Transpiration + Plant minerals

How water moves into the roots:

• Just behind the root tips are root hair cells.
• Water in the soil has a dilute solution of salts.
• The cell sap in the root hair cell has a more concentrated solution so water passes into the cell via osmosis.
• The root hair cell now has a more dilute cell sap than the neighbouring cell, so water passes from it into the other cell via osmosis.
• This continues through the root until the water reaches the xylem, where it is carried up to the leaves.

Transpiration is the loss of water vapour from the leaf surface.

• Water enters root hair cells by osmosis, and minerals enter by active transport.
• The water is drawn up the xylem in the stem to the leaves.
• The water is used for photosynthesis (turned into glucose) to stop the plant from wilting.
• The water is evaporated from the leaves into the air (transpiration).

As water is used in photosynthesis or evaporated from the leaves, more is sucked up from the xylem vessels. This means there is a continuous flow of water from the roots to the leaves.

In the leaf…

• Water evaporates from the spongy mesophyll cells into the air spaces, which become full of water.
• Water vapour diffuses through the stomata into the air.

What effects the rate of transpiration:

• Time of day
• Humidity
• Warmth
• Light
• Dry conditions
• Wind

Plant Nutrients

Plants use nutrients from the soil to build the complex molecules they need to survive and grow.

Nitrates - supply Nitrogen

Nitrogen is needed to make amino acids for protein, which are needed for cell growth.

Deficiency causes stunted growth and yellow leaves.

Phosphates - supply Phosphorus

Needed to make DNA and cell membranes.

Deficiency causes poor root growth and discoloured leaves.

Potassium compounds - supply Potassium

Needed in enzymes involved in respiration and photosynthesis.

Deficiency causes stunted growth of fruit and flowers, and discoloured leaves.