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Section F: Plant Nutrition (Structure of a leaf (Palisade Mesophyll (this…
Section F: Plant Nutrition
the process of photosynthesis
Photosynthesis is the process that produces glucose in plants, from carbon dioxide and glucose.
Photosynthesis happens in the leaves of all green plants
photosynthesis turns light energy into glucose that the plant can use for respiration to produce chemical energy.
Photosynthesis Equations
Structure of a leaf
Upper Epidermis
Translucent to transmit light through(no chloroplasts)
Secretes the waxy cuticle which reduces water loss
Palisade Mesophyll
this is the
main
sight of photosynthesis
the cells contain
many
chloroplasts
Rectangular cells allow packing
Chloroplasts contain chlorophyll to absorb light energy
Positioned at the top of the leaf for maximum light
Spongy Mesophyll
Photosynthesise with the light not absorbed by the palisade mesophyll, therefore cells contain (fewer) chloroplasts
Many air spaces gives a large internal surface area to volume ratio for the diffusion (movement) of gases
Lower Epidermis
Contains specialised cells called guard cells
Guard cells contain chloroplasts
These control the diameter of the stoma(ta)
Stomata
Stomata allow exchange of gases by diffusion
CO2 diffuses in when photosynthesis is occurring
Vascular Bundle
The vascular bundle (vein) is important for support
The xylem brings water from the roots
The phloem removes sugars made by photosynthesis
Factors effecting photosynthesis
Light intensity
Without enough light, a plant cannot photosynthesise very quickly, even if there is plenty of water and carbon dioxide. Increasing the light intensity will boost the speed of photosynthesis.
Temperature
If it gets too cold, the rate of photosynthesis will decrease. Plants cannot photosynthesise if it gets too hot.
Carbon dioxide
Sometimes photosynthesis is limited by the concentration of carbon dioxide in the air. Even if there is plenty of light, a plant cannot photosynthesise if there is insufficient carbon dioxide.
