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C. Scoffoni , C. Vuong, S. Diep, H. Cochard and L. Sack Ecological Society of America

LEAF SHRINKABILITY WITH DEHYDRATION: A COMPONENT OF HYDRAULIC VULNERABILITY WITH ECOLOGICAL IMPLICATIONS?. C. Scoffoni , C. Vuong, S. Diep, H. Cochard and L. Sack Ecological Society of America August 6 th , 2012. Water movement in leaves. 2°. Water first moves through the xylem.

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C. Scoffoni , C. Vuong, S. Diep, H. Cochard and L. Sack Ecological Society of America

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  1. LEAF SHRINKABILITY WITH DEHYDRATION: A COMPONENT OF HYDRAULIC VULNERABILITY WITH ECOLOGICAL IMPLICATIONS? C. Scoffoni, C. Vuong, S. Diep, H. Cochardand L. Sack Ecological Society of America August 6th, 2012

  2. Water movement in leaves 2° Water first moves through the xylem 3° 4° 5° 6° Midrib (1°)

  3. Water movement in leaves Water exits the xylem and moves through living cells and diffuses throughstomata

  4. Leafhydraulicvulnerabilitycurves Lantana camara Heteromelesarbutifolia

  5. -0.1 MPa Water movement in leavesduringdrought Cavitation in the xylem -1.3 MPa -2.5 MPa http://herve.cochard.free.fr/ 100 μm Johnson et al. (2009) PC&E

  6. Leaf shrinkagewithdehydration Helianthusannuus Ψleaf = -0.49 MPa Ψ leaf = -1.5 MPa Ψ leaf = -2.1 MPa Fellows & Boyer 1978

  7. Water movement in leavesduringdrought Cellshrinkage in the mesophyll: Impacts on water movement?? Sancho-Knapiket al. (2011) JXB

  8. GeneratingvulnerabilitycurvesusingK_leaf, a spatially explicit model updated to include cavitation • Eachveinorder and mesophyll has a vulnerabilitycurvefollowing a Pammenter & Vander Willigen (1998) equation: • PLC = 100/ (1+ exp(slope/25*(Px-P50))) • Allows us to generatewholeleaf • vulnerabilitycurves Cochardet al. 2004PCE; Scoffoni, Vuong, Diep, Cochard and Sack, in prep

  9. GeneratingvulnerabilitycurvesusingK_leaf, a spatially explicit model updated to include cavitation • Eachveinorder and mesophyll has a vulnerabilitycurvefollowing a Pammenter & Vander Willigen (1998) equation: • PLC = 100/ (1+ exp(slope/25*(Px-P50))) • Allows us to generatewholeleaf • vulnerabilitycurves Cochardet al. 2004PCE; Scoffoni, Vuong, Diep, Cochard and Sack, in prep

  10. Computer simulations: impact of the decline of mesophyll conductance Veins and mesophylltolerant (P50 = -1 MPa) Mesophyll vulnerable (P50 mes= -0.25 MPa P50xyl= -1 MPa) Veins and mesophyll vulnerable (P50 = -0.25 MPa)

  11. Computer simulations: impact of the decline of mesophyll conductance Veins and mesophylltolerant (P50 = -1 MPa) Mesophyll vulnerable (P50 mes= -0.25 MPa P50xyl= -1 MPa) Veins and mesophyll vulnerable (P50 = -0.25 MPa)

  12. Leafshrinkabilitycurves Cellshrinkage Airspaceshrinkage

  13. Slope of the shrinkabilitycurve 28 1.7 Cellshrinkage Airspaceshrinkage

  14. % Loss of thicknessatturgorloss point 38% 5.1% Cellshrinkage Airspaceshrinkage

  15. Linkage of leafshrinkabilitywithvulnerability

  16. Ecologicaldifferences in shrinkability Heteromelesarbutifolia Speciesaverages for: Dry habitat Moist habitat Helianthusannuus

  17. Whatdeterminesleafshrinkability?

  18. Conclusions & Implications • Speciesvariedwidely in theirshrinkability, withdrought sensitive species more resistant to shrinkage. • Shrinkageisinfluenced by cellsaltiness and elasticity. • Leafshrinkageis a potentialphysical driver of wholeleafhydraulicvulnerability. To completelyunderstandleafvulnerabilityweneed a frameworkthatincludes not only cavitation and xylem conduit collapse, but also tissue shrinkage and aquaporindeactivation.

  19. What’snext? • Linkingshrinkabilityparameters to leafanatomical traits in collaboration withGrace John. See Poster Friday am PS 112-269 • DeterminingwithCryo-SEM the cavitation status of the xylem conduits and the shrinkage of mesophyllcells and activity of aquaporinsatdifferent water potentials and how these relate to Kleafdecline.

  20. THANK YOU!

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