BiologyBiology

Plant ClassificationPlant Classification

Transition Year

H. Jones, St. Columba’s College

Introduction to PlantsIntroduction to Plants Plants are classified into four main Plants are classified into four main

group:group:

1.1. Mosses and LiverwortMosses and Liverwort (Bryophyta) (Bryophyta)

2.2. FernsFerns (Pteridophyta) (Pteridophyta)

3.3. Conifers Conifers (Gymnosperms)(Gymnosperms)

4.4. Flowering PlantsFlowering Plants (Angiosperms) (Angiosperms)

All are distinctly different in All are distinctly different in

appearance, structure and behaviour.appearance, structure and behaviour.

Mosses - Mosses - BryophytaBryophyta Mosses are non-vascular plants -- they Mosses are non-vascular plants -- they

cannot transport fluids through their cannot transport fluids through their bodies. bodies.

Instead, they must rely on surrounding Instead, they must rely on surrounding moisture to do this job for them. moisture to do this job for them.

Though small in stature, mosses are Though small in stature, mosses are very important members of our very important members of our ecosystem. ecosystem.

They lay the foundations for other plant They lay the foundations for other plant growth, prevent erosion, and contribute growth, prevent erosion, and contribute to the lush green appearance of many to the lush green appearance of many forested areas. forested areas.

Mosses - 2Mosses - 2 The 24,000 bryophyte species, The 24,000 bryophyte species,

sometimes grouped into a single phylum sometimes grouped into a single phylum are now grouped in three phyla: are now grouped in three phyla:

1.1. MossesMosses ( (BryophytaBryophyta), ),

2.2. LiverwortsLiverworts ( (HepatophytaHepatophyta) and ) and

3.3. HornwortsHornworts ( (AnthoceraphytaAnthoceraphyta). ). They reproduce by They reproduce by sporesspores, never have , never have

flowers, and can be found growing on flowers, and can be found growing on the ground, on rocks, and on other the ground, on rocks, and on other plants.plants.

MossesMosses

Liverworts and HornwortsLiverworts and Hornworts

Life CycleLife Cycle Moss plants have two generations, the Moss plants have two generations, the

gametophytegametophyte and and sporophytesporophyte.. The first generation, the The first generation, the gametophytegametophyte, forms the , forms the

green leafy structure we ordinarily associate with green leafy structure we ordinarily associate with moss. moss.

It produces a sperm and an egg (the gametes) It produces a sperm and an egg (the gametes) which unite, when conditions are right, to grow into which unite, when conditions are right, to grow into the next generation: the the next generation: the sporophytesporophyte or spore- or spore-bearing structure.bearing structure.

The moss sporophyte is typically a capsule growing The moss sporophyte is typically a capsule growing on the end of a stalk called the on the end of a stalk called the setaseta. .

The sporophyte contains no chlorophyll of its own: The sporophyte contains no chlorophyll of its own: it grows parasitically on its gametophyte mother. it grows parasitically on its gametophyte mother.

As the sporophyte dries out, the capsule release As the sporophyte dries out, the capsule release spores which will grow into a new generation of spores which will grow into a new generation of gametophytes, if they germinate. gametophytes, if they germinate.

Life Cycle of the Moss Life Cycle of the Moss

The Fern - The Fern - PteridophytaPteridophyta Ferns have a vascular system to transport fluids Ferns have a vascular system to transport fluids

through their bodies but like the mosses, they through their bodies but like the mosses, they

reproduce from spores rather than seeds. reproduce from spores rather than seeds.

The main phylum, the The main phylum, the FernsFerns ( (PteridophytaPteridophyta) )

includes around 12,000 species.includes around 12,000 species.

Three other phyla are included as fern allies: Three other phyla are included as fern allies:

the the HorsetailsHorsetails, , Club MossesClub Mosses and and Whisk Whisk

FernsFerns

Ferns also have a Ferns also have a gametophytegametophyte and and

sporophytesporophyte stage, but the gametophyte stage stage, but the gametophyte stage

is much reduced.is much reduced.

Life Cycle of FernLife Cycle of Fern The gametophyte generation of ferns are The gametophyte generation of ferns are

small, heart-shaped, plants called small, heart-shaped, plants called prothalliaprothallia (singular: (singular: prothalliumprothallium). ).

They are less than an inch (1 - 2 cm) in They are less than an inch (1 - 2 cm) in diameter and look very much like thalloid diameter and look very much like thalloid liverworts or hornworts. liverworts or hornworts.

Male and female sex organs are located on Male and female sex organs are located on the underside of the prothallium and, when the underside of the prothallium and, when conditions are right, the sperm swims from conditions are right, the sperm swims from the male the male antheridiumantheridium to fertilize the egg in to fertilize the egg in the the archegoniumarchegonium. .

A new adult (sporophyte) fern plant will A new adult (sporophyte) fern plant will grow from the prothallium.grow from the prothallium.

Conifers - Conifers - GymnospermsGymnosperms The gymnosperms add the next level of complexity The gymnosperms add the next level of complexity

to plant evolution: they reproduce from seeds to plant evolution: they reproduce from seeds instead of spores. instead of spores.

The seeds, however, are "naked" (Greek: The seeds, however, are "naked" (Greek: gummnosgummnos) ) -- not covered by an ovary. -- not covered by an ovary.

Usually, the seed is produced inside a cone-like Usually, the seed is produced inside a cone-like structure such as a pine cone hence the name structure such as a pine cone hence the name "conifer." "conifer."

Some conifers, such as the Yew and Ginko, produce Some conifers, such as the Yew and Ginko, produce their seeds inside a berry-like structure. their seeds inside a berry-like structure.

Conifers are fairly easy to identify: In addition to the Conifers are fairly easy to identify: In addition to the aforementioned cones, these trees and shrubs aforementioned cones, these trees and shrubs typically have needle-like, scale-like or awl-like typically have needle-like, scale-like or awl-like leaves. leaves.

And they never have flowers. And they never have flowers.

Conifers - 2Conifers - 2 Approximately 600 species are counted as Approximately 600 species are counted as

conifers including the pines, firs, spruces, conifers including the pines, firs, spruces, cedars, junipers, and yew. cedars, junipers, and yew.

Species within the conifer ranks give us pine Species within the conifer ranks give us pine nuts -- pesto's magic ingredient -- as well as nuts -- pesto's magic ingredient -- as well as juniper berries for gin. juniper berries for gin.

Conifer allies include three small phyla Conifer allies include three small phyla containing fewer than 200 species all together: containing fewer than 200 species all together:

GinkoGinko ( (GinkophytaGinkophyta)) CycadsCycads ( (CycadophytaCycadophyta) ; ) ; And herb-like cone-bearing plants And herb-like cone-bearing plants

((GnetophytaGnetophyta) such as Ephedra. ) such as Ephedra.

Scientific Names and Scientific Names and ClassificationClassification

Species are named using a system developed in 1750 Species are named using a system developed in 1750 in Sweden by Linnaeus.in Sweden by Linnaeus.

Each species is given two names.Each species is given two names. The first is the The first is the genusgenus name. name. Each genus contains a number of Each genus contains a number of relatedrelated species. species. For example Buttercups belong to the genus For example Buttercups belong to the genus

RannunculusRannunculus.. Different types of buttercup then have a different Different types of buttercup then have a different

species name e.g. Creeping Buttercup is species name e.g. Creeping Buttercup is Rannunculus Rannunculus repensrepens while the common buttercup is called while the common buttercup is called Rannunculus flutans.Rannunculus flutans.

The genus and species are always written in The genus and species are always written in ItalicsItalics but when hand - written they should be but when hand - written they should be underlinedunderlined..

Also the genus should have a CAPITAL letter and the Also the genus should have a CAPITAL letter and the species should have a small letter.species should have a small letter.

Angiosperms: FamiliesAngiosperms: Families

Seed bearing plants of the Order Seed bearing plants of the Order

Angiosperm are further classified into Angiosperm are further classified into

plant families.plant families.

Plants belonging to the same family Plants belonging to the same family

share a common trait, usually based share a common trait, usually based

on flower structure.on flower structure.

The most important and common The most important and common

families are detailed next:families are detailed next:

CruciferaeCruciferae

This family include wallflowers and many This family include wallflowers and many

BrassicaBrassica vegetables like Cabbage, vegetables like Cabbage,

Brussels sprouts, Cauliflower, Turnips, Brussels sprouts, Cauliflower, Turnips,

Mustard plants etc.Mustard plants etc.

They are classified by floral parts, They are classified by floral parts,

arranged in fours. (4 sepals, petals & arranged in fours. (4 sepals, petals &

stamen).stamen).

Their flowers are in the shape of a cross, Their flowers are in the shape of a cross,

hence the name hence the name CruciferaeCruciferae..

RosacaeRosacae

Also known as the Also known as the RoseRose Family. Family.

It includes apple, pear, peach, plum, It includes apple, pear, peach, plum,

cherry, apricot, almond, nectarine, prune, cherry, apricot, almond, nectarine, prune,

raspberry, blackberry, dewberry and the raspberry, blackberry, dewberry and the

strawberry.strawberry.

They are characterised by five sepals and They are characterised by five sepals and

petals and numerous carpels and stamen.petals and numerous carpels and stamen.

LeguminosaeLeguminosae Also called the pea family, they are Also called the pea family, they are

characterised by five petals (One large, characterised by five petals (One large, two small and two even smaller “wings”).two small and two even smaller “wings”).

A common feature in the family is the A common feature in the family is the presence of root nodules containing presence of root nodules containing bacteria of the genus bacteria of the genus Rhizobium.Rhizobium.

These bacteria convert atmospheric N, These bacteria convert atmospheric N, which cannot be used by the plants, into which cannot be used by the plants, into nitrate (NO3-), a form that can be used.nitrate (NO3-), a form that can be used.

This family is the second most This family is the second most economically important family after economically important family after grasses and has over 18,000 species.grasses and has over 18,000 species.

LiliaceaeLiliaceae

This is a monocot family, whose This is a monocot family, whose

members include onions, garlic, lilies, members include onions, garlic, lilies,

tulips, bluebells and hyacinths.tulips, bluebells and hyacinths.

This family is characterised be This family is characterised be fusedfused

petals and sepals.petals and sepals.

Their floral parts are in multiples of Their floral parts are in multiples of

three – six sepals, six petals, six three – six sepals, six petals, six

stamen and three carpels.stamen and three carpels.

Gramineae Gramineae This is the grass family, and includes all This is the grass family, and includes all

grass species as well as cereals such as grass species as well as cereals such as wheat, oats, barley maize and rice.wheat, oats, barley maize and rice.

Grass species have flower structures based Grass species have flower structures based on the use of wind pollination.on the use of wind pollination.

Therefore they do not contain bright, Therefore they do not contain bright, colourful petals to attract insects, as this is colourful petals to attract insects, as this is not required.not required.

Grass plants produce high levels of pollen to Grass plants produce high levels of pollen to increase its chances of reproduction – this increase its chances of reproduction – this high level of pollen can cause hay fever.high level of pollen can cause hay fever.

Grass flowers are said to be Grass flowers are said to be hermaphroditehermaphrodite – – they contain both male and female parts.they contain both male and female parts.

These are formed on an These are formed on an inflorescenceinflorescence..

CompositaeCompositae This is the largest family of plants (NB) This is the largest family of plants (NB)

and includes daisies, dandelions, and includes daisies, dandelions,

thistles, lettuce and sunflowers.thistles, lettuce and sunflowers.

The family is called The family is called CompositaeCompositae

because each flower is actually a because each flower is actually a

composite of many “florets”.composite of many “florets”.

If you look at a daisy, you will find to If you look at a daisy, you will find to

different types of floret (the white “ray” different types of floret (the white “ray”

floret and the yellow “disc” floret.floret and the yellow “disc” floret.

Umbelliferae Umbelliferae Members of this family have a distinctive Members of this family have a distinctive

florescence (collection of flowers) shaped florescence (collection of flowers) shaped like an umbrella. like an umbrella.

Each of the flowers are small but contain Each of the flowers are small but contain five sepals, stamen and petals and two five sepals, stamen and petals and two carpels.carpels.

Members of this family include parsley, Members of this family include parsley, dill, celery, carrots and parsnips.dill, celery, carrots and parsnips.

Giant hogweeds and cow parsnip Giant hogweeds and cow parsnip (parsley) are also weeds belonging to (parsley) are also weeds belonging to this family. this family.

Other FamiliesOther Families

RaunculaceaeRaunculaceae

The buttercup family.The buttercup family.

SolanaceaeSolanaceae

This family contains potatoes, This family contains potatoes,

tomatoes, tobacco and the “deadly tomatoes, tobacco and the “deadly

nightshade”.nightshade”.

PolygonaceaePolygonaceae

Rhubarb family – rhubarb, dock and Rhubarb family – rhubarb, dock and

buckwheat.buckwheat.