Leaves

Question 1

Human Uses

Answer 1

Food (herbs, teas - camellia sinensis most popular leaf in world, vegetables, fruits) –> contain lots of vitamins & omega 3 fats (essential for brain and heart function), and protect cells from damage (ex. beta-carene)
Wax for car and furniture polish, religious ceremonies (ex. sweetgrass, palm leaves), thatched roofs

Question 2

Chemicals from Leaves

Answer 2

Protection for plants (ex. rhubarb leaves have oxalic acid, causing nausea, vomiting, etc.), but can also benefit us (ex. digitalis - heart disease treatment from foxglove, cancer drugs - from rosy periwinkle plant)

Question 3

Psychotropic Drugs

Answer 3

Partially debilitates herbivores that eat them by altering perception, emotion, and behaviour (ex. cannabis, cocaine, opium poppy)

Question 4

Photosynthesis

Answer 4

Leaves are primary source of photosynthesis –> how energy is made:
Energy from sunlight absorbed in chloroplasts by photopigments (pigments that undergo a physical or chemical change in the presence of light), mainly chlorophyll. Plant cells convert solar energy, carbon dioxide, and water into glucose and oxygen (light energy + CO2 + H2O → C6H12O6+ O2)

Question 5

Gas Exchange

Answer 5

Gases like carbon dioxide, oxygen, and water vapour pass in and out of most plants’ leaves through pores on the surface (epidermis) - necessary for photosynthesis and cellular respiration

Question 6

Parts of a Leaf

Answer 6

Veins, Blade, Petiole

Question 7

Parts of Inside of Leaf

Answer 7

Waxy Cuticle, Upper Epidermis, Mesophyll (Palisade, Spongy), Lower Epidermis, Waxy Cuticle containing Guard Cells and Stomata

Question 8

Waxy Cuticle

Answer 8

Prevent water loss

Question 9

Mesophyll

Answer 9

Photosynthetic layer of the leaf
- Palisade Mesophyll: tightly packed in columns
- Spongy Mesophyll: loosely packed with air spaces

Question 10

Guard Cells

Answer 10

Cells that control the opening and closing of the stomata

Question 11

Stomata

Answer 11

Openings in the epidermis to allow for gas exchange

Question 12

Arenchyma

Answer 12

Replaces spongy mesophyll in aquatic plants –> has lots of pores to help the leaves float

Question 13

Leaf Specializations

Answer 13

• Some produce defence chemicals (ex. tannins, caffeine, nicotine)
• Many specialized to store water or carbs (ex. onion bulbs, aloe vera, clade plants)
• Cactus leaves modified to protect plant
• Gymnosperms have leaves with thick cuticles and epidermis’, recessed stomata, and some have anti-freeze chemicals to prevent the leaf cells from freezing and falling off