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12.2 Leaves. Pages 546-551. Tea leaves. Camellia sinsensis. Leaves. Site of : Photosynthesis Gas exchange Storage Protection from predators. Photosynthesis. Glucose is used for fuelling cellular processes and as a building block for structural materials (cellulose ). Photosynthesis.

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12 2 leaves

12.2 Leaves

Pages 546-551

tea leaves
Tea leaves
  • Camellia sinsensis
leaves
Leaves

Site of :

  • Photosynthesis
  • Gas exchange
  • Storage
  • Protection from predators
photosynthesis
Photosynthesis
  • Glucose is used for fuelling cellular processes and as a building block for structural materials (cellulose)
photosynthesis1
Photosynthesis
  • Oxygen is produced, required by all organisms for cellular respiration
photosynthesis2
Photosynthesis
  • Carbon dioxide is a greenhouse gas, so photosynthesis reduces carbon dioxide in the atmosphere
chloroplasts
chloroplasts
  • Organelles in plants, site of photosynthesis
photopigments
Photopigments
  • Pigments absorb certain wavelengths of light and reflect others
  • Chlorophyll absorbs red and blue light and reflects green light
accessory pigments
Accessory pigments
  • Accessory pigmentsabsorb different colours of light
protection
Protection
  • Shape. For example: sharp spines in cacti
  • Surface hairs.
  • Toxins or bad-tasting chemicals to deter herbivores
structure of leaves
Structure of Leaves
  • Blade…flat part of the leaf
  • Petiole…stalk-like structure attaches leaf to stem
  • Simple leaf or compound leaf
veins
Veins
  • Venation is the pattern of veins
  • Parallel veins are seen in monocots
  • Branching veins are seen in eudicots
layers
Layers
  • Waxy cuticle - prevents water loss

-acts as a barrier for bacteria,

mould and insects

epidermis
Epidermis
  • Transparent cells
  • Single layer of cells
  • No photosynthesis
mesophyll
Mesophyll
  • Chloroplasts are found in mesophyll cells
  • Palisade…elongated, tightly packed, contain many chloroplasts
  • Spongy…loosely packed, large air spaces
stoma or stomata
Stoma (or stomata)
  • Tiny pores through which gases move
  • Guard cells control the opening and closing of the stomata
specialized leaves
Specialized Leaves
  • Storage of water and carbohydrates.

example: onions

storing water
Storing water

for example: aloe vera

protection1
Protection
  • Cacti Tobacco
protection against freezing
Protection against freezing
  • Conifers have needle-shaped leaves that shed easily, have thick waxy cuticles, sunken stomata, and may contain antifreeze chemicals.
human uses for leaves
Human uses for leaves
  • Teas
  • Herbs and spices
  • Food wraps (cabbage, grape, banana or bamboo leaves)
dark leafy greens
Dark leafy greens
  • Contain Ca, Mg, K and Fe
  • Vitamins B, C, E, and K
  • Beta-carotene, omega-3 fats etc.
other uses for leaves
Other uses for leaves
  • Waxes
  • Religious ceremonies
  • Construction materials
drugs
Drugs
  • Digitalis is used to treat heart disease
vincristine and vinblastine
Vincristine and vinblastine
  • Treats childhood leukemia and Hodgkin’s disease.
psychotropic drugs
Psychotropic Drugs
  • Alter perception, emotion or behaviour
  • THC tetrahydrocannabinol
  • Coca …cocaine
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