Botany

What structure defines where one leaf begins and ends?

The axillary bud marks a single leaf. Everything above it (blade or leaflets) is part of one leaf. Function: ensures we can distinguish true leaves from leaflets.

What is a simple leaf?

A leaf with a single undivided blade. Function: less complex but efficient for photosynthesis.

What is a compound leaf?

A leaf whose blade is divided into leaflets. No axillary buds at leaflets. Function: reduces wind damage, increases flexibility, disperses heat.

Palmately compound leaf arrangement?

Leaflets radiate from a central point (like fingers on a hand). Example: horse chestnut.

Pinnately compound leaf arrangement?

Leaflets arranged along a central axis.

Once-pinnate:

1 turn from bud to leaflet.

Twice-pinnate

2 turns (further branching).

Define node.

Region on a stem where leaves arise.

Opposite vs. Alternate leaves

• Opposite: 2 leaves directly across at one node.

• Alternate: 1 leaf per node, alternating sides.

Whorled arrangement.

3+ leaves at a single node. Function: maximizes photosynthesis in limited vertical space.

Digitalis (foxglove) phyllotaxis?

Spiral phyllotaxis. Use: Source of digoxin, a heart medication that strengthens cardiac contractions.

Basal leaves.

Leaves clustered at the base of the stem. Example: Steer’s head. Function: protects stem, conserves water near soil.

Entire vs. Lobed vs. Toothed margins.

• Entire = smooth edges (no teeth/lobes).

• Lobed = deep curves/extensions in outline (maple).

• Toothed = saw-like or spiny edges.
  Function: lobed = more light in shade, toothed = faster water runoff, temperature regulation.

Linear leaf shape.

Very narrow, long (e.g., spider plant). Function: reduces surface area → water conservation.

Ovate leaf shape.

Egg-shaped, wider in middle. Function: efficient light capture.

Elliptical leaf shape.

Uniform width, oval-like.

Blue Agave leaves adaptation?

Common leaf tip shapes?

Pointed, rounded, cleft. Function: affects water drip-off & light capture.

What are tendrils?

lender, coiling appendages that help plants climb. Example: peas, grapes. Function: support + reaching light.

Needle-like leaves example + function.

Pine needles. Function: reduced water loss, survive in cold/dry environments.

Scale-like leaves example.

Common in junipers. Function: minimize surface area, reduce water loss.

Awl-shaped leaves example

Giant Sequoia.

Three types of venation?

• Parallel = veins run side-by-side (monocots like grasses).

• Palmate = veins radiate from one point.

• Pinnate = veins branch off a central midrib.
  Function: venation patterns support leaf structure & transport.

Which venation is typical of monocots?

Parallel venation.

Eucalyptus leaf importance?

Main diet of koalas. Koalas rely on specialized gut microbiome to digest toxins. Conservation issue: koala populations threatened.