Plant Structure: Angiosperm Tissues

Plant Structure: Angiosperm Tissues

• Plant tissues are groups of cells that carry out similar functions
• Plant tissues are arranged in characteristic patterns and interconnected throughout the plant body
• Plants are multicellular eukaryotes with tissue differentiation
• Tissue differentiation results in specialized tissues
• Plant development involves growth, morphogenesis, and differentiation
• Growth is an irreversible increase in size due to cell division and enlargement
• Morphogenesis is the acquisition of a particular shape
• Differentiation is the process where cells that have identical genetic makeup develop into different cells from which they originated.
• In plants, continuous groups of differentiated and specialized tissues connect roots, stems, leaves, and sometimes flowers.
• This connectivity is essential for normal growth and development, and depends on the distribution of air, food, and other essential materials throughout the plant.

Plant Tissue Classification: By Complexity

• Simple Tissues: These are comprised of only one cell type. Examples include parenchyma, collenchyma, and sclerenchyma.

• Complex Tissues: These are composed of more than one cell type. Examples include epidermis, xylem, and phloem.

  • Xylem is responsible for water and mineral transport.
  • Phloem is responsible for transporting manufactured products.

• Parenchyma is the most common simple tissue, functioning in photosynthesis, storage, and secretion.

• Collenchyma features unevenly thickened primary walls, providing support to young, growing plant parts.

• Sclerenchyma has thick secondary walls, enhancing support in non-growing plant parts like seed coats and stems.

Plant Tissue Classification: By Function

• Meristematic Tissue: Undifferentiated tissue responsible for new growth. Dividing indefinitely, this tissue produces new growth throughout life.

• Dermal Tissue: The covering/protective tissue composed of epidermis (primary) and periderm (secondary).

• Vascular Tissue: The conducting tissue that transports water/minerals (xylem) and manufactured products (phloem) throughout the plant.

• Ground Tissue: All packing, storage, and strengthening tissues; including collenchyma, parenchyma, and sclerenchyma

Meristematic Tissue

• Shoot Apical Meristem: Located at tip of the shoot, responsible for producing new leaves and stems.
• Root Apical Meristem: Located at the tip of the root, responsible for producing new root tissues, including the root cap.

Dermal Tissue: Epithelium

• Epithelium forms the outer surface, functioning to line and protect various parts of the plant.

Vascular Tissue: Xylem

• Xylem: Contains vessels and tracheids for water and mineral transport.
  • Vessels are found in angiosperms
  • Tracheids are found in gymnosperms and pteridophytes
• Xylem parenchyma surrounds vessels, involved in metabolism and nutrient storage.

Vascular Tissue: Phloem

• Phloem: Transports manufactured products (organic compounds) throughout the plant.
  • Consists of sieve tubes and companion cells.
  • Sieve tubes are elongated, perforated cells that lack nuclei at maturity.
  • Companion cells support the sieve tube elements' metabolic functions.
  • Phloem fibers contribute structural support to the phloem.
  • Phloem parenchyma is a packing tissue that stores starch in the phloem.

Ground Tissue: Parenchyma

• Parenchyma: A most common ground tissue, primarily living when mature. Functions include photosynthesis, storage, secretion; found in mesophyll, cortex, pith, fleshy fruits, and vascular tissues.

Ground Tissue: Collenchyma

• Collenchyma: A living ground tissue with unevenly thickened cells, providing support to growing parts. Often found in flexible stems and petioles.

Ground Tissue: Sclerenchyma

• Sclerenchyma: Composed of thick-walled cells (lacking protoplasts in maturity).
• Strengthens non-growing plant parts like seed coats or gritty parts of fruits. Exists as fibers or sclerieds.