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Growth Efficiencies of Diverse Pinus taeda families as affected by Genetics of the Root system

Growth Efficiencies of Diverse Pinus taeda families as affected by Genetics of the Root system. James E. Grissom and Steven E. McKeand Department of Forestry North Carolina State University, Raleigh, NC, U.S.A. Objectives. Evaluate genetic effects of Roots upon Aboveground Growth process

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Growth Efficiencies of Diverse Pinus taeda families as affected by Genetics of the Root system

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  1. Growth Efficiencies ofDiverse Pinus taeda familiesas affected byGenetics of the Root system James E. Grissom and Steven E. McKeand Department of Forestry North Carolina State University, Raleigh, NC, U.S.A.

  2. Objectives • Evaluate genetic effects of Roots upon Aboveground Growth process • Determine whether Root system can alter Stemwood production; under what conditions • Identify physiological traits related to Root effects on Stemwood production

  3. Materials and Methods Loblolly pine seedlings from 2 contrasting provenances; 10 OP families; 5 fromfast-growing (ACP)prov. and 5 from slow-growing (LPT)prov. total 1800 seedlings Grafted reciprocally (fast type onto slow type, and vice versa) All possible combinations of genotypes Grafted at 12 weeks of age (June 1997)

  4. Methods Out-planted at 40 weeks of age (January 1998), on a sandy infertile site in Scotland County, NC Planted in split plot layout, of 6 blocks, full set of 150 trees per sub-plot ; half of the plots were fertilized by hand, twice each year. Fertilizer applications: Elemental dosage (kg/ha) Month N* P K Fe B Cu Zn March 50 23 40 0.5 -- -- -- June 50 23 40 0.5 0.1 0.2 0.2 * N - total 10% composed of 6% urea + 4% ammoniacal

  5. Methods • After two growing seasons, in early October 1999, Tree heights and diameters were measured, Roots were dug up and seedlings harvested. Total numbers of harvested seedlings: Type Fast-grow Slow-grow GRAFTED 260 260 NON-GRAFTED 40 40 300 + 300

  6. Methods • Roots were washed, dried and weighed. • Stems, branches and leaves were separately dried in 70oC oven for 72 hours, and then weighed.

  7. Methods Leaf Physiology: Gas Exchange Instantaneous Portable Photosynthesis System (Li-Cor LI-6400) Carbon isotope Integral Mass spectrometry composition(Finnigan Isotope Ratio Mass Spec.)

  8. Weather Data: During Summer of 1999, moderate drought occurred in central North Carolina: 15 13.1” Total Rainfall (inches) 10 7.9” 5 Deficit 0 Normal May-Aug. Actual May-Aug. -5 -5.2” -10

  9. Total Plant Biomass, Grafted Trees, Fertilized treatment, aged 2 years Top (scion) |-- Fast --| |-- Slow --| 1200 Total Biomass (g) = FAST 900 = SLOW 600 300 0 Fast Slow Fast Slow Rootstock type

  10. Biomass Allocation : For Fast-growing seedling top: For Slow-growing seedling top: = FAST = SLOW 900 900 750 750 600 600 Above-ground 450 450 300 300 Mass (g) Mass (g) 150 150 0 0 150 Below-ground 150 300 300 Fast Slow Fast Slow 450 450 Rootstock type Rootstocktype

  11. Stem Growth Efficiencies, Grafted treesFertilized treatment  Stem mass Leaf mass FAST SLOW Top 1.0 |-- Fast ---| |-- Slow --| ANOVA: Source P-value Top (scion) 0.01 Rootstock 0.09 0.8 (g/g) 0.6 0.4 0.2 0.0 Fast Slow Fast Slow Rootstock

  12. Water Use Efficiency Fast-growing family of shoot of is Raised when grown on -growing Rootstock. Slow Steeper slope means greater efficiency 10 9 /sec) 2 8 /m Photosynthetic umol 7 Rootstock type: Rate ( 6 SLOW FAST 5 4 0.06 0.08 0.10 0.12 0.14 0.16 Leaf Water Conductance ( mol /m /sec) 2

  13. Carbon Isotope Discriminationby Graft Class, Fertilized treatment FAST SLOW 22 Top |-- Fast ---| |-- Slow ---| ANOVA: Source P-value Top (scion) 0.035 Rootstock 0.006 21  (%o) 20 19 18 Fast Slow Fast Slow Rootstock

  14. Growth Efficiency vs. Carbon Isotope Discrimination 1 Higher Water Use Efficiency (?) 0.9 Growth Efficiency 0.8 s:Fast r:Slow Fast Fast 0.7 Slow Fast 0.6 Slow Slow 0.5 19.0 19.5 20.0 20.5 21.0 C Isotope Discrimination (%%)

  15. Summary of Important Results Biomass Allocation • Rootstocks can substantially impact allocation of mass to aboveground parts, including the main stem. • When fertilized, fast-growing provenance attains large mass both above- and below-ground, even when grafted to a slow-growing counterpart.

  16. Summary of Important Results Efficiency of Foliage • Stem Growth Efficiency is affected more by Scion stock, but Water Use Efficiency is affected more by Root stock.

  17. Conclusions • Genetic factors in Roots can alter Growth Efficiency, when soil nutrients are adequate for growth. • Growth Efficiency appears related to Water Use Efficiency, among genetic families. • Carbon isotope (13C) content in leaves shows promise as a physiological marker for “Efficiency of Foliage”.

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