Plant Cells and Tissues Overview

Plant Cells

• Plant cells are identifiable by their cell walls and large central vacuole.
• Plant cells have many types of cells adapted for specific purposes.
• Parenchyma Cells
  • Storage
  • Photosynthesis
  • Gas exchange
  • Protection
  • Tissue repair and replacement
• Collenchyma Cells
  • Support for surrounding tissues
  • Provides flexibility for plant
  • Tissue repair and replacement
• Sclerenchyma Cells
  • Support
  • Transport of materials

Plant Tissues

• A tissue is a group of cells that work together to perform a function.
• A plant tissue can be composed of one or many types of cells.
• There are four different tissue types found in plants:
  • Meristematic
  • Dermal
  • Vascular
  • Ground

Plant Tissues - Vascular

• Xylem: water carrying vascular tissue, composed of specialized cells called vessel elements & tracheid.
  • Vessel elements: tubular cells stacked end to end, lack end walls, allowing free movement of water from one element to the next.
  • Tracheid: tubular cells with pitted ends and end walls, less efficient at moving water than vessel elements.
• Phloem: main food-carrying tissue in vascular plants.
  • Contains two types of cells:
    • Sieve tube members: Contain cytoplasm but lack nuclei and ribosomes when mature.
    • Companion cells: Occur next to sieve tube cells and have a nucleus.

Roots

• The tip of a root is covered by the root cap.
• The root cap consists of parenchyma cells to help protect root tissues as the root grows.
• Between the epidermis and vascular tissue is the cortex.
• Next to the endodermis, towards the center of the root, is the pericycle, which produces lateral roots.

Stems

• Herbaceous stems: soft, flexible, and capable of photosynthesis.
• Woody stems: rigid and fibrous.
• Main function: support of leaves and reproductive structures.
• Stem Types & Functions:
  • Tuber: food storage
  • Rhizome: food storage, asexual reproduction.
  • Runner: asexual reproduction.
  • Bulb: food storage
  • Corm: food storage

Leaves

• Structure:
  • Water travels from the roots up through the stems and into the leaves, replacing water used in photosynthesis and lost from the plant by evaporation.
  • Water evaporates from the inside of a leaf to the outside through stomata in a process called transpiration, which helps pull the water column upward.
• Function:
  • The main function of leaves is photosynthesis, with many adaptations to optimize this purpose.
  • Most plants have a flattened portion called the blade with a large surface area.
  • The blade is attached to the stem by a stalk called a petiole