Plant Tissue Types

Overview of Plant Tissues

Plants consist of various types of tissues that enable them to perform vital functions. Tissues are organized groups of cells sharing common features and work together as structural and functional units.

Types of Plant Tissue Systems

Dermal Tissue System

• Functions as the outer covering of the plant.

• Provides protection and interacts with the environment (light passage, gas exchange, etc.).

Ground Tissue System

• Located between dermal and vascular tissues.

• In leaves, it contains mesophyll for photosynthesis.

• May store sugars or starches in roots.

Vascular Tissue System

• Conducts water, nutrients, and solutes throughout the plant.

• Composed of xylem (water transport) and phloem (food transport).

Dermal Tissue System

Generally occupies the outer "skin" layer of plant organs. Responsible for:

• Environmental interaction, light passage, gas exchange.

• Pathogen recognition and defense mechanisms.

• Color display for attracting pollinators.

Components of Dermal Tissue

• Guard Cells: Regulate the opening and closing of stomata for gas exchange.

• Stomata: Pores on the surface that allow for gas exchange.

• Epidermis: Outer layer; may have specialized structures like hair (trichomes) for protection.

Ground Tissue System

Located between dermal and vascular tissues. Functions include:

• Photosynthesis: Carried out primarily in mesophyll.

• Food Storage: Stores starches and sugars.

• Support: Provides structural support to the plant.

Types of Ground Tissue

• Parenchyma Tissue: Involved in photosynthesis, food storage, and healing. Thin primary cell walls; alive at maturity; large central vacuoles.

• Collenchyma Tissue: Provides support and flexibility, especially in young stems and petioles. Cells are elongated with unevenly thickened walls; alive at maturity.

• Sclerenchyma Tissue: Provides rigid support, often found in older plant parts. Cells are dead at maturity and have thick secondary cell walls. Includes fibers (elongated) and sclerids (irregular shapes).

Vascular Tissue System

Responsible for transportation within the plant. Comprised of two main types:

• Xylem: Conducts water and dissolved minerals. Provides structural support. Includes tracheids and vessel members.

• Phloem: Conducts food and organic substances. Composed of sieve-tube elements and companion cells.

Plant Cell Types

• Simple Tissues: Composed of one cell type:

  • Parenchyma: Thin-walled and alive at maturity.

  • Collenchyma: Provides support and is alive at maturity (elongated walls).

  • Sclerenchyma: Provides structure when dead (thickened secondary walls).

• Complex Tissues: Composed of multiple cell types (e.g., xylem consists of tracheids and vessel elements).

• Cork Tissues: Produced by cork cambium; functions as a protective layer. Cork tissues are waterproof due to suberin (fatty lipid). These tissues die and contribute to the formation of outer bark. Some unsuberized tissues persist as lenticels, allowing for gas exchange within the bark.