Biology / 06 Anatomy of Flowering Plant
Types of Tissue Systems
Types of Tissue Systems
Introduction
Plants have three main tissue systems: the epidermal, ground, and vascular tissue systems. These systems serve various functions, including protection, support, and transport.
Types of Tissue Systems
1. Epidermal Tissue System:
o Structure: Outermost protective layer covering the entire surface of the plant.
o Components:
§ Epidermis: A single layer of cells, usually covered by a waxy layer called the cuticle to reduce water loss.
§ Stomata: Openings in the epidermis that facilitate gaseous exchange. Each stoma is surrounded by two guard cells that control its opening and closing. These are more prominent in leaves.
§ Trichomes: Hair-like structures, present on the stems and leaves, play a role in reducing water loss and protecting the plant from herbivores.
§ Root Hairs: Extensions of the root epidermal cells that increase the surface area for water and nutrient absorption.
o Function: Provides protection against water loss, pathogens, and physical damage.
showing the epidermal system.
2. Ground Tissue System:
o Structure: Composed of parenchyma, collenchyma, and sclerenchyma cells.
o Parenchyma: Most abundant and responsible for photosynthesis, storage, and tissue repair. It’s present in the cortex, pith, and mesophyll.
o Collenchyma: Provides support to growing parts of the plant, especially young stems and leaves, due to its ability to stretch.
o Sclerenchyma: Dead cells providing mechanical support, consisting of fibers and sclereids.
o Function: Provides mechanical support and stores nutrients.
GROUND TISSUE SYSTEM
FIG-Depicting parenchyma and collenchyma cells.
3. Vascular Tissue System:
o Structure: Made up of xylem and phloem tissues.
§ Xylem: Transports water and minerals from the roots to the rest of the plant. Components include tracheids, vessels, xylem fibers, and xylem parenchyma.
§ Phloem: Transports the products of photosynthesis from the leaves to other parts of the plant. Components include sieve tube elements, companion cells, phloem fibers, and phloem parenchyma.
o Function: Conduction of water, minerals, and food, as well as mechanical support.
Illustrating xylem and phloem tissues.
Types of Meristems
Types of Meristems
Introduction
Meristems are regions in plants where active cell division occurs, giving rise to new cells for growth. Based on location and function, meristems are classified into various types.
Types of Meristems
1. Apical Meristem:
o Location: Found at the tips of roots and shoots.
o Function: Responsible for primary growth, increasing the length of the plant.
o Divisions: It differentiates into protoderm, procambium, and ground meristem, which further develop into different tissues.
2. Lateral Meristem:
o Location: Found along the sides of roots and stems, includes vascular cambium and cork cambium.
o Function: Responsible for secondary growth, increasing the thickness (girth) of stems and roots.
3. Intercalary Meristem:
o Location: Present at the base of internodes or leaf blades (especially in monocots like grasses).
o Function: Contributes to the elongation of internodes and helps in regrowth when parts of the plant are damaged.
showing different types of meristems.
Anatomy of Dicotyledonous Root
Anatomy of Dicotyledonous Root
Introduction
Dicotyledonous roots (e.g., sunflower) have distinct tissue layers that contribute to water absorption and the conduction of nutrients. The structure differs from monocot roots.
Internal Structure
1. Epidermis (Epiblema):
o Structure: The outermost layer, consisting of thin-walled cells. Root hairs emerge from the epidermis, increasing surface area for absorption.
o Function: Absorption of water and minerals.
2. Cortex:
o Structure: Made of parenchymatous cells that allow the passage of water and dissolved nutrients.
o Function: Provides support and stores nutrients.
3. Endodermis:
o Structure: A single layer of barrel-shaped cells with characteristic Casparian strips that are impermeable to water, ensuring controlled entry of water into the vascular system.
o Function: Regulates the movement of water and nutrients into the vascular bundles.
4. Pericycle:
o Structure: A thin layer of cells just inside the endodermis.
o Function: Gives rise to lateral roots and the vascular cambium during secondary growth.
5. Vascular Tissue:
o Structure: Radially arranged xylem and phloem bundles.
o Function: Xylem transports water, and phloem transports nutrients. Vascular cambium forms during secondary growth.
showing the cross-section of a dicot root.
Vascular Tissue System
Vascular Tissue System
Introduction
The vascular tissue system is vital for the transport of water, minerals, and organic compounds throughout the plant. It consists of xylem and phloem.
Components of Vascular Tissue System
1. Xylem:
o Components:
§ Tracheids: Elongated cells that transport water and provide structural support.
§ Vessels: Wider than tracheids, vessels form continuous tubes for efficient water transport.
§ Xylem Fibers: Provide mechanical strength.
§ Xylem Parenchyma: Stores food and aids in water transport.
o Function: Conducts water and minerals from roots to leaves.
2. Phloem:
o Components:
§ Sieve Tubes: Long, tube-like structures that conduct sugars and organic nutrients.
§ Companion Cells: Regulate the functioning of sieve tubes.
§ Phloem Fibers: Provide mechanical support.
§ Phloem Parenchyma: Assists in storage and transport.
o Function: Conducts food from the leaves to different parts of the plant.
, showing vascular bundles.
Epidermal Tissue System
Epidermal Tissue System
Introduction
The epidermal tissue system provides the first line of defense against environmental factors and helps regulate water loss through transpiration.
Components
1. Epidermis:
o Structure: Single layer of cells, often covered with a waxy cuticle.
o Function: Protects against water loss and mechanical injury.
2. Stomata:
o Structure: Pores in the epidermis surrounded by guard cells.
o Function: Regulates gas exchange and transpiration.
3. Trichomes:
o Structure: Hair-like outgrowths on stems and leaves.
o Function: Reduces water loss, provides protection, and sometimes aids in secretion.
showing stomata and trichomes.
Anatomy of Dicotyledonous Stem
Anatomy of Dicotyledonous Stem
Introduction
The dicot stem (e.g., sunflower) shows clear differentiation into the epidermis, cortex, and vascular bundles, arranged in a characteristic ring pattern.
Structure
1. Epidermis:
o Outermost layer, covered with a cuticle, with stomata and trichomes for protection.
2. Cortex:
o Composed of three zones: hypodermis (collenchymatous), middle cortex (parenchymatous), and endodermis (starch sheath).
3. Vascular Bundles:
o Arranged in a ring, a defining feature of dicot stems.
o Open bundles: With cambium between xylem and phloem, allowing for secondary growth.
4. Pith:
o Central region, composed of parenchyma, serves as a storage tissue.
cross-section of a dicot stem.
Anatomy of Monocotyledonous Leaf
Anatomy of Monocotyledonous Leaf
Introduction
Monocot leaves, such as those of grasses, exhibit an isobilateral structure, meaning that both sides of the leaf (adaxial and abaxial) look similar. These leaves typically have parallel venation.
Structure
1. Epidermis:
o Structure: Both the upper and lower surfaces of the leaf are covered by epidermal cells.
o Stomata: Stomata are present on both surfaces, unlike dicot leaves where they are mostly on the lower surface.
o Bulliform Cells: Large, bubble-like cells located in the upper epidermis that help in leaf folding during water stress.
o Function: Protects the leaf from excessive water loss and external damage.
2. Mesophyll:
o Structure: The mesophyll is not differentiated into palisade and spongy tissues, unlike in dicots.
o Function: Facilitates photosynthesis.
3. Vascular Bundles:
o Structure: Vascular bundles are arranged in parallel rows due to the parallel venation of monocot leaves.
o Bundle Sheath: The vascular bundles are surrounded by a bundle sheath, which is involved in C4 photosynthesis (common in grasses).
showing the anatomy of a monocot leaf.
Anatomy of Dicotyledonous Leaf
Anatomy of Dicotyledonous Leaf
Introduction
Dicot leaves, such as those of sunflower, are dorsiventral, meaning that the upper and lower surfaces are different in structure and function. They typically have reticulate venation.
Structure
1. Epidermis:
o Upper and Lower Epidermis: The upper epidermis is usually thicker, and stomata are more abundant on the lower epidermis.
o Cuticle: A waxy layer is present on the epidermis, particularly on the upper surface to prevent water loss.
o Trichomes: Hair-like structures for protection and reducing water loss.
2. Mesophyll:
o Palisade Parenchyma: Located beneath the upper epidermis, these cells are closely packed and contain chloroplasts, maximizing photosynthesis.
o Spongy Parenchyma: Located below the palisade layer, the cells are loosely arranged with large air spaces for gaseous exchange.
o Function: Responsible for photosynthesis and gaseous exchange.
3. Vascular Bundles:
o Structure: The vascular bundles are arranged according to the reticulate venation pattern, with prominent midrib and lateral veins.
o Bundle Sheath: A bundle sheath surrounds the vascular bundles.
showing the anatomy of a dicot leaf.