Plant Taxonomy PDF

PLANT TA X O N O M Y Plant nomenclature kingdom Protista Dr. Sanaa Abdel Rahman Mostafa Zaghlool Dr. Fatma Saeed Agric Botany Department  Binomial system of nomenclature ❑ It has become vital to us to be able to consistently distinguish among existing organisms (estimated to be at least...

PLANT TA X O N O M Y Plant nomenclature kingdom Protista Dr. Sanaa Abdel Rahman Mostafa Zaghlool Dr. Fatma Saeed Agric Botany Department  Binomial system of nomenclature ❑ It has become vital to us to be able to consistently distinguish among existing organisms (estimated to be at least 10 million). ❑ At present, all living organisms are given a single, two words Latin scientific name. ❑ Only one correct scientific name applies to The widespread weed with the scientific name Plantago all individuals of a species, no matter where major, for example, is often called broad-leaved plantain they’re found, in English, but it also has no fewer than 45 other English names, 11 French names, 75 Dutch names, 106 German ❑ but many common names may be given to names, and possibly as many as several hundred more names in other languages. the same species, ❑The Swedish naturalist Carolus Linnaeus (1707–1778) began improving the way organisms were named and classified. ❑ Linnaeus’s system is now used throughout the entire world. ❑ He set out to classify all known plants and animals according to their genera. ❑ All organisms were grouped into genera (singular: genus). ❑ For example, all known mints were given the word Mentha, the name of the genus. ❑ Because of their two parts, these abbreviated names became known as binomials, and the method of naming became known as the Binomial System of Nomenclature. The second part of the scientific name of a species, called the specific epithet, is followed by the name of the author, usually in abbreviated form. The author is the person (or persons) who originally named the plant or placed the species in a particular genus. ❑ For example, refers to the., the L. standing for Linnaeus. ❑ The scientific name is written in italics, and the genus name is capitalized, while the species name is not  Development of the kingdom concept ❑ When classification schemes were first developed, all living organisms placed according to the highest category of “kingdom,” in either the Plant Kingdom or the Animal Kingdom. ❑ While this distinction still works well for the more complex plants and animals, it breaks down for some of the so-called simpler organisms. ❑ The biologists John Hogg and Ernst Haeckel proposed a third kingdom in the 1860s. ❑ All organisms that did not develop complex tissues (e.g., algae, fungi, and sponges) were placed in a third kingdom called Protoctista. ❑ This third kingdom included such a heterogeneous variety of organisms. ❑ In 1938, Herbert F. Copeland proposed that Some Differences Between Eukaryotic and Procaryotic third kingdom again be divided. Eukaryotic cells Prokaryotic cells ❑ He assigned the name Monera to all single- 1. Have a nuclear envelope 1. Lack a nuclear envelope celled organisms with prokaryotic cells, leaving the algae, fungi, and single-celled 2. Have two to hundreds of 2. Have a single closed loop of organisms with eukaryotic cells in the chromosomes per cell; DNA is double-stranded DNA plus double strand (usually) several to 40 plasmids Kingdom Protoctista. 3. Have membrane-bound 3. Lack membrane-bound ❑ In Whittaker’s system 1969, three kingdoms organelles(e.g. plastids, organelles of more complex organisms based on three mitochondria) basic forms of nutrition (photosynthesis, 4. Have 80S ribosomes 4. Have 70S ribosomes ingestion of food, and absorption of food in 5.Have asexual reproduction 5.Have asexual reproduction solution) were recognized, by mitosis by fission ❑ along with two kingdoms of protists, which were distinguished on the basis of differences 6.Have sexual reproduction Sexual reproduction unknwon by fusion in cellular structure. ❑If we were to give a complete classification of the common onion according to this particular arrangement, it would look like this: ▪ Kingdom: Plantae ▪ Phylum: Magnoliophyta ▪ Class: Liliopsida ▪ Order: Liliales ▪ Family: Liliaceae ▪ Genus: Allium ▪ Species: Allium cepa L.  Features of kingdom Protista ❑The organisms of Kingdom Protista including the euglenoids, protozoans, and some algae, consist of a single cell, whereas other algae are multicellular or occur as colonies or filaments. ❑ Nutrition is equally varied, with the algae being photosynthetic, the slime molds and protozoans ingesting their food, the euglenoids either carrying on photosynthesis or ingesting their food. ❑ Individual life cycles vary considerably, but reproduction is generally by cell division and sexual processes. ❑ Many protists (mostly single-celled members of Kingdom Protista) are motile (capable of spontaneous movement), usually by means of flagella, but other members, especially those that are multicellular, are nonmotile, although most of the multicellular members produce some motile cells. Algae Phylum Chlorophyta ❑ Phylum Chlorophyta includes about 7,500 species of organisms commonly known as the green algae. ❑Some are unicellular and microscopic; in fact, the green alga Micromonas is only 1 μm in diameter, the smallest eukaryotic cell known. Most unicellular green algae are, however, considerably larger. ❑Some green algae are seaweeds, resembling lettuce leaves Representative green algae. A. Volvox. The cells form hollow, spherical colonies that spin as the flagella of each or long, green ropes. cell beat in a coordinated motion. New colonies are ❑The chlorophylls (a and b) and other pigments of green produced within the older ones. B. Micrasterias, a desmid. These algae consist of single cells that often have a algae are similar to those of higher plants. constriction in the center. C. Pediastrum. A colonial alga ❑ Most green algae have a single nucleus in each cell. Most that forms flat plates. D. Part of a filament of Ulothrix, whose cells each have at their periphery a chloroplast in green algae reproduce both asexually and sexually. the form of a curved plate. E. Scenedesmus, a green alga that typically occurs in colonies of four cells. Chlamydomonas ❑ A small, actively moving little alga, Chlamydomonas is a common inhabitant of quiet freshwater pools. Chlamydomonas is unicellular, with a slightly oval cell surrounded by a complex multilayered. A pair of whiplike flagella at one end pull the cell very rapidly through the water. ❑ The cell itself is usually less than 25 micrometers long. Near the base of the flagella there are two or more vacuoles that contract and expand. They may regulate the water content of the cell and remove waste products. ❑ A dominant feature of each Chlamydomonas is a single, usually cup-shaped chloroplast that at least partially hides the centrally located nucleus. One or two roundish pyrenoids are located in each chloroplast. Pyrenoids are proteinaceous structures associated with the synthesis of starch. Most species also have a red eyespot on the chloroplast near the base of the flagella. Spirogyra ❑ Spirogyra has watery sheaths which make the alga feel slimy surrounding the filaments. ❑ These common freshwater algae, consisting of unbranched filaments of cylindrical cells, frequently float in masses at the surface of quiet waters. ❑ Each cell contains one or more long, frilly, ribbon- shaped chloroplasts that look as though they had Spirogyra (watersilk). A. A portion of a vegetative filament been spirally wrapped around an invisible pole showing the ribbonlike chloroplasts spirally arranged in each cell. The centrally located darker object in each cell is (vacuole) occupying most of the cell’s interior. a nucleus. B. Papillae have grown out from opposite cells of two closely adjacent filaments and formed conjugation ❑ Most Spirogyra species have one or two chloroplasts tubes. C. The condensed protoplasts in the cells on the left in each cell, but some have as many as 16. are functioning as male gametes that are migrating through the conjugation tubes to the stationary female gametes in ❑ Every one of these elegant green ribbons has the cells on the right. D. Zygotes have been produced in pyrenoids at regular intervals throughout its length. the cells on the right as a result of fusion of gametes. Other Green Algae Chlorella, another widespread green alga composed of tiny spherical cells. ❑Chlorella is very easy to culture and is a favorite organism of research scientists. ❑ It has been used in many major investigations of photosynthesis and respiration. ❑ In the future, it may become important in human nutrition. Chlorella could also play a key role in long-range space exploration. ❑ Because present exploration is severely limited by the weight of oxygen tanks and food supplies needed on a spacecraft, scientists have turned to Chlorella and similar algae as portable oxygen generators and food sources. ❑ Future spacecraft may be equipped with tanks of such algae. These would carry on photosynthesis, using available light and carbon dioxide given off by the astronauts, while furnishing them with oxygen. Sea lettuce (Ulva) is a multicellular seaweed with flattened crinkly-edged blades that may be up to 1 meter or more long. ❑ A basal holdfast anchors the bladesto rocks. Mermaid’s wineglass Mermaid.s (Acetabularia), a marine alga (Acetabularia). consisting of a single, huge cell shaped like a delicate mushroom. Each cell is up to 5 centimeters long. Sea lettuce (Ulva).  Yellow-Green Algae Yellow-green algae are Phylum Chromophyta mostly freshwater organisms, with a few marine ❑ About three-quarters of the roughly and terrestrial representatives. 7,600 members of Phylum Chromophyta are primarily ❑Sexual reproduction is relatively rare, but microscopic. when it does occur (as in Vaucheria), it may ❑ The algae in this phylum can be exhibit specialization, with oogonia and grouped into several classes, including antheridia being formed on special branches. the yellow-green algae, golden-brown algae, diatoms, and brown algae. ❑ The organisms of each class may appear unrelated to each other, but they do share several features, including food reserves, specialized pigments, and other cell characteristics. Vaucheria, yellow green algae. Diatoms ❑ Diatoms are among the best-known and economically most important members of the phylum. These mostly unicellular algae occur in astronomical numbers in both fresh and salt water but are particularly abundant in colder marine habitats. ❑A major constituent of the foam that accumulates at the wave line on beaches is an oil produced by diatoms. Diatoms usually also dominate the algal flora on damp cliffs, the bark of trees, bare soil, or the sides of buildings. ❑ More than 5,600 living species are recognized, with almost as many more known only as fossils. Some can withstand extreme drought. ❑ Diatoms look like tiny, ornate, glass boxes with lids. Half of the rigid, crystal-clear wall fits inside the other, overlapping half. ❑ As much as 95% of the wall content is silica, an ingredient of glass, deposited in an organic framework of pectin or other substances. ❑ The diatom walls usually have exquisitely fine grooves and pores that are exceptionally minute passageways connecting the protoplasm with the watery environment outside the shell. ❑ Each diatom may have one, two, or many chloroplasts per cell. In addition to chlorophyll a, the accessory pigments chlorophyll c1 and chlorophyll c2 are typically present. ❑ The chloroplasts usually are golden-brown in color because of the dominance of fucoxanthin, the brownish pigment also found in the brown algae. ❑ Food reserves are oils, fats, or the carbohydrate laminarin. ❑ Reproduction in diatoms is unique, with half of the cells becoming progressively smaller through several generations until, through a sexual process, the original cell size is restored. A Reproduction in diatoms. The two rigid halves of each pillboxlike cell separate and a new rigid half shell forms inside each original half. This results in half the new cells becoming smaller with each generation. At one point, however, the diploid nucleus of a reduced-size cell undergoes meiosis, and four B gametes are formed. The zygote produced when two gametes unite becomes considerably enlarged. The enlarged cell, called A. A living diatom and B. a an auxospore, develops into a diatom of the same size as the diatom wall. original diatom. Brown Algae There are more than 1,500 species of seaweeds and other algae that are brown to olive green in color. ❑ Many brown algae are relatively large, and none are unicellular or colonial. ❑ Many of the brown algae have a thallus (plural: thalli, the term for multicellular bodies that are usually flattened and not organized into leaves, stems, and roots) that is differentiated into a holdfast, a stipe, and flattened, leaflike blades. ❑ The holdfast is a tough, sinewy structure resembling a mass of intertwined roots. It holds the seaweed to rocks so Parts of the brown alga Nereocystis, a kelp. tenaciously that even the heaviest pounding of surf will not readily dislodge it. ❑The color of brown algae can vary from light yellow brown to almost black, reflecting the presence of varying amounts of the brown pigment fucoxanthin, in addition to chlorophylls a and c and several other pigments in the chloroplasts. ❑ The main food reserve is laminarin, a carbohydrate. Algin, or alginic acid occurs on or in the cell walls and can represent as much as 40% of the dry weight of some kelps. Phylum Rhodophyta The red algae ❑ Like many brown algae, most of the more than 5,000 species of red algae are seaweeds that tend, however, to occur in warmer and deeper waters than their brown counterparts. ❑ A few are unicellular, but most are filamentous. The filaments frequently are so tightly packed that the plants appear to have flattened blades or to form branching segments. ❑ The red to purplish colors of most red algae are due to the presence of varying amounts of red and blue accessory pigments called phycobilins. ❑ Several other pigments, including chlorophyll a and sometimes chlorophyll d, are also present in the chloroplasts. ❑ The principal reserve food is a carbohydrate called floridean starch. ❑ A number of red algae also produce agar, a gelatinous substance. Representative red algae. A. Botryocladia. B. Stenogramme. C. Gigartina. D. Gelidium. Phylum Euglenophyta The euglenoids ❑ A Euglena cell is spindle-shaped, has no rigid wall,. Just beneath the plasma membrane are fine strips that spiral around the cell parallel to one another. ❑ The strips and the plasma membrane are devoid of cellulose and together are called a pellicle. ❑ A single flagellum, with 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 long flagellum. ❑ Other features of Euglena include the presence of a gullet, or groove, through which food can be ingested. ❑ The food of most of the 500 Euglena species is ingested, with only about a third having several to many mostly disc-shaped chloroplasts that permit photosynthesis to take place. A red eyespot, which along with the short flagellum is associated with light detection, is located in the cytoplasm near the base of the flagella. ❑ A carbohydrate food reserve called paramylon normally is present in the form Diagram of a single Euglena of small, whitish bodies of various shapes.  Human and ecological relevance of the algae Diatoms ❑ Diatoms are consumed by fish that feed on plankton. Up to 40% of a diatom’s mass consists of oils that are converted into cod and other liver oils that are rich sources of vitamins for humans. ❑ As billions upon billions of them have reproduced and died, their microscopic, glassy shells have accumulated on the ocean floor, forming deposits of diatomaceous earth. ❑ Diatomaceous earth is light, porous, and powdery material that contains about 6 billion diatom shells per liter. ❑ It also has an exceptionally high melting point of 1,750°C and is A diatomaceous earth quarry insoluble in most acids and other liquids. ❑ These properties make it ideal for a variety of industrial and domestic uses, including many types of filtration. ❑ The sugar industry uses diatomaceous earth in sugar refining, and its use for swimming-pool filters is widespread. ❑ It is also used in silver and other metal polishes, in toothpaste, and in the manufacture of paint. Algin It is produced by several kinds of seaweeds, but a major source is the giant kelp found in the cooler ocean waters of the world, usually just offshore where there are strong currents. Some Uses of Algin ▪ As an emulsifier and suspension agent in soft drinks and concentrates. ▪ As a stabilizer in chocolate drinks, ice cream, sour cream, coffee creamers, buttermilk ▪ Provides better ink and varnish holdout on paper surfaces ▪ provides uniformity of ink acceptance, reduction in coating weight and improved holdout of oil, wax, and solvents in paperboard products. Makes improved coating for frozen food cartons ▪ Used for coating greaseproof papers. ▪ Thickens print paste and improves dye dispersal. ▪ As a thickening agent in cough syrups, suppositories, ointments, toothpastes, shampoos. ▪ As a smoothing agent in lotions, creams. Binder in manufacture of pills. Blood anticoagulant. ▪ As a suspension agent for liquid vitamins, mineral oil emulsions, antibiotics. ▪ Brown algae also produce a number of other useful substances. Many seaweeds, but particularly kelps, build up concentrations of iodine to as much as 20,000 times that of the surrounding sea water. ▪ Dried kelp has been used in some parts of the world in the treatment of goiter, which results from iodine deficiency. ▪ Kelps are relatively high in nitrogen and potassium and have been used as fertilizer for many years. ▪ They also have been used as livestock feed in northern Europe and elsewhere. ▪ In Asia, many marine algae are used for food—in soups, confections, meat dishes, vegetable dishes, and beverages. In Japan, acetic acid is produced through fermentation of seaweeds. Agar One of the most important of all algal substances is agar, produced most abundantly by the red alga Gelidium. Agar is used around the world in laboratories and medical institutions as a solidifier of nutrient culture media for the growth of bacteria.