Chapter 7 - Leaves Flashcards
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
Petiole
“Stem” of the leaf; for attachment; transport (sugar/water); strength (holds leaf out to the sun)
Blade
Does the photosynthesis work
Margin
Edge of the blade: entire (smooth), serrated (teeth); lobes (deep cuts, can be smooth edged overall)
Simple leaf
Has one leaf blade; leaf attached directly to the stem
Compound leaf
More than one leaf blade. 2 main groups: Pinnately compound leaves, Palmately compound leaves
Pinnately compound
- 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
Stomata
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
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
Palmately compound
One petiole, leaflets at end, all from some spot on petiole
Nodes
Area/region of stem where attachments form (leaves, other stems, flowers, etc.)
Internodes
Space between nodes where no attachments form
Alternate
Leaf arrangement on stem, one leaf per node
Opposite
Leaf arrangement on stem (usually 2 across from each other at same node)
Whorled
Leaf arrangement on stem (more than 2 leaves at same node, around the stem)
Pinnately veined
Veins spread like a map with branching
Midvein
a
Midrib
a
Palmately veined
Veins branch out from one point at end of petiole and fan out
Palisade mesophyll
- 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
Spongy mesophyll
- Leaf part, at bottom above the lower epidermis
* Parenchyma cells with intercellular space to facilitate gas exchange
Veins
- Leaf part, for transport
- Composed of xylem and phloem
- System like a road system (in dicots), or parallel (in monocots)
Cutin
Waxy substance of the cuticle layer on the outside of leaves. Protects from water loss, insect damage, etc.
Specialized leaves
Tendrils, spines, bulbs, floral tracts
Glands
a
Mesophyll
Inner parenchyma layers of a dicot leaf
Tendrils
Modified leaves, for attachment, hold the plant up
Spines
Modified leaves
Thorns
Modified stems
Prickles
Modified epidermis, not trichomes
Bundle sheath
a
Shade leaves
a
Leaves of arid regions
a
Hypodermis
a
Leaves of aquatic areas
a
Storage leaves
a
Flower-pot leaves
a
Window leaves
a
Reproductive leaves
a
Floral leaves (bracts)
a
Autumnal leaf color change
a
Abscission zone
Area that creates the leaf scar
