Table 1.

Relative sensitivities Ψ of the contact force to the parameters of Eq. 1

Sensitivities are shown for stiff cells walls (or low turgor pressure) and soft cells walls (or high turgor pressure) and two indenter sizes as well as two indentation depths. The small indenter corresponds to our experimental set-up, whereas the large indenter is similar in size to that found in ball tonometry setups. Large indentation depth was used in our experiments (light grey columns). The dark grey column approximates the reference configuration used for the interpretation of the experiments on BY2 cells.

	Stiff cell wall or low turgor (ε r=0.005, ε l=0.01)				Soft cell wall or high turgor (ε r=0.05, ε l=0.1)
	Small indenter (s/r=0.033)		Large indenter (s/r=1.0)		Small indenter (s/r=0.033)		Large indenter (s/r=1.0)
	x/r=0.7/15	x/r=2.4/15	x/r=0.7/15	x/r=2.4/15	x/r=0.7/15	x/r=2.4/15	x/r=0.7/15	x/r=2.4/15
Indentation depth (x)	0.96	1.20	1.06	1.18	1.04	1.11	1.15	1.18
Pressure (P)	0.67	0.69	0.77	0.79	0.79	0.75	0.81	0.84
Cell radius (r)	0.31	0.36	0.25	0.28	0.57	0.50	0.42	0.36
Wall thickness (t)	0.68	0.43	0.43	0.29	0.33	0.29	0.22	0.17
Young’s modulus longitudinal direction (E l)	0.14	0.17	0.08	0.12	0.08	0.12	0.05	0.06
Probe radius (s)	0.01	0.02	0.21	0.27	0.06	0.11	0.20	0.26
Young’s modulus transverse direction (E r)	0.10	0.06	0.09	0.05	0.06	0.07	0.06	0.05
Shear modulus (G)	0.09	0.08	0.06	0.04	0.07	0.06	0.06	0.05
Poisson ratio (υ rl)	0.03	0.02	0.02	0.02	0.01	0.02	0.005	0.01
Cell length (l)	0.04	–0.01	0.05	–0.03	–0.01	0.01	–0.01	0.02