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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

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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


Internal leaf structure

Internal Leaf Structure


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

  • CactiTobacco


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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