1. Xylem structure-function relations and trade-offs in conifers
Hervé Cochard
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012

2. Structure Function Environment
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012

3. Xylem structure Trunk structure Ring structure Cells structure
Sapwood/heartwood
Ring structure
Ring width, density
Earlywood/Latewood
Compression wood
Cells structure
Tracheid dimensions (length/width/volume)
Ray cells (volume, size, grouping)
Resin duck ?
Cell wall (ultra) structure
Secondary wall structure (thickness, microfibril angle) and composition (chemical, isotopic)
Pit number/structure/chemical composition
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 3 3

4. Tree environment Abiotic factors Biotic factors
Climate
temperature, precipitation, wind, sun, vpd, fire…
Soil
Depth, structure, texture, fertility, water reserve..
Biotic factors
Pathogens
Competition
Growth period, Water stresses (drought, flooding),
Mechanical stresses (wind, snow), Biotic stresses
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 4 4

5. Major xylem functions water Transport Storage Mechanical Support
nutriments
hormones
CO2
carbohydrates
Storage
C and N reserves
heat ?
Mechanical Support
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012

6. Trade-offs efficiency safety ‘energy’ Transport Storage Mechanics
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 6 6

7. How to proceed with xylem hydraulic functions?
Measure them directly (cf growth, density)
Derive them from correlations with xylem structure
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 7 7

8. Xylem water transport efficiency
Ks: Specific axial hydraulic conductivity
Mayr & Cochard PCE 2003
Can be measured directly
Problems with native embolism and heartwood
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 8 8

9. efficiency Ks can be derived from tracheids dimensions Interspecific
Intraspecific
Domec et al 2006
Pittermann et al 2006
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 9 9

10. efficiency What is the functional significance of Ks? Flux
Pleaf<< 0
Psol < 0
Flux
Kroot-soil
Kxylem
Kleaf
Impact of Kradial
on Kxylem?
Kxylem>>Ktree
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 10

11. Xylem water transport safety
Cavitation/Embolism
Collapse
Utsumi et al 2003
Cochard et al 2004
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 11 11

12. safety P50: Xylem vulnerability to embolism
Can be measured directly (eg, with a Cavitron)
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 12 12

13. safety Problems with: native embolism ageing heartwood HC, unpublished
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 13 13

14. safety
Can cavitation resistance be derived from xylem structure?
Interspecific
r²=0.25
Tracheid Lumen area, mm²
Pittermann et al 2006
Delzon et al 2010
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 14 14

15. safety Intraspecific (Scot Pine) Sterck et al 2012
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 15 15

16. safety Intra-ring (Douglas) Nano CT Native state -2 MPa -2.5 MPa
Badel et al, unpublished
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 16 16

17. safety
Looking closer
Delzon et al 2010

18. safety Looking even closer Jansen, Lamy et al 2012
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 18 18

19. safety Frost resistance Pittermann & Sperry 2003
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 19 19

20. Efficiency versus safety
interspecific
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 20 20

21. Efficiency versus safety
Intraspecific (maritime pine)
Within a tree (douglas fir)
Corcuera et al 2011
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 21 21

22. Safety versus energy Interspecific Delzon et al (in prep)
Hacke et al 2001
Delzon et al (in prep)
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 22 22

23. Safety versus energy Intraspecific maritime pine douglas
Dalla Salda et al 2011
Lamy et al (in prep)
The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 23 23

24. Xylem structure-function relations and trade-offs in conifers
Concluding remarks
Xylem structure-function relations and trade-offs in conifers
The situation is not (yet) totally clear
Lot of noise from techniques and plant material
(species, populations, individuals)
To assess phenotypic plasticity = same genotypes
Data on other xylem functions are largely missing (storage)
Data are still largely missing at the ring levels
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