Plant Tissues
Plant Tissues
Overview of Vascular Plants
A vascular plant consists of several crucial components including:
Root System
Shoot System
Shoot apex
Flower
Stipule
Shoot
Tendril
Axillary bud
Vein
Leaflet
Leaf
Internode
Blade
Petiole
Node
Vascular System
Primary root
Lateral root
Root apex
Plant Tissue Systems
Vascular plants possess three basic tissue systems:
Dermal Tissue
Ground Tissue
Vascular Tissue
Meristems
Definition: Meristems are clumps of small cells characterized by dense cytoplasm and large nuclei. They function similarly to stem cells in animals.
Cell Division: Each meristematic cell divides, leading to two outcomes:
A differentiating cell that will take on a specific function.
One meristematic cell that remains undifferentiated, maintaining the meristematic population.
Types of Meristems
Apical Meristems
Located at the tips of stems and roots.
Responsible for the formation of primary tissues.
Give rise to three primary meristems that develop into the major types of plant tissue:
Ground meristem
Procambium
Epidermis
Lateral Meristems
Responsible for secondary growth, allowing for an increase in the size of stems and roots.
Contribute to:
Secondary Root
Secondary Stem
Lateral Growth
Apical Growth
Meristem Types and Tissues
Ground Meristem
Procambium
Differentiated Tissues:
Primary Xylem
Primary Phloem
Vascular Cambium
Cork Cambium
Contributes to Secondary Xylem & Phloem.
Dermal Tissue
Forms the epidermis, typically consisting of a single cell layer.
Cuticle: A protective layer made of cutin. Example:
Carnauba Wax from the wax palm as a component of the cuticle.
Special Cells in Dermal Tissue
Root Hairs
Definition: Tubular extensions of individual epidermal cells, enhancing water and nutrient absorption.
Size Example: Approx. 1250 μm in length.
Ground Tissue
Comprised of three primary cell types:
Parenchyma Cells:
Most common type of plant cell.
Functions:
Storage (e.g., starch)
Photosynthesis
Secretion
Provides little to no structural support.
Collenchyma Cells:
Provide flexible support for growing plant organs.
Example Size: Approximately 120 μm in length.
Sclerenchyma Cells:
Characterized by thick walls and are dead at maturity.
Contain lignin.
Two Types:
Sclerids
Fibers
Vascular Tissue
Xylem:
Responsible for transporting water and minerals.
Composed of:
Vessels: Continuous tubes formed from dead cylindrical cells facilitating effective water transport.
Tracheids: Dead cells tapering at the ends, overlapping, and slower in water conduction compared to vessels.
Efficiency Comparison: Vessels conduct water more efficiently than tracheids due to their larger size.
Phloem:
Main tissue responsible for the transport of food and other long-distance signals within the plant.
Two Types of Cells:
Sieve Cells: Basic conducting units.
Sieve Tube Members: Specialized cells associated with companion cells, which provide metabolic support to sieve tube members.
Leaves
Primary function: Main site of photosynthesis in vascular plants.
Features:
Determinate Growth: Growth that stops after a certain size or stage.
Veins: Consist of both xylem and phloem and are distributed throughout the leaf blades.
Serve the function of waste accumulation as well.
Leaf Structures
Leaf Blades:
Variety of forms:
Simple Leaves: Have undivided blades; may feature teeth, indentations, or lobes.
Compound Leaves: Blades divided into multiple leaflets.
Mesophyll in Leaves
Mesophyll Types:
Some leaves feature a single type of mesophyll (commonly seen in monocots).
Others exhibit two types:
Palisade Mesophyll: Typically composed of two rows of tightly packed cells, primarily responsible for photosynthesis.
Spongy Mesophyll: Consists of loosely arranged cells with air spaces aimed at facilitating gas exchange.