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Sven E. Svenson and F. T. Davies Jr.

Pinus taeda L. seedlings inoculated with the ectomycorrhizal fungus, Pisolithus tinctorius, were grown in a glasshouse for eight months, and then subjected to rapidly developing cyclic water deficits, or to a single slowly developing water deficit. Water deficits developed at a rate of -0.16 MPa per day (predawn total water potential) for five cyclic water deficits, and at -0.04 MPa per day for the slow water deficit. In unstressed seedlings, carbon exchange rates (CER) did not differ between noninoculated and inoculated seedlings. During slow water deficit development, CER steadily declined. During rapid water deficit development, CER remained unchanged, then declined rapidly when water potentials fell below -1.3 MPa. Inoculated seedlings had higher CER when water potential was lower than -1.5 MPa.

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Sven E. Svenson and F. T. Davies Jr.

Pinus taeda L. seedlings inoculated with the ectomycorrhizal fungus, Pisolithus tinctorius, were grown in a glasshouse for eight months, and then subjected to rapidly developing cyclic water deficits, or to a single slowly developing water deficit. Water deficits developed at a rate of -0.16 MPa per day (predawn total water potential) for five cyclic water deficits, and at -0.04 MPa per day for the slow water deficit. In unstressed seedlings, carbon exchange rates (CER) did not differ between noninoculated and inoculated seedlings. During slow water deficit development, CER steadily declined. During rapid water deficit development, CER remained unchanged, then declined rapidly when water potentials fell below -1.3 MPa. Inoculated seedlings had higher CER when water potential was lower than -1.5 MPa.

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Wei Qiang Yang, Amy K. Dunbar and Mary A. Topa

Loblolly pine (Pinus taeda L.) is the most widely planted tree species in the Atlantic Coastal Plain. To maximize its aboveground yield, it is vital to understand how root production, particularly fine root production, affects root carbon allocation to its root systems under various environmental conditions. Over a 2-year period (1998-99), we conducted a field study using minirhizotron technology to investigate fine root production and turn over in four families of a 6-year-old loblolly pine stand in Scotland County, N.C. A total of 144 minirhizotron tubes were installed to examine potential genetic differences in fertilizer effects on fine root turnover. Data analyses indicated an interaction between these families and fertilizer treatments for total fine root length and total fine root number. The effect of treatment on total root length was less clear in the faster-growing families. However, fertilization increased total root length in a slow-growing family but decreased total root length in a faster-growing family. Total root number was decreased by fertilizer treatment in the two fastest-growing families, but increased in the two slowest-growing families. Because ectomycorrhizae are significant carbon sinks in pine root systems and more than 90% of short roots in these loblolly pine families were colonized, ectomycorrhizal short roots (clusters) were classified into nine different morphotypes. No treatment and family interactions were found. Fertilizer treatment decreased the number of mycorrhizal clusters per unit root length. Dark and brown morphotypes were dominant mycorrhizal morphotypes among all the families. Our results suggest possible genetic differences and treatment effects on root system carbon demands of loblolly pine.

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Robert D. Wright, Brian E. Jackson, Jake F. Browder and Joyce G. Latimer

properties of coconut coir dust HortScience 31 965 967 Gillman, E.F. Watson, D.G. 1994 Pinus taeda , loblolly pine U.S. Dept. Agr., Forest Service, Fact Sheet ST-478 Gruda, N. Schnitzler, W.H. 1999 Influence of wood fiber substrates and N application rates on

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Glenn B. Fain, Charles H. Gilliam, Jeff L. Sibley, Cheryl R. Boyer and Anthony L. Witcher

-grown herbaceous annual crops. Materials and Methods Studies were conducted at the USDA-ARS Southern Horticultural Laboratory in Poplarville, MS, and Young's Plant Farm in Auburn, AL. Loblolly pine ( Pinus taeda ) was harvested from a 12-year-old plantation

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Farrell C. Wise, Laura L. Greenwood and D. Bradley Rowe

Clonal propagation of recalcitrant conifers like loblolly pine depends on producing juvenile cuttings on hedges sheared several times annually. Although dormant cuttings root well, it will be economically important to also root softwood shoots produced between shearings. Several variables were therefore evaluated in a factorial experiment to enhance rooting and handling of summer cuttings. Rooting percentages were equivalent for 3 media after a 5-week hardening period (56% overall), but open flats of 1 perlite:1 vermiculite induced larger root systems at the end of rooting and hardening phases. Extending the rooting period from 10 to 14 weeks increased rooting from about 45% to 58% by the end of hardening. Primary root length per cutting increased 12-63% during hardening, depending on medium. After transplanting, overwintering survival was 98%. Foam rooting wedges produced smallest root systems, and resulting plants were consistently shortest through the following growing season. Weekly applications of soluble fertilizer during the last 6 weeks of rooting did not improve rooting or subsequent growth

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Linda L. Taylor, Alexander X. Niemiera, Robert D. Wright, Gregory K. Evanylo and Wade E. Thomason

peat-based substrates ( Wright and Browder, 2005 ; Wright et al., 2008 ), but nitrification in PTS has not been documented. Pine tree substrate is manufactured from trunks of ≈15-year-old loblolly pine trees ( Pinus taeda L.) by chipping and

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Linda L. Taylor, Alexander X. Niemiera, Robert D. Wright and J. Roger Harris

distribution, and BD was studied. The influence of PTS storage time on marigold growth was also studied. Materials and Methods Preparation of substrates. Fifteen-year-old loblolly pine ( Pinus taeda L.) trees growing in Blackstone, VA, were harvested and

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Brian E. Jackson, Robert D. Wright and Mark M. Alley

the mineral soil and forest floor of a warm-temperate forest Soil Biol. Biochem. 26 1409 1415 Gough, C.M. Seiler, J.R. 2004 Belowground carbon dynamics in loblolly pine ( Pinus taeda ) immediately following diammonium phosphate fertilization Tree

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Anthony L. Witcher, Eugene K. Blythe, Glenn B. Fain and Kenneth J. Curry

Wood-based substrates have been extensively evaluated for greenhouse and nursery crop production, yet these substrates have not been evaluated for propagation. The objective of this study was to evaluate processed whole loblolly pine trees (WPT) (Pinus taeda) as a rooting substrate for stem cutting propagation of a range of ornamental crops. Substrates included processed WPT, pine (Pinus sp.) bark (PB), and each mixed with equal parts (by volume) peatmoss (PM) (WPT:PM and PB:PM, respectively). Substrate physical (air space, container capacity, total porosity, bulk density, and particle size distribution) and chemical [pH and electrical conductivity (EC)] properties were determined for all substrates. Rooting percentage, total root length, total root volume, and total shoot length were evaluated for four species in 2008 and five species in 2009. Substrate air space was similar between PB and WPT in the 2008 experiment, and likewise between PB:PM and WPT:PM. In the 2009 experiment, PB and WPT had similar substrate air space. The addition of PM to PB and WPT resulted in reduced air space and increased container capacity in both experiments. The proportion of fine particles doubled for PB:PM and WPT:PM compared with PB and WPT, respectively. Substrate pH for all substrates ranged from 6.0 to 6.9 at 7 days after sticking (DAS) cuttings and 6.9 to 7.1 at 79 DAS. Substrate EC was below the acceptable range for all substrates except at 7 DAS. Rooting percentage was similar among substrates within each species in both experiments. The addition of PM resulted in significantly greater total root length for PB:PM and WPT:PM compared with PB and WPT, respectively, for five of the eight species. Shoot growth was most vigorous for PB:PM compared with the other substrates for all species. The study demonstrated a range of plant species can be propagated from stem cuttings in whole pine tree substrates alone or combined with PM.