Plants and Fungi

By the end of this class you should understand:

• The differences between algae, plants and fungi, and between groups of plants

• The role of vascular structures in organisms• The reproductive cycles of different plants and

fungi• The functions of major structures and

materials unique to each group

Algae, Plants, and Fungi

• Algae, plants, and fungi are all different groups of living things– Easy to lump together

because they are all immobile

• Commonality: Cell walls!• Major differences exist

between the three groups

Structure and Lifestyle

• Algae: Photosynthetic and have cell walls but their cells are not organized into tissues and organs– Also can’t live on land

• Fungi: Have cell walls but are not photosynthetic– Fungi must grow on their food

• Plants are photosynthetic and have tissues/organs

Apparent Tangent:

• If you want to build a building with bathrooms on every floor but you don’t have good pipes, how tall can you make the building?

• If you have good pipes, how tall can you make the building?

Plant Structures• A major development that

separates most plants from algae is being vascular– A vascular plant has xylem and

phloem• Vascular structures help bring

water from roots up to the leaves, and sugar from leaves to the roots– Xylem brings water up– Phloem brings sugar down

Algae, Mosses and Ferns

• There are clearly more advanced structures in each of these groups– Algae are completely

nonvascular and live in water– Bryophytes (including mosses)

are plants that can live on land but are restricted in height because they are not vascular

– Ferns are vascular plants• Date back to before the dinosaurs

Moss & Fern Life Cycle• Mosses and ferns are clearly

related because they have similar life cycles

• Rather than produce gametes that immediately fertilize to make new plants, their gametes undergo mitosis and grow into a gametophyte

• Gametophytes produce gametes through mitosis that fertilize to make a sporophyte

Behold the Multistage Life Cycle!

Additional Note on Plant Sex

• Some plants are divided into male plants and female plants– One plant produces male

gametes or pollen, another plant produces female gametes

• Other plants are hermaphrodites, and each plant can make both male and female gametes– Some of these hermaphrodites

can self-pollinate, others are restricted from doing so

Plant-Only Structures

• Plants grow their sturdy structures (including xylem and phloem) using carbohydrates– Made from photosynthesis!

• Sugars linked into a mesh called lignin are super-durable– Wood is made with lignin

• Cell walls are usually made of another carbohydrate compound called cellulose

Additional Plant Structures• Unlike algae, plants can

grow on land– Use lignin to stand up

straight– Use vascular structures to

bring water into plant• Plants have different

organs to adapt to living on land– Roots– Stems– Leaves

Plant Groups

• Bryophytes– Mosses

• Seedless vascular plants– Ferns

• Seed plants– Gymnosperms

• Plants with pinecones (pine, redwood, etc)

– Angiosperms• Flowering and fruiting plants

Bryophytes• Mosses and similar small plants

such as liverworts• The large part of the plant is

usually the gametophyte (haploid)– Produces small sporophytes that

produce new spores through meiosis

• No xylem/phloem, allow nutrients and water to diffuse across its surface– Thus limited in size

Seedless Vascular Plants• Ferns are the most common

example of seedless vascular plants– Seedless: sporophyte/gametophyte

stages– Vascular: have xylem/phloem so

can get tall• The sporophyte is the main plant– Gametophytes are produced by the

small structures on the underside of the leaves

– Produce spores that grow into new ferns

Seed Plants• Seeds are a more recent

invention of plants– First gymnosperms appeared

around 300 million years ago• Seeds are useful because they

are durable and can wait for the right moment to start growing– As opposed to new sporophytes

which don’t have a protective covering at any point

• Divided into gymnosperms and angiosperms

Seed Structure• Seeds are formed from the

fertilization of a microspore (pollen) and megaspore (ovule)– This occurs at the flower

• A seed always has a protective coating around the new embryo, stored food for the embryo, and usually a delivery system for getting it away from the parent plant– In angiosperms this delivery system

is called a fruit (not always delicious)

Gymnosperm• Gymnos refers to nudity– The gymnasium is so called

because the Greeks always exercised naked

• Gymnosperms have “naked seeds” with no fruit– Does have a protective armor

around the seeds– These are what we think of as

pinecones• Pines, redwoods, conifers

Angiosperm• Angiosperms have flowers for

improved fertilization– All other plants must depend on

wind fertilization only, and some angiosperms do as well

• Angiosperms all produce fruits for their seeds– The fruit serves as a delivery

system for separating the offspring from parents (seed dispersal)

– Reduces competition

Examples of Seeds and Fruits

Flower Anatomy• Flowers vary wildly in structure (of course) but all

have certain features in common:– Petals (often to attract pollinators)– Stamen (produce pollen)– Carpel (holds ovule and allows fertilization)

• Flowers often have some method of attracting animals to bring the pollen from one flower to another– Edible pollen– Nectar– Structures that resemble female insects

Generic Flower

Fungi

• Fungi diverged from protists around the time of the Cambrian Explosion (500+ mya)

• Fungi are actually more closely related to animals than to plants– Their cell walls are made of chitin,

the same material in an insect exoskeleton

• Mushrooms, molds, and yeasts are all fungi

Fungal Anatomy

• All fungi live as tiny interconnected threads that grow inside their environment such as the soil– Each thread is called a hypha (plural

hyphae)– A cluster of hyphae is called a

mycelium• The large cap that grows out of

the ground is the reproductive fruiting body of the fungus which remains buried underneath

Fungus Food

• Fungi grow on their food and digest it externally– No internal digestive system

• By secreting enzymes on their food, they break it down, then absorb the nutrients through their cell walls– Nutrients can diffuse from one cell to the next, but they

have no vascular system and so are limited in height

Giant Fungi?

• Since fungi have no vascular system they cannot grow very tall– They can, however, grow sideways

a very large distance• The largest known organism on

earth is a fungus that covers at least 4 square miles (over 2000 acres) in Oregon– WTF

Hyphae in Action

• Many fungi do not produce any fruiting body and are entirely made of hyphae– These are called molds or yeasts

• The hyphae are actually haploid and only fertilize to make a zygote during mating season– The zygote immediately undergoes

meiosis to make more hyphae

Mushroom Anatomy• In mushroom species, the stalk and cap are formed by

the hyphae after they have undergone cytoplasmic fusion– This means that two haploid cells have fused their cytoplasm

but not their nuclei– This is written as the cells being n+n instead of 2n

• In the mushroom cap, the nuclei fuse, a zygote is formed, and then it undergoes meiosis to make more new spores for hyphae

Fungus Environments

• Fungi grow on their food since they can’t chase after it– Fungal spores are spread by the wind

and land on all sorts of things that are edible

• Many fungi grow in soil eating dead things

• Some fungi grow on our food (bread molds)

• Some fungi grow on our flesh!

Fungal Infections• Fungi that grow on a living thing

are using a parasitic feeding strategy

• In humans and other animals, fungal infections can be a source of disease (athlete’s foot, yeast infections, ringworm)

• Many fungi can grow on specific plants and kill them for food (often called rusts)– The famous potato blight in

Ireland was a protist similar in structure to a fungus

Fungi as Partners• Some fungi live in a symbiotic

relationship (mutually beneficial) with other organisms

• Lichen are a composite organism with algae or cyanobacteria living inside the cell walls of fungi– How does each side benefit?

• Some fungi grow on roots of plants, call mycorrhizae (singular: mycorrhiza)– How does each side benefit?

See you in lab!