2) Plant Cells and Tissues

Two giant categories used in lecture

  • Undifferentiated cells = meristems (growth)

  • Differentiated cells = tissues (simple + complex)

Simple tissues (single main cell type; focus = structure/function)

Sclerenchyma (heavy-duty support/protection)

  • Sclerenchyma includes sclereids:

    • “Short cells, often branched”

    • Found in hard seed coats, nut shells, pear flesh

  • Also includes fibers (example: flax)

(Your full lecture set also covers parenchyma + collenchyma in detail—if you want, I can turn those specific slides into a giant “compare/contrast” chart for flashcards too.)

Complex tissues (multiple cell types, multiple functions)

  • Defined as:

    • “More than one cell type per tissue”

    • Often “more than one function”

    • Specialization: protection, exchange, uptake, transport, support, storage

  • Four complex tissues named in lecture:

    • Epidermis

    • Periderm

    • Xylem

    • Phloem

Epidermis (roots, shoots, leaves): what it includes + what each part does

Core components list from lecture:

  • Epidermis cells: protection

  • Cuticle: protection (especially water loss + defense)

  • Stoma: 2 guard cells; water + gas exchange

  • Glands: protection

  • Hairs / trichomes: protection; water + nutrient uptake

  • In non-woody plants: one cell layer thick, alive

Cuticle (super testable)

  • Waxy layer made of cutin (fatty substance)

  • Links to:

    • reduced water loss

    • defense (resistance to bacteria/pests)

  • “Thickness ≈ water permeability”

  • Mentioned as ~420 million years old

Stomata (structure + what the lecture emphasizes)

  • Stoma = two guard cells (specialized epidermal cells)

  • Stomata respond to water pressure:

    • Dry conditions → low H₂O pressure

    • Wet conditions → high H₂O pressure

Epidermal “extras” (examples shown)

  • Trichomes include:

    • classic hair, glandular trichome, platelet trichome

  • Roles/examples:

    • hairs help defend against herbivores + heat

    • stinging hairs (stinging nettle) = defense

    • root hairs = “completely vital for water uptake,” short-lived

    • conical epidermis in rose flowers → insect attraction

    • lotus epidermis → water-repellent/self-cleaning effect

    • Venus flytrap sensing hairs