2. BIOSYST-MeBioS Turgor

3. BIOSYST-MeBioS Objective To investigate the influence of turgor on micromechanical properties of apple parenchyma To investigate the relation between micromechanical properties and cellular deformations in tensile and compression tests Development of detailed mathematical models to predict behaviour of fruits under mechanical loading

4. BIOSYST-MeBioSwww.biw.kuleuven.be Influence of Turgor on Micromechanical and Structural Properties of Apple Tissue M. Oey, E. Vanstreels, J. De Baerdemaeker, E. Tijskens, H. Ramon, B. Nicolaï

5. BIOSYST-MeBioS Materials and Methods Apple cultivar: Jonagored fresh/stored (15 apples each) Samples: green side, radial orientation 11 x 5 x 2 mm Tensile Compression Testing speed: 5 mm/s Testing speed: 2 mm/s 3 x 11 x 5 mm

6. BIOSYST-MeBioS Turgor manipulation Manipulating of turgor by overnight soaking in Isotonic solution (0.65M)  no change of turgor Hypotonic solution (0.45M)  turgor increases as cells take up water Hypertonic solution (0.85M)  turgor decreases as cells release water

7. BIOSYST-MeBioS Mechanical tests Miniature tensile stage Staining of samples Tensile and compression tests until rupture, 3 cycles Simultanous recording of cell deformations

8. BIOSYST-MeBioS Data analysis – micromechanical parameters Force-deformation data  stress-strain data σ max ε max E1E1 E2E2 Maximum stress (σ max ) Strain at failure (ε max ) Initial modulus (E 1 ) Modulus at 80% stress (E 2 )

9. BIOSYST-MeBioS Data analysis – image processing Area Aspect Perimeter Roundness Length Width

10. BIOSYST-MeBioS Video – Tensile Test

11. BIOSYST-MeBioS Results: Typical curves

12. BIOSYST-MeBioS Results: Micromechanical Parameters Influence of storage in tensile tests

13. BIOSYST-MeBioS Results: Micromechanical Parameters Influence of turgor in tensile tests

14. BIOSYST-MeBioS Results: Micromechanical Parameters Influence of turgor in compression tests

15. BIOSYST-MeBioS Results: Cell Parameters Initial Parameters Not influenced by apple or firmness Not influenced when turgor is manipulated Area: 22.500 µm² Perimeter: 557 µm Aspect: 1,12 Roundness: 1,16 190µm 170µm

16. BIOSYST-MeBioS Results: Cell Deformations - Tensile High Turgor Normal Turgor Low Turgor Fresh Apples +6,8% -4,9% +13,8% -10,5% +20,2% -16,8% +4,1% -1,2% -6,9% +14,4% +15,3% -11,3% Stored Apples +8,7% +15,8% +19,5% +14,6% +12,3% +4,6% 190µm 170µm

17. BIOSYST-MeBioS Results: Cell Deformations - Compression 190µm 170µm High Turgor Normal Turgor Low Turgor Fresh Apples -5,9% +0,3% -11,3% +5,4% Stored Apples +7,1% -16,5% +7,0% -13,5% -33,1% -36,5% -46,1% +5,5% -22,1% - 34,7 % -24,1% -16,6% +4,1% -12,9%

18. BIOSYST-MeBioS Conclusions Micromechanical parameters Strongly affected by test method and firmness Turgor has effect on tissue extensibility and initial stiffness but influence on firmness and stiffness at higher strains is not clear Initial cell parameters Not affected by turgor manipulation Cell deformations Turgor has influence on deformations in length, width and aspect Cell deformations are closely related to micromechanical deformations

19. BIOSYST-MeBioS Thank you!