Introduction to Plant Anatomy

Introduction to Plant Anatomy

• Plant anatomy studies the internal structure of plants.
• Anatomical studies are important because:
  • They help understand plant function.
  • They help solve taxonomic problems.
  • They are essential for pharmacognosy.

Plant Body Organization

• Plant bodies are composed of cells.
• Cells are the smallest structural and functional units of life.
• Cells organize into tissues.
• Tissues form different organs.
• Organs form organ systems.

The Plant Cell

• Plant cells are formed from protoplasm surrounded by a cell wall.
• The cell wall provides:
  • Shape
  • Protection
  • Support
  • Strength

Cell Wall Structure

• The middle lamella is the first layer of the cell wall.
• It forms at the end of cell division.
• It is composed of pectin.
• Pectin adheres cells to each other.
• The primary cell wall is thin, elastic, and expands during cell growth.
• It is made of cellulose fibres, embedded in a matrix of pectin, hemicellulose, and protein.
• The secondary cell wall is rigid and non-elastic.
• It forms after cell maturation.
• It is reinforced with lignin, cutin, or suberin.
• These materials add strength and hardening to the cell wall.

Mature Plant Cell

• The mature plant cell has multiple layers to the cell wall:
  • Middle lamella
  • Primary cell wall
  • Secondary cell wall
  • Plasma membrane
  • Cellulose
  • Hemicellulose
  • Lignin

The Cell Wall Structure

• The middle lamella is the first layer of the cell wall formed during cell division
• It adhers cells together to form tissue
• The primary cell wall is deposited on both sides of the middle lamella
• Composed of cellulose and hemicellulose
• The secondary cell wall is rigid and non-elastic
• Forms after the cell is fully grown and functions like hardening agents like lignin, cutin, or suberin to provided strength

Pits and Plasmodesmata

• Pits are pores in the cell wall without deposition of cell wall components.
• They are commonly seen in pairs on adjacent cells.
• Plasmodesmata are cytoplasmic strands passing through pits.
• They link the cytoplasm of neighbouring cells.
• They facilitate transport of materials and stimuli between cells.

The Protoplasm and its Components (1) - Protoplasmic Contents

• Protoplasm contains the plasma membrane, cytoplasm, and organelles.
• The nucleus is surrounded by a double membrane.
• The nucleus contains nucleoli and chromatin which condenses to form chromosomes during cell division.
• The endoplasmic reticulum is a continuous membrane system of flattened sacs and tubules.
• Some ER is coated with ribosomes.
• Mitochondria are surrounded by double membranes.
• They are responsible for respiration and energy production.

The Plastids

• Plastids are surrounded by double membranes.
• They are clasified based on their function:
  • Chloroplasts contain chlorophyll, specialized for photosynthesis in green plant tissues.
  • Chromoplasts contain colorful pigments, responsible for colors in flowers and fruits.
  • Leucoplasts are non-pigmented plastids.
  • They are found in non-photosynthetic tissues of plants, such as roots, bulbs, and seeds.
  • They function in nutrient storage (starch).

The Protoplasm and its Components (2) - Non-Protoplasmic Contents

• The non-protoplasmic contents include storage or waste compounds.
  • Starch grains are formed in amyloplasts.
  • Starch grains have layering around a point called the hilum.
  • Starch grains can be concentric or excentric in structure.
  • Calcium oxalate crystals are formed in vacuoles of actively growing cells.
  • Druse crystals are star-shaped.
  • Raphide crystals are needle-like bundles.

Plant Tissues

• Tissues are grouped cells with common origin and function.
• Tissues are classified as meristematic or permanent.
• Meristematic cells divide continuously.
• Permanent cells do not divide.
• Growth activity is confined to meristems, regions of active cell division.

Meristematic Tissues

• Meristematic tissues are undifferentiated cells that divide continuously.
• Meristematic cells:
  • Have various shapes (oval, rounded, polygonal).
  • Have thin cell walls due to the absence of secondary walls.
  • Have large nuclei.
  • Have dense cytoplasm.
  • Have few or no vacuoles.
  • Lack intercellular spaces.

Types of Meristems

• Meristems are grouped based on position:
  • Apical meristems are located at the tips of stems and roots, responsible for primary growth (increase in length).
  • Intercalary meristems are located between mature tissues, increasing the length of organs like leaves and stems.
  • Lateral meristems are parallel to the axis of organs and responsible for increasing thickness.

This quiz explores the fundamental concepts of plant anatomy, including cell structure, tissue organization, and the significance of anatomical studies in understanding plant functions. Delve into the essential components that contribute to the growth and stability of plants.