Sugars produced in plant leaves (outlined in dark green) are transported to the roots (blue) or other “sink tissues” around the plant (not shown). Knoblauch et al. grew morning glory plants to different heights and removed the lower leaves so that the only leaves remaining were on the top four meters of each plant. All of the plants have similarly low turgor pressures in the root phloem. Plants with a short distance between the leaves and the roots (black text; distance (l) is given in meters) maintain relatively low turgor pressures (red text; pressure (p) is given in megapascals) in the phloem within the leaves. Taller plants maintain higher turgor pressures in their leaf phloem. The ability of fluid to flow through the phloem (conductivity) is also higher in the taller plants (not shown). Illustration adapted from Knoblauch et al. (2016).