Plant Trans

Xylem

-transports water and dissolved nutrients

Phloem

• transports sugars

• Plants move water AGAINST gravity

TRANSPORT IN THE XYLEM

This is accomplished using:

1. Root Pressure

2. Cohesion -tension and Transpiration

GENERATING ROOT PRESSURE

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Materials need to move in and out of the root

•

Transport into the root cells occurs via:

• Osmosis (water enters)

• Active transport (nutrients enter)

• 
  

• Water can move in by osmosis because there is MORE water in the soil than in the plant’s cells

  
  

However, there are more nutrients in the plant’s cells than in the soil (thus uses active transport)

PATHWAYS FOR WATER MOVEMENT

Two pathways for water movement in the root:

Apoplastic pathway - movement around the cells and walls without crossing into the cell membrane

Symplastic pathway - movement through the cell

membranes

• Once water molecules and nutrients reach the

endodermis, they MUST take the

symplastic pathway, as the Casparian strip blocks the apoplastic pathway

This keeps water and nutrients from leaking back into the cortex

High concentrations of dissolved minerals actively transported into the xylem cause more water to move into the xylem due to osmosis

•

The Casparian strip keeps water from exiting the xylem as more nutrients are pumped in, causing pressure to build up and more water to be forced UP the stem

•

This Root Pressure pushes water and nutrients UP the plant

⚬ This is helped by the adhesion (sticking) of water molecules to the cell wall of the xylem (capillary action)