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H2O is essential for plants (factors effecting transpiration (Light…
H
2
O is essential for plants
Opening and closing of stomata
Water turgor pressure gives support for young plants and gives structure
Pholem
Seive tube elements, companion cells
Sugars, amino acids, hormones
Undirectional (upwards)
Passive process (capillary action, transpiration)
Xylem
Dead cells, end walls absent,
Lignin
makes cell wall stronger
Water and mineral salts
Bidirectional (
Translocation
made in the leaves -> growing regions, eg: new shoots, **Storage organs, eg: Tubers)
Active process (uses of energy)A
Vascular bundle travels through leaf, stem, root
Stem
Leaf
Root
Cohesion Tension
Water enters the xylem vessel through the roots
As water leaves the xylem vessel the pressure in the xylem decreases
This causes tension to increase within the xylem vessel
This causes the water molecules to move up the xylem vessel into the leaf
Water molecules are sticky meaning they stick to eachother
Photosynthesis
factors effecting transpiration
Temp
An increase in temperature will increase the rate of transpiration
An increase in temperature will decrease the humidity outside the plant
Increasing the temperature will increase the
kinetic energy
within the plant
Increased movement will cause a rise in evaporation
Air movement
If the air movement is rapid then the wind will blow away the water molecules from around the stomata
This will therefore increase the concentration gradient
Therefore, the more air movement there is then the faster the rate of transpiration
Humindity
If the air is dry then the concentration gradient will increase
Therefore, a decrease in humidity will cause a rise in the rate of transpiration
Light intensity
Increasing light intensity will increase the rate of photosynthesis
Stomata open when there is light and close when it is dark
An increase in light intensity will increase the temperature
Increases the rate of transpiration
Transpiration
Transpiration
is the loss of water from the leaves of a plant into the atmosphere via
evaporation.
Water evaporates (liquid to gas) into air spaces of the leaf.
Water diffuses through stomata into the outside air.
Water travels between mesophyll cells by osmosis.
majority of water loss by plants. Water use in photosynthesis is minimal in comparison.
Cells
Substance carried
Direction
Mechanism of transport
