Biology Lecture: Plant Organs

Introduction

• Lecture by Miss Angus on plant organs.
• Prior knowledge on plant tissues required.
• Video structure:
  • Plant systems: Shoot system & Root system.
  • Understanding differences in plant organs above and below ground.

Plant Systems

Shoot System

• Comprises above-ground parts: leaves and stems.

Root System

• Comprises roots and root hairs below ground.

Key Plant Tissues

Dermal Tissue

• Covers the outside of plants (stem, leaf, roots).
• Example: Stomata, a specialized dermal tissue.

Vascular Tissue

• Two types:
  • Xylem: Transports water, moves upwards from roots.
  • Phloem: Transports food, moves both up and down.

Ground Tissue

• Building tissues or foundational tissues.
• Types:
  • Parenchyma: Packaging tissue, large cells.
  • Collenchyma: Provides support, often green, thickened corners.
  • Sclerenchyma: Very hard connective tissue (e.g., husk of seeds, bark).

Plant Organs

Leaves

• Function as solar panels, crucial for photosynthesis.
• Cuticle: Transparent, waterproof layer that prevents water loss.
• Epidermis: Protection, one cell layer thick.
• Mesophyll: Middle layer, contains palisade and spongy cells.
  • Palisade Cells: Elongated, packed with chloroplasts.
  • Spongy Cells: Irregular shapes, aid in water evaporation.
• Vascular Tissues: Xylem and phloem present in leaf veins.
• Stomata: Modified epidermal cells allowing gas exchange.

Stems

• Dicot Stems: Focus on dicotyledonous stems.
• Recognizable by cylindrical shape and egg-shaped bundles.
• Epidermis: May contain chloroplasts.
• Cortex: Contains collenchyma, can have chlorenchyma.
• Vascular Bundles: Xylem inside, phloem outside.
• Cambium: Growth tissue, allows lateral growth.
• Pith: Central tissue, mostly parenchyma.

Roots

• Specialized structure with root hairs to increase surface area.
• Root Hairs: Increase water absorption.
• Cortex: Ground tissue, no chlorenchyma.
• Endodermis: Funnels water, includes Casparian strip.
• Vascular Tissues: Xylem and phloem positioned differently than stems.
• Pericycle & Vascular Cambium: Growth regions, allow tissue differentiation.

Terminology Recap

• Epidermal Tissue: Outer protective layer.
• Ground Tissue: Fills plant, provides support.
• Vascular Tissue: Xylem and Phloem.
• Cuticle: Waxy, waterproof layer.
• Mesophyll: Middle layer of the leaf.
• Cortex: Packaging region under epidermis in stems and roots.
• Cambium: Growth tissue, semi-permanent.
• Pericycle: Region for growth, not a tissue.
• Endodermis: Inner layer for water funneling.
• Casparian Strip: Waterproof layer aiding water movement in roots.
• Root Hairs & Stomata: Specialized cells for absorption and gas exchange respectively.

Conclusion

• Importance of understanding plant organ structure and function.
• Use terminology for study aids such as flashcards.
• Encouragement to engage with further content for detailed exploration of plant transportation and support.