Plant Kingdom

Plant Kingdom INTRODUCTION In the previous chapter, we looked at the broad classification of living organisms under the system proposed by Whittaker (1969) wherein he suggested the Five Kingdom classification viz. Monera, Protista, Fungi, Animalia and Plantae. In this chapter, we will deal in detail with further classification within Kingdom Plantae popularly known as the ‘plant kingdom’. We must stress here that our understanding of the plant kingdom has changed over time. Fungi, and members of the Monera and Protista having cell walls have now been excluded from Plantae though earlier classifications put them in the same kingdom. So, the cyanobacteria that are also referred to as blue green algae are not ‘algae’ any more. In this chapter, we will describe Plantae under Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms. Let us also look at classification within angiosperms to understand some of the concerns that influenced the classification systems. The earliest systems of classification used only gross superficial morphological characters such as habit, colour, number and shape of leaves, etc. They were based mainly on vegetative characters or on the androecium structure (system given by Linnaeus). Such systems were artificial; they separated the closely related species since they were based on a few characteristics. Also, the artificial systems gave equal weightage to vegetative and sexual characteristics; this is not acceptable since we know that often the vegetative characters are more easily affected by environment. As against this, natural classification systems developed, which were based on natural affinities among the organisms and consider, not only the external features, but also internal features, like ultrastructure, anatomy, embryology and phytochemistry. Such a classification for flowering plants was given by George Bentham and Joseph Dalton Hooker. At present phylogenetic classification systems based on evolutionary relationships between the various organisms are acceptable. This assumes that organisms belonging to the same taxa have a common ancestor. We now use information from many other sources too to help resolve difficulties in classification. These become more important when there is no supporting fossil evidence. Numerical Taxonomy which is now easily carried out using computers is based on all observable characteristics. Number and codes are assigned to all the characters and the data are then processed. In this way each character is Plant Kingdom given equal importance and at the same time hundreds (ix) Embryo stage is absent. Mainly zygotic meiosis of characters can be considered. Cytotaxonomy takes place except brown algae (sporic meiosis). that is based on cytological information like (x) Life cycle is mostly haplontic type (Diplontic type chromosome number, structure, behaviour and in brown Algae). chemotaxonomy that uses the chemical constituents of the plant to resolve confusions, are also used by o Whittaker classified three types of Algae in plant kingdom – Red algae, brown algae and green taxonomists these days. algae. ALGAE (= sea weed) o It involves those organisms that have thallus like plant (I) Class – Rhodophyceae (Red Algae) : o General characters : body, chlorophyll, accessory spores for asexual multiplication nonjacketed gametangia, absence of (i) These are mainly found in marine water except few embryo stage. species Ex: Batrachospermum – Fresh water algae. Red algae are usually autotrophic but Study of Algae is called Phycology or Algology. F. Harveyella is colourless and parasite on other red E. Fristch is known as ‘Father of phycology’. He algae. classified Algae in to 11 classes on the basis of their pigments, storage products, type of flagella, nucleus (ii) Its thallus shows variations in different members – reproduction etc. unicellular Characters of Algae : (i) They are usually found in water (either marine or fresh water). (ii) Its plant body is covered by mucilage that provides protection from water currents and epiphytic growth. Ex: Porphyridium, ribbon like Ex:Chondrus, parenchymatous sheet Ex: Porphyra, multiaxial poysiphonous filaments Ex: Polysiphonia, uniaxial monosiphonous branched filaments Ex: Batrachospermum, graceful lace like Ex: (iii) Plant body is thallus that can be unicellular, Gelidium. filamentous, colonial and composed of true paren(iii) Flagellated cells are completely absent in life chyma. Mechanical tissue is absent. cycle. (iv) Cell wall consists of cellulose. Nutrition is autotrophic, chlorophyll a and  carotene are (iv) Cell wall is mucilaginous and contains cellulose, pectin and abundant sulphated phycocolloids universal pigments. (like agar, carrageenin, funori). In some red algae (v) Reserve food is mainly starch. it has deposition of calcium carbonate and appear (vi) Vegetative and asexual reproduction are quite coral like and called coralline Ex: Corallina. common. One celled mitospores perform asexual (v) Photosynthetic pigments involve chlorophyll a, reproduction. – carotenes and phycobilins. Chlorophyll d has (vii) Sexual reproduction comprises isogamy (Ex: been reported in some cases. Phycobilins are of Chlamydomonas debaryanum, Ulothrix), two types anisogamy (Ex: Chlamydomonas braunii) and (a) red coloured r-phycoerythrin – It is oogamy (Ex: Chlamydomonas coccifera) in responsible for red colour of red algae. different forms. (b) Blue coloured r-phycocyanin and (viii) Sex organs are nonjacketed gametangia that may allophycocyanin. be unicellular or multicellular. (vi) Reserve food is floridean starch. It is highly branched as cyanophycian starch. Thus floridean starch and cyanophycian starch both are similar as glycogen in structure. (vii) Reproduction : (a) Vegetative reproduction – By fragmentation and regeneration of hold fast. Plant Kingdom (b)Carrageenin is obtained from cell wall of chondrus crispus and Gigartina. It is used in confectionary, bakery, jelly, creams, as clearing agent in liquors (Beer) and leather finishing, as emulsifier in chocolates, icecreams, sauces, toothpastes paints and costmetics. (c) Funori is obtained from Gloiopeltis. It is a glue (b) Asexual reproduction – By many types of used as adhesive and in sizing textiles, papers etc. spores like monospores, carpospores, tetraspores. (II) Class – Phaeophyceae (Brown Algae) : (c) Sexual reproduction – It is most advanced General characters : type. Male sex organ is called spermatangium (i) They are mostly marine lithophytes. that forms nonmotile spermatia. Female sex organ is a flask shaped carpogonium that (ii) Unicellular, unbranched, filamentous and colonial forms are absent. contains basal swollen carpogyne & upper long neck like trichogyne which receives spermatia (iii) The body is composed of heterotrichous branched from water. filamentous structure in lower forms Ex: Ectocarpus and parenchymatous structures in higher forms Ex: Laminaria, Sargassum, Fucus. (iv) Some brown algae are giant (large sized) that are called kelps or sea weeds Ex: Macrocystis – length is 30–60 m, Nereocystis–length is 20– 30 m, Laminaria–Length is 2–12 m. Economic importance : (i) Food : (v) Plant body is differentiated into hold fast (for fixation), stipe and lamina (for photosynthesis). Sargassum (gulf weed) is free floating and has air filled floats called vesicles that provide buoyancy. North Atlantic sea is called sargasso sea due to abundant occurrence of free floating Sargassum fluitans. (vi) Conducting tubes or trumpet hyphae are found in larger brown algae or kelps. Some red algae are edible Ex: Laver (Porphyra), (vii) Cell wall contains cellulose and nonsulphated Dulse (Rhodymenia), Irish moss (Chondrus). phycocolloids like fucin, fucoidin and algin. (ii) Phycocolloids : (viii) Main pigments are chlorphyll a, c,  carotene. (a)Agar-agar is obtained from Gelidium, Brown pigment fucoxanthin provides brown Gracilaria etc (these algae are called agarophytes). colour to the brown algae. It is used to solidify culture medium. It is also used as laxative stabilizer or thickener in preparing jams, (ix) Reserve food is laminarin, mannitol and oil. jellies, creams, pudding, baby food, ice cream, (x) Flagella two, unequal heterokont. Pyrenoids are naked. bakery products. Plant Kingdom (xi) They reproduce asexually by biflagellated zoospores. (iv) Food : Some brown algae are used as food in some countries. Kombu is rich in carbohydrate and formed Sexual reproduction varies from isogamy to oogamy. by Laminaria. Alaria yields a product called Zygotic meiosis absent but sporic meiosis sarumen in japan. occurs. (v) Potash : It is extracted from Macrocystis and (xii) Alternation of generation is isomorphic Nereocystis and used as fertilizer in germany. (Ex: Ectocarpus, Dictyota) or heteromorphic (Ex: Laminaria). (III)Class Chlorophyceae (Green Algae) : (i) Most of species are found in fresh water. Some species are marine Ex: Caulerpa, Acetabularia, Codium. (ii) Thallus may be in various forms (a) Unicellular motile Ex: Chlamydomonas. (b) Cocooid or nonmotile Ex: Chlorella. (c) Filamentous Ex:Ulothrix, Spirogyra. (d) Colonial : Motile colony Ex: Volvox (iii) They bear chl a, b, carotenes( and type), xanthophyll like lutein. (iv) 2, apical and isokont flagella are present. (v) Chloroplast are agranal (grana is absent). Starch is reserve food material and stored as sheets in pyrenoids, present in the chloroplast. (vi) Cell wall consists of cellulose and also have pectin & xylan. (vii) Vegetative reproduction takes place through fragmentation, stolons and tubers. (viii) Asexual reproduction occurs by mitospores and meiospores. (ix) Sexual reproduction takes place through isogamy, Fig: Laminaria (a), Fucus (b), Dictyota anisogamy and oogamy. (TB) (x) In green algae, three types of life cycle occur. Economic importance : (a) Haplontic (b) Diplontic (i) Algin : It is nonsulphated phycocolloid and (c) Diplohaplontic obtained from Laminaria, macrocystis, Fucus, sargassum. It is used in flame proof plastics, security glass, gauze and surgical threads, shaving creams, tooth paste, cosmetic creams, shampoos, sauces, sizing textiles, etc. (ii) Mannitol : It is used as food and added to inks, plastic, paints and varnishes. It is half as sweet as sugar and is a good substitute of sugar for diabetic patients. (iii) Iodine : It is extracted from Laminaria and Fucus. Plant Kingdom (a) Haplontic : The dominant phase is haploid. The diploid phase is represented only by zygote or zygospore. Meiosis takes place during germination of zygote or zygospore (zygotic meiosis) Ex: Ulothrix, Chlamydomonas, Spirogyra. Economic importance : (i) Food : Chlorella pyrenoidosa (called space alga) is used by exobiologists for food, O2, disposal of CO2 in prolonged space flight. Chlorella has proteins (upto 50%), fats (20%), carboydrates (20%), vit (b) Diplontic : The dominant phase of Algae is A, B1, B2 B12, C and E. It is used as SCP (single diploid. It forms haploid gametes by meiosis. The cell protein) and its nutritional value is equal to gametes fuse to form zygote that regenerates the soybean and spinach. Ulva (see lettuce) and codium diploid phase. Ex: Caulerpa. are used as salad. (ii) Sewage oxidation : Chlamydomonas, Scenedesmus and Chlorella are found in sewage oxidation tanks where they produce O2. The latter helps aerobic bacteria to decompose sewage. (iii) Antibiotic : Chlorellin is extracted from Chlorella. It is effective against bacteria. (iv) Larvicidal property : Chara show larvicidal property. They kill mosquito larvae. o Land plants have been evolved from chara like green algae. (c) Haplodiplontic : In this type of life cycle, well developed multicellular haploid and diploid phases occur which are respectively called gametophyte and sporophyte. The haploid gametophyte forms haploid gametes and after fusion of gametes diploid zygote is formed that gives rise to diploid sporophyte. The latter forms haploid spores by meiosis (Sporic meiosis). Meiospores form new gametophytes after germination. Ex: Ulva, Cladophora. Plant Kingdom Bryophytes (Bryon = moss; phyton = Plant) : CHLAMYDOMONAS o It is unicellular, eukaryotic, microscopic (10–30m), Introduction : pyriform, biflagellate green alga. o These are first land inhabiting or terrestrial o It is found in both stationary fresh water and marine plants. Bryophytes are non vascular, autotrophic, habitats (rich in ammonia salts). seedless, nonflowering plants. These are known as amphibians of plant kingdom. o The term Bryophytes coined by Robert Braun (1864). He included algae, fungi, lichen and moss in it. o On the basis of evolution, It is placed between thallophyta and pteridophyta. o Study of Bryophytes is called Bryology. Hedwing is known as Father of Bryology while S.R. kashyap is known as the Father of Indian Bryology. o These are the most primitive plants of the kingdom embryophyta. Volvox : Commonly called Rolling ball alga General characters : (i) These are found in moist, shady and cool places. They form green carpets or mats on damp soil, rocks, walls tree trunks. Plant Kingdom (ii) Some Bryophytes are aquatic like Riccia flutians, Riccia abuensis, Ricciocarpus natans, Riella, some sp. of Sphagnum, Fontinalis etc. In india, they are abundantly found in Himalyan region. Hence western himalaya is known as gold mine of bryophytes. (iii) The main plant body is haploid independent thalloid or foliose gametophyte which does not differentiate into true roots, stem & leaves but foliose plants bear root like nonvascular rhizoids, leaf like phylloid and stem like cauloid Ex : Funaria, Sphagnum. (iv) Thallus is multicellular, dichotomously branched, thick having unicellular or multicellular rhizoids for fixation. (v) Cell wall in liverworts is composed of cellulose and pectose whereas in mosses it is of hemicellulose and pentosan. Reserve food is starch. (vi) Vascular tissues (xylem and phloem) are absent in both gametophytic and sporophytic phases. The conduction takes place through specialized parenchyma. (vii) Vegetative reproduction takes place through fragmentation, buds, gemmae, tubers, protonema, adventitious branches etc. (viii) Asexual reproduction absent. (ix) Sexual reproduction is oogamous type. Sex organs are multicellular and surrounded by single layered sterile jacket. (x) Male sex organ is called antheridium which is globular and forms biflagellated antherozoids or sperms (motile male gamete). Flask shaped female sex organ is called archegonium that consists of a swollen venter and a tubular neck. (xi) Water is essential for fertilization. Archegonia secretes mucilage rich in potassium salts / proteins / sucrose for attracting antherozoids in water. (xii) Fertilization is internal and takes place by zoodiogamy. Diploid zygote forms in the venter by the fusion of one antherozoid with egg cell. (xiii) After fertilization zygote immediately divides and form multicellular embryo. The Development of embryo is exoscopic (The apex of embryo develops from outer cell). Plant Kingdom Bryophytes: A liverwort – Marchantia (a) Female thallus (b) Male thallus (xiv) Embryo gives rise to multicellular sporogonium or sporophyte. The latter differentiates into either capsule only or foot, seta and capsule. Sporophyte is completely (Ex: Riccia) or partially (Ex: Funaria) parasite on gametophyte. (xv) Spore mother cells or sporocytes of capsule of sporophyte undergo sporic meiosis and form haploid meiospores which are alike or homosporous. (xvi) On germination, spore forms new gametophytic plant either directly (Ex: liverworts and hornworts) or by juvenile filamentous protonema stage (Ex: moss). (xvii) Life cycle is diplohaplontic and alternation of generation is heteromorphic. Classification of Bryophyta : o Bryophytes are Classified into three classes. (i) Hepaticopsida – (Ex: Liverworts) (ii)Anthocerotopsida – (Ex: Hornworts) (ii)Bryopsida – (Ex: Mosses) Plant Kingdom Marchantia : (v) Sphagnum has good water holding capacity therefore it is widely used for packing of young 1. It is a thalloid liverwort, grow prostrately on the seedlings, flowers, vegetables, fruits, corrosive surface and show dichotomous branching. materials, glasses etc during transportation. 2. The thallus have dorsal groove on the upper surface and rhizoids and scales on lower (ventral) surface. (vi) Dry clean, disinfected sphagnum is used as a replacement of absorptive cotton for wound 3. Rhizoids are unicellular. dressing. 4. Vegetative reproduction occur by progressive death, regeneration, adventitious, branches and gemmae. (vii) Sphagnol, an antibiotic that is derived from distillation of peat tar which is effective against skin 5. Gemmae are formed inside small gemma cups diseases. developing middorsally on vegetative thalli. gemma cups have eight shaped (8) gemmae and (viii) Polytrichum has ability to dissolve stones in kidney and gall bladder. mucilagenous hairs. 6. Each gemma is an elliptical and biconvex structure, Point of Remember having unicellular stalk and two lateral notches. On 1. Largest bryophyte is Dawsonia (moss - 70 cm) germination one daughter thallus is produced from and smallest bryophyte is zoopsis argentea each notch. Thus each gemma produce two (liver wort) daugther thalli. 2. Terrestrial Amphibians : Bryophytes are considered as terrestrial Ampibians because they Sexual reproduction : require external water on the soil surface for 7. Marchantia is dioecious. Sex organs are borne on following reasons. disc-shaped receptacles borne at the tips of vertical 8. gametophores. Male receptacle on antheridiophore and femate receptacle on archegoniophore. (i) Dehisence of archegonia and antheridia. Male receptacle is 8 lobed and slightly concave on upper side. (iii) Supply of water to all parts by capillarity in the absence of vascular tissues. (ii)Swimming of male gametes to archegonia. 9. Archegonia are shortly stalked, having 6 vertical (iv) Protection from transpiration. rows of neck cells, enclosing 4-6 neck canal cells. Venter has only one venter canal cell and egg PTERIDOPHYTES cell or oosphere. (Pteris = feather, phyton = plant) : Economic importance : o These are most primitive, seedless, spore producing (i) Mosses grow in tufts over the soil surface and bind soil particles thus they prevent soil erosion. (ii) Both mosses and lichens produce soil cover over the barren rocks during succession. (iii) Sphagnum grows in acidic bogs where it helps in o formation of peat hence called peat moss. (iv) Peat is used as fuel as well in making alcohol, ammonium sulphate, tar, tanning material and paraffin and dye. land plants which are popularly knownas botanical snakes (because, reptiles are first land animals) or vascular cryptogams (vascular tissues xylem and phloem present). The term pteridophyta coined by Haeckel (1866). The study of pteridophytes is called pteridology. F.O. Bowers is called ‘Father of pteridology’ while S.S. Bir is known as ‘Father of Indian Pteridology’. Plant Kingdom General characters : (ix) Sporangia are borne on abaxial side of fertile leaves. Sporangia bearing leaves are called sporophylls (i) Most of the plants are terrestrial and grow well in Ex: Ferns, in other pteridophytes sporangia are damp and shady places. Some pteridophytes are developed in the axil of leaves on stem Ex: found in xerophytic conditions Ex: Selaginella Selaginella, or on sporangiophores Ex: lepidophylla, S. rupestis, Equisetum arvense. Equisetum or in sporocarp. Some are epiphytic Ex: Lycopodium phlegmaria, Pleopeltis, Ophioglossum. Some are aquatic Ex: (x) Sporangia are developed singly or in groups. The Marsilea, Azolla, Salvinia, Isoetes. latter is called sori which is protected by true or (ii) Most of the pteridophytes are herbaceous except tree ferns like Cyathaea, Alsophila. (iii) The main plant body is sporophyte that is differentiated into root, stem and leaves. false indusium or both. True inducium arise from placenta e.g. Dryopteris and false inducium formed by curling of leaf margin e.g. Pteris and Adiantum. In Pteridium both true and false inducium are found. (iv) Primary root is short lived. Later on the former is replaced by adventitious roots developed by stem. (v) Stems may be underground or aerial. The branching of stem may be dichotomous Ex: Marsilea, Lygodium or monopodial Ex: Lycopodium, Selaginella. (vi) All the vegetative parts bear vascular tissues that form different types of steles. Vessels are usually absent in xylem similarly companion cells, sieve tubes and fibres are absent in Phloem but sieve cells are present. Secondary growth is absent except in Isoetes. (vii) Leaves are of two types microphyllous and megaphyllous. In microphyllous types, Leaves are small and unveined while stem is comparatively longer and leaf traces do not leave leaf gaps in the stele Ex: Lycopodium, Selaginella, Equisetum while in megaphyllous types stems are short and leaves are large (called frond) with branched venation. Leaf (xi) In heterosporous pteridophyta, sporangia are of gaps are found in stele Ex: ferns (Pteridium, two types-microsporangia and megasporangia Dryopteris, Pteris). that form microspores and megaspores (viii) Meiospores are formed by sporic meiosis in respectively by sporic meiosis. sporangia during asexual reproduction. The former are either same type (homosporous Ex: ferns like (xii) Gametophyte is small/reduced, independent, nonvascular. pteridium, Adiantum, Pteris) or different types (heterosporous Ex: Selaginella, Marsilea, Salvinia, Azolla). Plant Kingdom (xiii) Sex organs are multicellular, jacketed and developed on gametophyte. Male sex organs are Antheridia that are reduced and sessile. Antheridium forms motile sperms (usually multiflagellated but biflagellated in Selaginella). Female sex organs are archegonia embedded in gametophyte. Archegonium consists of neck and swollen venter. Neck is composed of four vertical rows of cells and it has 1–4 Neck canal cells while venter is non motile having a venter canal cell and an egg cell or oosphere. (xiv) Sexual reproduction is oogamous type. Water is required for movement of sperms from antheridia to archegonia (chemotactic movement due to malic acid rich mucilage secreted by archegonia) during fertilization. (xv) After fertilization, deploid zygote is formed that is first cell of sporophytic generation. Point of Remember 1. Sori : Sporangia are borne in groups called sori that are of three types. 2. Azolla : It is smallest pteridophyta. It is aquatic fern that is used as biofertilizer due to presence of ntirogen fixing cyanobacteria- Anabaena in its leaves. 3. Aquatic ferns–Ex: Marsilea, Salvinia, Azolla. 4. Seed habit in pteridophytes : Seed habit is seen is some pteridophytes like Selaginella. Economic importance : (i) Food : Sporocarps of marsilea (a water fern) contains starch and are used as food article by certain tribes. (ii) Medicines : An antihelminthic drug is obtained from rhizomes of Dryopteris. Homeopathic medicine is obtained from Lycopodium. (iii) Selaginella is helpful in soil conservation. (iv) Ornamentals : Ferns are grown as ornmental plants. (xvi) The development of embryo is holoblastic or Classification of Pteridophytes : meroblastic, exoscopic/endoscopic/lateral. Life o Pteridophytes are classified in to 4 classes. (i) Psilopsida (ii) Lycopsida cycle is diplohaplontic and distinct heteromorphic (iii) Sphenopsida (iv) Pteropsida alternation of generations occurs. S.No. Common name Botanical name 1 Walking fern, Maiden hair fern. Adiantum caudatum 2 Club moss, trailing evergreen Lycopodium 3 Horse tail, Scouring rushes Equisetum Plant Kingdom GYMNOSPERMS (gymnos–naked, sperm–seed) o These are perennial woody plants or ancient seed bearing phanerogamic sporophytic plants without flowers, ovary and fruits. They are popularly called naked seeded vascular plants. o It is the smallest group of plant kingdom and involves only 70 living genera and 900 species. In india, its 16 genera and 54 species have been reported. These are found in cold temperate climates but cycads occur in warmer areas. o The term Gymnosperm coined by Theophrastus (300 BC) in his book ‘Enquiry into plants’. o The study of Gymnosperm is called Gymnospermology. General characters : (i) The main plant body is diploid sporophyte which is differentiated into true roots, stem and leaves. (ii) Root is tap root. In some members, roots are symbiotically associated with blue green algae Ex: coralloid roots in Cycas or with fungus Ex: mycorrhizal roots of Pinus. (iii) Stem bears eustelic condition. Vessels are absent in xylem of gymnosperms except gnetales Sieve tubes and companion cells absent in phloem. But the latter has sieve cells and albuminous cells. Secondary growth occurs in stem and root. (iv) Wood of gymnosperms is homoxylous, noporous and soft. Wood is of two types. (v) Mostly unisexual monosporangiate cones are found instead of flowers. All gymnosperms are heterosporous. (a) (vi) Two types of sporophylls are found– micropsorphylls and megasporophylls. Both types of sporophylls form cones or strobili (the male cone and female cone). In case of Cycas megasporophylls do not form cone. (vii) Microsporophyll (stamen) has microsporangia or pollensacs (900–1000 microsporangia in sori of Cycas and two microsporangia in Pinus sps.) while megasporophylls (carpel) has megasporangia or ovules. (b) (viii) The distinction into anther and filament is absent in Microsporophyll. Similarly Megasporophylls are not organised and rolled into carpels. Stigma and ovary are absent. (ix) Ovules lie exposed on megasporophyll. Ovule is orthotropous, sessile, unitegtmic. Single integument is usually divisible into 3 layers. (c) Fig: Cycas (a), Pinus(b), Ginkgo(c) (TB) (x) Megaspores are formed by sporic meiosis in ovule. The former forms haploid female gametophyte (called endosperm) before fertilization. (xi) In microsporangia, microspores (pollen grains or androspore) are formed by sporic meiosis. On germination, microspore forms male gametophyte. Plant Kingdom (xii) Pollination is anemophilous (Wind pollination) Economic Importance : and direct (Pollen grains reach directly into (i) The wood of conifers like Pinus roxburghii (chir pine), Cedrus deodara (deodar, strongest of ovule). Pollen grain is released in 3 celled stage in all soft wood), Sequoia (red wood tree) is used Cycas and 4 celled in Pinus in making light furniture, plywood, packing (xiii) Male gametophyte has two male gametes. Female cases, railway sleepers, drawing board, pencils,match boxes and sticks. gametophyte contains archegonia Neck canal cells (ii) Paper is composed of wood of Pinus, Picea are absent in archegonia. (spruce), Gnetum, Larix (Larck), Abies (fir). (xiv) Water is not required for transport of male gametes. (iii) Sago a kind of starch is obtained from cortex and Actually malegametes are carried by pollen pith of stem and seeds of Cycas. The Roasted tube (that is called siphonogamy). One male seeds of Pinus gerardiana (Chilgoza) are used as dry fruit. Seeds of Ginkgo biloba are eaten in gamete fuses with egg cell to form zygote. china and japan. (xv) Fertilization, ovule is converted into seed. (iv) Ephedrine is obtained from stem branches of (xvi) Seeds are naked (they do not enclose in ovary), Ephedra and used to cure cough, cold, bronchitis, asthma and fever. endospermic and having three generations. (v) Many Gymnosperms are grown in the gardens as Polyembryony is common in gymnosperms. ornamental plants Ex: Cycas Point of Remember 1. Ephedra foliata is naturally occurring gymnosperm 4. in Rajasthan. Ginkgo bears root nodules formed by a Nitrogen fixing nonleguminous actinomycete bacte ria-Frankia. 2. Double Fertilization is usually absent in Gymnosperms 5. but found in Ephedra. 3. Ephedra has largest pollen chamber & longest neck of archegonium (32 celled in 8 tiers). Gnetum : Gnetum show many similarities with angiosperms like reticulate veinnation in their leaves, presence of vessels in xylem absence of archegonia and presence of two cotyledons. But stile it is gymonosperm because ovules are naked. ANGIOSPERMS (angeion = vessel, sperma = Seed) o Angiosperms are most advanced plants, that have flowers, covered ovules, seeds. It involves 12500 genera and 2.70 lakh species (2.20 lac are dicots and 50000 are monocots). o They are most dominant and highest evolved plants on this earth. Tertiary period of coenozoic era is called Age of angiosperms. o Angiosperms have been reported in every habitat. All types of catagories of plants involve in angiosperms–annuals/biennials/perennials; autotrophs/Parasites/epiphytes/insectivorous/ Saprophytes. General characters : (i) The main plant body is sporophyte that is differentiated into roots, stem and leaves. (ii) The characteristic features is presence of vessels in xylem and presence of companion cells in phloem. (iii) Wood is hard, porous, monoxylic. Secondary growth is found in dicots. Plant Kingdom (iv) Antheridia and archegonia are absent. Presence of flowers is most important feature. Sex organs enclosed in the flower. (v) Flower consists of 4 whorls – Calyx, Corolla, Androecium, Gynoecium. Androecium (stamen) is microsporophyll and Gynoaecium (carpel) is megasporophyll. (vi) Megasporophyll or carpel contains ovary, style and stigma. (vii) Ovules are enclosed within ovary. Pollen grains are shed at 2-3 celled stage and fall on stigma. (viii) Double fertilization (syngamy and triple fusion) is characteristic feature that is found in angiosperms only. (ix) Endosperm is triploid (3n) and formed after double fertilization. (x) Ovules & ovary are converted into seeds and fruits respectively after fertilization. (xi) Seed has two generations–a parent sporophyte and future sporophyte but gametophytic generation is absent in seeds. (xii) Seed bears 1–2 cotyledons. Plant Kingdom Point of Remember 1. Smallest angiospermic plant is Wolffia microscopica (1 mm) while largest angiospermic plant is Eucalyptus regnans (114 mt or 375 feet– tallest angiospermic tree). 2. Zostera arina : Thalassia are marine angiosperms.