What Is the Difference Between Annuals, Biennials and Perennials? Plants are often classified based on their life cycles. Even though gymnosperms and

What Is the Difference Between Annuals, Biennials and Perennials?

• Plants are often classified based on their life cycles.

• Even though gymnosperms and angiosperms reproduce by seed, there are different strategies for passing the seeds on to future generations.

Annuals• Plants grow from seed,

flower, produce new seeds all in one season.

• It dies after producing new seeds.

• Have an herbaceous stem – green & fleshy.– Ex. Impatiens, corn,

snapdragons.

Courtesy of Wm. C. Brown Publishers

Corn – Zea mays

See life cycle

Biennials• Plants that live for two

years, then flower and die.

• Food is produced during the first year, flowers the second year.– Ex. Foxglove, carrot,

queen Anne’s lace.

Foxglove – Digitals purpurea

Courtesy of Wm. C. Brown PublishersSee life cycle

Perennials• Plants that live for three or

more years• Flower for a short time• Do not die after flowering• Can be herbaceous or woody

– having thick stems made of wood– Ex. Tulips, Kentucky bluegrass,

trees and shrubs

Bristlecone pine – Pinus longaeva

Courtesy of Wm. C. Brown PublishersSee life cycle

Courtesy of Interstate Publishing

Germination----Growth---Flowering----Death

Germination---- Growth---Flowering----Dormancy

One or more flowering cycles

Germination---Growth---Dormancy---Growth---Flowering---Death

Season 1 Season 2

Back to Annuals

Back to Perennials

Back to Biennials

What Are the Functions of a Plant’s Roots?

• A plant’s health is directly related to its roots.

• Weak and diseased roots decrease a plant’s health.

What Are the Functions of a Plant’s Roots?

• Roots need to continuously grow in order to stay healthy.

• This is why plants become pot-bound: the roots start growing out of the pot because it is too small.

A pot bound plant in need of

transplanting

Courtesy of Delmar Publishing

Functions of a Root System• 1. Absorb water and minerals

from the environment.• 2. Anchor the plant in the

ground.• 3. Store food that has been

made in the leaves by photosynthesis.– Can be used later by the plant to

grow and survive.

Taraxacum officinale – the common dandelion


What Are the Parts of a Root?

• When a seed germinates, the first structure to appear is the root, or radicle.

• A. It becomes the primary root– Usually the most important root in some plants.

• B. Other roots branch out from the primary root; called secondary roots.


Cotyledon Radicle = Primary root; notice all the root hairsCourtesy of McGraw Hill


• C. The apical meristem, found at the root tip, is where new cells develop.– It is covered by the root cap – protects it from

damage as it passes through coarse soil particles.

Epidermis

Vascular cylinder (xylem & phloem)

Cortex (food storage)

Root Cap

Apical meristem

Courtesy of Dorling Kindersley, Inc.

What Are the Parts of a Root?• D. The surface of the root is protected by skin

cells called the epidermis.– Where water and minerals enter the root by osmosis

& diffusion.– Can grow long, hair like projections called root hairs.– They greatly increase the surface area of the root to

allow more water intake.

Courtesy of Delmar Publishing

Two Types of Root Systems• Plant root systems are organized in two

basic ways; It has to do with primary and secondary roots

• A. A root system comprising one main primary root and many secondary roots branching off the primary root is called a taproot system– Ex. Carrot, Parsnip, Oak – Their roots reach far into the ground; they can

be several feet long

Examples of Taproots

Carrot Beet Sweet potato


Two Types of Root Systems• B. A system which has no dominant

primary root but is made of many primary and secondary roots of similar size is called a fibrous root system

• Ex. Grasses, Magnolia, Rhododendron, Euonymus

• The roots are smaller, shorter and more compact; They usually never grow below the first 6-12 inches of soil– These roots form a large network underground

Fibrous Root System of Grass

Courtesy of McGraw Hill Publishing

What Does a Healthy Root System Look Like?

• A healthy root system is white or nearly white in color and smells fresh, or earthy.

• If roots are black, brown, or dark orange and smell rotten or sour, the root system is having some problems.

• Watering a plant properly is one of the most important ways to keep the root system healthy.

What Does a Healthy Root System Look Like?

• If the plants are grown in pots, be sure that there are drainage holes in the bottom to allow excess water to drain.– Soak the pot until the growing medium is

saturated and water drips out of the drainage holes.

– This encourages the roots to grow through the entire pot.

What Are the Functions of a Stem?

• Stems have many important jobs in a plant.• They are responsible for the size and shape of

a plant.• Some are made of wood and some are

herbaceous.• There are four functions of the stem.

Functions of a Stem

• 1. Stems support the leaves.– Able to stretch the leaves into the best

positions for catching sunlight.• 2. Move water, minerals and food

through the whole plant.• 3. Can also produced food through

photosynthesis.– Not its main job, but will occur in plants

with small or no leaves.

Functions of a Stem

• 4. Store food that has been manufactured by the plant.

Stems of bamboo plant

Courtesy of McGraw Hill Publishing

What Are Some of the Structures on the Outside of a Stem?

• There are many structures on the stem which are very useful to us in identifying plants.– Sometimes it is easier to identify a plant by its

stem rather than its leaves.• There are eight structures found on the

outside of a stem:– 1. Terminal bud – contains apical meristem;

found at the tip of a stem; it increases the length of a stem.


• 2. Node – where the leaf and bud attaches to the stem.

• 3. Internode – distance between two nodes; tells how much the tree grew in one season.


• 4. Lateral bud – also called the axillary bud; develops into a leaf or flower.

• 5. Lateral and terminal buds are protected by bud scales – helps the bud survive harsh climate changes; when the bud opens in the spring, the scales fall off leaving a bud scale scar.


• 6. Leaf scar – is the remains of the leaf after it has fallen off of the tree; it is just below the lateral bud.– If you look closely at the scar, you can see the

remains of the vascular tissue (xylem & phloem).

• 7. Lenticels – are small spots on the stem that allow a stem to exchange gases (oxygen & carbon dioxide) with the environment.

External Parts of a Stem

Terminal bud

Leaf scar with vascular bundle scars

Lateral bud

Lenticel

Bud scale scar

Node – where leaf & bud attach

Internode – distance between 2 nodes

What Are Some of the Internal Structures of a Stem?

• Inside of the stem, there are tissues that are used for transport of materials through the plants.

• Stem tissues are organized in one of the following ways:– They are found in small bundles scattered

throughout the stem.• They look like smiley faces.• Characteristic of monocots.

Courtesy of Corinne Banowski

Monocot bundle


• They are also found in rings around the stem.– They look like candy-corns.– Characteristic of dicots.– This is what gives the plant annual rings.

• Determines the age of a plant.

Dicot bundle

Courtesy of McGraw Hill Publishers


• There are three important tissues found inside the stem:

• A) xylem – conducts the water and minerals upward throughout the plant.– Made of tube-like cells which grow together to

conduct liquids.– Tends to be found closer to the center of the stem.


• B) Phloem – conducts the food that is produced in the leaf downward to the rest of the plant.– These cells also form tubes.– Tends to be found towards the outside of the

stem.


• C) Cambium – the tissue responsible for the production of new xylem & phloem.– Also increases the girth (width) of a stem.– Generally found between the xylem and phloem.

Location of Vascular Tissues

Xylem

Phloem

Vascular Cambium

Notice that monocots do not have cambium

What Are Some Different Kinds of Specialized Stems?

• We generally expect stems to be upright and above ground; however there are many stems that do not fit this mold.

• Some stems are modified to store food or help the plant reproduce.

• Some stems grow beneath the soil instead of above it.

• There are five types of specialized stems.

Five Types of Specialized Stems

1. Bulb• A very short, flattened stem.• Has several fleshy leaves.• Tend to be found beneath the soil.

– Ex. Onion, garlic



2. Corm • A spherical structure similar to a bulb.• Most of the corm is stem (unlike the bulb which

is mostly leaves).– Ex. Gladiolus



3. Rhizome• A thick underground stem. • Lies horizontally.

– Ex. Hosta, – Mother-in-Law’s Tongue

Leaf

Scale like leaf at each node

Adventitious rootsCourtesy of McGraw Hill Publishers


4. Stolon• A horizontal stem.• Lies above ground.• Sometimes called runners.• Tend to be involved in spreading the plant.

– Ex. Strawberries



5. Tuber• A rhizome with a tip that is swollen with

stored food.– Ex. Potatoes


What Are the Main Parts of a Leaf?

• Leaves are the primary food producing organs of a plant.

• They are designed to efficiently collect light and use that light energy to produce food.– Remember that this process is called

photosynthesis.

• There are several parts of a leaf:

Main Parts of a Leaf

• 1. Tip or apex – this is the top of the leaf; It can be pointed, round, smooth, etc.

• 2. Margin – is the edge of the blade; This is quite specific to each species of plant.– Some are smooth, toothed, lobed or incised.


• 3. Midrib – the central vein running down the center of the blade.

• 4. Veins – contain the xylem & phloem of the plant.– They can be parallel or netted in arrangement.


• 5. Base – is found at the bottom of the blade; Like the apex, it can be round, heart shaped, flat, etc.

• 6. Petiole – is known as the leaf stem; It is not exactly like a stem, but it does hold xylem & phloem; Holds the blade away from the stem.


• 7. Blade – the main collecting structure of the leaf; Has a large, broad surface.– Has many layers which help the plant move and

store photosynthetic materials and by-products.


Tip/Apex

Midrib

Margin

Veins

Base

Petiole

Blade

Leaf

Courtesy of Corinne Banowski

What Are Some of the Major Types of Leaves?

• There are many different types of leaves.• Some are adapted to hot, dry climates.

– They store water in their leaves or are smaller in size.

• Some have very large blades to collect maximum light in shady locations.

• Some plants have their blades broken into many sections.


• A leaf which has only one blade on its petiole is called a simple leaf.– Most plants have simple leaves.



• When the blade is divided into three or more sections, it is said to be a compound leaf.– There are many different kinds.


Types of Compound Leaves

Odd Pinnately

Compound

Even Pinnately

Compound

Palmately Compound


What Are Some Vein Patterns Found in Leaves?

• Veins of flowering plants are found in several patterns.– Most patterns can be categorized into two main

groups.– A. Parallel veins – found in monocots.

• None of the veins on the whole leaf will cross each other.

• It may look like they fuse together at the top or bottom of the blade.

What Are Some Vein Patterns Found in Leaves?

• B. Netted veins – found in dicots.– They connect & branch from each other.– Some have several smaller veins branching out

of a dominant midrib.• Known as pinnately netted.

– Other leaves have several dominant veins (midribs) branching from the petiole.• Known as palmately netted.

– A few have a spreading vein pattern called dichotomous venation.• Seen in the Ginkgo tree.

Types of Leaf Venation

Parallel Netted Veins

Pinnately Netted Veins

Palmately Netted Veins

Courtesy of Wm. C. Brown and McGraw Hill Publishers

Dichotomous Netted Veins

How Is A Leaf Organized?

• A leaf is organized to collect sunlight and turn it, through photosynthesis, into food.

• The leaf has many layers of tissue to allow this to happen:– 1. Cuticle – on top of the leaf is a waxy non-

cellular layer.• Prevents water from escaping the leaf.• It is usually very thick on plants in arid regions.


• 2. Epidermis – the next layer of the leaf.– Used for protection.– Skin-like layer found on the top & bottom of the

leaf surface.– May be one or more cell layers thick.

• 3. Palisade mesophyll – directly beneath the epidermis.– Standing on end & packed very tightly.– Responsible for most photosynthesis.


• 4. Spongy mesophyll – under the palisade layer.– Loosely packed cells.– Have numerous air spaces which hold the raw

materials used and products of photosynthesis.


• 5. Stomata – usually on the lower epidermis.– Tiny holes for gas exchange; They can open &

close.

• 6. Guard cells – control the opening & closing of the stomata.– Found on either side of the stomata.

Internal Parts of A Leaf

Petiole

Blade

CuticleUpper EpidermisPalisade Mesophyll

VeinSpongy Mesophyll

Lower Epidermis

Guard CellStomataAir Spaces

Stoma, singular


Summary

• How is a blade different from a leaf?• Compare a midrib to a vein.• What is the edge of a leaf called?• How is a simple leaf different from a

compound leaf?• Can you give an example of a simple or

compound leaf?• What are the four types of venation within

the leaf?

Summary

• What protects the leaf on the outside? (It is a waxy coating).

• What is the function of the epidermis?• Compare the palisade layer with the spongy

layer.• What is the purpose of a guard cell?• Where does gas exchange occur on the

leaf?

What Are the Parts of A Flower?

• Flowers are the most obvious part of most plants.

• They are made of many intricate and important parts.

• Most flowers contain male and female parts.


Parts of a Flower

• 1. Stamen – the male part of a flower; Made up of two parts:– Filament – stalk of a stamen; Holds up the

anther.– Anther – sack-like portion containing the

pollen.• Pollen – grain released by the flowers; Contains

the sperm.– Flowers containing only stamens are called

staminate.

Parts of a Flower

• 2. Pistil – female part of the flower; Made up of three parts:– Stigma – sticky organ which receives the pollen

grains.– Style – a rod shaped middle part; Similar to the

stalk of the stamen.– Ovary – swollen base containing the eggs or

ovules.– Flowers having only female parts are called

pistillate.

Parts of a Flower• 3. Petals – the showy, colorful leaf-like

structures which often attract animals or insects for pollination.– When all the petals are fused together, it is

called the corolla.• 4. Sepals – beneath the petals; More leaf-

like structures usually green in color– Protect the flower before it opens.– When all the sepals are fused together, it is

called the calyx.

Parts of a Flower

StamenAnther

Filament

PetalsSepals

PedicelStem of the flower

Ovule

ReceptacleSwollen base where are parts attach

Stigma

Style

Ovary

Pistil


What is the Purpose of a Flower?

• We use flowers for many practical purposes like food, clothing and medicine; We also use them for aesthetic purposes – to beautify our homes.

• The main purpose of a flower is to reproduce sexually with other flowers or with itself.


• The first step of reproduction begins with pollination (the process of transferring pollen to stigma), and there are two types:


• A) Cross-pollination is when the pollen of one plant lands on the stigma of a different plant;

• Keep in mind that the plants must be of the same species (for example, two dandelions)


• B) Self-pollination occurs when the pollen of the anther lands on the stigma of the same plant.

• Pollen is carried to plants by animals, wind, gravity, water and many other methods.


• Once the pollen reaches the stigma, it starts to grown down the style depositing the sperm in the ovary.

• When the sperm and egg combine, it is called fertilization.

Courtesy of Interstate Publishers

Pollination and FertilizationThis picture shows self-pollination (pollen is being transferred from the anther to stigma of the same plant)

Notice that one or more pollen grains will start to grow a tube down towards the ovary

The sperm nucleus will then fuse with the nucleus of the egg(s) (ovule).


What Are Some of the Different Types of Flowers?

• Flowers come in many shapes, sizes and colors.

• Not all of them have all the structures mentioned before.


• A. Complete flowers have all the major parts: stamens, pistils, sepals & petals.

• B. Incomplete flowers are missing one or more of these major parts; for example a flower could be missing sepals or pistils.


• C. Perfect flowers have both stamens and pistils on the same flower.

• D. Imperfect flowers are missing either the stamens or pistils.

How is a Monocot Flower Different From a Dicot Flower?

• A good way to tell the difference between a monocot and a dicot is to look closely at the flowers.

• Monocots have flower parts in multiples of 3 (3,6,9,12).

• Dicots have flower parts in multiples of 4 or 5 (4,12,16 or 5,10,15).

Summary • What is the male part of a flower called?• What are the two parts of the stamen and what

do they do?• What is a pistil? And what are its three parts?• What is a staminate flower? Is it perfect or

imperfect?• How is the corolla different from the calyx?• What part of the flower usually attracts

pollinators? • How is pollination different from fertilization?

Summary• What are some ways in which a plant can be

pollinated?• What are the two types of pollination and how are

they different?• Describe how the sperm gets to the egg of the

flower?• Can you have a perfect, incomplete flower and why?• Can you have an imperfect, complete flower and

why?• How can you tell the difference between a monocot

and a dicot flower?

Documents

What Is the Difference Between Annuals, Biennials and Perennials? Plants are often classified based on their life cycles. Even though gymnosperms and