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Pre-Medical : Biology, , GYMNOSPERM, 1., , The gymnosperms (gymnos = naked, sperma = seed) and plants in which the ovule are not enclosed by any, ovary wall and remain exposed, both before and after fertilization., , 2., , Study of Gymnosperm known as Gymnospermology., l, , Main plant body of Gymnosperm is divided in to Root, Stem and leaves., , l, , The roots are generally tap roots., Note : - Roots in some genera have fungal association in the form of mycorrhiza (Pinus), while in some, others (Cycas) small speciallised roots called coralloid roots are associated with N2-fixing cyanobacteria., , l, , In Cycas roots are of two types i.e. tap root and coralloid roots., , l, , The stems are unbranched (Cycas) or branched (Pinus, Cedrus)., , l, , The leaves may be simple or compound., , l, , In Cycas the pinnate leaves persist for a few years., , l, , The leaves in gymnosperms are well-adapted to extreme conditions like temperature, humidity and wind., , l, , In conifers the needle like leaves reduce the surface area, their thick cuticle and sunken stomata also, help to reduce water loss., , 3., , Gymnosperm & Angiosperm are collectively included under spermatophyta i.e. seed bearing plants., , 4., , Gymnosperms are naked seeded plant i.e. no fruit formation takes place in these plant., In gymnosperm embryo & seed formation takes place but no fruit formation occur., , 5., , Gymnosperms are very limited in distribution. They are mainly found in cold regions.In India Gymnosperms, are found on Himaliayan mountains. They usually occur on slopes of mountain in cold region therefore, , Z:\NODE02\B0AI-B0\TARGET\BIO\ENG\MODULE_4\01-PLANT DIVERSITY\03-PLANT.P65, , gymnosperms are xerophyte., , E, , 6., , All gymnosperms are vascular plants. Therefore vascular tissue present i.e. xylem & phloem. Xylem lacks, vessels & phloem lacks companion cells., Note :-, , 7., , l, , Exceptionally in xylem of Gnetum, Ephedra, Welwitschia true vessels are present., , l, , Secondary growth takes place in gymnosperms stem, so Gymnosperms stem is woody., , Most of the gymnosperms are arborescent (woody) and tree habit - but some are present as shrub., eg., , Ephedra, , Some Gymnosperm are liana or woody climbers., eg., , Gnetum ula, , 71
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Pre-Medical : Biology, LIFE CYCLE OF GYMNOSPERM 1., , All gymnosperms are heterosporeus plants. They produce two kinds of haploid spores; microspores and, megaspores within microsporangium and megasporangium respectively., , 2., , Sporangia are borne on sporophylls which are arranged spirally along an axis to born lax (loose) or compact, strobilli or cones., , 3., , The strobilli (sing strobilus) bearing microsporophylls and microsporangia are called microsporangiate cones or, male strobilli or male cone., , 4., , Within microsporangium many microspore mother cells are present which undergo meiosis and produce many, haploid microspores. Germination of microspore takes place with in microsporangium hence it is called, endosporic germination., , 5., , The microspore develop into pollen grain and then male gametophyte which is highly reduced and is confined, to made of only a limited number of cells (e.g. In Cycas-5 cells and Pinus-6 cells are present in mature, male gametophyte)., , 6., , The development of pollen grains take place within the microsporangium., , 7., , The cones/strobilli bearing cluster group of megasporophylls with megasporangia are called megasporangiate, cones or female cones., , 8., , When the male and female cones are produced on the same tree, the member is known as monoecious eg., Pinus and when male and female cones or megasporophylls are borne on different trees, the member is, called dioecious. In Cycas male cones and megasporophylls are borne on different tree, so it is dioecious., , 9., , In gymnospersm the megasporangium is made of a diploid tissue also called nucellus. It is covered with integument, (envelope) also hence this composite structure is called integumented megasporangium or ovule., , 10., , One cell of nucellus (2n) is differentiated into megaspore mother cell and undergoes meiosis to form four, haploid megaspores. Three of them degenerate and only one megaspore remains functional., The functional megaspore germinate inside the megasporangium (endosporic germination) and developes into, a multicellular female gametophyte also called endosperm(n)., , 12., , The female gametophyte (endosperm) produces two or more archegonia or female sex organs in one ovule., , 13., , This multicellular but less developed female gametophyte is retained within megasporangium (ovule)., , l, , In bryophytes and pteridophytes, the male and female gametophytes have an independent free living existence., , l, , In gymnosperm and angiosperm male and female gametophyte do not have free living existence. They remain, within the sporangia retained on the sporophyte., , 14., , The pollen grain are released from the microsporangium and are carried in air currents (wind pollination =, Anemophily) and come in contact with the opening (micropyle) of ovules on megasporophylls., , 72, , Z:\NODE02\B0AI-B0\TARGET\BIO\ENG\MODULE_4\01-PLANT DIVERSITY\03-PLANT.P65, , 11., , E
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Pre-Medical : Biology, 15., , Each plllen grain produces pollen tube carrying two male gametes which grows towards archegonia in the, ovule and release (discharge) its content (two male gametes) near the mouth of archegonia., , 16., , One male gamete fuses with female gamete and another male gamete degenerates. The fertilisation is performed, which results in zygote and then embryo formation within the ovule., , 17., , Now fertilized ovule having embryo is called seed., , 18., , These seed are not covered with ovary wall or fruit wall so they are called naked seeds., , 19., , Means in gymnosperm seeds are formed but ovary or fruits are not formed, so they are called as naked, seeded plants., , 20., , Seeds containing embryo (2n) form new diploid sporophytic plants on germination., l, , Pollinated pollens are strored in pollen chamber of ovule., , FERTILIZATION &, Two types of fertilization take place in gymnosperms, (1), , Zoido-siphonogamy & This type of fertilization occurs in lower gymnosperms. Male gametes are motile and, transfered to female gamate by pollen tube., , (2), , Siphonogamy & This type of fertilization occur in higher gymnosperms. Male gametes are non motile transferred to, female gamete (egg) by pollen tube. After Pollination male & female gametes are fused & form a diploid zygote., l, , In gymnosperm single fertilization takes place so only zygote is formed through fertilization. In Angiosperm, double fertilization takes places so two product are formed after it (i) Zygote (ii) Endosperm., , Z:\NODE02\B0AI-B0\TARGET\BIO\ENG\MODULE_4\01-PLANT DIVERSITY\03-PLANT.P65, , l, , E, , In gymnosperm, endosperm is formed before fertilization by megaspore so it is haploid but in angiosperm, endosperm is formed after fertilization by triple fusion (sec. nucleus (2n) + male gamete (n). So, endosperm, of angiosperm is triploid., , l, , In angiosperm, fertilization take place by siphonogamy., Gymnosperm + Angiosperm = Siphonogama, , Note :- Different types of polyembryony are found in gymnosperm i.e. occurence of more than one, embryos with in seed., LIFE CYCLE :, Life cycle of Gymnosperm & angiosperm is diplontic because gametophytic generation is short, lived. Gametophyte is very reduced & depends on its sporophyte., , 73
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Pre-Medical : Biology, (iii), , Cycadales (a), , Presently living cycadophytes are included in this order., , (b), , All the plants of this group are living fossils., l, , Zamia pygmea, , -, , Smallest Gymnosperm, , l, , Cycas, , -, , Fern palm or Sago palm, Sago is obtained from its stem., The diameter of its ovules is 7 cm. Its ovule, male gametes, egg and, male cone are largest in plant kingdom. In embryo of Cycas two, cotyledons are present. In Cycas male gamates are top shaped., In Cycas female cone is absent., Leaves, , Male cone, , Megasporophylls, , Stem, Stem, , Cycas :- (A) Female Plant,, , Cycas, , (B) Male plant, , CONIFEROPHYTA, Four orders are included in this group, Ginkgoales :(a), , It is the oldest order of coniferophyta. Maximum plants of this group are extinct., Ginkgo biloba - living fossil - It is also known as "Maiden hair tree"., Note : Exceptionally Ginkgo biloba belongs to higher gymnosperm but its male gametes are motile., Dwarf Shoot, , Long Shoot, , Seeds, , (ii), , Cordaitales :(a), , 76, , It is completely extinct group, , Ginkgo, , Z:\NODE02\B0AI-B0\TARGET\BIO\ENG\MODULE_4\01-PLANT DIVERSITY\03-PLANT.P65, , (i), , E
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Pre-Medical : Biology, (iii), , Coniferales :(a), , Conifers are included in this group., , (b), , It is the largest group of gymnosperm, , Examples of Coniferales (a), , Pinus (Pines), , –, , A resin "turpentine" is obtained from it., , –, , It is known as "chilgoza pine" or "chirpine"., , (b), , Cedrus, , –, , It is known as deodar., , (c), , Taxus, , –, , It is known as Yew tree. An anticancer medicine "Taxol" is obtained, from its bark., , (f), , Araucaria, , –, , It is known as Christmas tree., , (g), , Sequoia, , –, , The plants in this genus are heavy. It is the largest or tallest tree, so that it is called as father of forest., It is called Red wood tree or Sherman tree., , (h), , Metasequoia, , –, , It is a living fossil., , Male cones, , Wing, , Z:\NODE02\B0AI-B0\TARGET\BIO\ENG\MODULE_4\01-PLANT DIVERSITY\03-PLANT.P65, , Female, cones, , E, , Pinus, (iv), , Microspore (Pollen grain) of Pinus, (Winged Pollen grain), , Pinus [Monoecious plant], , Gnetales (a), , They are the most advanced gymnosperms., , (b), , Exceptionally members of this group have vessels in xylem., , (c), , Archegonia is absent in the members of this group., , eg., , (1) Gnetum, (2) Welwitschia, (3) Ephedra, , – Exceptionally archegonia are present in Ephedra., , Ephedra - This gymnosperm is commonly found in Rajasthan. Ephedra is a medicinal plant. Ephedrine (Medicine), is obtained from it. It is an effective medicine in asthma. Athletes misuse it, so ephedrine is restricted for them., , 77
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Pre-Medical : Biology, There is mainly two requirements for seed formation, (1) Plant should be heterosporus (2) Germination of megaspore should be endosporic, , SOME IMPORTANT POINTS :, 1., , Antheridia is absent in gymnosperm & angiosperm i.e. pteridophyte is last group having antheridia., But archegonia is also absent in angiosperm. So gymnosperm is last group having archegonia., , 2., , During evolution Gametophyte becomes reduced & sporophyte becomes well-developed., , Gametophyte, , ì, í, î, ì, , Very reduced, , –, , In Angiosperm, , Well developed, , –, , In Moss, , Very reduced, , –, , In Thallophyta (Only zygote), , Well developed, , –, , In Angiosperm, , Sporophyte í, , î, , GOLDEN KEY POINTS, 1., , Plant body of algae is not differentiated into root, stem and leaves, such plant body is called thallus/thalloid., , 2., , Algal sex organs are unicellular and jacketless but exceptionally sex organ of Chara are multicellular and jacketed., , 3., , Spirullina-BGA and Chlorella is used as a source of food and O2 by space travellers., , 4., , Algin protects seaweeds against dessication and shocks., , 5., , Major pigments of Rhodophyceae are chlorophyll–a, d and phycoerythrin., , 6., , Gaudikov's effect is found in both red algae and blue green algae., , 7., , Bryophytes are amphibians of the plant kingdom because these plants can live in soil but are dependent on water, , 8., , In bryophyta the sporophyte is depend on gametophyte., , 9., , Most developed gametophyte in kingdom plantae is found in mosses., , 10., , Mosses along with lichens are the first organisms to colonise rocks hence are of great ecological importance., , 11., , Pteridophytes are vascular cryptogams and first successful terrestrial plants., , 12., , Prothallus is independent and mostly photosynthetic gametophyte., , 13., , Selaginella, Salvinia, Marsilea and Azolla are heterosporous pteridophytes, which show precursor of seed habit., , 14., , Gametophyte is monoecious in homosporous pteridophytes., , 15., , The ovules are not enclosed by ovary wall and remain exposed, both before and after fertilization in, gymnosperms., , 16., , Integumented megasporangium is called ovule., , 17., , In gymnosperm single fertilization takes place so only zygote is formed through fertilization., , 18., , Pollen grains and seeds are winged in Pinus., , 19., , Ephedra and Taxus are medicinal gymnosperms., , 78, , Z:\NODE02\B0AI-B0\TARGET\BIO\ENG\MODULE_4\01-PLANT DIVERSITY\03-PLANT.P65, , for fertilization., , E