Plants-leaves

Question 1

Functions

Answer 1

• Photosynthesis – chloroplast absorbs energy from sun (pigment chlorophyll absorbs some light and reflects green light)
• Gas exchange to provide gases for photosynthesis and cellular respiration
• Protection from herbivores

Question 2

External structure

Answer 2

• PETIOLE (stalk):attaches the leaf BLADE (flat part) to the stem
• VENATION: arrangement of vascular tissue

Question 3

Internal structure

Answer 3

1. EPIDERMIS – single layer of transparent cells on top and underside of leaf
   ~Covered in cuticle (non-living, outermost layer)
   2.MESOPHYLL – middle layer, made of two types:
   ~PALISADE – upper layer made of tall, closely packed cells that are full of chloroplasts – maximizes light absorption (photosynthesis)
   ~SPONGY – lower layer made of loosely packed cells that create large air spaces for gas exchange between atmosphere and palisade
   3.GUARD CELLS and STOMATA – for gas exchange and water loss, mostly in lower epidermis
   ~Plant hydrated – guard cells swell and bend to create stoma
   ~Plant dehydrated – guard cells shrink and close stoma

Question 4

Specializations

Answer 4

• Protection from herbivores through spines, hairs and chemicals (irritating, bad-tasting, or toxic)
  -Adaptations to cold:
  ~Angiosperms – controlled leaf drop to conserve nutrients and water
  ~Gymnosperms – small, needle-like leaves, have chemicals to prevent cells from freezing (no leaf drop)

Question 5

Human Uses

Answer 5

• Dietary – herbs, teas, leafy vegetables
• Waxy cuticle used to make car and furniture polish, chocolate and lipstick
• Medicines – digitalis from foxglove for heart disease, vincristine/vinblastine periwinkle for chemotherapy
• Psychotropic (psychoactive) drugs –chemicals that affect the nervous system and debilitate herbivores, e.g. nicotine from tobacco leaves and cocaine from coca leaves