Abstract
We aimed to reveal the mechanisms for equal water supply to all leaves in the branches using mathematical model. The high production requires the large amount of water delivered from roots to leaves. The transport distance of water distinctively differs among the position of the leaves in a large plant. The velocity of water transport decreases with transport distance. Theoretically, therefore, the water supply is much less in the more distal leaves in taller plants.
We analyzed the mechanism for equal water supply to all leaves in the branches using the mathematical model assumed that water moves according to the Fick's law. The model predicted that 1)It is important that the lateral pathways (leaves or twigs) is less conductive than the axial pathway (branch or stunk), 2)larger difference in hydraulic conductance between the lateral and the axial pathways is essential for more branched pathways.
These predictions were tested by the measurements using over 10 m long shoot of kudzu (Pueraria lobata). The results indicated that the high conductance of the stem and the low conductance of the leaf lamina prevent the water flow in a shoot from being favored at the base.
