Plant Tissue System

• Plants need strong supportive tissue because they don't move, giving them structural strength.
• Most supportive tissues in plants are dead, providing mechanical strength while needing less energy to maintain.
• Plant growth is limited to specific regions where growing tissues can divide throughout the plant's life.

Classification of Plant Tissues

• Plant tissues are classified into meristematic and permanent tissues.

Meristematic Tissue

• Living tissues which can divide throughout the plant's life.
• Found in growing regions.
• Cells have thin walls, are tightly packed with no space between them.
• Cells feature dense cytoplasm and lack vacuoles, containing prominent and large nucleus.

Types of Meristematic Tissue

• Apical meristem increases shoot and root length and is at the tips of shoots and roots.
• Intercalary meristem is at the base of leaves or internodes and helps plant organs grow in length.
• Lateral meristem (cambium) increases plant diameter (girth) for secondary growth and lies on the sides of stems and roots.

Permanent Tissue

• Formed from meristematic tissue division and differentiation.
• Cells lose the ability to divide and gain a permanent shape, size, and function.
• Cells may be living or dead, with two types: simple and complex.

Simple Permanent Tissue

• Includes one cell type for support and storage.
• Parenchyma: living cells with thin walls, loosely arranged, often storing food or containing chlorophyll (chlorenchyma) for photosynthesis.
• Aerenchyma: Parenchyma with air cavities, helping aquatic plants float.
• Collenchyma: Provides flexibility and mechanical support, allowing bending without breaking.
• Sclerenchyma: Composed of dead cells, providing a hard, stiff structure in stems and seed coverings.

Complex Permanent Tissue

• Includes more than one cell type, such as Xylem and Phloem, which transport water, nutrients, and food.
• Xylem consists of tracheids, vessels, xylem parenchyma, and fibers.
• Phloem consists of sieve cells, companion cells, and phloem parenchyma.

Xylem

• Xylem consists of four cell types.
• Tracheids: Elongated cells with tapered ends; water moves through pits from cell to cell; the main water-conducting element in gymnosperms (non-flowering plants).
• Vessels: Long, tube-like structures formed by cells placed end to end with dissolved transverse walls, forming continuous channels; present only in angiosperms (flowering plants); aid in long-distance vertical water and mineral conduction and provide mechanical support.
• Xylem fiber: Dead, lignified sclerenchymatous cells provide support.
• Xylem parenchyma: Living parenchymatous cells store food and conduct water and minerals radially

Phloem

• Also comprises four cell types.
• Sieve tubes are slender, tube-like structures made of elongated, thin-walled cells placed end to end, with sieve plates (perforated end walls).
• Companion cells are smaller cells with dense cytoplasm and a prominent nucleus that aids sieve tubes in food conduction
• Phloem parenchyma consists of living, thin-walled cells for sideways food conduction, storing resin, latex, and mucilage.
• Phloem fiber are dead sclerenchymatous cells; some are sources of commercial fibers like jute, hemp, and flax.

Protective Tissue

• Epidermis:
  • It is the outermost layer of plant organs made of parenchymal cells.
  • Outer walls of epidermal cells are thicker than inner walls.
  • Typically single-layered but multilayered in desert plants to prevent water loss.
  • Protects internal tissues from injury and germs.
• Cork (phellem):
  • Outer tissue of old stems and roots in woody trees, formed by cork cambium (phellogen).
  • Cork cambium (phellogen) produces cork (phellem) on the outside and secondary cortex (phelloderm) on the inside.
  • Consists of dead cells with thick walls and no intercellular spaces.

Animal Tissues

• Animals perform vital functions like respiration, ingestion, excretion, and reproduction, whether unicellular or multicellular.

Types of Animal Tissue

• Based on location and function, animal tissues are divided into four types: epithelial, connective, muscular, and nervous.

Epithelial Tissue

• Protective tissue that covers most organs and body cavities forming a barrier between body systems.
• Cells are closely packed with little intercellular space due to cementing material.
• Lacks blood vessels, lymph vessels, and capillaries, so cells get nutrients from underlying connective tissue.

Types of Epithelial Tissue

• Squamous Epithelium:
  • Flattened, thin cells in blood vessel walls, lung air sacs, esophagus, and mouth lining.
  • Aids in diffusion.
• Cuboidal Epithelium:
  • Cube-like cells, sometimes with microvilli, in kidney tubules and salivary gland ducts and forms germinal epithelium of gonads
  • Functions include secretion, absorption, mechanical support, and excretion.
• Columnar Epithelium:
  • Tall, slender cells, sometimes with microvilli, lining the intestine and respiratory tract.
  • Functions in secretion and absorption.
  • Glandular: Modified columnar cells forming goblet cells to secrete mucus in intestines, glands, trachea, and bronchi.
  • Ciliated: Tall, slender cells with cilia to move substances like mucus in nasal passages or eggs in oviducts.

Connective Tissue

• Cells are loosely spaced in a non-cellular matrix that can be solid (bone), soft (loose connective tissue), or liquid (blood).

Loose Connective Tissue

• Has widely scattered cells within a matrix of loosely woven fibers, including strong collagen fibers.
• Found beneath the skin and between organs, providing support to hold tissues and organs in place.

Adipose Tissue

• Adipose tissues consist of adipocytes filled with fat globules in the loose connective tissue.
• Contains adipocytes storing fat droplets for energy; pads and insulates the body.

Fluid/Vascular Connective Tissue

• Maintains connections among body parts.
• Transports materials, forming the animal's transport system.
• Includes blood and lymph.
  • Blood includes cells separated by plasma and lacks fibers in its matrix.
    • Plasma (55%) contains water, salts, sugars, lipids, and amino acids.
    • Blood corpuscles (45%) include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).
  • Lymph, filtered blood, lacks RBCs and platelets, has abundant WBCs, and is colorless due to no hemoglobin.

Fibrous/Dense Regular Connective Tissue

• Consisting mainly of fibers.
  • Collagen fibers provide mechanical strength.
  • Elastin fibers can stretch and return to their original length.

Skeletal Connective Tissue

• Consists of bones and cartilage, providing body support.
• Matrix has fibers plus calcium salts in some cases.
  • Bone is rigid with collagen fibers and calcium/phosphorus salts.
    • Most of the skeletal system is bone.
    • Haversian systems are the structural units in mammalian bone.

Muscular Tissue

• Contracts and relaxes to perform mechanical work.
• Responsible for movement of body organs and locomotion.
• Muscle cells (fibers) contain contractile proteins (actin and myosin).

Types of Muscle Tissue

• Skeletal:
  • Attached to bones for voluntary movement.
  • Striated with many nuclei, cylindrical and unbranched.
• Cardiac:
  • Only in the heart wall.
  • Involuntary, striated with one nucleus, cylindrical, and branched.
• Smooth:
  • In walls of hollow internal structures for involuntary actions.
  • Nonstriated with one nucleus, spindle-shaped, and unbranched.

Nervous Tissue

• Composed of densely packed nerve cells (neurons) in the brain, spinal cord, and nerves.
• Neurons conduct nerve impulses (signals).
• Functional nerve and muscle tissue combinations allows fast movement in response to stimuli.
  • Neurons consist of:
    • Cyton (cell body) contains a nucleus and Nissl's granules (ribosomes and rough endoplasmic reticulum).
    • Cell Processes
      • Dendrites: Short, branched afferent processes receive impulses.
      • Axon: Single, long efferent process conducts impulses away from the cyton.
        • The longest cell in the body is the neuron because the axon can be more than one meter long.

Test your knowledge of plant tissues! This quiz assesses your understanding of meristematic and permanent tissues, including their types, characteristics, and functions. Learn about xylem, phloem, and their roles in plant structure and support.