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QUIZ Diagram. 2. Plant Structure: Leaves. Organs attached to stems of vascular plants. Plant leaves. Usually site of photosynthesis. Today. Leaf structure. Types of leaves. Leaf arrangements. Types of leaf venation. Internal leaf anatomy. Types of modified leaves.
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Plant Structure: Leaves • Organs attached to stems of vascular plants • Plant leaves • Usually site of photosynthesis • Today... • Leaf structure • Types of leaves • Leaf arrangements • Types of leaf venation • Internal leaf anatomy • Types of modified leaves
Petiole = leaf stalk • Blade = flattened portion of leaf • Stipules = leaf-like tissue attached to base of petiole Plant Structure: Leaves • Leaf structure
Plant Structure: Leaves • Simple = blade not divided into smaller leaflets • Compound = blade divided into smaller parts that look like small leaves (but lack axillary buds) • Type of leaves
Parallel = veins run roughly parallel to midrib • Palmate = veins arise from common point of origin at base of midrib (above petiole) • Pinnate = veins project laterally on either side of midrib Plant Structure: Leaves • Monocots such as Families Agavaceae and Orchidaceae • Type of leaf venation • Palmate and pinnate occur in dicots such as Families Moraceae and Euphorbiaceae
Plant Structure: Leaves • Alternate = leaves occur at nodes singly • Opposite = leaves occur at nodes in pairs • Type of leaf arrangements (on stem) • Whorled = more than 2 leaves at each node
Plant Structure: Leaves • Cuticle • Epidermis • Internal leaf anatomy • Pallisade cells • Spongy mesophyll • Stomata • Guard cells • Xylem & phloem
Plant Structure: Leaves • Stomata = pores in epidermis used for gas exchange • CO2 into cell for photosynthesis • Stomata • H2O out of leaf by evaporation to facilitate transpiration (process by which water pulled up plant) • Guard cells = epidermal cells that open and close stomata • Stomata open when guard cells swell with water • Stomata close when guard cells collapse together (shrivel)
Plant Structure: Leaves • Bulb leaves = leaves wrapped around short, swollen stem of bulb (e.g. onion) • Types of modified leaves • Bracts = large, colorful leaves surrounding flowers (e.g. poinsettas) • Spines = sharp projections (e.g. cacti) • Insectivorous leaves = leaves designed to trap insect (e.g. venus flytrap)