Leaves-Organs of Compromise

I. Important traits a leaf must possess

• A. Formula for photosynthesis

• 1. broad flat and thin

• 2. chloroplasts closes to sun

• 3. moist exchange surfaces

• 4. openings to allow gas in and out

• 5. ample water

• 6. system for product export

B. Consequences of design needs

• 1. fragile• 2. susceptible to predation• 3. easily dessicated• 4. structures that we will see are compromises

between habitat that leaf is found in and the traits mentioned above

II. Examples of leaves

• A. Design Ligustrum leaf

Cross section of Ligustrum leaf

B. Zea leaf

• 1. Growth characteristics• a. Vertical nature of

plant• b. Hot dry sunny

conditions• c. Difference between

monocots and dicots• 2. Leaf structure

Zea leaf

C. Pinus needle

• 1. Growth conditions• 2. Structure of needle

Pine Needle

What environment might the plant that possesses this leaf occupy?

1. Desert

2. High altitude mountain

3. Aquatic floater

4. Temperate forest

III. Examples of stems

• A. Dicot annual• Medicago

Medicago stem cross section

Higher power

B. Dicot perennial

• Tilia

Tilia stem

C. Zea Stem

Zea stem

Zea stem

IV. Examples of roots

• A. Dicot root Ranunculus

Ranunculus root

Ranunculus root

Ranunculus root

B. Zea root