Chapter 7 - Leaves

Functions: 1) Photosynthesis: converting light into a chemical energy (sugar/glucose) sun+H2O+CO2 2) Transpiration: water loss back into atmosphere; cooling procedure (like sweating); moves more nutrients through the plant; water acts like wick, loss through top pulls woter up from the bottom via hydrogen bonds 3) Shading/physical cooling: keeps soil cool to reduce water loss under the trees

“Stem” of the leaf; for attachment; transport (sugar/water); strength (holds leaf out to the sun)

Does the photosynthesis work

Edge of the blade: entire (smooth), serrated (teeth); lobes (deep cuts, can be smooth edged overall)

Has one leaf blade; leaf attached directly to the stem

More than one leaf blade. 2 main groups: Pinnately compound leaves, Palmately compound leaves

• Usually have odd numbers of leaflets due to one on the end. Once central petiole with multiple leaflettes. • Trifoliate leaf: like poison ivy, has 3 leaves on one petiole • Bipinnately compound: Has 2 petioles, then leaflettes • Tripinnately compound: Has 3 petioles, then leaflets

Openings on leaves to allow gas exchanges, controlled by guard cells. On dicots, are on lower epidermis; on monocots (corn, grass), are on both sides of leaves

water loss back into atmosphere; cooling procedure (like sweating); moves more nutrients through the plant; water acts like wick, loss through top pulls woter up from the bottom via hydrogen bonds

One petiole, leaflets at end, all from some spot on petiole

Area/region of stem where attachments form (leaves, other stems, flowers, etc.)

Space between nodes where no attachments form

Leaf arrangement on stem, one leaf per node

Leaf arrangement on stem (usually 2 across from each other at same node)

Leaf arrangement on stem (more than 2 leaves at same node, around the stem)

Veins spread like a map with branching

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Veins branch out from one point at end of petiole and fan out

• Leaf part, under the upper epidermis • Vertical parenchyma cells; synthesize sugar - main photosynthetic cells, contain chloroplasts; cytoplasmic streaming collects sunlight at top of the “skyscraper” and produce sugars at the bottom

• Leaf part, at bottom above the lower epidermis * Parenchyma cells with intercellular space to facilitate gas exchange

• Leaf part, for transport • Composed of xylem and phloem • System like a road system (in dicots), or parallel (in monocots)

Waxy substance of the cuticle layer on the outside of leaves. Protects from water loss, insect damage, etc.

Tendrils, spines, bulbs, floral tracts