Leaves

• Photosynthesis is the process by which plants make their own food
• Leaves are the main sites for photosynthesis in plants
• Leaves are usually green due to the presence of chlorophyll
• Leaves have a flattened structure which maximizes the surface area for photosynthesis
• Leaves have different parts:

  • Apex (leaf tip)
  • Margin
  • Leafstalk/petiole
  • Base
  • Midrib
  • Blade
• A leaf consists of the broad part, also called the blade, and a leaf stalk (petiole) that attaches the leaf to the stem
• The main functions of leaves include:

  • Photosynthesis
  • Gas exchange
  • Transpiration
• Monocotyledonous leaf:

  • Functions of each part of the leaf:
  • Leaf base: Connects the leaf to the stem/branch
  • Midrib: Supports the leaf blade
  • Leaf vein: Stretches the length of the leaf & branches to each side, forming veins of vascular tissue
  • Petiole: In monocotyledonous plants, runs along the length of the leaf with parallel venation
• Grass leaf:

  • Functions:
  • Suitable position to receive sunlight
  • Connects the leaf base to the leaf blade
• Dicotyledonous leaf (Bean leaf):

  • Functions of each part of the leaf:
  • Leaf base: Supports the leaf blade
  • Midrib: Suitable position to receive sunlight
  • Leaf vein: Connects the leaf base to the leaf blade
  • Petiole: Stretches the length of the leaf & branches to each side, forming veins of vascular tissue
• Leaves:

  • Key functions:
  • Manufacture food due to the presence of chlorophyll
  • Enable gas exchange through stomata
  • Collect water and mineral salts received from the soil and collect manufactured food from the stem
• Parallel venation is found in dicotyledonous plants
• In parallel venation, the veins of the leaf run along the length of the leaf without meeting at a point
• The veins in parallel venation form a network-like pattern known as parallel venation
• The main functions of leaves in plants include:

  • Manufacturing food for the plant through photosynthesis, facilitated by the green pigment chlorophyll that traps light
  • Enabling gas exchange and transpiration in plants
• Classification of leaves is based on observable characteristics and features
• Features used to distinguish leaves include:

  • Nature of the leaf margin
  • Types of venation
  • Description of the leaf
  • Stalk and shape of the leaf apex
• The leaf vein it distributes water and mineral salts received from the stem via out the lamina and manufactured food from the lamina of the stem
• The leaf stalk connects the leaf base to the leaf blade and it supports the leafblade suitable position to receive sunlight
• The midrib it stretches the length of the leaf and branches each side forming vein of vascular
• The leaf base connects the leaf to the stem/
• The leaf blade is in a suitable position to receive sunlight and collects manufactured food from the stem
• Compound leaf structure:

  • Compound leaves have a lamina or leaf blade completely divided into leaflets
  • In some plants, each leaflet may have its own stalk attached to the same midrib
  • The divided area forms different types of compound leaves:
  • Compound trifoliate leaves
  • Compound pinnate leaves
  • Compound bi-pinnate leaves
  • Compound digitate leaves
• Simple leaf structure:

  • Simple leaves have a lamina that is not divided into leaflets like mango, avocado, or banana leaves
  • Some simple leaves may have a divided lamina, but the separation doesn't reach the midrib
• Features used to distinguish between simple and compound leaves:

  • When observing leaves closely, you can differentiate them based on the structure of their leaf blades (lamina)
  • If the leaf blade is not divided into leaflets, it is classified as a simple leaf
  • If the leaf blade is divided into leaflets, it is classified as a compound leaf
• Leaf margin

  • It forms edge of Leaf hence giving shape to the leaf
• Description of trifoliate leaves:

  • Have three leaflets
  • Emerging from a single point
• Compound pinnate leaflets are arranged in pairs opposite one another or alternately along the middle rib of a leaf
• Compound bipinnate leaflets are divided into pinnates
• Compound digitate leaves have leaflets radiating out from the end of the leafstalk like fingers of the palm