Angiosperm Tissues - Practical 2

Angiosperm Tissues - Practical 2

• Plants have three types of organs: leaves, stems, and roots.
• Each organ is composed of tissues.
• A tissue is a group of cells with a common structure and function.

Epidermis

• Trichomes are hairs on the epidermis.
• Root hairs are tubular extensions of epidermal cells.

Ground Tissues

• Parenchyma cells are thin-walled and alive at maturity.
• Collenchyma cells are thick-walled and alive at maturity.
• Sclerenchyma cells are thick-walled and dead at maturity.

Vascular Tissues

• Xylem transports water.
• Phloem transports food products.

Meristematic Tissues

• Apical meristems are at the tips of roots and shoots.
• Lateral meristems are in the stems and roots.

Leaf Epidermis (Ficus Leaf)

• Ficus has two layers of epidermal cells.
• Epidermal cells provide support to the leaf, holding the leaf's shape to collect light.
• Epidermal cells secrete a waxy cuticle that provides a waterproof layer, vital in arid regions.

Leaf and Stem Trichomes

• Trichomes are extensions of epidermal cells that form hairs.
• Trichomes come in various types with different functions.
  • Examples: Aerva, Forsskaolea, Poppy (Papaver or Lewisia stems), Stachys, Teucrium.

Poppy (Papaver) or Lewisia Stems

• These stems have a dense layer of long stiff hairs.
• These hairs protect against insect herbivores, as insects cannot push through them.

Teucrium

• Teucrium is an example of a high-altitude plant.
• Exposed to strong UV light, dehydrating winds and cold winter nights.
• Its stems and leaves have white UV-reflecting hairs that protect from wind, cold, and UV light.

Aerva

• Aerva lives in extreme arid conditions.
• Its stems and leaves have small umbrella-shaped trichomes that shade the plant from the sun.

Stachys

• Stachys is a native plant of Turkey.
• Its hairy leaves are an adaptation to reduce water loss and trap surface humidity.

Root Epidermis and Root Hairs

• Roots have a thin cuticle allowing easy water entrance.
• Most water is absorbed through root hairs.
• Root hairs are tubular extensions of epidermal cells, increasing the root's surface area for absorption.

Ground Tissues (Parenchyma, Collenchyma, and Sclerenchyma)

• Parenchyma cells are living cells with cell walls, storing water and food.
• In leaves, parenchyma cells conduct photosynthesis.
• Collenchyma cells have thickened cell walls at the corners, providing mechanical strength.
• Sclerenchyma cells are dead cells with thick walls, offering rigid support.

Vascular Tissues (Xylem and Phloem)

• Xylem transports water in a X pattern in the centre of the root.
• Phloem transports food in small polygonal cells between the xylem arms.

Meristems (Onion root tip)

• The root tip has different regions:
  • Root cap: protects the apical meristem.
  • Apical meristem: cells with rapid mitotic divisions (tiny cells).
  • Elongation zone: cells enlarge, pushing the root down.
  • Maturation zone: cells start functioning.

Tasks (General)

• Specific tasks for observing and drawing various plant tissues (leaf epidermis, trichomes, root epidermis, root hairs, ground tissues, vascular tissues, and meristem) are provided. Page numbers for location of the relevant material are provided in the slides.