Fundamentals of Plant Cell and Tissue Organization PDF

Fundamentals of Plant Cell and Tissue Organization FBS 33 Lesson 2 CELL The fundamental membrane- bound entity that contains the key molecules of life and constitutes the building blocks of all living beings. Unicellular organism – Does not allow division of labor or specialization. Each cell must...

Fundamentals of Plant Cell and Tissue Organization FBS 33 Lesson 2 CELL The fundamental membrane- bound entity that contains the key molecules of life and constitutes the building blocks of all living beings. Unicellular organism – Does not allow division of labor or specialization. Each cell must perform all tasks. Multicellular organisms - specialized for different tasks. There is division of labor. EXAMPLES OF PLANT CELL TYPES AND THEIR SPECIALIZATIONS Cell Type Specialization Cells of shoot/root tips Cell division; produce new protoplasm Epidermis Water retention; cutin and wax are barriers against fungi and insects Epidermal gland cells Protection; produce poisons that inhibit animals from harming plants Green leaf cells Collect solar energy by photosynthesis Root epidermal cells Collect water and minerals Vascular cells Transport water, minerals, and organic molecules EXAMPLES OF PLANT CELL TYPES AND THEIR SPECIALIZATIONS Cell Type Specialization Flower cells Petal cells Pigments that attract pollinators Scent cells Fragrances that attract pollinators Nectary cells Sugars that attract pollinators Stamen cells Indirectly involved in producing sperm cells Carpel cells Indirectly involved in producing egg cells Fruit cells Produce sugars, aromas, flavorful compounds that attract fruit- eating/seed-dispersing animals EXAMPLES OF PLANT CELL TYPES AND THEIR SPECIALIZATIONS Ground cells (stem c.s.) Vascular bundle (stem c.s.) EXAMPLES OF PLANT CELL TYPES AND THEIR SPECIALIZATIONS Dicot leaf (c.s.)  MEMBRANES Regulate the passage of molecules into and out of cells and organelles. Divide the cell into numerous compartments. Act as surfaces that hold enzymes Electron micrograph of cell membrane MEMBRANES MEMBRANES PROPERTIES OF MEMBRANES Membranes can grow (pieces are moved as vesicles) Membrane fusion allows the transport of material Vesicle movement may also release material to the outside of the cell (exocytosis & endocytosis) PROPERTIES OF MEMBRANES Biological membranes are selectively permeable (also called differentially permeable) They are dynamic, constantly changing. BASIC CELL TYPES Prokaryotic Cells Found in Bacteria and Archaea No membrane-bound nucleus No Membrane-bound organelles Eukaryotic Cells Found in plants, animals, fungi, and protists Presence of a true membrane-bounded nucleus Has many organelles that allow them to be more diverse and complex, both morphologically and physiologically. P L A N T C E L L S Protoplasm Protoplasm is a mass of proteins, lipids, nucleic acids, and water within a cell Except for the wall, everything in the cell is protoplasm Plasma Membrane/ Plasmalemma The membrane that completely covers the surface of the protoplasm. selectively permeable Nucleus Storage place for the organism’s genetic information nuclear envelope separates nuclear material from the rest of the cell, and it contains numerous small holes, nuclear pores. Nucleus Nuclear pores are involved in the transport of material between the nucleus and the rest of the protoplasm. Nucleoplasm is the substance within a nucleus. Nucleus Nucleolus are areas where the components of ribosomes are synthesized and partially assembled Central Vacuole Stores mostly water and salt as well as visible crystals, starch, protein bodies, and various types of granules or fibrous materials Single vacuole membrane also called the tonoplast Central Vacuole The water-soluble pigments in many flowers, fruits, occur in vacuoles. Metabolic waste products are pumped across the vacuole membrane and stored permanently in the central vacuole The central vacuole is a digestive organelle as well. Cytoplasm If the nucleus and vacuole are excluded from the protoplasm, the remaining material is referred to as cytoplasm and contains the following structures: Mitochondria Plastids Ribosomes Endoplasmic Reticulum Dictyosomes Microbodies Cytosol Microtubules Microfilaments Storage Products Mitochondria Organelles that carry out this cell respiration Consists of two membranes; the inner mitochondrial membrane and outer mitochondrial mebrane Mitochondria Mitochondrial membranes are folded, forming large sheets or tubes known as cristae. Reactions that do not involve highly reactive intermediates take place in the liquid matrix between the cristae. Plastids Plastids are a group of dynamic organelles able to perform many functions. Diverse types of metabolism occur in different classes of plastid: synthesis, storage, and export of specialized lipid molecules; storage of carbohydrates and iron; and formation of colors in some flowers and fruits. Plastids Thylakoid – Light dependent reactions Stroma – Light- independent reactions Plastids Types of Plastids and Their Function Amyloplasts - Store starch; considered to be leucoplasts Chloroplasts - Carry out photosynthesis Chromoplasts - Contain abundant colored lipids; in flowers and fruits Etioplasts - A specific stage in the transformation of proplastids to chloroplasts; occur when tissues are grown without light Leucoplasts - Colorless plastids; synthesize lipids and other materials Proplastids - Small, undifferentiated plastids Plastids Potato cells Cells of orange bell pepper Ribosomes These are particles responsible for protein synthesis. Ribosomes are aggregates of three molecules of RNA (ribosomal RNA) and approximately 50 types of protein that associate and form two subunits. Endoplasmic Reticulum A system of narrow tubes and sheets of membrane that form a network throughout the cytoplasm. A large proportion of a cell’s ribosomes are attached to the ER, giving it a rough appearance; consequently, this ER is called rough ER (RER) Endoplasmic Reticulum ER that lacks ribosomes is smooth ER (SER), and it is involved in lipid synthesis and membrane assembly. Dictyosomes A stack of thin vesicles held together in a flat or curved array. Much of the material secreted by a cell must first be modified by a dictyosome. Dictyosomes Dictyosomes can form large, complex associations. In animal cells that secrete very large amounts of protein, hundreds of dictyosomes associate side by side and form a cup-shaped structure called a Golgi body or Mucilage cell of root hairs Golgi apparatus. cisterna Microbodies Two classes: peroxisomes and glyoxysomes Both isolate reactions that either produce or use the dangerous compound peroxide (H2O2) Microbodies Peroxisomes are involved in detoxifying certain byproducts of photosynthesis and are found closely associated with chloroplasts Glyoxysomes, which occur only in plants, are involved in converting stored fats into sugars. Cytosol cytosol or hyaloplasm is a clear substance mostly water, enzymes, and numerous chemical precursors, intermediates, and products of enzymatic reactions. Within cytosol are free ribosomes, as well as skeletal structures—the microtubules and microfilaments Microtubules The most abundant and easily studied of the structural elements of a cell. They act as a “cytoskeleton”. Means of motility for both organelles and whole cells. Microtubules Microtubules guide movement of vesicles. They are involved in pulling chromosomes to the ends of the cells. Microtubules Microtubules are composed of two types of protein with a globular tertiary structure: alpha-tubulin and beta- tubulin. Microtubules A centriole is made up of nine sets of three short microtubules. Centrioles were assumed to be responsible for the organization and polymerization of the spindle microtubules even though plants never have centrioles. Microtubules Cilia and Flagella “9 + 2” arrangement Dynein arms convert the chemical energy of ATP Cilia and flagella is always associated with a basal body. Microfilaments Like microtubules, microfilaments are constructed by the assembly of globular proteins— in this case, just one type, actin. Microfilaments are narrower than microtubules (only 3 to 6 nm in diameter), and they have been implicated in different types of structure and movement. Storage Products Calcium oxalate Tannins in Tannins in crystals in wood cactus stem leaves Cell Wall A rigid, protective layer that surrounds the cell membrane in plant cells, fungi, bacteria, algae, and some archaea. It provides structural support and protection, helping to maintain the shape of the cell. Cell Wall Plant cell wall consists mostly of cellulose. Adjacent, parallel cellulose molecules crystallize into an extremely strong microfibril. Cell Wall Cellulose microfibrils are bound together by other polysaccharides called hemicelluloses. Cell Wall Cells located at the growing tip Primary cell walls – of Pinus (pine) thin Secondary cell wall – thick and infused with the compound Stone cells in lignin. coconut shell Cell Wall Associations of Cells Direct physical contact between cells cannot occur in plants because the two primary walls and middle lamella are located between any two adjacent protoplasts. Cell Wall Associations of Cells plant cells are interconnected by fine holes (plasmodesmata) in the walls primary pit field - regions of clustered plasmodesmata Cell Wall Associations of Cells plant cells are interconnected by fine holes (plasmodesmata) in the walls primary pit field - regions of clustered plasmodesmata Cell Wall Associations of Cells The symplast is the network of cytoplasm connected by plasmodesmata the apoplast is the network of cell walls and intercellular spaces through which water and solutes move freely without crossing any membranes. Evolution of Plants Evolutionary scenario for the conquest of land by streptophyte algae. Fürst-Jansen, Janine & De Vries, Sophie & de Vries, Jan. (2020). Evo-physio: On stress responses and the earliest land plants. Journal of experimental botany. 71. 10.1093/jxb/eraa007. Types of Plant Body Primary plant body Derived from shoot and root apical meristems. Composed of primary tissues. Constitutes the herbaceous parts of a plant. An herb consists only of a primary plant body. Secondary plant body Derived from meristems other than apical meristems. Composed of secondary tissues: wood and bark. Constitutes the woody, bark-covered parts of a plant. Basic Types of Cells and Tissues Parenchyma Thin primary walls. Typically alive at maturity. Many functions. Collenchyma Unevenly thickened primary walls. Typically alive at maturity. Provide plastic support. Sclerenchyma Primary walls plus secondary walls. Many dead at maturity. Provide elastic support and some (tracheary elements) are involved in water transport. Parenchyma Constitutes all soft parts of a plant: soft leaves, petals, fruits, and seeds Parenchyma Chlorenchyma cells are parenchyma cells involved in photosynthesis Other types of pigmented cells, as in flower petals and fruits, are also parenchyma cells Parenchyma Glandular cells that secrete nectar, fragrances, mucilage, resins, and oils are also parenchyma cells. Parenchyma Glandular cells that secrete nectar, fragrances, mucilage, resins, and oils are also parenchyma cells. Parenchyma Transfer cells are parenchyma cells that mediate short-distance transport of material by means of a large, extensive plasma membrane capable of holding numerous molecular pumps. Collenchyma Collenchyma cells have a primary wall that remains thin in some areas but becomes thickened in other areas, most often in the corners Collenchyma Present in elongating shoot tips that must be long and flexible It is present as a layer just under the epidermis or as bands located next to vascular bundles. Sclerenchyma Has both a primary wall and a thick secondary wall that is almost always lignified Elastic; can be deformed, but they return to their original size and shape when the pressure or tension is released. Sclerenchyma cells are of two types: conducting sclerenchyma and mechanical sclerenchyma. Sclerenchyma Fiber cell bundles in leaf Fiber cells of bamboo Sclerenchyma Sclereids Asterosclereids in waterlillies Sclerenchyma Thank You for Listening! FBS 33 Lesson 2