Lecture-10---PDF-Slides

Lecture Overview

• Lecture 10: Plant Anatomy & Physiology

• Reading: Chapters 10.5, 35.1, 36

Plant Anatomy

• Definition: Study of structural parts and systems that make up a plant: cell, tissues, organs, organs systems , organism

• Organ systems in vascular plants:

  • Root System: made of organs called roots

  • Shoot System: made of organs called stems and leaves

Plant Organs: Roots

• Function:

  • Anchor plants in soil

  • Absorb water and minerals

  • Store carbohydrates

• Types of Root Systems:

  • Taproot System (Eudicots):

    • One main vertical root (e.g., carrot) used for storage

  • Fibrous Root System (Monocots):

    • Many thin, branching roots with many lateral roots

    • Combats soil erosion

• Interaction with Mycorrhizal Fungi:

  • Symbiotic relationship that enhances nutrient absorption

Plant Organs: Stems

• Function:

  • Elongate the plant

  • Elevate leaves and reproductive structures

• Key Structures:

  • Node: Point of leaf attachment

  • Internode: Stem sections between leaves

  • Apical Bud: Contains actively dividing tissues for growth. location of active cel divisions at the tips

  • Axillary Bud: Can form lateral branches or thorn. located at nodes

Plant Organs: Leaves

• • leaf: Primary photosynthetic organ in plants

• Structures:

  • Blade: Broad portion of the leaf

  • Petiole: Joins leaf to stem at a node

• Possible Modifications:

  • Leaves may be modified

    for additional functions:

    protection, support,

    storage, propagation,

    and more

Types of Plant Tissues

• Three main tissue types:

  1. Dermal Tissue: outer Protective covering

  2. Vascular Tissue:

  3. Ground Tissue: Includes various cell types for support and storage

Dermal Tissue and Cell Types

• Dermal Tissue: Protects inner cells

• Cell Types:

  • Cuticle: Wax-like covering

  • Pavement Cells: Flat cells of the epidermis

  • Guard Cells: Control opening/closing of stomata, regulate gas exchange

Vascular Tissue: Xylem

• Xylem Functions: Transport water and minerals

• Cell Types:

  • Tracheids: Long, thin, tapered dead cells

  • Vessel Elements: Shorter, wider dead cells with openings

Vascular Tissue: Phloem

• Phloem Functions: Transports sugars from sources to sinks

• Cell Types:

  • Sieve-Tube Elements: Living cells that transport sugars

  • Companion Cells: Support metabolism of sieve-tube elements

Plant Tissue Structures

• Stem Cross-section:

  • Eudicots: Vascular bundles in a ring

  • Monocots: Scattered vascular bundles

Ground Tissue: Parenchyma

• Parenchyma Cells:

  • Thin, flexible walls, large vacuoles

  • Function: Photosynthesis in leaves; storage in roots and fruits

Plant Physiology

• Definition: Internal activities relating to metabolism, reproduction, growth, and defense

• Processes: Water uptake, mineral absorption, gas exchange

Transport Mechanisms

• Short Distance Transport - Solutes:

  • Active Transport: Pumps and co-transports solutes

  • Passive Transport: Ion channels and carriers

• Short Distance Transport - Water:

  • Water moves via osmosis down concentration gradients

Long Distance Transport

• Two transport continuums:

  • Apoplastic Route: Movement outside cell membranes

  • Symplastic Route: Movement through the cytosol via plasmodesmata

Water and Mineral Transport

• Water and minerals absorbed by root cells

• Apoplastic & Symplastic Routes: Must navigate Casparian strip to enter xylem

Bulk Flow: Xylem Sap Transport

• Cohesion-Tension Hypothesis: Water molecules evaporating from leaves create a pull, aiding upward movement of xylem sap

Stomata Regulation

• Guard cells regulate water loss:

  • Accumulation of K+ ions opens stomata, increasing turgor pressure

  • Loss of K+ ions causes stomata to close, reducing water loss

Phloem Transport of Sugar

• Sugar translocation from sources (mature leaves) to sinks (growing organs)

• Pressure-Driven Flow: Turgor pressure drives phloem sap from source to sink

Adaptations to Hot and Dry Conditions

• Strategies:

  • Close Stomata: Minimizes water loss

  • Water storage in stems

  • Reduced Leaf Size: Decreases surface area

  • Reflecting sunlight

  • Photosynthetic adaptations (C4 and CAM pathways)

Photosynthetic Adaptations

• C4 Photosynthesis: Utilizes PEP carboxylase to fix CO2 when stomata close

• CAM Photosynthesis: Stomata open at night to fix CO2 into organic acids

Lecture Objectives

• Describe features of the three plant organs

• Compare the three main tissue types in roots, shoots, and leaves

• Explain short distance transport mechanisms

• Discuss long distance transport of xylem and phloem

• Discuss adaptations to hot and arid environments

Vocabulary

• Key Terms:

  • Roots, Stem, Leaf, Dermal tissue, Vascular tissue, Ground tissue, Xylem, Phloem, Translocation, Osmosis, C4 and CAM photosynthesis, etc.