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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

safety Looking closer Delzon et al 2010

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

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

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

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

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

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

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 The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 24 24