Plant Anatomy Notes

Lecture 1

• Plant Anatomy: Branch of botany focused on the internal structure of plants.
• Deals with structures observed under high-powered light or electron microscopes.
• Microscopes: Instruments used to observe small objects, like cells.
• Important diagnostic tools in cell biology and histology.
• Allowed observation of plant cells' tiniest details and molecular structures.

Types of Microscopes

• Two categories:
  • Light or optical microscope: Uses a system of optical lenses and light waves for magnification.
    • Can be simple (single lens) or compound (multiple lenses).
  • Electron Microscope: Uses electromagnetic lenses and electron beams to form images.
    • Two Types:
      • Transmission Electron Microscope (TEM):
        • Magnifies over 1,000,000x.
        • Used to view thin specimens (tissue sections, molecules).
        • Specimens are transmitted through to form an image.
        • Provides detailed information on the inner structure of samples.
      • Scanning Electron Microscope (SEM):
        • Provides detailed images of surfaces.
        • Offers 3D images of the sample surface.

Light Microscope vs. Electron Microscope

Plant Anatomy Evolution

• Key event: Transformation of green, photosynthetic algae from aquatic life to terrestrial plants.
• Plants developed traits to survive on land.
• First plants evolved from freshwater green algae.
• Algae evolved into Charophytes, then mosses, ferns, gymnosperms, and angiosperms.
• Adaptations to land include physiological, behavioral, and structural changes.
• Plants need sunlight, proper temperature, moisture, air, and nutrients to grow.
• Plant adaptations:
  • Water-repellent cuticle
  • Stomata regulate water evaporation.
  • Specialized cells for rigid support and resource acquisition.
  • Structures to collect sunlight (chloroplasts), reproduce, and disperse without water.
• Plants evolved from simplest to most complex, primitive to advanced, and oldest to most recently evolved.

Land Plant Features

• Maintain moisture with waxy cuticles and stomata.
• Waxy layer prevents water loss.
• Stomata allow gas exchange.
• Obtain water and minerals from roots, CO₂ from air, and sunlight through leaves.
• Growth regions of cell division (apical meristems) at stem and root tips enable length extension.
• Vascular tissues transport water and minerals.
• Lignin supports bodies against gravity.
• Produce gametes and embryos within gametangia.
• Seeds protected within fruit.

Plant Classification

• Bryophytes:
  • Most primitive, non-vascular, live in moist environments.
  • Include mosses, liverworts, and hornworts.
• Pteridophytes:
  • Seedless, vascular plants that reproduce via spores.
  • Found in damp, shady places, e.g., ferns and horsetails.
• Gymnosperms:
  • Early seed plants with naked seeds and vascular tissue.
  • Example: Conifers.
• Angiosperms:
  • Seeds protected by ovaries.
  • Flowering plants with vascular tissue.
  • Most modern and diverse.

Lecture 2

Levels of Organization

• Atoms > Molecules > Cells > Tissues > Organs > Organ Systems > Organisms.

• All matter is made of atoms (e.g., carbon, oxygen, hydrogen, nitrogen).
• Atoms combine to form molecules (e.g., water, glucose, amino acids, $(R-CH(NH_2)-COOH)$).
• Cell is the basic unit of structure and function.
• Cells composed of molecules like water, proteins, amino acids.

Molecules in Cells

• Starch:
  • Insoluble, storage form of carbohydrate, many glucose molecules joined.
• Cellulose:
  • Used to build cell walls, adds strength.
• Lipids (fats/oils):
  • Used for storage in seeds.
• Amino acids:
  • Used for making proteins.

Tissues

• Groups of specialized cells similar in structure and function.
  • Example: Dermal tissue (protection), vascular tissue (transports), ground tissue (storage and support).

Organs

• Groups of different tissues working together to perform specific functions.
  • Example: Leaves specialized for photosynthesis.

Organ Systems

• Groups of organs that work together to perform major activities.
  • Example: Shoot system and root system.

Cell Theory

• Coined by Robert Hooke in the 1600s.
• Proposed by Matthias Schleiden and Theodor Schwann.
  1. All living organisms are composed of one or more cells.
  2. Cells are the basic unit of structure and organization of all living organisms.
  3. Cells arise only from previously existing cells, passing genetic material to daughter cells.

Eukaryotes and Prokaryotes

• Bacteria are the simplest organisms, made of single cells with a simpler structure.
  • Cells of bacteria are called prokaryotic cells.
• Cells of animals, plants, and fungi are called eukaryotic cells.

Comparing Cell Types

Animal Cell

• Components:
  • Nucleus: Contains genetic material (DNA), controls cell activities.
  • Cytoplasm: Liquid where chemical reactions happen.
  • Cell membrane: Outer layer controlling substance passage.
  • Mitochondria: Release energy from glucose.

Plant Cell

• Eukaryotic cells with a true nucleus.
• Capable of reproduction and growth.
• They absorb nutrients, produce waste, and are capable of responding to stimuli in their environment.
• Components:
  • Same as animal cells (nucleus, cell membrane, cytoplasm, mitochondria)
  • Cell wall: Provides strength and support (cellulose).
  • Vacuole: Contains cell sap, maintains cell firmness.
  • Chloroplasts: Contain chlorophyll, site of photosynthesis.

Plant Cell Structures

• Cell wall, chloroplasts, central vacuole are not found in other eukaryotes.
• Plasmodesmata: Channels connect two plant cells
• Endoplasmic Reticulum:
  • Smooth
  • Rough
• Nucleus: contains chromatin, a nuclear envelope, and a nucleolus
• Cell wall: maintains cell shape
• Plasma membrane
• Cytoplasm
• Central Vacuole: Filled with cell sap that maintains pressure against cell wall
• Cytoskeleton
  • microtubules
  • intermediate filaments
  • microfilaments
• Chloroplast: Site of photosynthesis
• Plastid: store pigments
• Ribosomes
• Golgi apparatus
• Mitochondria
• Peroxisome

Shared Structures

• Cytoplasm: Jelly-like, chemical reactions happen here.
• Nucleus: Contains DNA, controls cell activities.
• Cell membrane: Controls substance movement.
• Mitochondria: Enzymes for respiration, releases energy.
• Ribosomes: Protein synthesis occurs.

Difference Cell Structures

• Chloroplast: Photosynthesis, contains chlorophyll.
• Cell wall: Strengthens the cell, supports the plant comprised of cellulose fibers
• Permanent vacuole: Cell sap, keeps the cell turgid.

Lecture 3

Plant Cell Contents

• Living Contents
  • Organelles: Structures with specialized functions (e.g., mitochondria, ribosomes, chloroplast, endoplasmic reticulum).
• Non-living Contents
  • Cell Wall
  • Vacuoles
  • Cell inclusions (Ergastic) are considered to be nonliving components of the cell that do not possess metabolic activity and are not bounded by membranes.

Cell Membrane (Plasma Membrane)

• Thin semi-permeable membrane surrounds the cytoplasm inside the cell wall.
• Composed of a phospholipid bilayer and embedded proteins.

Functions of Cell Membrane

• Protecting the integrity of the interior cell. Separates the cell's contents from the surrounding environment.
• Regulating transport of substances: controls the movement of materials into and out of the cell.
• Signal Transduction: Reception of extracellular signals, transfer to the inside of the cell and the production of signals.
• Interactions with other cells: cell fusion, tissue formation, and communication.

Cytoplasm

• Gel-like substance fluid inside the cell membrane.
• Consists mostly of 80% water, ions, molecules, proteins
• Comprised of:
  1. Cytosol fluid portion of the cytoplasm.
  2. Organelles - cell “organs” or functional parts.

Function of the Cytoplasm

• Site of many biochemical reactions.
• Site where the cell expands and the growth of the cell takes place.
• Provides a medium for the organelles to remain suspended.

Nucleus

• Large, round structure.
• Surrounded by nuclear envelope.
• Contains chromatin (DNA and proteins) and the nucleolus.

Function of the Nucleus

• Contains the genetic material of the cell.
• Controls cell’s activities by controlling transcription.
• Responsible for protein synthesis, cell division, growth, and differentiation.

Nucleolus

• Located inside the nucleus.
• Ribosomes are produced and assembled here.

Nuclear Membrane

• A membrane surrounding the nucleus that helps keep DNA safe.

Ribosomes

• Consisting of RNA and proteins.
• Main site of protein synthesis.
• Free in the cytoplasm or attached to the endoplasmic reticulum.

Endoplasmic Reticulum (ER)

• Series of sacs and tubes used to process substances and transport them to Golgi bodies for further distribution.
  • Rough ER: Has ribosomes, involved in protein synthesis.
  • Smooth ER (SER): Lacks ribosomes, involved in lipid and carbohydrate metabolism.

Golgi Body

• Made up of a series of flattened, stacked pouches called cisternae.
• Responsible for packaging and transporting proteins and carbohydrates to be exported from cells.
• Sorting, modifying, and packaging of macro- molecules that are secreted by the cell or used within the cell for various functions.

Mitochondria

• Spherical to rods-shaped organelles .