Plant Anatomy Lecture Notes

Plant Anatomy Lecture Notes

• Cytology is the study of cells, the basic units of living organisms.
• Plant cells are characterized by a cell wall surrounding the plasma membrane.
• The cytoplasm, containing organelles, is enclosed within the cell wall.
• The cytoplasm and nucleus together form the protoplasm.

Plant Cell Organelles

• Nucleus: Located in the center of most cells, responsible for storing and transmitting genetic information.
• Mitochondria: Sites of various chemical processes involved in energy production (ATP synthesis).

Ribosomes and Endoplasmic Reticulum

• Ribosomes: Synthesize protein molecules from amino acids.
• Endoplasmic Reticulum (ER): A network of membranes.
  • Rough ER: Associated with ribosomes, involved in protein packaging for the Golgi apparatus.
  • Smooth ER: Lacks ribosomes, site of lipid synthesis and calcium ion storage/release.

Golgi Apparatus and Plastids

• Golgi apparatus: Modifies and sorts proteins, using transport vesicles.
• Plastids: Specialized organelles, including chloroplasts.
  • Chloroplasts: Contain chlorophyll, responsible for photosynthesis.

Vacuoles

• Vacuoles: Plant cells have large vacuoles, sometimes taking up to 90% of the cell's volume.
• Function: Store useful materials, digest waste proteins and organelles.

Plant Cell Characteristics

• Plant cells are distinguished from other eukaryotic cells by specific features:
  • Cell wall composed of cellulose, hemicellulose, pectin, lignin.
  • Presence of plastids.
  • Presence of large vacuoles.
  • Plasmodesmata, connecting neighboring protoplasts.

Plant Anatomy, Microscopic Structure

• Plant anatomy is also known as micropathology and plant histology.
• It's concerned with the microscopic structures of plant tissues, cells, and organs.

Plant Cells and Tissues

• Cell: Fundamental unit of a living organism, consisting of a cell wall surrounding protoplasmic and non-protoplasmic materials.
• Groups of cells with identical form and function are known as tissues.
• Plant tissues are divided into three main groups: dermal, ground, and vascular.

Types of Plant Tissues

• Plant Tissues: Permanent and Meristematic tissues
• Permanent Tissues: Simple and Complex permanent tissues
• Simple Permanent Tissues:
  • Parenchyma
  • Collenchyma
  • Sclerenchyma
• Complex Permanent Tissues:
  • Xylem (tracheids, vessels, xylem parenchyma, xylem fibres)
  • Phloem (sieve tube elements, companion cells, phloem parenchyma, phloem fibres)
• Meristematic Tissues: Apical, Intercalary, Lateral meristems

Dermal Tissues

• Dermal tissues are on the surface of plants, a complex tissue.
• Consists of epidermal cells, stomata, and trichomes (hairs).
  • Epidermal cells:
    • Single layer
    • No intercellular spaces
    • Varies in shape and size across plants
    • Covered with a cuticle (water-impermeable substance)
    • Upper epidermis differs from lower epidermis

Stomata

• Stomata are openings in the epidermis.
• Made of guard cells, with an opening in the center (ostiole) for gas exchange.
• Located on both surfaces of leaves or only on the lower surface.
• Stomata have subsidiary (surrounding epidermal) cells.
• Stomata types based on arrangements of subsidiary cells:
  • Ranunculaceous (Anomocytic)
  • Cruciferous (Anisocytic)
  • Rubiaceous (Paracytic)
  • Caryophyllaceous (Diacytic)

Trichomes (Hairs)

• Trichomes are projections of epidermal cells, varying in shape and size.
• Short, conical trichomes are called papillae.
• Types of trichomes: glandular and non-glandular or covering hairs
  • Non-glandular hairs are further classified as unicellular and multicellular, further divided based on branching.
  • Glandular hairs (Unicellular & Multicellular): Unicellular hairs are unusual, Multicellular are more common.
    • further subdivided into various types based on stalk and head structure.