Plant Internal Structure and Growth Lesson Plan NRES B5-2

Anticipated Problems What are the functions of plant cell components? What is the role of cell division, cell elongation, and cell differentiation in plant growth? What are the different types of plant tissue? What are the basic types of plant cells? How do primary and secondary plant growth compare?

Terms apical meristem bud primordia cell cell differentiation cell division cell elongation cell wall cellulose chlorophyll chloroplasts chromatin chromosomes collenchyma cells companion cells cork cambium cork cells cytoplasm dermal tissues

Terms endoplasmic reticulum fiber golgi complex ground tissue lateral meristem leaf primordia lignin meristems mitochondria nucleolus nucleus organelles parenchyma cells periderm phloem pith plasma membrane plastids

Terms primary plant growth ribosomes rough endoplasmic reticulum sclereid sclerenchyma cells secondary plant growth sieve tube member smooth endoplasmic reticulum tracheid cells vacuole vascular cambium vascular tissues vessel elements xylem

The Cell The cell is the most basic unit of life. The smallest unit that can perform functions of life.

Plant Cell Components: Cellulose The cell wall is made of multiple layers of cellulose, which is a polysaccharide or complex sugar molecule. The layers of cellulose offer great strength. Cellulose is the primary ingredient of wood. Once a cell has stopped growing, the cell wall thickens and becomes rigid.

Plant Cell Components: Plasma Membrane The feature that really defines a cell is the plasma membrane or cell membrane, which is a thin sheet that holds the contents of the cell together and serves as a protective barrier from the surrounding environment.

Plant Cell Components: Plasma Membrane The fluid mosaic model of the plasma membrane consists of a lipid bi-layer in which proteins are imbedded. Restricts the movement of some materials Allows and even initiates the movement of other materials into and out of the cell

Plant Cell Components: Cytoplasm Cytoplasm is the living semi-fluid material inside the cell membrane and is home to a number of specialized structures called organelles.

Plant Cell Components: Organelles Organelles are small structures inside the cell that carry out the physiological processes of the organism.

Plant Cell Components: Plastids Plastids are organelles that produce and store food. Chloroplasts are a type of plastid that contains green pigments called chlorophyll. Chlorophyll traps light energy for photosynthesis. Chloroplasts are found in cells exposed to light, they are abundant in leaves and absent from root cells.

Plant Cell Components: Endoplasmic Reticulum The endoplasmic reticulum (ER) is an internal network of membranes extending throughout the cytoplasm. The endoplasmic reticulum contains many types of enzymes that catalyze different types of chemical reactions. There are two distinct forms of endoplasmic reticulum: smooth and rough.

Plant Cell Components: Endoplasmic Reticulum The smooth endoplasmic reticulum is the site for the production of lipids (fats) and hormones. It is also a site that breaks down toxic chemicals. The rough endoplasmic reticulum produces the proteins for the cell secretion and cell membranes.

Plant Cell Components: Golgi Complex Proteins are processed, sorted, or modified in the golgi complex. These processes result in the complex molecules needed for plant growth. Many proteins manufactured in the ER pass through the golgi complex.

Plant Cell Components: Mitochondria Mitochondria convert sugar into energy through cellular respiration. The plant is able to convert the food that it has made and stored into a form of energy.

Plant Cell Components: Nucleus The nucleus is the command center of the cell. It holds the genetic information for a cell’s activities within a nuclear membrane. Flowing through the nuclear membrane are materials needed for protein synthesis and fluids carrying chemical messages between the cytoplasm and the nucleus.

Plant Cell Components: Chromosomes Chromosomes contained in the nucleus hold the genetic blueprint of the organism and direct all functions of the cell, including protein synthesis. Chromosomes are made of chromatin. Chromatin is a complex of deoxyribonucleic acid or DNA molecules (35%), RNA (5%), protein (60%).

Plant Cell Components: Chromosomes Segments of chromosomes, or genes, are units of hereditary data that dictate the activity and structure of a cell. Each chromosome contains thousands of genes.

Plant Cell Components: Nucleolus A nucleolus is a specialized structure in a nucleus that is the site of ribosome synthesis.

Plant Cell Components: Ribosomes Ribosomes are bead-like structures found on the endoplasmic reticulum. Ribosomes are the major site for the assembly of amino acids into proteins.

Plant Cell Components: Vacuole The vacuole is a large sac bound by a membrane. May occupy up to 90% of the cell Serves to transport and store water, foods, salts, minerals, pigments, proteins, and wastes.

Plant Cell Components: Organelles The organelles within a cell have thin membranes used to compartmentalize or isolate different conditions from other organelles. Mitochondria and chloroplasts are bound with membranes. Different intracellular pH, enzyme systems, and more can be noted within each organelle. This enables the cell to perform different metabolic activities at the same time.

Growth of Higher Plants Growth of higher plants takes place through three essential processes, and vascular plants have three types of mature tissues. Cell division Cell elongation Cell differentiation

Growth of Higher Plants Cell division is simply the increase in the number of cells, which is accomplished through mitosis.

Growth of Higher Plants Cell elongation is the enlargement of the individual cells, which results in growth of the entire tissue or organ. Auxins and gibberellins are responsible for cell elongation.

Growth of Higher Plants Cell differentiation allows cells to take on specific functions. Important to multicellular plants Single-cell plants have no need to have different cell types

Growth of Higher Plants Cell differentiation- The cells of the higher plants are programmed to become specialized and make up the various plant organs. Some cells specialize as root cells that absorb water and nutrients. Some conduct water and minerals throughout the plant. Others become leaf cells containing chloroplasts and function to produce food for the plant.

Growth of Higher Plants Vascular plants have three types of mature tissues. Dermal tissues Vascular tissues Ground tissue

Growth of Higher Plants Dermal tissues consist of the epidermis or external covering of the leaves, stems, and roots. Offer a barrier to infectious organisms and other invaders

Growth of Higher Plants Vascular tissues are the conductive vessels of the plant. They transport water, minerals, food, and hormones. Specialized vascular tissues include the xylem, which conducts water and minerals upward from the roots, and the phloem, which transports food.

Growth of Higher Plants Ground tissue (fundamental tissue) includes all the parts of the plant other than dermal or vascular tissues. The bulk of a plant consists of ground tissue consisting of parenchyma, collenchyma, and sclerenchyma cells.

Genetic Information Genetic information and environmental conditions determine the types of cells that a plant produces. With the appropriate signals, various types of cells are produced.

Parenchyma Cells Parenchyma cells are found throughout a plant and typically lack a secondary cell wall associated with rigid strength for support. The palisade layer and spongy mesophyll cells in leaves are parenchyma cells. Modified parenchyma cells compose a large portion of the pith (the center part of a stem). Serve as storage facilities for starch, oil, water, salt

Collenchyma Cells Collenchyma cells are located under the epidermis of the stem, along leaf veins, and at corners of angular stems. They have thick, yet flexible cell walls that provide structural support for the plant.

Sclerenchyma Cells Sclerenchyma cells are found throughout a plant and function as a support. These cells have a hard, thick secondary cell wall composed, in part, of a material called lignin, which is a molecule that provides strength and rigidity to the cell. A long type of sclerenchyma cell is called fiber. A form of sclerenchyma cell that is short and cubical is the sclereid.

Tracheid Cells Tracheid cells are one of four types of cells found in the xylem. The others are vessel elements, parenchyma, and fibers.

Tracheid Cells Tracheid cells are long and tapering in shape. They are dead cells and hollow. Their role is to conduct water and minerals throughout the plant. Water passes from one cell to another through thin places in the cell wall called pits. Also contributes to the structural support of the plant.

Vessel Elements The vessel elements are found in the xylem where they conduct water and minerals and provide structural support for the plant. Vessel element cells are hollow. At the end of the cell walls, there are perforations or holes that allow the free flow of water from one cell to the next. Vessel cells also have pits along the sides of the cells that permit the lateral movement of water.

Sieve Tube Member The sieve tube member is a major element of the phloem. Other cells that compose phloem tissue are companion cells, parenchyma, and fibers.

Sieve Tube Members The sieve tube members are stacked end to end to form sieve tubes. There are holes at the end of each cell called sieve plates through which sugars are moved. Sieve tube members are living cells at maturity, but many organelles—including the nucleus, vacuole, and ribosomes—vanish as the cell matures.

Companion Cells Companion cells are associated with sieve tube members. They have many connections with adjacent sieve tube members. Do not conduct sugar throughout the plant. The play an important role in transporting sugars from photosynthetic parenchyma cells to the sieve tube members.

Cork Cells Cork cells are produced to the outside of the cork cambium and result in the outer covering of secondary growth. Waterproof characteristics and fire-retardant attributes

Meristems The growth of a plant takes place in specialized areas of the plant called the meristems. The meristem tissue consists of unspecialized cells that are capable of mitosis. Two types of growth result from cell division in meristem regions: primary and secondary growth.

Meristems Primary Plant Growth Primary plant growth occurs in areas called apical meristems. Apical meristem tissue is found at the tips of roots and at the end of stems. Growth at the apical meristem increases the length of the plant. Primary growth occurs in herbaceous and woody plants.

Meristems The meristem of the shoot has areas of cell division, cell elongation, and cell maturation. The structure of the stem apical meristem differs from the root apical meristem in that it has embryonic leaves known as leaf primordia and embryonic buds called bud primordia. As the cells in these immature structures divide, elongate, and mature, they become the leaves and stems of the plant.

Secondary Plant Growth Secondary plant growth takes place only in woody plants. It takes place in the lateral meristem; this tissue is found on the sides of roots and stems. Secondary plant growth involves cell division in layers ringing the stem. The result is an increase in the width of the stem or trunk of the plant. Two lateral meristems are involved in secondary growth.

Vascular Cambium Vascular cambium is a layer of meristematic tissue found between the wood and the bark. It produces secondary xylem to the inside of the vascular cambium and secondary phloem to the outside. Cell division occurs only when the plant is actively growing, primarily during the spring and summer.

Cork Cambium The cork cambium is located in the outer bark region, and the cells produced there form the periderm (the outer bark). Cork cambium produces cork cells that replace the epidermis present during primary growth. The periderm ranges from several cells in thickness to many cells.

REVIEW 1. What is home to a number of specialized structures called organelles? 2. Name the three types of mature tissues that Vascular plants have? 3. What are the four types of cells found in the xylem? 4. What is the role of the tracheid cells?