Introduction to Plants

Classification of plants• Kingdom Plantae

– Phylums• Lycodiophyta (Club Mosses)• Equisetophyta (Horsetails)• Psilotophyta (Wisk Ferns)• Polypodiophyta (Ferns)• Cycadophyta (Cycads)• Ginkgophyta (Ginkoes)• Pinophyta (Conifers)• Gnetophyta (Vessel-bearing Gymnosperms)• Magnoliophyta (Flowering Plants)

Facts…• critical to other life on this planet because they

form the basis of all food webs

• Most plants are autotrophic

• earliest fossils found have been aged at 3.8 billion years

• scientific study of plants, known as botany

• identified about 350,000 extant (living) species of plants – ~258,650 are flowering and ~18,000 bryophytes

What are plants?

• Multi-cellular organisms

• Make own food (photosynthesis)

• Have chloroplasts

• Have rigid cell walls made of cellulose

• Found all over the world

Plants provide:• Food• Oxygen• Medicines• Building

materials• Textiles (fibers)• Coloring

pigments

Plant Classification

E X : G in ko E X : con ife rs

G ym n osp e rm s"n a ke d se ed s"

co n es , no f low e rsn e e d le -like lea ves

E X : g ra sses E X : o rch ids

M o no co ts

E X : o a k tree E X : b ro cco li

D ico ts

A n g io sp e rm sflo w erin g p la n ts

la rg es t g ro up

W ith se e ds

M o sses F e rns L ive rw o rts H o rse ta ils

W itho u t se e dsn e ed w a te r to

re p ro d uce ;sp o res

P la n ts

Plants Without Seeds

• Need water to reproduce• Reproduce with spores• Include

–Mosses–Ferns–Horsetails–Bladderworts

Plants with Seeds

• 2 types

• Found all over the world

Gymnosperms• Means “naked seed”

• Often have cones & needle-like leaves

• Do not have flowers

–Ex: conifers, gingko

Angiosperms

• Flowering plants

• Largest group– Moncots

– Dicots

Monocots

Dicots

Evolution

• Principal photosynthetic organisms were microscopic cells floating below the surface of the water, closer to the sun’s rays

• As they multiplied, depleted resources of the open ocean, so colonies could be found nearer to the shores, in order to get minerals and nutrients from runoff

• About 650million years ago, diversity of these organisms abounded on the rocky shores, and some even integrated into multicelluar bodies

Evolution

• These new multicelluar photosynthetic forms developed a cell wall due to the rough waters of the rocky coastline

• As size increased, they developed internal structures that linked the photosynthesizing parts to the non-photosynthesizing parts

Evolution to land..

• Oxygen & carbon dioxide not as abundant in the water, as it is not as free circulating as it is on land

• Critical factor to adapting to land is water resources

• Development of root systems to be able to keep plant stable on land and to seek out water resources without moving

RootsWhat do they do for the plant???

Are you Rooted?

• Roots help to keep plants in place.

• They spread out into the soil and “attached” themselves to the particles of the soil.

• Why do they reach and probe?– To find nutrients and water, thus in the end

the plant gets anchored into the soil.

Are you Rooted?• Plants get the water they need

for photosynthesis through their roots.

• The roots have a type of cell called a root hair cell - these project out from the root into the soil. Roots have a big surface area and thin walls, which allow water to pass into them easily.

• Note that root cells do not contain chloroplasts, as they are normally in the dark and cannot photosynthesis.

Are you Rooted?• The water absorbed by

the root hair cells passes through the plant in xylem tubes, and eventually reaches the leaves. If a plant does not absorb enough water, it will wilt or go floppy. Without water it may also not photosynthesis quickly enough, and it may die.

Root Hairs• Water in the soil is

taken up by root hairs and then passes from cell to cell to the xylem.

Types of Roots

• Generally grasses have this type of root

• Many roots extend into the soil from base of plant

• One or more large roots extending into the soil

• Smaller roots branch off

Fibrous Roots Tap Roots

Types of Roots• Shallow roots

– Desert roots

– Quickly growing plants

• Deep underground roots

– Areas with little rainfall

• Deep and Shallow Roots– Takes

advantage of underground water sources and occasional showers.

Root Growth

• Amount of moisture in the soil

• Type of soil

• How quickly the plants grow and go to seed

• Type of rainfall in that area

• Type of plant – prop roots are used to help support the plant

What does it depend on?

Lastly…• Roots are used as food storage for

plants. They store sugars and starches to help plants over winter.

• Sugar storage in roots also help to send up new shoots each spring, and to regenerate stems and leaves that were eaten or burned.

• Radishes, carrots, turnips – store large amounts of food in the form of starch in their roots. We eat these roots as a source of energy.

Plant Functions

What do stems & leaves do for a plant???

Stems

Stems also carry water and minerals up from the roots to the leaves to help with photosynthesis and take food back down to be stored and distributed to the plant as it has need.

The stem is a part of the plant that holds up other structures such as the leaves and flowers. This is important as the leaves need to be held up to the sun to get its light for photosynthesis and the flowers need to be held up to be available for pollination.

StemsThe tubes in the stem that take the water and minerals up into the plant are the xylem and the tubes that carry the food back down are called the phloem.

Transport of Materials

• Phloem (2)– Carries sugars (food)

up & down in plant

• Xylem (1)– Carries water &

mineral up from roots to all parts of plants

Leaves

The leaf is a part of the plant that is charge of making food for the plant. This food making process is called photosynthesis.

Parts of the leaf• Petiole - a thin

stalk that connects the blade of the leaf to the plant's stem. These veins are called

• Blade - a thin, flat part of the leaf that extends off the end of the petiole. It is green as it contains chlorophyll which is necessary in making the plant's food.

Primary vein: is the main vein starting at the base of the leaf. It is noticeably wide than the other veins.

Secondary veins: veins usually branching off the primary vein, are noticeably narrower than the primary vein.

Leaf Cross Section

• Plants get carbon dioxide from the air through their leaves. The carbon dioxide diffuses through small holes in the underside of the leaf called stomata.

Leaf Cross Section

• The lower part of the leaf has loose-fitting cells, to allow carbon dioxide to reach the other cells in the leaf. This also allow the oxygen produced in photosynthesis to leave the leaf easily.

Leaf Cross Section• A leaf usually has a large

surface area, so that it can absorb a lot of light. Its top surface is protected from water loss, disease and weather damage by a waxy layer.

• The upper part of the leaf is where the light falls, and it contains a type of cell called a palisade cell. This is adapted to absorb a lot of light. It has lots of chloroplasts and is shaped like a tall box.

Photosynthesis

• Leaves collect sunlight, water and carbon dioxide to make sugar (food) for the plant

• The chemical equation for this process is

• 6 H2O + 6 CO2 C6H12O6 + 6 O2

sugar

Sun en

ergy

Respiration

• Leaves break down sugars to get energy

• This process releases excess water as waste

• The chemical equation is C6H12O6 + 6 O2 energy + 6 H2O + 6 CO2

Ener

gy re

leas

ed

To h

elp

plan

t gro

w

sugar

Transpiration

• Taking in CO2 and releasing O2 and H2O as waste products after respiration

Angiosperms Monocots

Has 1 food part Parallel veins Petals in groups

of 3, 6, 9 Xylem & phloem

scattered throughout stem

Angiosperms Dicots

Have 2 food parts

Net-like veins Petals in groups

of 4 or 5 Xylem & phloem

are ring-like in stem