Leaf Structure and Function PDF
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This document covers leaf structure and function, including parts, arrangements, composition, venation, anatomy, and modifications. It provides details about different types of leaves and photosynthesis processes.
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LEAF STRUCTURE AND FUNCTION Parts of a Leaf Petiole: Attaches leaf to stem. Midrib: Provides structure; central vein. Lateral Bud: Growth point for shoots/branches/flowers. Stipules: Protect developing leaves or buds. Leaf Blade: Photosynthesis and material storage....
LEAF STRUCTURE AND FUNCTION Parts of a Leaf Petiole: Attaches leaf to stem. Midrib: Provides structure; central vein. Lateral Bud: Growth point for shoots/branches/flowers. Stipules: Protect developing leaves or buds. Leaf Blade: Photosynthesis and material storage. Leaf: Photosynthesis (food production and oxygen release). LEAF ARRANGEMENTS & TYPES Leaf Arrangement Alternate: 1 leaf per node. Opposite: 2 leaves per node. Whorled: 3+ leaves per node. Fascicled: Leaves in tight bundles. Leaf Composition Simple: Single, undivided blade. Compound: Divided into multiple leaflets. ○ Palmately Compound: Radiate from one point. ○ Pinnately Compound: Symmetrical along central axis. Leaf Venation Parallel: Veins run parallel (monocots). Reticulate: Veins form a net-like pattern (eudicots). LEAF ANATOMY AND PHOTOSYNTHESIS Anatomy Mesophyll: Internal leaf tissue. ○ Palisade Mesophyll: Tightly packed; light absorption. ○ Spongy Mesophyll: Loosely arranged; gas exchange. Veins: Xylem (top) and phloem (bottom) connect to plant vascular bundles. Photosynthesis Overview Inputs: CO₂, H₂O, sunlight. Outputs: Sugar, O₂. Rubisco: Enzyme for CO₂ fixation in Calvin cycle. Photorespiration Conditions: High O₂, low CO₂. Avoidance in C4 Plants: ○ Adaptations: Spatial separation in bundle sheath and mesophyll cells. ○ Extra Step: Fix CO₂ into a 4-carbon compound using PEP. LEAF MODIFICATIONS Environment-Based Sun Leaves: Thicker, smaller, more chloroplasts. Shade Leaves: Thinner, larger, fewer chloroplasts. Xerophytes (Dry): Thick, leathery leaves; water storage. Hydrophytes (Aquatic): Air spaces, stomata on upper surface. Other Modifications Bulbs: Storage leaves (e.g., onion). Tendrils: Climbing (e.g., pea plants). Spines: Leaves replaced by sclerenchyma (e.g., cacti). Thorns: Modified stems. Bracts: Specialized leaves near flowers.
