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Len Burkhart, Martin Meyer Jr., and S. Dorner Dr.

Rooting of shoots from in vitro culture of most conifers can be difficult. An antigibberellin, ancymidol, has been shown to promote rooting of in vitro proliferated shoots of asparagus clones, but it has not been tested on conifers. Ancymidol and flurprimidol was tested for rooting on established cultures of Lake States white pine (Pinus strobus). Pulse treatments containing 5 uM ancymidol and 0.5 uM NAA gave 43% rooting, while pulse treatment with 0.5 uM NAA resulted in 7% root formation. Flurprimidol also stimulated root formation on white pine shoots, but was less than ancymidol. Thuja occidentalis `Hetz's Wintergreen' formed roots on 87% of in vitro proliferated shoots when given a pulse treatment with 5 uM ancymidol and 50 uM NAA. Shoots initiated an average of 10 roots after 60 days on vermiculite containing 1/2 liquid MCM medium.

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Len Burkhart, Martin Meyer Jr., and S. Dorner Dr.

Rooting of shoots from in vitro culture of most conifers can be difficult. An antigibberellin, ancymidol, has been shown to promote rooting of in vitro proliferated shoots of asparagus clones, but it has not been tested on conifers. Ancymidol and flurprimidol was tested for rooting on established cultures of Lake States white pine (Pinus strobus). Pulse treatments containing 5 uM ancymidol and 0.5 uM NAA gave 43% rooting, while pulse treatment with 0.5 uM NAA resulted in 7% root formation. Flurprimidol also stimulated root formation on white pine shoots, but was less than ancymidol. Thuja occidentalis `Hetz's Wintergreen' formed roots on 87% of in vitro proliferated shoots when given a pulse treatment with 5 uM ancymidol and 50 uM NAA. Shoots initiated an average of 10 roots after 60 days on vermiculite containing 1/2 liquid MCM medium.

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M.E. Ostry

White pine blister rust (Cronartium ribicola J.C. Fisch.) (WPBR) was discovered on Ribes L. in New York in 1906, although it was accidentally introduced from Europe on pine (Pinus L.) seedlings. The spread of this destructive fungus has changed the forests in North America. After decades of reduced planting because of the concern over the impact of WPBR, white pine (Pinus strobus L.) is now being restored in the lake states of Minnesota, Wisconsin and Michigan. Although the potential for growing white pine is high on many sites, the disappearance of a seed source because of logging and fires means that reestablishment of white pine to these areas will require active management. A series of plantings have been established on three national forests in Minnesota and Michigan to evaluate various silvicultural treatments intended to minimize the incidence of WPBR and to compare the performance of seedlings selected for disease resistance to nonselected planting stock.

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L.E. Hinesley and L.K. Snelling

Branches of Fraser fir [Abies fraseri (Pursh) Poir.] and eastern white pine (Pinus strobus L.) were subjected to various temperatures, vapor pressure deficits (VPD), and light regimes in controlled-environment chambers. Drying rates, based on measurements of needle water potential (ψ), were accelerated by increasing VPD, high temperature, and light. Fraser fir and white pine dried to – 4.0 MPa and – 3.0 MPa, respectively, in about the same time. The relationship of moisture content (MC) to ψ was linear for Fraser fir, quadratic for white pine. The MC of Fraser fir at – 4.0 MPa was also a linear function of VPD during drying. Water loss was greatest early in the drying cycle, and high temperature (25C) promoted rapid drying, even at low VPD.

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L.E. Hinesley, D.M. Pharr, L.K. Snelling, and S.R. Funderburk

Foliar raffinose and sucrose concentrations in eastern white pine (Pinus strobus L.), eastern redcedar (Juniperus virginiana L.), Leyland cypress (×Cupressocyparis leylandii Dallim.), and Virginia pine (Pinus virginiana L.) were measured monthly over 2 years. During cold weather, foliage of white pine and redcedar contained higher concentrations of raffinose and sucrose than did Leyland cypress and Virginia pine. Rafflnose concentrations were highest during winter and were best correlated with the frequency of occurrence of daily minima ≤ 1.7C during the 30 days before sampling. Sucrose concentrations, which also reached maximum levels during the winter, were best correlated with the frequency of occurrence of daily minima ≤ 7.2C in the prior 30 days. Sucrose concentrations were relatively high during fall and spring. Raffinose and sucrose concentrations increased in response to recurring low temperature, with correlations highest for raffinose.

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L. Eric Hinesley and Layne K. Snelling

Drying and rehydration characteristics were measured for Atlantic white cedar [Chamaecyparis thyoides (L.) B.S.P.], Arizona cypress [Cupressus arizonica var. glabra `Carolina Sapphire' (Sudworth) Little], Leyland cypress [× Cupressocyparis leylandii (A. B. Jacks. & Dallim.)], Virginia pine (Pinus virginiana L.), and eastern white pine (Pinus strobus L.) Christmas trees. Species varied in drying rate, loss of mass during display, water use after rehydration, the relationship between moisture content and xylem water potential (Ψ), and keeping quality. Leyland cypress and Arizona cypress rehydrated from Ψ values as low as –5.0 MPa, and remained in good condition after rehydration. The critical moisture content for Virginia pine and white pine was between –2.5 and –3.0 MPa. The ability of Atlantic white cedar to rehydrate decreased quickly with time out of water, and water consumption dropped sharply within a few days after placement in water. Change in fresh mass varied from +1% for Arizona cypress to –29% for Atlantic white cedar. Keeping quality of Virginia pine was poor, even for trees that were placed in water the day of cutting.

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Amanda J. Taylor, R. Thomas Fernandez, Pascal Nzokou, and Bert Cregg

. glauca Regel), black hills spruce [ Picea glauca (Moench) Voss var. densata ], and eastern white pine ( Pinus strobus L.) ( Table 1 ). All plants were originally obtained from a local nursery (Petersons Riverview Farm, LLC, Allegan, MI) as seedling

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Wendy S. Klooster, Bert M. Cregg, R. Thomas Fernandez, and Pascal Nzokou

Engelm. var. glauca Regel, and Pinus strobus L. ( Table 1 ) were potted in 11.2-L (#3) containers (EG1200; Nursery Supplies, Inc.). Table 1. Means (± se ) of initial caliper and height, taken 18 May 2006, for four conifer species grown in a

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Dwight R. Tingley and Timothy A. Prince

A survey of 16 cut evergreen species found six clustered groupings of species based on ethylene production at 2 and 21C. Ethylene production (in nanoliters per kilogram of fresh weight per hour) at 21C ranged from 26 for Juniperus virginiana to 2800 for Sequoia sempervirens. Exposure to 0.1 or 1.0 ppm ethylene for 72 hours at 2C resulted in minor effects on two species, while significantly delaying senescence of Sequoia sempervirens. Silver thiosulfate (STS) pretreatment decreased or increased longevity of six species, but all effects were minor. Longevity of cut evergreens when held in preservative solution ranged from 14 days for Pinus sylvestris to 56 days for Chamaecyparis lawsoniana. Senescence symptoms observed were needle abscission, desiccation, and/or chlorosis.

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Donglin Zhang, Hongwen Huang, and Dongyan Hu*

Horticultural plants include fruit, vegetable, ornamental, turf, medicinal, beverage, spice, and other economic species. Although these plants originally derive from wild populations and play a vital role in our daily life, their importance on protecting biodiversity has not been addressed. With tremendous driving force of their monetary value, farmers, gardeners, breeders, and researchers have domesticated, selected, and bred many new horticultural crops, which ultimately increase biological diversity in cultivated plant communities. Both morphological and molecular data from 90 accessions of cultivated Cephalotaxus and 48 accessions of cultivated Chamaecyparis thyoides demonstrated their wide range of morphological differences and more than 43% of genetic dissimilarity coefficients. In US alone, one new cultivar of Loropetalum chinense var. rubrum was released to the nursery industry every year since the first plant was introduced from Wuhan Botanical Garden in 1983. Obviously, human activities rapidly accelerate evolutions. To preserve and reproduce new and rare taxa, regeneration of these plants is challenging. Rooting of Magnolia grandiflora stem cuttings, overcoming Cephalotaxus seed dormancy, experimenting Pinus strobus embryogenesis, and overwintering Stewartia cuttings should be applied for reproduction studies of unusual horticultural clones. For plants that could not be regenerated with today's propagation methods, their seeds, tissues, pollen, and embryos should be preserved as some USDA labs do for heirloom horticultural crops. In the future, with aid of advanced science and technology, we should be able to regenerate those plants from preserved materials and increase biological diversity.