Leaves

• Leaf - is an organ of a vascular plant, and the food making factories of green plants. Leaves come in many different shapes and sizes.
• FUNCTIONS OF LEAVES

  • Produce oxygen for animals for respiration
  • Remove carbon dioxide from the air
  • Produce food for the plant
  • Create shade
  • Create hiding places for wildlife
  • Are a source of food (for animals and people)
  • Reduce soil erosion by intercepting rain as it falls
  • Lower the air temperature as a by product of transpiration
• Morphology of Leaves

  1. Stipules
  2. Petiole
  3. Leaf base
  4. Leaf Blade/Lamina
• Stipules - outgrowths, usually paired at the base of some dicot leaves.
• Leaves with stipules are stipulate, and those without stipules are exstipulate.
• Petiole - the stalk of the leaf which is attached to the stem.
• When the petiole is absent, it is called sessile and when present it is called petiolate.
• Leaf Base - the part near the petiole. In monocots, the leaf base is expanded into a structure called the leaf sheath, which partially or completely covers the stem.
• Leaf Blade/Lamina -the green flattened portion which performs most of the photosynthesis in the plant.
• Midrib - A strong or thick vein, runs through the leaf blade from its base to the apex.
• Veinlets - The midrib branches into thinner lateral veins that give rise to still thinner lateral veins.
• Monocots - have parallel leaf veins and longer slender blades
• Most dicots - have branch-like veins and palmate shape leaf
• PHYLLOTAXY

  1. Alternate or Spiral
  2. Opposite
  3. Whorled
• PHYLLOTAXY - leaf arrangement
• Alternate or Spiral - A single leaf is present at each node. This is the most common arrangement, plants with this type of phyllotaxy are lansones, sunflower, five fingers, santol and mango.
• Opposite - Two leaves arise from each node opposite each other. They may be at right angles to the upper or lower pair. Examples: guava, Japanese bamboo and makopa
• Whorled - There are more than two leaves at each node in a circle or whorl. Examples: yellow bell
• LEAF TYPES

  1. Simple Leaf
  2. Compound Leaf
  3. Pinnately Compound
  4. Unipinnate
  5. Bipinnate
  6. Tripinnate
  7. Palmately Compound
• Simple Leaf - Consist of a single blade which may be entire, lobed or cleft but not down to the midrib. An axillary bud is always present in the axil of a simple leaf. Examples: santol, banana and gabi
• Compound Leaf - Has a blade divided into a number of segments called leaflets in various ways. Examples: five fingers and rain tree
• Pinnately Compound - The midrib, known as the rachis, bears leaflets arranged in a linear sequence.
• Unipinnate - The leaflets are attached directly on the rachis.
• Bipinnate - When the compound leaf is twice-pinnate
• Tripinnate - There are rachises of the first, second and third orders
• Palmately Compound - The leaflets are attached to the tip of the petiole from which they radiate. Examples: Octopus, Schefflera
• 2 Types of Leaf Venation

  1. Netted or Reticulate Venation
  2. Parallel Venation
• Venation - refers to the arrangement of veins within a leaf.
• Netted or Reticulate Venation - In this type, there may be one or more large veins from which smaller veins branch out and interconnect, forming a network pattern.
• Pinnately Reticulate - has one principal vein or midrib present, from which smaller veins and their branches spread out in all directions in the blade.
• Palmately Reticulate – has several large veins radiating from around the tip of the petiole
• Parallel Venation - veins run parallel to each other. This venation is characteristic of monocots.
•  margin - of a leaf refers to its outer edge or boundary line.
• Revolute - rolled under, but only at the margin
• Entire - smooth
• Repand - slightly and irregularly wavy
• Sinuate - shallowly indented, wavy in a horizontal plane
• Undulate - wavy in a vertical plane, also called crisped
• Crenate - with rounded or blunt teeth
• Crenulate - small crenation, or small teeth on rounded protrusions