Transpiration in Plants

STEP 1: STEP 2:

STEP 3:

STEP 4: STEP 5:

Pressure Flow Hypothesis

Pressure Flow Hypothesis

STEP 1: Food and water enters phloem of the stem through diffusion and osmosis.

STEP 2: Water from xylem is transferred to the phloem to help break down/dissolve food in the phloem. The water pressure is kept at low.

STEP 3: Water is being transferred in the xylem (going up) to keep balanced pressure.

STEP 4: water is being transferred from the phloem – to maintain pressure in the phloem due to excess water from xylem from step 2.

STEP 5: food is stored in the sink cell.

Movement of water in plantsProcess Explanation/details

1. Water moves down concentration gradients

Water moves through osmosis from an area of higher to lower concentration.

2. Water lost by transpiration is replaced by water from vessels

Water moves through osmosis from an area of higher to lower concentration. Water goes from a high water potential to area of lower water potential. (analogy: straw)

3. Vessel water column is maintained due to cohesion and adhesion

Charges in water molecules and xylem attract and repel each other to defy gravity.

4. Tension occurs in the columns of water in the xylem

A lot of water retained in xylem. Charges in water molecules and xylem attract and repel each other to defy gravity.

5. Water is pulled from the root cortex into xylem cells

This is caused by capillary action – this is when something is transport throughout the system through concentration difference.

6. Water is pulled from the soil into the roots

This is caused by capillary action – this is when something is transport throughout the system through concentration difference.