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Plant Kingdom, , , , , , Characteristics of Plantae, , The term plant is more commonly used for land, photoautotrophs with distinct root, stem and leaves. Study of, plants is called phytology., , Kingdom plantae includes green, brown and red algae,, liverworts, mosses, ferns and seed plants with or without flowers, They have the following characters., , (1) Member of the kingdom are multicellular, eukaryotes., However, unicellular and colonial members of green and red algae, are also included in kingdom plantae., , (2) Cells are surrounded by cell wall. It contain cellulose., (3) Mature cells usually possess a single central vacuole., , (4) Reserve food is starch in green algae and embryophyies,, floridean starch in red algae and laminarin in brown algae., , (5) They contain photosynthetic pigment in plastids., , (6) Principal mode of nutrition is photosynthesis but number, of plants have become absorptive., , (7) In lower member, organization is protoplasmic or cellular., In higher forms, the organization is of tissue and organ level., , (8) Branches are present. Therefore body form is iregular., , (9) Growth occur due to presence definite growing points or, cells. In higher forms, growing areas called meristems., , (10) Locomotion is absent except in some unicellular colonial, forms. Multicellular members are sedentary or fixed., , (11) The cells often contain inorganic crystals of different salts,, , (12) Vegetative reproduction is quite common., , (13) Asexual reproduction is found in algal group and occur, by means of spores., , (14) There is a progressive evolution in sexual reproduction., The reproductive organs are multicellular., , (15) A multicellular embryo is formed during development, from the zygote. Algae lack embryo stage. Life cycle consists of, alternating haploid gametophyte and diploid sporophyte, generation. This phenomenon is called alternation of generation,, , Classification of plantae, , August Wilhelm Eichler (1883) a Vinnese botanist, divided, plant kingdom into two subkingdoms mainly on the basis of, presence or absence of seeds,, , (1) Cryptogamae (Gr. Cryptos = hidden; gamos = marriage), + Lower plants in which sex organs are hidden and seeds and flowers, absent. It includes Thallophytes, Bryophytes, Pteridophytes., , (2) Phanerogamae (Gr. Phaneros = visible; gamos =, marriage) : Higher plants in which sex organs are evident; seeds, present. It includes Gymnosperms and Angiosperms., , Engler (1886) divided plants into Thallophyta (plant body, thallus like and there is no embryo formation) and Embryophyta, (zygote develops into multicellular embryo}., , Thallophyta (Gr. Thallos = undifferentiated; phyton = plant)., This term was coined by Endlicher (1836). It includes Algae, Fungi,, Bacteria, Lichens, Unger (1838) placed algae, fungi and lichens, under thallophyta, In modern system of clasification like Whittaker, (1969), Fungi, Lichens and Bacteria are excluded from this group, and are placed in separate kingdoms., , , , Algae, (Gk. Phycos = alga or sea weed), , The branch of botany dealing with the study of algae is called, a3 phycology or algology. They are simple, thallose, autotrophic, non-vascular plants having unicelled sex organs and no embryo, formation. In Whittaker's classification, algae are grouped in three, kingdom — Monera (blue green algae), Protista (dinoflagellates,, diaioms, euglenoids) and Plantae (green algae, red algae and, brown algae)., , According to Fritsch (Father of algalogy), (1935) the, designation alga must include all holophytic organisms, as well as, their numerous colourless derivatives, that fall to reach the level of, differentiation characteristic of archegoniatae plants., , Occurrence : The algae occur in a variety of habitats which, are summarised here under

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ft, , Fresh water forms : They occurs in rivers, ponds, pools,, lakes and ditches. Those forms which remain attached to bottom, soil are called as epipelic. Several forms remain attached to bottom, or at the bank or to submerged objects, They are described as, benthos. Many forms remain attached to rocks or stones. They are, described as epilthic or lithophytic. e.g,, Batrachospermum., , Marine forms : Most of the members of brown algae, red, algae some green and blue-green algae occur in sea, While some, occur as phytoplanktons and benthos, others occur as lithophytes., The giant forms like Macrocystis (60 meters) and Nereocustis (50, meters) are also marine., , Terrestrial forms : Several members of green and bluegreen algae and a few others occur on damp soil. While forms like, Oscillatoria and Nostoc occur on alkaline and calcareous soil,, Fritschiella grows on acidic soll. Xanthophyceae members like, Vaucheria and Botrydium growing on damp shady soil or on shady, walls, are often described as Saprophytes., , Specialized habitats, , Cryophytes : Plants growing on snow or ice are called as, eryophytes. Different algal forms produce a specific colour effect, while growing as cryophyte eg,, yellow-green by Chlamydomonas, yeliowstonensis, red by C. nivalis, black by Scotiella nivalis and, purple-brown by Ancylonema nordenskiolai, , Thermophytes : Plants growing in hot water are called as, thermophytes. Some blue-green algae grow in hot water springs, at about 70°C e.g,, Oseillatoria brevis., , Epiphytes : Several algal forms grow on other plants (algae,, angiosperms) as epiphytes. eg, Ocdogonium, Cladophora,, ‘Vaucheria ete., , , , Endophytes : Some blue-green algae grows as endophytes, le other plants e.g., Anabaena growing inside the leaf of Azolla, {fern}, Nostoc inside the thallus of Anthoceros (homwort) and, Anabaena, Nostoc, Oscillatoria inside the coralloid roots of Cycas,, , Eplzoic : Algae growing on the bodies of animals are, described as epizoic, e.g, Cladophora crispata grows on snail shell,, Characium grows on the antennae of mosquito larvae,, Cyanoderma {red alga) and Trichophilus (green alga) are grows on, scales of sloth,, , , , Endozoie : Algae growing inside the body of animals. e.9.,, Chlorella grow within the tissue of Hydra, Some blue-green algae, also grow in the respiratory tract of animals. The blue-green algae, which grow endozoically inside the protozoans are called as, cyanellae,, , ‘Symbiotic forms : Some algae like Chlorella, Nostoce. ete, growing in symbiotic relationship with members of Ascomycetes, and Basidiomycetes (Fungi) constitute the lichen., , ‘Some species of Cladophora live in symbiotic association in a, sponge Eplydatea, , Parasites : The alga Cephaleuros virescens grows as a, Parasite on the tea leaves. In addition, Rhodochyirium,, Phyllosiphon ate other parasitic algal forms,, , Phyllobium sphagnicolum is parasite on Sphagnum (moss), , Plant Kingdom 117, , , , Thallus organization, , The algae show a considerable variation in the organization of, the thallus, , (1) Uniceltular forms : Several members of algae are, unicelled. They may be motile (Chlamydomonas) or non-motile, (diatoms). Some forms have a thick wall and become sedentary for, certain duration in their life history. They are called as coccold, e,g,, Chlorella, Chlorococcus., , (2) Multicellular forms : Multicellular forms are following :, , Colonial : A colony consists of independent organisms., While the colony of Volvax is motile, that of Hydrodictyon is fixed., A colony having fixed number of cells and division of labour is, called as coenobium e.g,, Valuax., , Palmelloid : Here the vegetative cells of the alga get, surounded by a mucilagenous matrix eg, Tetraspora,, Aphanotheca., , Dendroid : Here the colony appears like a microscopic tree., ‘There is secretion of mucilage from the polar end e.g, Ecballocystis, , Rhizopodial : Cells are united through rhizopodia eg,, Chrysidiastrum., , Filamentous : Most of the algal forms are filamentous. The, filaments may be uniseriate or multisetiate, free floating (Spirogyra), cor attached (Ulothrix), unbranched (Ulothrix) or branched, (Cladophora). The branches may be monomorphic (Cladophora) or, dimorphic (Batrachospermum). The branching may be lateral or, dichotomous, true (Ectocarpus) or false (Scytonema). The filaments, may be monosiphonous (Batrachaspermum) or polysiphonous, (Polysiphonia). In some filamentous forms there is distinction of a, prostrate system and an erect system, thus constituting the, heterotrichous habit. ¢.g., Stigeoclonium., , Siphonous : An aseptate, mullinucleate (coenocytic), condition of a filament or thallus constitutes the siphonous habit, €.9,, Vaucheria., , , , Parenchymatous : Parenchymatous organization of the, thallus has been observed in many members of brown algae, (Sargassum, Laminaria), red algae (Gracillaria, Porphyra) and a, few green algae (Chara, Ulva) etc., , Cell organization, , Most of the algal groups (except blue-green and, dinoflagellates) show eukaryotic cell structure, The cell wall is made, up of cellulose. Some red algae (Corallina) have impregnation of, CaCO,, The cells possess a well organised nucleus. The minimum, chromosome number in algae is n = 2 (Porphyra linearis) and the, maximum number is n = 592 (Netrium digitalis). The cells possess, distinct mitochondria, plastids, E.R, ribosomes and golgi body,, There may be a single thylakoid in the granum of Rhodophyceae,, two in Cryptophyceae, three in Phaeophyceae and, Bacillariophyceae but generally many., , The motile forms also possess flagella, They show the usual 9, + 2 structure. They are of two types - acronematic (whiplash, type) and pleuronematic (tinsel type).

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Reproduction, , The algae reproduce vegetatively, asexually and sexually., Various method involved in reproduction are discussed in the, following account., , (1) Vegetative reproduction : It occurs by following types., , Fragmentation : It occurs due to breakage of filament or, thallus into fragments, each of which behaves as an independent, organism e.g., Ulothrix, Spirogyra etc., , Fission : The unicelled forms like diatoms, desmids multiply, by fission ie, simple cell division., , Budding : A bud arises as a papilla on the parent cell. It, enlarges and finally separates e.¢,, Protosiphon., , Akinetes : Due to deposition of food material followed by, thickening of the parent wall, a cell is transformed into an akinete., They may be formed in a chain. On the arrival of favourable, conditions, they germinate to form a new plant e.g., Cladophora,, Ulothrie, Nostoc etc., , (2) Asexual reproduction : It occurs by the formation of, various types of spores in sporangia. Except the zoospores, all, other types of spores are non-motile., , Zoospores : These are thin walled motile spores. They are, anteriorly billagellate and the two flagella are similar in, Cladophora. In Vaucheria and Ectocorpus they are laterally, biflagellate and the two flagella are dissimilar. Multilagellate, zoospores are formed in Oedogonium and Vaucheria. In Vaucheria, the flagella are present all over the surface in pairs and hence it is, called as synzoospore., , Aplanospores : They are thin walled and non-motile spores, commonly formed in Chlamydomonas, Ulothrix etc., , Autospores : They are also thin walled, non-motile spores, which resemble the parent cell e.g,, Chlorella,, , Hypnospores : These are thick walled non-motile spores, formed to tide over unfavourable condition. They germinate on the, artival of favourable conditions e.g., Chlamydomonas, Ulothrix., , Carpospores : In red algae, carposporangia are formed at, the tip of gonimoblast filaments which produce a single haploid or, diploid carpospore e.g., Batrachospermum, Polysiphonia,, , Tetraspores : Four non-motile tetraspores are formed inside, a tetrasporangium as a result of mitosis in brown algae (eg.,, Dictyota) or by meiosis in red algae (e.g., Polysiphonia)., , Monospore : The juvenile stage of Batrachospermum, a red, alga, multiplies by forming a single monospore formed in side a, ‘monosporangiurn., , Palmella stage : In dry conditions, zoospores or, aplanospores get surrounded by mucilaginous sheath. The, divisions continue and they take the shape of colony. This is, known as palmella stage. Under favourable conditions each, zoospore gives rise to a new plant. e.g., Chlamydomonas., , (3) Sexual reproduction : The sexual reproduction in algae, {s broadly of three types as under =, , Isogamy : It involves fusion of gametes which are, morphologically and physiologically similar. They are called as, isogametes e.g., Chlamydomonas eugametos. In diatoms, there is, simplification of isogamous reproduction,, , , , Anisogamy : When the two gametes are morphologically, dissimilar, the anisogamy is said to be morphological eg.,, Chlamydomonas braunii, Ectocarpus secundus. Here the smaller, gamete may be called as male and the large one as female. When, the two gametes are morphologically similar but differ in their, behaviour, the anisogamy is said to be physiological ec,, Spirogyra, Ectocarpus siliculosus., , Oogamy : In this process there is formation of unicelled sex, organs. The male sex organ is called as antheridium and the, female as oogonium. The antheridium forms the male gametes, called antherozoids which are generally flagellate. The oogonium, forms a non-motile female gamete called egg. The oogamy, involves fusion of antherozoids with egg. The simplest type of, ‘ogamy is seen in Chlamydomonas coccifera, Important features of some selected classes, , Chlorophyceae or Green algae : Plants are fresh water or, marine and forms unicelled to parenchymatous. Chief, photosynthetic pigments are chlorophyll a, b; « B, 1+ carotenes,, lycopene; lutein, violaxanthin. Reserve food is starch. Zoospore, are formed and male gametes are flagellate. Flagella identical., Sexual reproduction - Isogamous, anisogamous or cogamous, type. e.g,, Chlamydomonas, Spirogyra., , Xanthophyceae or Yellow green algae : Plants are, generally fresh water and forms unicelled to siphonous. Chief, photosynthetic pigments are chlorophyll a, e; carotene,, Violaxanthin, neoxanthin. Reserve food is chrysolaminarin and, oils. Zoospore are formed and male gametes flagellate. Flagella, non-identical (unequal). Sexual reproduction - Isogamous,, anisogamous or oogamous type. e.g., Vaucheria., , , , , , Branches, , Axis, , , , gry, ee, na Holdfast, (o) (oii) eta), Frond 8 Main axis, Branches,, , cy fe, Fig: 1.641, Algae : (a) Green algae (1) Volvox (It) Chlamydomonas (ti) Chara, (b) Brown algae ()) Laminaria (i)Fucus (i) Dietyota, (e) Red algae () Porphyra (it) Polysiphonta

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Phaeophyceae or Brown algae : Plants are marine and, forms unicelled to parenchymatous. Chief photosynthetic pigments, are chlorophyll a, c; -carotene, fucoxanthin (brown colour),, lutein, violaxanthin, diatoxanthin, Reserve food is laminarin,, mannitol and oils. Zoospore are formed and male gametes, flagellate. Flagella unequal. Sexual reproduction — Isogamous,, anisogamous or oogamous type. e.g., Fucus, Dictyota., , Rhodophyceae or Red algae : Plants are generally marine, and forms filamentous to parenchymatous, Chief photosynthetic, pigments are chlorophyll a, d is present but chlorophyll c is absent;, G, B-carotene, lutein, violaxanthin, fucoxanthin, myxoxanthin,, phycoerythrin (red colour), y-phycocyanin (blue. pigment) and, allophycocyanin, Reserve food is floridean starch, galactan SO,, polymers. Zoospores are not formed and male gametes are nonflagellate. Sexual reproduction by specialized type of oogamy. Life, cycle haplobiontic or diplobiontic. e.g,, Polusiphonia, Porphyra, , Myxophyceae or Cyanophyceae : Plants are generally, fresh water, a few forms marine and forms unicelled to, filamentous. Cells showing prokaryotic organization. Chief, photosynthetic pigments are chlorophyll a; -carotene; Iuteit, myxoxanthin, oscillaxanthin, c-phycocyanin, _c-phycoerythrin,, allophycocyanin. Reserve food is cyanophycean starch, (glycogen) and cyanophycin (protein). Zoospore are not formed, and no flagellate bodies. Sexual reproduction is absent. e.g.,, Nostoc, Anabaena,, , Economic importance, , Useful aspects, , Nitrogen fixation : Some fifty species of blue-creen algae, are capable of fixing atmospheric nitrogen in the soil eg,, Anabaena, Aulosira, Cylindrospermum, Nosioc and Tolypothric, etc. Under aerobic conditions, nitrogen is fixed by heteracysts only,, Under anaerobic condition the vegetative cells also show, nitrogenase activity., , Algae as food : Many green algae such as Chlorella, Ulva,, Caulerpa, Enteromorpha, etc. are used as food, Chlorella has about, 50% protein and 20% of lipid and carbohydrates. The Chlorella, protein contains all the amino acids essential for human nutrition., Ulva factuca has formerly used in salad and soup in Scotland., , Green algae in space research : In recent years biologists, have realized that unicellular green algae (e.g., Chlorella) could be, used fo provide O, during space flight trips., , Antibiotics : The genus Chlorella yields an antibiotic, chlorellin, which is used against Gram +ve and Gram -ve, bacteria, especially Escherichia coll, Shigella dysenteriae and, Staphylococcus aureus. The genus Caulerpa also yields antibiotics., , Alginates : Alginic acid is a polymer of carbohydrate, It, ‘occurs in the cell wall and middle lamella, They are obtained from, Laminaria, Ascophyllum, Fucus, Nereocystis, Turbinaria etc. They, are used in pharmaceuticals as emulsifiers and stabilizers as well as, for making pills, antibiotic capsules ete. They are also used in the, preparation of soups, jellies, cosmetics, toothpastes, polishes, hair, dyes, compact powers, lotions, shampoos etc., , Carrageenin : It is a polysaccharide colloid (phycocolloid), obtained from the red algae Chondrus crispus and Gigartina stellata., Itis widely used in soups, sauces, milk shakes, cheese, jellies, cream, and fruit juices. It is also used in painting and printing,, , , , , , , , , , Plant Kingdom 119 |, , , , Agar-agar : It is a non-nitrogenous carbohydrate consisting of, ‘two polysaccharides namely agarose and agaropectin. It is obtained, from several red algae e.g, Gracilaria, Gelidium, Gigartina and, Chondrus etc, It is insoluble in cold water but soluble in hot. It is, used as a base for a variety of culture media., , Source of minerals and elements : The members of, brown algae called 'kelps’ have been the source for obtaining, jodine eg,, Laminaria, Macrocystis, Fucus. About 25% of total, iodine is extracted from kelps. Similarly red algae like Rhodomela,, Polysiphonia and Rhadymenia are sources of bromine., , Sewage disposal : Green unicellular algae such as Chlorella, and Chlamydomonas are used in sewage disposal ponds. They, remove CO, and restore O, by the process of photosynthesis., , Medicines : Sodium lamining sulphate are used as blood, anticoagulant and obtained from Laminaria and Durivillea has, antiworm (vermifuge) properties., , Source of protein : The protein of Chlorella is superior to, cereals as it contains all essential amino acids. Its nutritional value, is equal to soybean and spinach., , Harmful aspects, , Algal toxicity : Some dinoflagellates like Prumnesium,, Gymnodinium are extremely poisonous to fishes. The blue-green, alga Microcystis secretes hydroxylamine which not only kills, aquatic life but also the birds and cattles who care to drink water., While Lyngbya and Chlorella may cause skin allergies in human, , , , , , Algal parasitism : The red alga Cephaleuros virescens, causes red rust of tea thus destroying the tea leaves, Similar, disease are caused by the species of Cephaleuros to coffee plant,, Piper and Citrus sp., , Spoilage of drinking water : Forms like Anabaena,, Microcystis not only spoil the taste of drinking water but also, produces toxic effect. The growth of algae is controlled by using, algicides such as dichlorophen, sodium perborate, phygon Xl,, exalgae, delrad etc., , Water blooms : Algae grow abundantly in water reservoirs, ‘where excess of nutrients are available to them, This algal growth, floats on the water surface and look like foam or soap lather. It is, called water bloom. e.g,, Microcystis, Anabaena, Oscillatoria etc, , , , Some representative algae, , | Spirogyra |, Habitat, , Spirogyra was discovered by Link. It'is an unbranched, filamentous green alga of stagnant fresh waters which forms floating, masses (supported by bubbles of oxygen) called pond scum. A, sheath of mucilage occurs on the outside. It gives a silky touch. Hence, ‘Spirogyra is also called water silk or mermaid’s tresses., Structure, , ‘The thallus is an unbranched and uniseriate filament where, cells are arranged in a single row. In some species hold fast is, present (e.g., S. fluviatilis), The cells are elongated and cylindrical, The cell wall is two layered the outer is of pectic substance and the, inner of cellulose. The outer part (pectin) dissolves in water to form, ‘a mucilaginous sheath,

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120 Plant Kingdom, , , , , , Due to this reason Spirogyra filament's are slippery., Transverse or septum can be plane, colligate (with H-shaped, piece), replicate (ring like ingrowths) and unduliseptate (undulate)., The protoplast is differentiated into plasma membrane, thin layer, of cytoplasm, single nucleus, one (eg. Ssahni and S., venkataramanni) or many (16 in S.rectispora) ribbon (spiral), shaped chloroplasts (wavy margin) with pyrenoids and a large, central vacuole. Pyrenoid is made of protein surrounded by starch, plate or starch grains and it is the centre of starch formation., Nucleus occurs inside the central vacuole where it is suspended by, means of cytoplasmic strands., , , , , , Lt — cet wall, , , , , , , , SS. chioropiast, , , , , , , , , , , , , , , , , , Fig : 1,6-2 Spirogyra (a) Two filaments:, (b) and (c) Detailed structure of a cell, Reproduction, , Spirogyra reproduces by vegetative, asexual and sexual, methods., , (1) Vegetative reproduction : It takes place by, fragmentation of filament. Later on, each segment gives rise to, new plant., , (2) Asexual reproduction : Normally asexual reproduction, Is absent in Spirogyra, It occurs only occasionally by the formation, of akinetes, aplanospores and azygospores (Parthenospores}., , Akinetes : Under unfavourable conditions, the cells of the, filament develop into thick walled structures, which are known, as akinetes. On the onset of favourable conditions, these give, rise to new plants. Their wall is made up of cellulose and pectin, e.g, S. farlowl., , Aplanospores : These nonmotile aplanospores are either, round or oval. These later on under favourable condition give rise, to the new individuals. Aplanospores are known to occur in S,, eplanosporo, S. articulate etc, , Azygospores or Parthenospores : If there is sudden, change in the environment, the gametes fail to fuse and each, functions as parthenospore., , (3) Sexual reproduction : The sexual reproduction in, Spirogyra is called conjugation, It involves the fusion of two, morphologically identical, but physiologically dissimilar gametes., , ‘The conjugation is of two types, , (1) Scalariform conjugation : This is the most common, and advanced type of conjugation. It involves two filaments of, Spirogyra and takes place between two recently formed cells. The, cells of one filament show the formation of papilla towards the, other filament,, , It stimulates the formation of similar papilla in cells lying, ‘opposite to them. The two papillae fuse by enzymatic dissolution of, the wall thus forming a conjugation canal, , , , , , , , (b) Conjugation, , be tube, , Fig: 1.6-3 (a)-(d) Sexual reproduction showing, scalariform conjugation in Splrogyra, , ‘The conjugation tube between the two filaments looks like a, ladder, through which gamete from one of the gametangia passes, through to fuse with the passive gamete of another filament. The, gametes are formed singly and both active and passive, gametes are considered male and female gametes respectively., The fusion of both kinds of gametes with each other results into, formation of zygospore., , The zygospore wall is differentiated into three layers, the, outer exospore which is thin, the middle mesospore which is, a thick layer of cellulose, chitinized and pale yellow to brown in, colour, and inner endospore which is thin and cellulose in, nature., , (2) Lateral conjugation : It takes place between two nearest, cells of the same filament (homothallic), Both male and female, gametes are found in same filament. It is of two types., , {i) Indirect lateral conjugation : Two outgrowths appear, on both sides of a transverse septum of two adjacent cells which, later on form a conjugation tube. Of the two cells, one behaves as, male gametangium from which gamete passes through the tube, into female gametangium. By fusion, zygospore is formed. Thus in, each second cell of a filament zygospore is formed. It is commonly, seen in S. affinis and S. tenutssima., , , , , , , , Female'gamete, , Male gamete, , (o), , Zygospore, , ea, i), , Fig: 1.6-4 Sexual reproduction showing, , iateral (indirect) conjugation in Spirogyra, , (ii) Direct lateral conjugation : In this type of conjugation,, the male gamete after passing through an aperture in the, transverse septum of adjoining gametangium enters the female