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Plant SciencePlant SciencePlant StructuresPlant Structures

Instructional Materials ServiceInstructional Materials ServiceTexas A&M UniversityTexas A&M University

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Plant StructuresPlant Structures

Parts of a Vascular PlantParts of a Vascular Plant Root StructureRoot Structure Stem Structure (External) Stem Structure (External) Leaf StructureLeaf Structure Parts of a Complete Flower Parts of a Complete Flower

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Plant Cell AnatomyPlant Cell Anatomy

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Parts of a Vascular PlantParts of a Vascular Plant

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Plant OrgansPlant Organs

Plant organs include their roots, stems, Plant organs include their roots, stems, leaves, and reproductive structures. Each leaves, and reproductive structures. Each plant organ performs a specialized task in plant organ performs a specialized task in the life of a plant.the life of a plant.

Roots, stems, and leaves are all vegetative Roots, stems, and leaves are all vegetative structures. structures.

Flowers, seeds, and fruits make up Flowers, seeds, and fruits make up reproductive structures. reproductive structures.

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Plant Organ FunctionsPlant Organ Functions

Roots support the plant and supply it with water Roots support the plant and supply it with water and nutrients. and nutrients.

Stems connect the root and leaves.Stems connect the root and leaves.

Leaves capture energy from the sunlight and Leaves capture energy from the sunlight and use it to make food for the plant.use it to make food for the plant.

Reproductive structures attract pollinators and Reproductive structures attract pollinators and produce seeds and fruits.produce seeds and fruits.

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To help prevent soil To help prevent soil erosion, which root system erosion, which root system would be best?would be best?

FibrousFibrous

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TaprootsTaproots AdvantagesAdvantages Penetrates Penetrates

deeperdeeper Obtain water Obtain water

from other from other levelslevels

Anchor plantAnchor plant

DisadvantagesDisadvantages Difficult to Difficult to

remove or remove or harvestharvest

do not stabilize do not stabilize wellwell

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PARTS OF PLANT ROOTPARTS OF PLANT ROOT

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FibrousFibrous

AdvantagesAdvantages Shallower, Shallower,

better for better for fertilization & fertilization & WaterWater

Stabilize in soil Stabilize in soil betterbetter

DisadvantageDisadvantage Less drought Less drought

resistantresistant Tend to get Tend to get

exposed during exposed during cultivationcultivation

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Primary RootsPrimary Roots Grow Grow downdown into the into the

soil and may branch soil and may branch repeatedly into repeatedly into lateral roots lateral roots

Taproot is a primary Taproot is a primary rootroot

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Lateral RootsLateral Roots

Called Secondary rootsCalled Secondary roots grow horizontally away from the grow horizontally away from the

primary root primary root Some grow downwardSome grow downward

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Root StructureRoot Structure

Xylem (water transport)

Meristem

Root Hairs

Epidermis

Cortex

Phloem Tubes

Root Cap

Zone of Elongation

Zone ofDifferentiation

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The EpidermisThe Epidermis

EpidermisThe epidermis is the outermost layer of cells surrounding the root.

The cells of the epidermis are responsible for absorbing water and minerals from the soil

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The CortexThe Cortex

Cortex

The cortex is a layer of tissue between the epidermis and the vascular tissue.

Cortex cells function in the movement of water and in food storage.

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Root HairsRoot Hairs

Root Hairs

Root hairs are found along the main root and perform much of the actual work of water and nutrient absorption.

Most plants produce root hairs that only live a few days or a few weeks. As a plant grows, new root hairs form.

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XylemXylem

Xylem is the supporting and water conducting tissue of vascular plants.

Xylem

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PhloemPhloem

Phloem is the food conducting tissue of vascular plants, made up of sieve tubes and other cellular material.

Phloem

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MeristemMeristem

Meristem

The meristem is at the tip of the root and is responsible for manufacturing new cells.

This is the area where cell division and growth occur.

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RootsRoots The root is the first plant structure to The root is the first plant structure to

emerge from a seed during germination.emerge from a seed during germination.

Roots are mostly found below the soil Roots are mostly found below the soil surface and represent about 50% of a surface and represent about 50% of a plant’s weight.plant’s weight.

The primary functions of roots are to absorb The primary functions of roots are to absorb water and nutrients from the soil and to water and nutrients from the soil and to support the plant in an upright position.support the plant in an upright position.

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Roots distribute the food energy produced Roots distribute the food energy produced in the leaves to the rapidly growing areas in the leaves to the rapidly growing areas found at the root tips.found at the root tips.

Some plants use their roots as a Some plants use their roots as a specialized food storage reserve.specialized food storage reserve.

The first root to emerge from a seed is the The first root to emerge from a seed is the primary root, or radicle.primary root, or radicle.

Root FunctionsRoot Functions

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Plant root systems are classified based on Plant root systems are classified based on the relative sizes of their primary and the relative sizes of their primary and secondary roots.secondary roots.

Plants such as dandelions, carrots, turnips, Plants such as dandelions, carrots, turnips, and most trees have a and most trees have a taproottaproot..

In taproot systems, the primary root thickens In taproot systems, the primary root thickens and becomes the dominant root.and becomes the dominant root.

RootsRoots (taproot)(taproot)

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In fibrous root systems, the primary and In fibrous root systems, the primary and secondary roots are of similar diameter.secondary roots are of similar diameter.

They remain fairly close to the soil surface.They remain fairly close to the soil surface.

FibrousFibrous root systems help to prevent the root systems help to prevent the erosion of topsoil during heavy rains.erosion of topsoil during heavy rains.

Plants such as onions, grasses, and corn Plants such as onions, grasses, and corn have have fibrousfibrous root systems. root systems.

Roots (fibrous)Roots (fibrous)

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Root TypesRoot Types

Fibrous RootsTap Root

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Stem CharacteristicsStem Characteristics

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StemsStems

Stems function as supportive structures. They hold a plant’s leaves up toward the sun so the leaves can capture energy from sunlight.

Stems transport water and nutrients from the roots to the leaves, and food energy from the leaves to the roots.

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Leaf StructureLeaf Structure

Bladestalk (Petiole)

Axillary Bud

Node

Internode Base of Leaf

Midrib

Vein

Expanded Portion of Blade (Lamina)

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Leaf CharacteristicsLeaf Characteristics

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Midrib & VeinsMidrib & Veins

Midrib The midrib is the most prominent, central vein in a leaf.

Lateral veins are secondary veins that branch from the midrib.

Both midribs and lateral veins contain vascular tissue.

Vein

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Leaf Blade (Lamina)Leaf Blade (Lamina)

Leaf Blade (Lamina)

The expanded flat portion of a leaf is the leaf blade, or lamina.

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Petiole (Bladestalk)Petiole (Bladestalk)

Petiole

The petiole attaches the lamina to the plant stem.

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Axillary BudAxillary Bud

Axillary Bud

An axillary bud exists on the stem just above the point where the leaf petiole attaches to the stem.

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Petal

Sepal

Parts of a FlowerParts of a Flower

Stigma

Anther

Receptacle

Filament

Pollen Tube

Ovary

Ovule

Embryo Sac

Microphyle

Style

Integuments

Pollen Grains

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Complete FlowersComplete Flowers

Compete flowers have four basic parts:

1. Sepals

2. Petals

3. Stamens

4. Pistil

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SepalsSepals

Sepals

Sepals are leaf-like structures that form an outer ring around the base of a flower.

Sepals enclose and protect a flower bud before it opens.

The complete ring of sepals is called the calyx.

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PetalsPetals

Petals

Petals are often the bright and colored part of a flower.

Petal colors and scents attract specific pollinators.

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StamensStamens

Anther The stamen contains both the filament and the anther.

The filament is a stalk-like structure that holds the anther.

Stamens are the male reproductive parts of a flower.

Filament

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PistilPistil

Stigma

Style

Ovary

The pistil includes three parts:

1. Stigma2. Style3. Ovary

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Pistil 1. Pistil 1. StigmaStigma

Stigma The stigma is a sticky, flattened surface that projects upwards towards the pollinator.

Birds and insects collect nectar from previously visited plants and brush against the sticky surface of the stigma.

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Pistil 2. Pistil 2. StyleStyle

Style

The style is a supportive structure that holds the stigma in a position to maximize the chances of pollination.

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Pistil 3. Pistil 3. OvaryOvary

Ovary

Pollen Tube

Ovule

The ovary is an enlarged structure that contains the female sex cells, or ovules. The pollen tube grows through the ovary and into an ovule.

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ReceptacleReceptacle

The enlarged part of the pedicel where it joins the flower is the receptacle.

Receptacle

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PedicelPedicel

Pedicel

The pedicel (flower stalk) supports the flower.

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AcknowledgementsAcknowledgements

Kristi Falco, Graduate Assistant, Instructional Materials Kristi Falco, Graduate Assistant, Instructional Materials Service, researched and developed the information used in Service, researched and developed the information used in this PowerPoint Presentation.this PowerPoint Presentation.

Christine Stetter, Artist, Instructional Materials Service, Christine Stetter, Artist, Instructional Materials Service, developed and illustrated this PowerPoint Presentation.developed and illustrated this PowerPoint Presentation...

Keith Zamzow, Curriculum Specialist, Instructional Materials Keith Zamzow, Curriculum Specialist, Instructional Materials Service, edited and reviewed this PowerPoint Presentation.Service, edited and reviewed this PowerPoint Presentation.

Vickie Marriott, Office Software Associate, Instructional Vickie Marriott, Office Software Associate, Instructional Materials Service, edited this PowerPoint Presentation.Materials Service, edited this PowerPoint Presentation.

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Instructional Materials ServiceInstructional Materials Service

Texas A&M UniversityTexas A&M University

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College Station, Texas 77843-2588College Station, Texas 77843-2588

http://www-ims.tamu.eduhttp://www-ims.tamu.edu  20062006