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Plants Part 1: Leaves

Plants Part 1: Leaves. Text ref 12.1-12.2. Background. Basic Needs : Energy/nutrients/water Gas exchange Repro capability Protection (herbivores/disease) ...and they are sessile! (immobile..). Background... cont. Nutrition... carbon dioxide + water  glucose + oxygen

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Plants Part 1: Leaves

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  1. Plants Part 1: Leaves Text ref 12.1-12.2

  2. Background... • Basic Needs: • Energy/nutrients/water • Gas exchange • Repro capability • Protection (herbivores/disease) • ...and they are sessile! (immobile..)

  3. Background...cont. • Nutrition... • carbon dioxide + water  glucose + oxygen • CO2 + H2O  C6H12O6 + O2 • Carbohydrate rich! • Stored as starch • Also need water... N, P, K (dissolved in water)

  4. Vascular Plant Body: • Roots • Shoots (leaf/stem) • Three main tissue types: • Dermal tissues • Vascular tissues • Ground tissues

  5. Table 1 page 543 – Basic Tissue Types in Vascular Plants

  6. Also... • Meristematic Tissue • Undifferentiated cells • Active division/growth • Develop into specialized cells/tissues

  7. Phylogeny: • Recall: 3 major groups of vascular plants; • Ferns • Gymnosperms = conifers • Angiosperms = flowering plants

  8. Monocots vs. Dicots • Used to think there were 2 main types of angiosperms based on cotyledons in seeds; • Monocots = one cotyledon • Dicot = two cotyledons • Now we know there are 4 types of dicots.... (DNA) • We will only be talking about eudicots (“true” dicots) – main group

  9. Leaves: • Basic Functions: • Defence – many contain toxins, or sharp spines/hairs • Photosynthesis – photopigments in chloroplasts absorb certain wavelengths of light • Gas exchange – for photosynthesis and cellular respiration

  10. Structure: • Simple leaf = one blade attached to stem by petiole (leaf stalk) • Compound leaf = several leaflets attached to petiole

  11. Veins for transport.... • Can be parallel or branching (netted) • Monocots = parallel • Eudicots = branching

  12. Internal Leaf Structure • Epidermal cells (outside) covered in waxy cuticle • Mesophyll cells (middle) contain chloroplast • Palisade = closely packed, contain chloroplasts – upper layer • Spongy = under palisade, loosely packed, air spaces for gas exchange

  13. Internal Leaf Structure cont. • Stoma (pl. stomata) – gases pass in and out • Guard cells – control opening/closing of stoma • Usually both GCs and stoma are on lower surface

  14. Leaf Specializations • Protection – chemical and structural • i.e. nicotine in tobacco plants • i.e. spikes • Storage (carbs and water) • Cold weather • i.e. conifers

  15. Homework • Page 551 #1-5, 7, 10

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