Plant Structure and Function


Overview of Plant Biology

Opening Questions

  • Excitement for learning about plants

  • Thoughts on plant structures

Big Ideas to Understand Today

  • Vascular plant organs including root and shoot systems

  • Fundamental tissue types

Evolution of Land Plants

  • Lineage of land plants:

    • Evolution from green algal ancestors leading to:

    • Hornworts

    • Liverworts

    • Mosses

    • Vascular plants evolve further into:

      • Seedless vascular plants (e.g., ferns)

      • Seed plants (gymnosperms & angiosperms)

  • Distinction between plant groups:

    • Non-vascular Bryophytes

    • Vascular Seedless Plants

    • Vascular Seed Plants:

    • Gymnosperms

    • Angiosperms

Interactive Question on Plant Success

  • Which group of land plants is most successful?

    • Options:

    • A. Bryophytes

    • B. Ferns

    • C. Gymnosperms

    • D. Angiosperms

    • Correct answer: D. Angiosperms

Plant Structure Overview

Overview of a Flowering Plant

  • Plant Organs:

    • Root System

    • Shoot System

  • Components of root and shoot systems articulated clearly:

    • Reproductive shoot (flower), Apical bud, Node, Internode, Leaf blade, Petiole, Axillary bud, Stem

Root System Characteristics

  • Function of the root system:

    • Absorb water and minerals

    • Anchor the plant in soil

    • Store carbohydrates (food)

  • Structure:

    • Primary root emerges from seed

    • Lateral roots branch off for increased stability and absorption

Root Hairs

  • Function of root hairs:

    • Absorption occurs through finger-like extensions of epidermal cells

    • Increased absorptive surface for roots

Taproot vs. Fibrous Root Comparison Activity

  • Group discussion:

    1. Compare taproot and fibrous root.

    2. Discuss advantages of each type.

    3. Determine best type for desert settings and explain reasoning.

    4. Classification of taproot and fibrous root in angiosperms.

Monocots vs. Eudicots

  • Monocots:

    • One cotyledon

    • Leaf veins typically parallel

    • Vascular tissue scattered

    • Root system usually fibrous

    • Pollen grain with one opening

    • Floral organs usually in multiples of three

  • Eudicots:

    • Two cotyledons

    • Leaf veins typically net-like

    • Vascular tissue usually in a ring

    • Taproot as main root

    • Pollen grain with three openings

    • Floral organs usually in multiples of four

Activity Summary

  • Assertion: The taproot would be best in a desert setting.

Evolutionary Adaptations of Roots

  • Examples of root adaptations:

    • Corn plants support tall structures

    • Beet plants store food and water

    • Strangler fig wraps around other plants for support

    • Mangroves possess air roots for oxygen access in swamps

    • Tropical trees' base roots for support

Shoot System

Overview of the Shoot System

  • Contains stems and leaves, typically above ground

  • Purpose: to acquire sunlight and CO2 for photosynthesis

Functions of Stems

  • Main role to elongate and orient the shoot for maximum photosynthesis

  • Elevate reproductive structures for pollination

Buds and Shoot Structure

  • Components:

    • Reproductive shoot (flower)

    • Apical bud, Node, Internode, Vegetative shoot

Adaptations of Stems

  • Evolutionary modifications:

    • Horizontal shoots adapt below or above the surface

    • Storage in rhizomes or stolons

Leaves and Their Functions

Structure of Leaves

  • Main photosynthetic organ

  • Composed of:

    • Flattened blade

    • Petiole (connects leaf to stem)

Leaf Venation

  • Monocots: Veins typically parallel

  • Eudicots: Branched veins

Specialized Leaf Structures

  • Spines, tendrils, storage leaves, reproductive leaves

Plant Structure Assessment

Question: Which structure is most important?

  • Options:

    • A. Stem

    • B. Root

    • C. Leaves

  • Correct Answers: (A) Stem, (B) Root, (C) Leaves

Dermal Tissue

  • Description: A protective outer layer

  • In nonwoody plants, typically a single layer called the epidermis covered with a waxy cuticle.

  • In older woody stems, the epidermis is replaced with a protective layer called the periderm.

Specialized Epidermal Cells

  • Discussion prompt regarding the function of guard cells and trichomes based on cell structures.

Vascular Tissue

  • Function: transport materials throughout the plant, providing mechanical support.

  • Includes:

    • Xylem:

    • Conducts water and dissolved minerals upward from roots to shoots

    • Cell types: Tracheids & Vessel Elements (both dead at maturity)

    • Phloem:

    • Transports sugars from production sites (mainly leaves) to growing or storage parts

    • Consists of sugar conducting cells known as sieve-tube elements and companion cells (alive at maturity)

Important Comparison of Xylem and Phloem

  • Xylem conduces water only upward; Phloem conducts sugar only downward.

Ground Tissue

  • Composition and function:

    • Internal areas known as pith

    • External areas known as cortex

  • Roles in storage, photosynthesis, support, and short-distance transport.

Other Types of Plant Cells

  • Description of cell types:

    • Thin and flexible for storage, secretion, and photosynthesis

    • Rigid cells for support and strength

    • Grouped in strands providing flexible support.