Leaves

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Leaves

  1. 1. Leaves- lateral outgrowth of the stem- flattened,expanded- leaf primordia- leaf buttress
  2. 2. Leaf Parts:1. Petiole - cylindrical part Sessile or apetiolated - attaches blade to the stem Petiolated2. Lamina or Blade - flattened greenpart
  3. 3. Monocot leaf• Supported by leaf sheath• Ligules and auriclesFunctions: 1. protection from dirt water
  4. 4. 3. Stipule- two leaflike flaps of the petiole- dicot leaves a. Stipulate – w/ stipule b. Exstipulate – without4. Midrib - central vein5. Veins - conducting tissue of the leaf6. Veinlets - secondary veins7. Margin - edge of the leaf
  5. 5. Simple leaf - one blade or laminaCompound leaf- blade is divided into two or more leaflets or (pinnae)- petioluleRachis – continuation of the petiole where the leaflets are attached
  6. 6. Types of Compound LeavesA. Pinnately Compound - leaflets are arranged laterally along the rachis (featherlike fashion)
  7. 7. 1. Simple Pinnate a. Even pinnate - each leaflet has a pair b. Odd pinnate - terminal leaflet has no pair
  8. 8. 2. Bipinnate- primary rachis branches into secondary rachis that bears the leaflets3. Tripinnate- with primary, secondary and tertiary rachises
  9. 9. B. Palmately Compound- leaflets radiate from a common point 1. Unifoliate - single leaflet at the tip of the stalk 2. Bifoliate 3. Trifoliate 4. quadrifoliate
  10. 10. PHYLLOTAXY
  11. 11. Phyllotaxy1. Alternate - one leaf at each node2. Opposite - two leaves opposite each other at each node3. Whorled/verticillate - several leaves at equal distance around the node
  12. 12. 4. Spiral - leaves arise succeedingly around the stem5. Decussate - two opposite leaves at right angles to the one below or above it
  13. 13. Shape
  14. 14. Margin
  15. 15. Leaf Venation
  16. 16. 2 Systems of Venation:1. Reticulated/Netted - main vein branches - forms network a. Pinnately netted - main vein - veins and veinlets arise from the midrib and ramify throughout the lamina
  17. 17. b. Palmately netted - principal veins arise at one point at the base of the leaf
  18. 18. c. Radiately netted - principal veins radiate at the tip of the petiole Colocasiaesculenta (gabi)
  19. 19. 2. Parallel/Striate Venation - veins are parallel with the midrib - common in monocots a. Radial Parallel - parallel veins form acute/right angles to the midrib
  20. 20. Diagram of Dicot Leaf
  21. 21. Dicot Leaf Cross section
  22. 22. 1. Epidermis - upper and lower - single layer of cells - derived from protoderm Functions: a. Protects leaf from dessication –(cuticle) b. Abrasion c. Prevents entry of fungi and bacteria d. Regulates exchange of gases (Oxygen and carbon dioxide
  23. 23. 1. Trichomes - protection against water loss2. Stomata - more stomata in lower epidermis - high temperatures - high concentration of CO2 close stomata
  24. 24. 2. Mesophyll - located between the upper and lower epidermis - dicots (2 distinct layers) a. Palisade mesophyll - arranged in compact columnar fashion - most photosynthetic activity takes place b. Spongy mesophyll - irregularly shaped - prominent intercellular air spaces - diffussion of carbon dioxide to other parts of leaf
  25. 25. 3. Vascular bundle/Leaf Vein
  26. 26. 3.xylem- part that faces upper surface of the leaf phloem - part that faces the lower surface of the leaf bundle sheath cells - for added strength and protection
  27. 27. Diagram of Monocot Leaf
  28. 28. Monocot leaf cross section
  29. 29. Internal Anatomy of Monocot Leaf1. Upper epidermis - covered with cuticle - bulliform cells - stomata present in upper and lower epidermisGuard cells monocot - dumbbell in shapeGuard cells dicot - kidney shaped2. Mesophyll - not differentiated into palisade and spongy mesophyll
  30. 30. Pine leaf cross sectionCuticle - much thickerEpidermis - multilayeredMesophyll
  31. 31. Modified Leaves
  32. 32. Spines - modified leaves or modified stipules - for protection
  33. 33. Tendrils - slender, coiling structures - for support - exhibit thigmotropism (opposite side begins to grow rapidly )
  34. 34. bBracts - modified leaves at the base of the flowers - colored bracts for attraction ex. Poinsettiabougainvilla
  35. 35. Uncutiniced leaves - for absorption ex. Digman
  36. 36. Expanded leaf like petiole - for additional photosynthesis ex. Pomelo
  37. 37. Fleshy and succulent leaves - for storage ex. Sabila
  38. 38. Plantlets at the tip of the leaves - for reproduction ex. kalanchoe
  39. 39. Insectivorous leaf - for absorption

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