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12.2 Leaves

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)

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12.2 Leaves

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  1. 12.2 Leaves Pages 546-551

  2. Tea leaves • Camellia sinsensis

  3. Leaves Site of : • Photosynthesis • Gas exchange • Storage • Protection from predators

  4. Photosynthesis • Glucose is used for fuelling cellular processes and as a building block for structural materials (cellulose) • Oxygen is produced, required by all organisms for cellular respiration • Carbon dioxide is a greenhouse gas, so photosynthesis reduces Carbon dioxide in the atmosphere

  5. chloroplasts • Organelles in plants, site of photosynthesis

  6. Photopigments • Pigments absorb certain wavelengths of light and reflect others • Chlorophyll absorbs red and blue light and reflects green light

  7. Accessory pigments • Accessory pigments include carotenoids, flavonoids and betalains • Absorb different colours of light

  8. Protection • Shape. For example: sharp spines in cacti • Surface hairs. • Toxins or bad-tasting chemicals to deter herbivores

  9. Structure of Leaves • Blade…flat part of the leaf • Petiole…stalk-like structure attaches leaf to stem • Simple leaf or compound leaf

  10. Veins • Venation is the pattern of veins • Parallel veins are seen in monocots • Branching veins are seen in eudicots

  11. Internal Leaf Structure

  12. Layers • Waxy cuticle - prevents water loss -acts as a barrier for bacteria, mould and insects

  13. Epidermis • Transparent cells • Single layer of cells • No photosynthesis

  14. Mesophyll • Chloroplasts are found in mesophyll cells • Palisade…elongated, tightly packed, contain many chloroplasts • Spongy…loosely packed, large air spaces

  15. Stoma (or stomata) • Tiny pores through which gases move • Guard cells control the opening and closing of the stomata

  16. Specialized Leaves • Storage of water and carbohydrates. example: onions

  17. Storing water for example: aloe vera

  18. Protection • Cacti Tobacco

  19. Protection against freezing • Conifers have needle-shaped leaves that shed easily, have thick waxy cuticles, sunken stomata, and may contain antifreeze chemicals.

  20. Human uses for leaves • Teas • Herbs and spices • Food wraps (cabbage, grape, banana or bamboo leaves)

  21. Dark leafy greens • Contain Calcium, magnesium, potassium and iron • Vitamins B, C, E, and K • Beta-carotene, lutein and zeozanthin, omega-3 fats

  22. Other uses for leaves • Waxes • Religious ceremonies • Construction materials

  23. Drugs • Digitalis is used to treat heart disease

  24. Vincristine and vinblastine • Treats childhood leukemia and Hodgkin’s disease.

  25. Psychotropic Drugs • Alter perception, emotion or behaviour • THC tetrahydrocannabinol • Coca …cocaine

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