Lecture 6 - Leaves Flashcards
What is leaf phyllotaxy?
Distinct arrangement of primordial at the shoot apex.
What does primordia arrangement lead to?
Leaf arrangement
Phyllotaxy types:
Helical, whorled, opposite, distichous, decussate
Helical (alternate, spiral)
One leaf per node
Whorled
3+ leaves around a single node
Opposite
Pair of leaves per node
Distichous
Leaves in 2 vertical columns on opposite sides of stem
Decussate
Successive leaf pairs are at right angles
What does a leaf consist of?
Blade (or lamina), petiole, stipules
What is the blade?
Expanded portion
Describe petiole.
Stalk-like
What are stipules?
Scale-like structures at base of some leaves
What is a leaf called if it lacks a petiole?
Sessile
Simple leaves
Undivided blade. May have lobes but gaps do not reach the vein
Compound leaves
Divided blades. Each leaflet is separated along a vein
Where is the bud found on compound leaves?
Found at the base of a leaf, but not a leaflet.
What plane do compound leaves and leaflets lie?
Leaflets- lie in same plane
leaves- extend from stem in various planes
What are the types of compound leaves?
Palmately compound, pinnately compound
Describe palmately compound
Leaflets radiate from end of petiole
No rachis
Describe pinnately compound
Leaflets arranged along rachis
pinnately compound: the rachis is an extension of what?
The petiole
pinnately compound: bipinnately compound leaves
Each leaflet is divided into smaller leaflets
What are the functions of a leaf?
Photosynthesis, transpiration, gas exchange
Leaf function: photosynthesis
Major function - need water, light, carbon dioxide, and chlorophyll
Leaf function: transpiration
Evaporation of water through leaf surfaces.
Leaf function: how does transpiration help?
Helps create negative pressure that draws water upward through the Xylem from roots
Leaf function: gas exchange
- Carbon dioxide in for photosynthesis
- oxygen in or out depending on concentration gradient
Leaf function: gas exchange: what are the functions of oxygen?
- Byproduct of photosynthesis
- used in aerobic respiration
What is included in the internal anatomy of the leaf?
Cuticle, epidermis, stomata, guard cells, mesophyll, vascular bundles (xylem, phloem)
What is the cuticle?
Waxy material on leaf surface
What is the function of the cuticle?
Moisture conservation, barrier against water loss
What does the epidermis do?
Produces the cuticle, protects enclosed tissue
What is the stomata?
Pores in the upper and lower epidermis
What is stomata function?
Allows gas exchange
Where are guard cells?
Surrounding stomata
What is guard cell function?
Open and close for gas exchange and water conservation
What is the mesophyll?
Bulk of cells between upper and lower epidermis
What is mesophyll shape?
Relatively irregular
What is mesophyll function?
Site of most photosynthetic activity of the leaf
What do vascular bundles consist of?
Xylem and phloem
What is Xylem function of the leaf?
Transports water and minerals to the leaf