Plant Names and Classifications -...

Plant Names and

Classifications

Plant

Classification

Grouping plants by their similar

characteristics

Plant Taxonomy

Taxonomy = Classification

Scientific Classification

Binomial Nomenclature (2 names)

Latin - Never changes, a universal language

Developed by Carolus Linnaeus

Circumstances have dictated the necessity of

distinguishing among 10 million types of

organisms, as well as those that have become

extinct, in a manner that will identify them

anywhere, regardless of the language spoken

locally.

At present all living organisms are given a single

two-part Latin scientific name, and mostly also have

applied to all individuals of a specific kind of

organisms, no matter where they may be found, but

many common names may be given to the same

organism, and one common name may be applied to

a number of different organisms.

In Europe, with its many languages, common names can

become very numerous indeed. The widespread weed with

the scientific name Plantago major, for example, is often

called broad-leaved plantain in English, but also has no

fewer than 45 other English names, 11 French names, 75

Dutch names, 106 German names,

Plantago major,

and possibly as many as several hundred more names

in other languages, with literally dozens of these

names also applying to quite different plants.

If it were not for the early recognition by biologists

in naming and classifying all organisms, utter chaos

eventually might have prevailed in communications

concerning them.

Development of the binomial system of nomenclature

The first person of note attempt to organize and classify

plants was Theophrastus.

His third century B.C. classification of nearly 500

plants into trees, shrubs, and herbs, along with his

distinction plants on the basis of leaf characteristic, was

used for hundreds of years

It was not until the thirteen century A.D. that a

distinction was made between monocots and dicots

on the basis of stem structure.

After this, herbalists added considerably to

Theophrastus list, and by the beginning of

eighteenth century, details of fruit and flower

structure were utilized in classification scheme in

addition to form and habit.

All organisms were grouped into genera (singular:

genus), with the first word of the Latin phrase

indicating the particular genus to which organisms

belonged. For example, all known mints were given

phrase names beginning with the word Mentha, the

name of the genus. Likewise the phrase of Lupinus

began with Lupinus.

At this point, the Swedish botanist, Carolus Linnaeus

(1707-1778), began improving the way the

organisms were named and classified, and the

system he established worked so well that it has

persisted to the present.

When Linnaeus began his work, he set out to classify

all known plants and animals according to their

genera. He limited each Latin phrase to a maximum of

12 words and in the margin next to the phrase he listed

a single word, which when combined with the generic

name, formed a convenient abbreviated designation for

species. The word for spearmint was spicata.

Linnaeus and those who followed him eventually

replaced all the phrase names with abbreviated one.

Because of their two parts, these names became

known as Binomial System of Nomenclature.

Today all organisms are named according to this

system, which in current use also includes the

authority for the name, either in abbreviated form or

in full, after the Latin name.

Thus the full scientific name for spearmint is now

written Mentha spicata L., the L standing for

Linnaeus, and the full scientific name for the

common dandelion is written Taraxacum officinals

Wiggers, because F.H. Wiggers was the first who

described the species.

Taraxacum officinals Wiggers,

Development of the Kingdom Concept

When classification schemes were first developed,

all living organisms were placed in either the Plant

kingdom or the Animal kingdom. Many microscopic

organisms have characteristic of both plants and

animals, however and in the 1860 Hogg and

Haeckel proposed a third kingdom (Protista) for all

organisms that did not develop complex tissues.

In 1939, H.F. Copeland divided the Protista into two

kingdoms, with organisms have prokaryotic cell

placed in the Kingdom Monera, and those with

eukaryotic cells being left in the Kingdom

Protoctista or Protista.

Comparison Between Prokaryotic and Eukaryotic Cells

Characteristic Prokaryotes Eukaryotes

Size of cell Typically 0.2-2.0 m m in diameter Typically 10-100 m m in diameter

Nucleus No nuclear membrane or nucleoli (nucleoid) True nucleus, consisting of nuclear membrane &

nucleoli

Membrane-

enclosed

organelles

Absent Present; examples include lysosomes, Golgi

complex, endoplasmic reticulum, mitochondria &

chloroplasts

Flagella Consist of two protein building blocks Complex; consist of multiple microtubules

Glycocalyx Present as a capsule or slime layer Present in some cells that lack a cell wall

Cell wall Usually present; chemically complex (typical

bacterial cell wall includes peptidoglycan)

When present, chemically simple

Plasma

membrane

No carbohydrates and generally lacks sterols Sterols and carbohydrates that serve as receptors

present

Cytoplasm No cytoskeleton or cytoplasmic streaming Cytoskeleton; cytoplasmic streaming

Ribosomes Smaller size (70S) Larger size (80S)

Chromosome

(DNA)

arrangement

Single circular chromosome; lacks histones Multiple linear chromosomes with histones

Cell division Binary fission Mitosis

Sexual

reproduction

No meiosis; transfer of DNA fragments only

(conjugation)

Involves meiosis

Since there are differences in the mode of nutrition

of organisms in Copeland’s Kingdom Protoctista,

many biologists now favor five kingdoms, as

proposed by R.H. Whittaker in 1969. In Whittaker’s

system, there are three kingdoms based on forms

of nutrition (photosynthetic, ingestion of food,

absorption of food solutions) and two kingdom of

protesta based on differences in cellular structure.

Slime modes, which have no cell walls at certain

stages and do have walls at others, still do not fit

well into the five-kingdom system, but this system

appears to be the most satisfactory arrangement so

far proposed.

Scientific Classification

Animalia Planta Protista

Monera Fungi

Kingdom

Classification of Major groups

Since Linnaeus time, a number of classification

categories have been added between the levels of

kingdom and genus. Genera are now grouped into

divisions, and divisions into kingdoms. Depending

on which system of classification is used, there may

be between 12 and 30 divisions of plants recognized.

The following is a classification of major groups of

living organisms utilizing a modification of Wittaker’s

five-kingdom system.

If we are to give a complete classification of an onion

according to this particular arrangement, it would look

like this;

It is customary to give binomials in italics (or to

underline the words).

Scientific Classification

KingdomDivision (Phylum)

Class

Subclass

Order

Family

Genus

Species

Kingdom Plantae – Plants

Subkingdom Tracheobionta – Vascular plants

Superdivision Spermatophyta – Seed plants

Division Magnoliophyta – Flowering plants

Class Liliopsida – Monocotyledons

Subclass Liliidae

Order Liliales

Family Liliaceae – Lily family

Genus Allium cepa L. – onion

Species: A population of individuals capable of

interbreeding in nature but not generally

interbreeding with members of another species.

Kingdom Protista

Kingdom Protista includes organisms that all have

eukaryotic cells but are otherwise diverse. Members

may be unicellular or multicellular, and occurs as

either colonies or filament. Modes of nutrition

includes photosynthesis, ingestion of food, and

absorption of food in solutions. Some are nonmotile

but most are motile by means of flagella or by

amoeboid movement.

Division Chrysophyta -

The Golden-brown algae

The golden-brown algae are grouped into four

classes that include:

the yellow-green algae, the true golden-brown algae,

the diatoms, and the cryptophytes.

Diatoms

Diatoms, which have a glassy shell that consist of two

“halves” that fit together like a pillbox, are extremely

abundant, particularly in colder marine waters.

The shells are usually etched with fine grooves and pores

through which the cytoplasm is in contact with the

environment.

Kingdom Protista

SubKingdom Phycobionta - Algae

Division Chrysophyta –

The Golden – Brown Algae

Diatoms

Diatoms are often golden-brown in color due to the

presence of the brownish pigment fucoxanthin in the

one to many chloroplasts occurring in each cell.

Diatoms move in caterpillar fashion by contact of the

cytoplasm with a surface as it protrudes through the

pores.

In asexual reproduction, the two “halves” of a cell

separate after mitosis of the protoplast, and a new

half forms within each original portion.

An auxospore (zygote) is produced through a sexual

process involving the fusion of gametes.

Division Euglenophyta-

The Euglenoids

The euglenoids have no rigid cell wall, only one

functional flagellum, a gullet, and a carbohydrate

food reserve called paramylon. Reproduction is by

cell division.

Sexual reproduction has not been confirmed.

Euglena

Euglena cell, which is spindle-shaped, can be seen to

change shape even as the organism moves along. Just

beneath the plasma membrane are fine strips that

spiral around the cell parallel to one another. The

strips and the plasma are devoid cellulose and

together are called a pellicle.

Division Euglenophyta –

The Euglenoids

A single functional flagellum, which has numerous

tiny hairs along one side, pulls the cell through the

water. A second very short flagellum is present

within a reservoir at the base of the functional

flagellum. There is a gullet or groove, through which

food can be ingested. A red eyespot is located in the

cytoplasm near the base of the flagella.

Reproduction is by cell division, starts to divide at

the flagella end and eventually split lengthwise, to

form two complete cells.

Division Chlorophyta-

The Green algae

Occur in wide variety of aquatic habitats. Their cells

have the same pigments and reserve food (starch) as

those of higher plants.

Chlamydomonas

Unicellular green algae, has a pair of flagella that

enable the cell to move rapidly. Within the cell, there

is a chloroplast containing one or two pyrenoids, two

or more vacuoles, and often a red eyespot.

Asexual reproduction is by mitosis, sexual

reproduction is by union of like gametes.

Division Chlorophyta-

The Green Algae

Chlamdomonas

Spirogyra

Spirogyra is a floating, filament green algae with

spiral, ribbonlike chloroplasts. It does not produce

flagellated cells of any kind. Asexual reproduction is

by fragmentation (breaking of filaments with each

fragment adding new cells by mitosis). Sexual

reproduction is by conjugation.

Spirogyra

A- A portion of a vegetative filament; B-

D Sexual Reproduction

Other green algae

Other green algae include Chlorella, a tiny

unicellular alga that ease to culture and has been used

in experiments to produce oxygen for space vehicles;

Acetabularia which produces huge mushroom like

cell. Volvox is a colonial alga that forms motile

hollow balls of hundred to thousands of cells; Sea

lettuce (Ulva) has blades that anchored to rocks by

means of holdfast.

Other Green Algae

ChlorellaVolvox

Division Phaeophyta-

The Brown algae

The brown algae include the largest seaweed. Many

are differentiated into a stalk (stripe), flattened blades

and a tough, sinewy that holds the seaweed to the

rocks. Fucoxanthin is largely responsible for the

color brown algae whose main carbohydrate food is

laminarin. Some produce algin (alginic acid), a

useful gelatinous substance.

Division phaeophyta –

The Brown Algae

Nereocystis, a

kelp

Sargassum,

a floating brown algae

Division Rhodophyta-

The Red Algae

Red algae tend to be smaller than those of the brown

algae, have relatively complex live cycle. The color

of red algae are partially due to the presence of red

and blue phycobilins.

Division Rhodophyta –

The Red Algae

Human Relevance of Algae

Algae are important in aquatic food chains and in

numerous other ways.

Diatom shells have accumulated for thousand of

years on ocean floors and make up diatomaceous

earth that is used for filtering, polishes, insulation

and reflectorized paint.

Chlorella is a potentially important food and oxygen

source. Future spacecraft may be equipped with

tanks of such algae.

Algin is used as stabilizer and thickening agent in

hundreds of food products, paints, medicines, papers,

ceramic and others.

Brown algae are a source of fertilizer and iodine and

some serve as food for both of livestock and humans.

Red algae are a source of agar, which is used as

cultural medium for bacteria and other organisms or

tissues; some are also used for human food.

Plant Classes

Tracheophyta

Gymnosperms Angiosperms

Plant Order

Angiosperms

Subclasses

Monocotyledon Dicotyledon

Seed Plants Tracheophyta

Division Pinophyta

Gymenosperms

The name gymnosperm is derived from two Greek

words gymnos, meaning naked, and sperma, a seed.

The name refers to the exposed nature of seeds,

which are produced on the surface of sporophylls or

similar structures instead of being enclosed within a

fruit as they usually are in the flowering plants.

Seed

Plants

Gymnosperms

The seed-bearing sporophylls are often spirally

arranged in female strobili (cones), which develop on

the sporophyte along with smaller male strobili that

produce pollen grains.

The female gametophyte within an ovule containing

a fleshy, nutritive diploid nucellus that is itself

enclosed within one or more outer layers of diploid

tissue.

These outer layers of tissues constitute an

integuments, which become a seed coat after the

fertilization and development of an embryo occurred.

The division Pinophyta, which includes all living

gymnosperms, is divided into three subdivisions.

Cycadicae includes the superficially palm like

cycade, which produce their seeds in cones,

Pinicae includes the Conifers and Ginkgo,

Gnetica includes three genera of genophytes.

Conifers constitute the largest and most significant

group by far, totaling some 575 species. Pines,

spruces, hemlocks, redwoods, cedars and others

belong to this class.

Fossils of some conifers extend back 290 million

year to the late carboniferous period.

Division Pinophyta, Class Pinatae

The conifers

Pines:

The largest genus of conifers, Pinus (pines) has over

100 living species. They are the predominant trees in

the vast coniferous forests of the Northen

Hemisphere. They have also been planted

extensively in the Southern Hemisphere. They

include the world’s oldest known living organisms.

Division Pinophyta, CalssPinatae- The Conifers

Reproduction

Microspores occur in microsporangia that develop in

pairs toward the basis of papery or membranous scales

arranged in a spiral or whorls around an axis, forming a

strobilus or male cone.

Male cones which are usually produced in the spring in

clusters of up to 50 or more toward the tips of the lower

branches, are commonly not more than 1-4 cm. They

become shriveled and spent within a few weeks and then

fall from the trees, after the pollen has been released.

Microspore mother cells in the microsporangia each

undergo meiosis, producing the four haploid

microspores. These then develop into pollen grains,

each consisting of four cells and a pair of external air

sacs.

Megaspores are produced in megasporangia

located within ovules at the base of the female cone

scales.

The female cones (or strobili), are much larger than

the male cones. When they mature they have woody

scales, with inconspicuous bracts between them,

arranged in spiral around the axis.

They are produced on the upper branches of the same

tree on which the male cones appear. The ovules occur

in pairs toward the base of each scale of the immature

cones. Each ovule contains a megasporangium within

multicelluar nutritive tissue called the nucellus, which

in turn, enclosed by a thick, layered integuments. The

integuments has a channel or pore called a micropyle.

One of the integuments layers later becomes the seed

coat of the seed.

A single megasporangium of each ovule undergoes

meiosis, producing a row of relatively large

megaspores. All except one of the megaspores soon

degenerate. The remaining one slowly develops over

a period of month into a female gametophyte.

Toward the end of the gametophyte development,

two to six archegonia become differentiated at the

end facing the micropyle.

Each archegonium contains a single large egg.

Female cones, which are usually reddish at first,

commonly take two seasons to mature into green and

finally the brownish woody structure that are

familiar.

During the first spring, the immature, radish cone

scales spread apart, and pollen grains carried by the

wind shift down between the scales. There they catch

in sticky drops of fluid oozing out of the micropyles.

As the fluid evaporates, the pollen is drawn down

through the micropyle to the top of nucellus.

After pollination, the scales grow together and

close, protecting the developing ovule.

The female gametophyte is not mature with

archegonia for more than a year after that.

Meanwhile the pollen grain (immature male

gametophyte) forms an outgrowth called a pollen

tube, which slowly digests its way through the

nucellus to the area where the archegonia develop.

While the pollen grains enter it.

One of these called the generative cell divides and

forms two more cells, called the sterile cell and the

spermatogenous cell.

The latter divides again, producing two male

gametes, or sperms.

This germinated pollen grain, with its pollen tube

and two sperms, constitute the mature male

gametophyte.

About 15 months after pollination the pollen tube

reaches the now present archegonium. One sperm

unites with the egg, forming a zygote, the other

sperm and remaining cells of the pollen grain

degenerate.

The zygote begins to develop into an embryo. At a

later stage, an embryo may divide in such a way as

to produce the equivalent of identical twins.

Normally one embryo completes development.

While this development is occurring one of the layers

of the integuments hardens, becoming a seed coat. A

thin membranous layer of the cone scale becomes a

“wing” on each seed, which aids in the seed’s

dispersal.

Subdivision Cycadicae – The cycads

Cycads are slow-growing plants of the tropics and

subtropics that look like a cross between a tree fern

and a palm.

They have unbranched trunks that grow to more than

15 meters tall in a few species with a crown of large

pinnately divided leaves.

Several of the approximately 100 known living

species are presently facing extinction.

Their life cycle are similar to conifers. Cycads are

dioecious, the male and female strobili, which are

sometimes massive, being produced on separate

plants.

The scale of female strobili of some species are

covered with feltlike or wooly hairs and grow to as

much as 1 meter long.

Subdivision

Cycadicae- The Cycads

AB