Plant Tissues and Meristems Quiz

Plant Tissues

• Plants have three or four major organ groups: Roots, Stems, Leaves, and Flowers.
• Each organ is composed of tissues.
• A tissue is a group of cells performing a similar function.
• There may be more than one tissue per organ.

Meristematic Tissues

• Meristems are permanent regions of growth and active cell division.
• Apical meristems are found at the tips of roots and shoots.
• Roots and shoots grow in length due to the production of new cells by apical meristems.
• Primary growth is a result of apical meristems.
• Primary meristems develop from apical meristems.
• Protoderm develops into the epidermis.
• Ground meristem develops into the ground tissues.
• Procambium develops into the vascular tissues.
• Primary meristems produce primary tissues.

Lateral Meristems

• Lateral meristems produce secondary tissues that increase the girth of roots and stems (secondary growth).
• Vascular cambium produces tissues that function primarily in support and conduction.
• It is a thin cylinder of brick-shaped cells that extends the length of stems and roots.
• Cork cambium lies outside the vascular cambium, just inside the outer bark, and produces bark.

Intercalary Meristems

• Grasses and related plants do not have vascular cambium or cork cambium.
• They have intercalary meristems, which are located near nodes (leaf attachment areas).
• Intercalary meristems add to stem length.

Simple Tissues

• Parenchyma - Composed of parenchyma cells.
  • Parenchyma cells have thin, pliable walls.
  • Usually 14-sided at maturity.
  • Living cytoplasm, often containing large vacuoles and various secretions.
  • May remain alive for a long time.
  • Have spaces between them.
• Aerenchyma - Parenchyma tissue with extensive connected air spaces, usually in aquatic plants.
• Chlorenchyma - Parenchyma cells containing chloroplasts that function in photosynthesis.
• Transfer cells - Develop irregular extensions of the inner wall to greatly increase the surface area of the plasma membrane.
  • Found in nectaries of flowers.
• Collenchyma - Contains collenchyma cells.
  • Living cytoplasm.
  • May remain alive for a long time.
  • Cell walls are thick with uneven thickness.
  • Pliable and strong, providing flexible support.
• Sclerenchyma - Contains sclerenchyma cells.
  • Thick, tough, secondary walls; normally impregnated with lignin.
  • Dead at maturity.
  • Function in support.
  • Two types: sclereids and fibers.
• Sclereids (stone cells) are scattered in tissue, and are as long as they are wide.
• Fibers are much longer than they are wide and contain a lumen (tiny cavity).

Complex Tissues

• Complex tissues are composed of two or more kinds of cells.
  • Vascular tissues include xylem and phloem.
• Xylem - Chief conducting tissue for water and minerals absorbed by the roots.
  • Composed of parenchyma cells, fibers, vessels, tracheids, and ray cells.
• Vessels - Long tubes made of vessel elements.
  • Have thick secondary cell walls, open at both ends, and secondary walls develop irregularly.
  • Perforation plate between end walls.
• Tracheids - Tapered at the ends with pairs of pits that allow water to pass from cell to cell.
  • Dead at maturity.
  • Thick secondary cell walls.
  • May have spiral thickenings on cell walls.
• Rays - Composed of long-lived parenchyma cells.
• Phloem - Conducts dissolved food materials produced by photosynthesis throughout the plant.
  • Composed of sieve tube members, companion cells, fibers, parenchyma cells, and ray cells.
  • Sieve tube members
    • Lack secondary cell walls and nuclei.
    • Lay end-to-end to form sieve tubes.
    • Walls have sieve plates with small pores.
    • Callose forms callus plug to prevent leaking of sieve tube contents when cells are injured.
• Companion cells are associated with sieve tube members.
• Epidermis - Protective layer that is one cell layer thick covering all plant organs.
  • Composed mostly of parenchyma cells, guard cells of stomata, secretory glands, and hairs.
• Cutin is a fatty substance on the surface of outer walls of epidermis that forms the cuticle.
  • Wax is secreted on the cuticle.
  • The cuticle and wax prevent water loss by evaporation.
  • Resistant to bacteria and other disease organisms.
• Periderm replaces epidermis when cork cambium begins producing new tissue.
• Constitutes outer bark. -Primarily composed of cork cells and are dead at maturity. -While still alive, cytoplasm secretes suberin (fatty substance) into the walls, which makes the cork cells waterproof and helps protect phloem. -Lenticels are loosely arranged pockets of parenchyma cells formed by cork cambium that protrude through the surface of periderm, allowing for gaseous exchange
• Secretory cells may function individually or as part of a secretory tissue.

Test your knowledge on plant tissues and meristematic growth. This quiz covers the major organ groups of plants and the functions of different types of meristems. Understand how primary and secondary growth occurs in plants through their tissue systems.