Question

Write the requirement of this in atmosphere, leaf, xylem, roots and soil.

Answer 1

To facilitate the continuous upward movement of water (transpiration pull), a decreasing water potential gradient (from soil to atmosphere) is required. The typical values in MegaPascals (MPa) from highest to lowest potential are:

• Soil: −0.3 MPa (Highest water potential)
• Roots: −0.6 MPa
• Xylem: −0.8 MPa
• Leaf: −1.5 MPa
• Atmosphere: −100 MPa (Lowest water potential)