Plant Anatomy: Cells, Tissues, and Systems

• Plant Anatomy is a branch of botany studying the internal structure of plant organs, and the cells and tissues that compose them.
• It is essential to use a magnifying tool like a microscope
• A higher flowering plant's body has a shoot system and root system.
• This study focuses on the anatomy of the root, stem, and leaf.

Levels of organization

• Cell: The basic structural and functional unit of a living organism.
• Tissue: Groups of cells with similar structures working together to perform a shared function.
• Organ: Groups of tissues working together to perform a specific function.
• System: Groups of organs with related functions working together to perform body functions.
• Organism: A living thing performing all life processes.

The Cell

• The cell is the structural and functional unit in living organisms.
• Plant cell has a cell wall, protoplasm, true protoplasmic components, and non-protoplasmic components.

Protoplasm vs. Protoplast

• Protoplasm: The living content inside a cell, including the cytoplasm, nucleus, and organelles, found in all living cells, and responsible for all vital activities of the cell.
• Protoplast: A plant, bacterial, or fungal cell that has had its cell wall removed, leaving only the plasma membrane and internal structures, mainly found in plant.
• Protoplasm = Cytoplasm + Nucleoplasm
• Cytoplasm = Only the part outside the nucleus
• All cytoplasm is protoplasm, but not all protoplasm is cytoplasm.

Plant Cell Details

• Plant cells are enclosed by a permeable cell wall and have a selectively permeable plasma membrane.
• Contains plastids, and often have a vacuole.
• Mature cells have a large central vacuole, lack a centrosome.

Cell Wall

• Encloses plant cells externally, distinguishing them from animal cells.
• It is non-living, rigid, thick, porous, and permeable
• Protects and supports the cell and gives the cell its distinctive shape.
• Allows materials to pass into and out of the cell.

Cell Wall Composition

• Cellulose
• Hemicellulose
• Lignin
• Suberin
• Pectin
• Cutin
• Gelatin
• Silica
• Waxes
• Gums

Cell Wall differentiation

Primary Wall:

• Composed primarily of cellulose and hemicellulose, is highly flexible.
• Allows cell expansion during growth has a high ability of imbibition due to its colloidal nature.
• The cell wall is porous, facilitating the movement of materials/solutions to and from the cell.

Middle Lamella:

• Located between the primary walls of adjacent cells binding individual cells together to form tissues
• Composed of pectin substances combined with calcium.

Secondary Wall:

• Forms near the end of cell growth from deposited substances such as lignin, suberin, cutin, gelatin, silica, waxes, or gums
• It Increases the wall's rigidity and makes it impermeable to water.
• Some areas without deposition are known as "pits."
• Other openings are called "plasmodesmata," allowing cytoplasmic filaments passage.

Comparison of cell walls

• Primary Walls: Mainly cellulose and hemicellulose. Surrounds the cell, innermost layer Allows for growth and expansion due to flexibility, porosity facilitates transport
• Middle Lamellae: Pectin substances combined with calcium. Located between the primary walls of adjacent cells Binds cells together to form tissues, provides adhesion
• Secondary Walls: Lignin, suberin, cutin, gelatin, silica, waxes, gums. Forms inside the primary wall, often at the end of cell growth Increases rigidity, water impermeability, and structural support, contains plasmodesmata for communication

The Plasma Membrane

• A thin layer located just inside the cell wall
• Is a double layer of phospholipids with carbohydrate molecules attached to proteins on its outer surface.
• Selectively permeable barrier for material passage and provides protection for a cell.
• Facilitates the connection and communication between cells.

Comparison of plasma membranes

• Cell Wall: Encloses the cell externally, thick, porous and permeable. Composed of cellulose, hemicellulose, pectin, lignin, and other materials
• Plasma Membrane: Located just inside the cell wall, Very thin, selectively permeable, allowing only certain substances
• Is composed of a double layer of phospholipids with attached carbohydrate molecules and proteins

The Cytoplasm

• The lining or filling of the cell is a semi-transparent, gel-like substance (like egg white).
• Constantly moves in a constant, unidirectional flow.
• Primarily consists of water with organic and inorganic substances, suspending organelles.
• A heterogeneous medium of protoplasmic (organelles) & non-protoplasmic components.

The Nucleus

• Is one of the most distinctive cell structures because of its dark color and shape (spherical, semi-spherical, oval, or irregular).
• The diameter is around 5 and 10 microns.
• Its position is usually located peripherally, and the cell contains typically one nucleus.
• The structure contains a fluid known as nucleoplasm, composed of nucleic acids and proteins.
• Nucleic acids include deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), forming chromosomes and genes.
• Nuclear proteins are primarily histones; the nucleoplasm may also contain lipids, phospholipids, and some enzymes.
• It is surrounded by a nuclear membrane akin to that of the plasma membrane Characterized by pores/holes that allow communication between the nucleus/cytoplasm via the endoplasmic reticulum.
• It may contain one/more nucleoli that is the center of cellular activity.
• Controls all of the vital processes occurring within.