1. Leaf structure
By Martin Samaj

2. Leaf basics Above ground plant organ specialized for photosynthesis
Leaves are the site where transpiration and guttation takes place
Leaves can store food and water, in other plants they can serve different purposes

3. Leaf anatomy Leaf of an angiosperm consists of:
Petiole (leaf stem)
Lamina (leaf blade)
Stipules
Leaf consists of the following tissues:
Epidermis
Mesophyll
Arrangement of veins

4. Leaf anatomy

5. Epidermis
Outer layer of cells covering the leaf, covered by a thick waxy cuticle
It isolates the plant’s inner parts from the outside
Serves several functions: regulation of gas exchange, secretion of metabolic compounds, prevents water loss from the upper surface

6. Mesophyll
Palisade mesophyll consists of densely packed cylindrical cells with many chloroplasts
Palisade mesophyll is the main photosynthetic tissue and is positioned where the light intensity is the highest
Spongy mesophyll consists of loosely packed cells with few chloroplast
This tissue provides the main gas exchange surface

7. Leaves and transpiration
Photosynthesis depends on gas exchange over a moist surface.
Spongy mesophyll cells provide this surface
Water often evaporates from the surface and is lost and this process is called transpiration
Transpiration is the loss of water vapor from the leaves and stems of plants

8. Factors affecting transpiration
The rate of water loss through transpiration depends on internal and external conditions
Abiotic factors that have effect on the rate of transpiration
There are 4 main factors: Light, Temperature, Humidity and Wind

9. The 4 abiotic factors
Light - gurad cells close the stomata in the night = greater rate of transpiration
Temperature - as the temperature rises the rate of transpiration increases 
Humidity - The lower the humidity outside the leaf the faster the rate of transpiration
Wind - Wind blows the saturated air away and so increases the rate of transpiration