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Explain the process of transportation of food and water in plants?
Transport in Plants:
Absorption of water and minerals by roots: 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. 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. Specific carrier proteins in the plasma membrane attract and carry their specific mineral into the cell.

ASCENT of XYLEM SAP:
Water transported up from the roots must replace water lost by transpiration.

WATER POTENTIAL: 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.

ROOT PRESSURE: 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.

Phloem Transport:
Translocation refers to the transport of produced products to the rest of the plant via the phloem. Phloem carries sucrose, minerals, amino acids, and hormones.

Source to Sink Transport:
Source refers to the origin of the sugar produced. Sink refers to the organ that consumes or stores the sugar.
Flow is always from the source to the sink.
Phloem is loaded by active transport.


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