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Learn about the structure of leaves, essential tissues like epidermis and mesophyll, and factors influencing transpiration such as light, temperature, humidity, and wind.
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Leaf structure By Martin Samaj
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 Leaf basics
Leaf of an angiosperm consists of: • Petiole (leaf stem) • Lamina (leaf blade) • Stipules • Leaf consists of the following tissues: • Epidermis • Mesophyll • Arrangement of veins Leaf anatomy
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 Epidermis
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 Mesophyll
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 Leaves and 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 Factors affecting transpiration
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