Form and Structure of Plants

Botany: the study of plants

What is a plant?

Living organisms which are eukaryotic and multicellular

Have organized tissues Have plastids (such as chloroplasts) Have cell walls containing cellulose

One reason the study of botany is so important to man is …

Because all the food eaten by man comes directly or indirectly from green plants. About 2/3 of the food we eat comes directly from plants and 1/3 comes from animals which eat plants.

Ways Plants are Beneficial:

Provide most of man's food Release O2 needed by man and animals

Plants are raw materials for many manufactured goods

Plants are a source of beauty

Misconceptions:

All green things are plants. All plants

are green. All plants

are

autotrophic.

morphology

the shape or form of an organism

Anatomy

the bodily structure of an organism (deals with how cells and tissues are put together)

Types of organs in plants

Roots Stems Leaves flowers

Flower

StemLeaf

Root

Plant organs are determined by their relationships to nodes

Node: a region where a leaf is or was

attached

Plant organs are determined by their relationships to nodes

Roots do not have nodes. Stems have nodes. Leaves do not have nodes but are

attached to stems at nodes.

Roots

Roots are the organs of the root system.

A root system is all the roots of a plant.

Functions of Roots

Anchors Absorbs Transports Stores food

Two Types of Root Systems

Taproots

Fibrous roots

Taproots commonly found in dicots

penetrates the soil with very little branching

often stores food (fleshy roots)

Taproots has one or a few main roots that are thicker and longer than the other roots of the plant

examples: carrots and dandelions

Fibrous Root System

commonly found in monocots

have no main section but branch out into the soil in all directions

Fibrous Root System

Has a cluster of roots that are approximately equal in size

They branch several times

Example: grasses

Types of stems

Herbaceous stems Woody stems

Herbaceous stems Softer, more flexible

type of stem Supported by cell

walls and turgor pressure

Woody plants often begin as herbaceous and then become woody as the grow older

Woody stems Hard and not very

felxible Capable of

supporting a lot of weight

Examples: trees and shurbs

Stem Functions manufacture, support, and display leaves

conduct materials

External Structures of LeavesBlade: the flat portion of a leaf

Petiole: the stalk of a leaf; attaches leaf to stem

Margin: the edge of a leaf’s blade

Veins: the pipelines that carry food & water

Node: place on stem where leaves are attached

Margin

Stipule: a small leaflike or scalelike structure on a plant that helps to cover a leaf while it is devleoping

External Structures of Leaves

Leaf Venation

Two basic patterns of leaf venation:

• Parallel Venation

• Netted Venation

Parallel Venation

A series of veins which originate at the stem and proceeds to the tip of the leaf

Occurs in monocots – corn, grass, irises, orchids

Netted Venation

Palmate: two or more main veins coming from a single point

Examples: maple, ivy, geraniums

Pinnate: if the veins branch off one large central vein called a midrib

Examples: oaks, apple trees, African violets

Classification of Leaves

Simple leaves Compound leaves

Simple or Compound?

Simple Leaves: one blade on each petiole

Simple or Compound?

Compound: more than one blade on each petiole

Each small blade on a compound leaf is referred to as a leaflet

Sessile Leaves

Sessile leaves lack petioles

Sessile Leaves

Grasses and certain other monocots have sessile leaves that attach to the stem by way of a sheath that seems to wrap around the stem

Leaf Mosaic

Alternate Opposite Whored

Leaf mosaic: the arrangement of leaves on a stem

Leaf MosaicAlternate Mosaic: leaves alternate from opposite sides of the stem (one petiole per node)

Leaf MosaicOpposite Mosaic: two leaves grow from the same point on the stem (two petioles per node)

Leaf Mosaic

Whorled Mosaic: three or more leaves grow from a single point on a stem (3 or more petioles per node)

Leaf Mosaic

Leaf Shapes

Linear Cordate DeltoidLobed

Circular

Linear Leaf Shape

long and narrow 

Lobed Leaf Shape

 

Cordate Leaf Shape

kidney or heart-shaped

Deltoid Leaf Shape

deltoid-shaped

Circular Leaf Shape

Leaf Margins

Entire Serrate Undulate Dentate

Entire Leaf Margin

smooth margin with no teeth

Serrate Leaf Margin

toothed margins

Undulate Leaf Margin

wavy margins

Dentate Leaf Margin

teeth point out