Determination of the dynamic viscosity of vascular saps (η)
The measuring instruction of the dynamic viscosity was described in Adam et al. (2009). The dynamic viscosity of the phloem sap was quantified with 0.5 µl glass capillaries (CAMAG®, Muttenz, Switzerland). The calibration required the determination of the specific viscometer constant (κ = mPa l g-1) by using H2O as reference solution with known dynamic viscosity (η0 = 1.0087 mPa s) and density (ρ0 = 997.9 g l-1) for 20 °C. Following the measurement of elapsed time (t0), the specific viscometer constant was calculated:
\begin{equation} \kappa\ =\ \frac{\eta_{0}}{\rho_{0}\ t_{0}\ }\ (\frac{\text{mPa\ l}}{g})\nonumber \\ \end{equation}
The dynamic viscosity of the phloem sap was calculated after the measurement of elapsed time (t) and determination of density (ρ):
η = κ * ρ * t (mPa s)