Examining Plant Structures Examining Plant Structures and Functionsand Functions

Eric StormerEric Stormer

Virginia Cooperative ExtensionVirginia Cooperative Extension

THE CELLULAR STRUCTURE OF THE CELLULAR STRUCTURE OF PLANTSPLANTS

A A cell cell is a tiny structure that forms the is a tiny structure that forms the basic building blocks of plants.basic building blocks of plants.– All organisms are made of one or more cells.All organisms are made of one or more cells.– Protoplasm in cells carries out life processes.Protoplasm in cells carries out life processes.

Cellular structure of plants, Cellular structure of plants, cont’d.cont’d.

Plants are Plants are multi-cellularmulti-cellular organisms, organisms, meaning that they have many cells.meaning that they have many cells.– Some cells have specific functions.Some cells have specific functions.– Cell specializationCell specialization is the presence of cells is the presence of cells

that perform unique activities for a plant. that perform unique activities for a plant. (Flowers, leaves, roots and stems are made (Flowers, leaves, roots and stems are made of specialized cells.)of specialized cells.)

Cellular structure of plants, Cellular structure of plants, cont’d. cont’d.

Cells are formed into groups that are alike Cells are formed into groups that are alike in activity and structure.in activity and structure.– TissueTissue is formed by groups of cells that are is formed by groups of cells that are

alike in activity and structure.alike in activity and structure.– An An organorgan is formed by tissues that work is formed by tissues that work

together to perform specific functions.together to perform specific functions.– An An organ systemorgan system is a group of organs that is a group of organs that

work well together to perform a function.work well together to perform a function.

Cellular structure of plants, Cellular structure of plants, cont’d.cont’d.

Cell structure is the organization of the Cell structure is the organization of the material that forms a cell.material that forms a cell.– Plant cells have three parts: wall, nucleus and Plant cells have three parts: wall, nucleus and

cytoplasm.cytoplasm.– The The cell wallcell wall surrounds the cell and controls surrounds the cell and controls

the movement of materials in and out of the the movement of materials in and out of the cell.cell.

– The The nucleus nucleus is near the center of the cell and is near the center of the cell and contains protoplasm, chromosomes, and contains protoplasm, chromosomes, and other structures that control cell activity.other structures that control cell activity.

Cellular structure of plants, Cellular structure of plants, cont’d.cont’d.

The The cytoplasmcytoplasm is a thick solution inside is a thick solution inside the cell wall surrounding the nucleus.the cell wall surrounding the nucleus.

Plant cells have many additional parts, Plant cells have many additional parts, including: chloroplasts, nucleolus, including: chloroplasts, nucleolus, vacuole, mitochondria and golgi bodies.vacuole, mitochondria and golgi bodies.

Major parts of a plant and their Major parts of a plant and their functionsfunctions

The major The major vegetative partsvegetative parts of plants are of plants are stems, leaves and roots.stems, leaves and roots.

A A stemstem is the central axis that supports is the central axis that supports the leaves, connects them with the roots, the leaves, connects them with the roots, and transports water and other materials and transports water and other materials between the leaves and roots. Stems vary between the leaves and roots. Stems vary widely in appearance based on the widely in appearance based on the species of plant. species of plant.

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

Stems may be vertical or horizontal and Stems may be vertical or horizontal and modified for climbing and to store water modified for climbing and to store water and food. Several specialized kinds of and food. Several specialized kinds of stems are important.stems are important.– RhizomeRhizome – an underground stem that grows – an underground stem that grows

horizontally. It may grow adventitious roots horizontally. It may grow adventitious roots and stems to develop as a separate plant. and stems to develop as a separate plant. Examples: Iris and Wild GingerExamples: Iris and Wild Ginger

Rhizomatous PlantsRhizomatous Plants

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

TuberTuber – an enlarged – an enlarged part of a stem that part of a stem that grows underground. grows underground. It can develop into a It can develop into a separate plant. separate plant. Examples include Examples include potatoes and yams.potatoes and yams.

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

A A tendriltendril is a threadlike, leafless growth is a threadlike, leafless growth on a stem that attaches itself around other on a stem that attaches itself around other stems and objects. Tendrils typically grow stems and objects. Tendrils typically grow in a spiral shape. After attaching itself, it in a spiral shape. After attaching itself, it holds the stems in position. Vines and holds the stems in position. Vines and climbing plants often have tendrils. climbing plants often have tendrils.

Examples include sweet peas and Examples include sweet peas and cucumbers.cucumbers.

Sweet Peas, CucumbersSweet Peas, Cucumbers

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

A A stolonstolon is an above ground stem that is an above ground stem that grows horizontally and propagates new grows horizontally and propagates new plants. Strawberries are well known as plants. Strawberries are well known as examples of plants that multiply using examples of plants that multiply using stolons.stolons.

StrawberriesStrawberries

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

A A bulbbulb is an underground food storage is an underground food storage organ consisting of flattened, fleshy stem-organ consisting of flattened, fleshy stem-like leaves with roots on the lower side. like leaves with roots on the lower side. Examples include onions and daffodils.Examples include onions and daffodils.

DaffodilDaffodil

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

A A cormcorm is a food storage organ at the end is a food storage organ at the end of a stem that grows underground. It is an of a stem that grows underground. It is an enlarged or swollen stem base. Examples enlarged or swollen stem base. Examples include gladiolus and crocus.include gladiolus and crocus.

GladiolusGladiolus

CrocusCrocus

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

A A rootroot is the part of a plant that grows in is the part of a plant that grows in the soil or other media. These anchor the soil or other media. These anchor plants, absorb water and minerals, and plants, absorb water and minerals, and store food. The root system structure store food. The root system structure varies widely depending on the species of varies widely depending on the species of plant. Overall, roots can be classified as plant. Overall, roots can be classified as two major types.two major types.

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

Fibrous – a Fibrous – a fibrous roots system is fibrous roots system is is is made of many small roots and spread made of many small roots and spread throughout the soil.throughout the soil.

Taproot – A Taproot – A taproot systemtaproot system is made of is made of one primary root with a number of small one primary root with a number of small secondary roots.secondary roots.

Fibrous RootsFibrous Roots

TaprootsTaproots

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

A A leaf leaf is typically a large, flat, green organ is typically a large, flat, green organ attached to the stem. Leaves carry out attached to the stem. Leaves carry out photosynthesis, transpiration, and may photosynthesis, transpiration, and may store food. Shape, arrangement and store food. Shape, arrangement and other features vary widely with the species other features vary widely with the species of the plant. There are two major kinds of of the plant. There are two major kinds of leave and three major types of leaf leave and three major types of leaf arrangement.arrangement.

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

Simple – a leaf that has only one blade.Simple – a leaf that has only one blade.Compound - a leaf divided into two or more leaflets.Compound - a leaf divided into two or more leaflets.

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

Leaf attachment also varies. This refers to Leaf attachment also varies. This refers to the spacing and arrangement of leaves on the spacing and arrangement of leaves on the stem of a plant. The major kinds of the stem of a plant. The major kinds of attachment are: attachment are: – Alternate – leaf arrangement is one leaf at Alternate – leaf arrangement is one leaf at

each node on a stemeach node on a stem– Opposite – leaf arrangement is two leaves Opposite – leaf arrangement is two leaves

attached at nodes opposite each otherattached at nodes opposite each other– Whorled – leaf arrangement is where three or Whorled – leaf arrangement is where three or

more leaves are attached at each nodemore leaves are attached at each node

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

The major The major reproductive partsreproductive parts of flowers, of flowers, seeds and fruit.seeds and fruit.– A A flowerflower is a part containing the reproductive is a part containing the reproductive

organs. The types which exist vary organs. The types which exist vary considerably. In general, they produce pollen considerably. In general, they produce pollen and ovules. Fertilization occurs when a pollen and ovules. Fertilization occurs when a pollen cell unites with an ovule.cell unites with an ovule.

– Seed are produced by fertilized ovules and Seed are produced by fertilized ovules and contain new plant life.contain new plant life.

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

Fruit are ovaries which develop to protect Fruit are ovaries which develop to protect and nourish the developing seed. The and nourish the developing seed. The kinds which exist vary widely.kinds which exist vary widely.

Distinguishing between plants Distinguishing between plants based on seed cotyledonsbased on seed cotyledons

A A cotyledoncotyledon is the fleshy structure within is the fleshy structure within a seed that contains food for a developing a seed that contains food for a developing embryo. embryo.

Depending on the species, a seed may Depending on the species, a seed may have one or two cotyledons.have one or two cotyledons.

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

A plant species producing seed with A plant species producing seed with one one cotyledon, or seed leaf, is a cotyledon, or seed leaf, is a monocotyledon, or monocot.monocotyledon, or monocot.– All grasses are monocots. Corn, wheat, oats, All grasses are monocots. Corn, wheat, oats,

Bermuda grass and sugarcane are each Bermuda grass and sugarcane are each examples of monocots. All leaves branch examples of monocots. All leaves branch from the main stem. from the main stem.

– Stems are non-woody and tend to have a Stems are non-woody and tend to have a large area of pith in the center.large area of pith in the center.

Major parts of a plant and their Major parts of a plant and their functions, cont’d.functions, cont’d.

A plant species producing seed with two A plant species producing seed with two cotyledons is called a dicotyledon, or cotyledons is called a dicotyledon, or dicotdicot..– All plants other than grasses are dicots. All plants other than grasses are dicots.

Soybeans, trees, lettuce, sunflowers and Soybeans, trees, lettuce, sunflowers and petunias are dicots.petunias are dicots.

– Dicot plants have broad leaves with net-type Dicot plants have broad leaves with net-type veins.veins.

– Stems are often long and branching. They Stems are often long and branching. They may be woody or non-woody.may be woody or non-woody.

Monocots and DicotsMonocots and Dicots

Absorption and Transport Absorption and Transport SystemsSystems

Water and nutrients are primarily Water and nutrients are primarily absorbed by the roots and transported absorbed by the roots and transported throughout the plant by various tissues in throughout the plant by various tissues in the roots, stems and leaves. the roots, stems and leaves.

Absorption and Transport Absorption and Transport SystemsSystems

Roots have tiny root hairs covered by thin Roots have tiny root hairs covered by thin membranes that allow water and nutrients membranes that allow water and nutrients to enter. to enter. – OsmosisOsmosis is the movement of water from is the movement of water from

greater concentration in the soil, to lower greater concentration in the soil, to lower concentration in the root.concentration in the root.

– Water enters until the concentration in the Water enters until the concentration in the root is equal to the concentration outside the root is equal to the concentration outside the root.root.

– The water entering roots also carries The water entering roots also carries inorganic substances known as nutrients.inorganic substances known as nutrients.

Absorption and Transport Absorption and Transport SystemsSystems

After absorption by the roots, water is After absorption by the roots, water is passed from cell to cell until it reaches the passed from cell to cell until it reaches the xylemxylem..– Xylem is tissue, formed as tubes, that Xylem is tissue, formed as tubes, that

conducts water up the stem and to the leaves.conducts water up the stem and to the leaves.– The The petiole petiole of the leaf takes the water from of the leaf takes the water from

the xylem in the stem to the leaf veins, which the xylem in the stem to the leaf veins, which distribute it throughout the leaf.distribute it throughout the leaf.

Xylem, PhloemXylem, Phloem

Absorption and Transport Absorption and Transport SystemsSystems

Leaves lose water Leaves lose water through through transpirationtranspiration..– Transpiration occurs Transpiration occurs

through tiny through tiny stomatastomata in leaves.in leaves.

– Transpiration creates Transpiration creates somewhat of an somewhat of an upward pull that upward pull that assists the xylem in assists the xylem in moving water and moving water and nutrients. nutrients.

Absorption and Transport Absorption and Transport SystemsSystems

Manufactured food is conducted Manufactured food is conducted (transported) from the leaves through the (transported) from the leaves through the stems to the roots in the phloem tissue.stems to the roots in the phloem tissue.– Phloem is the tissue that conducts sugars, Phloem is the tissue that conducts sugars,

proteins, hormones dissolved minerals, and proteins, hormones dissolved minerals, and salts from leaves to other parts of a plant.salts from leaves to other parts of a plant.

– The structure is observed as elongated sieve-The structure is observed as elongated sieve-type cells that form tube structures in stems.type cells that form tube structures in stems.