The existence of a hydrostatic pressure gradient in phloem tubes can be accounted for by

Question

Quizplus · Accepted Answer

The hydrostatic pressure gradient in phloem tubes is created by the loading of sugars at source tissues, such as leaves, and the removal of sugars at sink
tissues, such as roots, fruits, and growing buds. The accumulation of sugar in the phloem tubes causes an increase in solute concentration, which in turn creates a gradient that drives water from xylem into phloem by osmosis. This creates a positive pressure, known as turgor pressure, within the phloem tubes, which pushes the sugars and other solutes through the tubes to the sinks. This process is known as the pressure flow hypothesis.

The Existence of a Hydrostatic Pressure Gradient in Phloem Tubes