How does water move up the Xylem?

Water and minerals move up from the roots to the plant in the xylem vessels.

Food made in the leaves by photosynthesis is carried to the rest of the plant in the phloem vessels.

Hope that helps!

First of all absorption of water and minerals by roots must occur. Water and mineral enter through root epidermis, cross the cortex, pass into the stele, and are carried upward in the xylem.

Active accumulation of Mineral Ions must occur since the cells cannot get enough mineral ions from the soil by diffusion alone. The soils solution is too dilute.

Active transport of these ions must occur. Water and minerals cross the cortex in one of two ways: Via symplast which is the living continuum of cytoplasm connected by plasmodesmata and via apoplast which is nonliving matrix of cell walls. At the endodermis the apoplastic route is blocked by the CASPARIAN STRIP. This is a ring of suberin around each endodermal cell. Here water and minerals must enter the stele through the cells of the endodermis. Water and minerals enter the stele via symplast, but xylem is part of the apoplast. Transfer cells selectively pump ions out of the symplast into the apoplast so they may enter the xylem. This action requires energy.

Water transported up from the roots must replace water lost by transpiration. Xylem sap rises against gravity, driven by a gradient of water potential. Water flows from an area of high potential to an area of low potential. When transpiration is low, ions pumped into the stele decrease water potential and cause water uptake by the stele. This uptake force is called root pressure. It Cannot keep pace with transpiration, and can only force water up a few meters.

TRANSPIRATION-COHESION-ADHESION THEORY:

a). water exits leaf through stomata.

b). this water loss is replaced by evaporation from mesophyll cells, lowering their water potential, causing them to take water from neighboring cells.

c). the process connects back to the tracheids causing water to be taken from the xylem.

d).Water travels from the tracheids to the air following a water potential gradient.

e). Waters cohesive and adhesive properties and the small diameter of xylem aid in its movement of up the tube.

f). This pull decreases water pressure in the xylem causing the roots to take water from the soil.

capillary action

transpiration

root pressure