for several agronomic crops, there is no information for woody ornamentals. An experiment was conducted to study the relationship between temperature and leaf appearance of container-grown sweet viburnum. Plants were grown in field conditions in Gainesville, Fla., during two growing periods (Apr. to Aug. 2004 and Aug. 2004 to Jan. 2005). Daily maximum and minimum temperature and leaf appearance were recorded. Linear regression equations were fitted to data and maximum and minimum temperature and leaf appearance were recorded. Linear regression equations were fitted to data and base temperature was assumed to be 8 °C. Thermal time (°C d) was calculated as daily average maximum and minimum air temperature minus the base temperature and was regressed against leaf number. The sum of accumulated thermal time was found to be linearly correlated with leaf number. Phyllochron, which is the thermal time between the appearances of successive leaves, was estimated 51 °C per day. The information presented in this study will be useful in modeling water use of sweet viburnum in response to environmental conditions.

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Carleton B. Wood, Timothy J. Smalley, Mark Rieger, and David E. Radcliffe

Container-grown Viburnum plicatum Thunb. var. tomentosum (Thunb.) Miq. `Mariesii' were planted in unamended planting holes, tilled plots, and tilled plots amended with aged pine bark. A 36-day drought was initiated 108 days after planting. Amending induced N deficiencies, reduced shoot growth, and increased root growth. Plants harvested from tilled and planting-hole plots at drought initiation had 63% and 68% more dry weight, respectively, than plants from amended plots. Between 8 and 19 days after drought (DAD) initiation, plants from tilled plots maintained higher relative leaf water content (RLWC) than plants from planting holes. Plants in amended plots maintained higher RLWC than both other treatments between 7 and 33 DAD. Amended and tilled treatments had higher relative leaf expansion rates (RLERs) than the planting-hole treatment 8, 11, 13, and 15 DAD. As the drought lengthened, plants in amended plots maintained higher RLERs than plants in tilled plots. While plants in pine bark-amended plots were more drought tolerant than those in tilled plots, it is unclear if increased drought tolerance was caused by the improved rooting environment or N deficiency.

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Sloane M. Scheiber, Maria Paz, Edward F. Gilman, Kimberly A. Moore, Sudeep Vyapari, and Richard C. Beeson Jr.

Landscape water consumption has become a prime target for water conservation and regulation. Imposing water restrictions during landscape establishment is detrimental to plants that have not developed sufficient root systems to compensate for transpirational water losses. Generally, municipalities regulate irrigation frequency but not application rate. Application frequency affects establishment rates of shade trees, but the effects on shrub establishment are not well documented. This study evaluated three irrigation frequencies during establishment of Ilex cornuta `Burfordii Nana' and Viburnum odoratissimumin a landscape. To simulate maximum stress, both species were transplanted into field plots in an open-sided, clear polyethylene covered shelter. Each species was irrigated either every 2, 4, or 7 days, and received 9 L of water per plant per event. Predawn, midday, and dusk water potentials were recorded at 28-day intervals and cumulative stress intervals calculated. Water potentials were taken the day prior to irrigation (maximum stress day) and the day of irrigation (minimum stress). Growth indices were also recorded. As days after transplant (DAT) increased, significant declines in cumulative water stress of Ilexwere found among treatments on the day of maximum stress. The 7-day treatment declined at a faster rate than the other treatments tested. No differences were found for Viburnum. No significant differences were found on the day of irrigation as DAT increased. Differences in canopy size were not significant among treatments for either species.

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Todd A. Russell, Joseph B. Morton, and Bradford Bearce

Nursery liners of Viburnum carlesii, Hemsl; Acer palmatum, Thunb., cv. 'Bloodgood'; and Buxus sempervirens L., cv. 'Vardar Valley' were planted in several root media at three P levels which had been inoculated or not inoculated with species of endomycorrhizal fungi. Analysis of extent of root infection (Trypan Blue staining procedure) revealed no root infection or colonization of any of the three species in any root medium. However, maples grown in an inoculated peat:sand (1:1, v/v) medium at .024 g P/liter grew taller than maples in the same non-inoculated medium at .24, .024, or .0024 g P/liter of medium. Mean height of maples in inoculated media were greater than heights of maples in non-inoculated media when height data from all three P levels in each medium were combined. Infection of Sorghum Sudanese, (Piper) Stapf, root: was inhibited when media was amended with composted or noncomposted pine bark but was not inhibited by pine bark leachates.

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Carleton B Wood, Timothy J. Smalley, and Mark Rieger

Container-grown Viburnum plicatum var. tomentosum `Mariesii' were planted in tilled beds and tilled beds amended with aged pine bark. After transplanting, plants were fertilized at three different rates: no fertilizer, 18.4 g of N m-2, and 36.8 g of N m-2. A 31 day drought was begun 73 days after planting. Fertilization of tilled plots induced ammonium toxicity, which caused a linear reduction in leaf area, shoot dry weight, and root dry weight. Fertilization of amended plots had no effect on shoot growth but reduced mot growth by 54%; thus, amendments ameliorated ammonium toxicity. Between 10 and 28 days after beginning the drought, plants in unfertilized-amended plots maintained higher relative leaf water contents (RLWC) and relative leaf expansion rates (RLER) than plants in unfertilized-tilled plots. Amendment induced nitrogen deficiencies contributed to the increased drought tolerance of plants from unfertilized-amended plots. Since fertilized plants developed symptoms of ammonium toxicity, we were unable to determine if increasing fertility would counteract the drought tolerance conferred by pine bark soil amendments.