Michael Knoblauch and Colleagues Have Developed Methods to Measure the Pressure

Michael Knoblauch and colleagues have developed methods to measure the pressure flow mechanism directly. Where would they measure high pressure vs. low pressure in a tree if the pressure flow mechanism is transporting sugar from leaves to roots?

A) High pressure near the leaves, and low pressure near the roots.
B) Low pressure near the leaves, and high pressure near the roots.
C) High pressure near both the leaves and roots.
D) Low pressure near both the leaves and roots.