Calculation of the volumetric flow rate
The volumetric flow rate (JV) was calculated by multiplying the measured phloem mass flow velocity (\(V_{a}\)) with the median area of ten measured sieve elements (\({\tilde{A}}_{\text{SE}}\)):
\begin{equation} J_{v}\ [\frac{cm^{3}}{h}]=V_{a}\ [\frac{\text{cm}}{h}]*{\ \tilde{A}}_{\text{SE}}\ [cm^{2}]\nonumber \\ \end{equation}