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Leaf structure

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:

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Leaf structure

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  1. Leaf structure By Martin Samaj

  2. 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

  3. 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

  4. Leaf anatomy

  5. 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

  6. 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

  7. 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

  8. 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

  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

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