p78 How many stomata?
p79 Water content and dry weight.
p85 Use of cobalt choride paper
Bioviewers Box 79
The leaf of a flowering plant
Leaf epidermis with stomata- scanning electron microscope
On the lower surface of the leaf there are tiny pores called stomata (singular- stoma) which open and close.
Stomata let CO2 diffuse in.
Water vapour and oxygen (O2) move out.
Stomata have guard cells surrounding them to control their opening & closing.
When there is plenty of water (daytime) the guard cells are turgid and curved.
This opens the stomata and water can escape.
When there is little water the guard cells are flaccid and less curved.
This closes the stomata and keeps water in the leaf. This happens at night.
Vast network of veins
supplies all parts of the plant with essential substances
Flat leaf blade
Has large surface area
Absorbs as much sunlight & CO2 as possible
CO2, reaches inner cells easily
Most in lower surface of leaf
Gas & water exchange
Leaf veins (and roots and stems) contain the xylem and phloem tubes in vascular bundles.
They run throughout the plant, transporting various substances up and down them.
Transport systems used for?
Plants need to allow:
Gases to get in and out of the leaves.
Water and nutrients to move into the plant from the soil.
Glucose made in photosynthesis to be carried to the rest of the plant.
Giant redwood trees carry water & nutrients over 100m from the soil
Roots have specialised cells called root hair cells, which are long and thin providing a large surface area for the uptake of water and minerals.
HOW DOES IT HAPPEN?
The water in the soil has a weak solution of salts
The cell sap has a more concentrated solution
Water moves from the soil into the root hair along a water concentration gradient
Water passes from the soil into root hairs by osmosis