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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:

    1. 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.