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4 New Course in Botany. (S.Y.B.Se.) (Sem lll & Ty), , (SEMESTER = IV) —, , , , , , CON cae eee, Chapter — 12, aca eet e PEE T, GPE HOROH Sete, , : GYMNOSPERMS, , z, &, qt, a, t, ?, a cet Sea, Se ch hhh EP, , , , The gymnosperms are most ancient seed plants that ons curing ae ete, plaeozoic era (250 million years ago) and flourish well during the Mesozoic, 8!, dinosaurs. The earlier members of the group have been extinct today., , The word "gymnosperm" was used by Theophrastus (300 B.C.) to comprise all those, plants whose ovules are exposed ie. not enclosed in the ovary (Gymno = naked,, Spermos = seed) and have single integument. The megaspore, which develops into female, gametophyte, is permanently retained in the ovule. The male gametophyte is developed, within the microspore and the female gametophyte is developed within the megaspore., Thus, development of gametophytes is endosporic. The male gametophyte is dispersed by, wind (Anemophilous pollination) while the female gametophyte is completely parasite on, the sporophyte. The sporophyte is well developed, autotrophic, independent plant,, differentiated into roots, stem and leaves, with well developed conductive tissue, exhibiting secondary growth. However, the xylem lacks vessels and phloem lacks, companion cells. In some characters, gymnosperms resemble pteridophytes while in some, other characters they resemble angiosperms., , Being an important group of plants, Gymnosperms have been variously classified by, different Botanists. However, the classification used in this book is as given by Charles, Joseph chamberlain (1934-35)., , SALIENT FEATURES OF CONIFEROPHYTES, , 1, Coniferophytes came into existence during the carboniferous period of palaeozoic, , era., , 2. The plant body is a sporophyte. It is differentiated into roots, stem and leaves. The, plants are called conifers due to their cone-like habit. d, , 3. The roots form tap root system. As the root system is fully developed, the new, young branches remain short and undergo frequent forking so that the cluctere of small, rootlets are formed. They get associated with mycorrhizae and called mycorrhizal root, (Pinus), They form symbiotic association. ‘ Core, , 4, The stem is tall, cylindrical, woody and usually covered with scales. The stem is, , branched and branches are restricted to the apical portion. The lower branches of the, longer than the upper ones and hence the plant gives appearance of a con ‘The baa, are of two types, viz; branches of unlimited growth or long shoots Ste be, growth or dwarf shoots (Pinus). Stem of Ginkgo also show, Pinus. In Taxus, dwarf shoots are absent. In Gne;, and shows two types of branches as in Pinus., , ; and branches of limited, 's two types of branches as in, tum, stem is woody climber called liana, , , , , , , , , , , dorsally 1, ssingle, and are s, mesophy, pundlesona, | dioeciou, ) 10.1, Inboth t, male cor, In Taxus, arrange’, microro, microsp, shows i, flower, Sporan;, showin, gameto, are 3-c¢, 11, female, female, atrang, vegeta, Secon,, termiy, €ach }, advar, Succe;, , q, It has, game

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Gymnosperms °° 2568 sa, , 5. The leaves are dimorphic (of two types) (Pinus and Ginkgo) or monomorphic, (Taxus and Gnetum). In Pinus, there are green, needle-like, photosynthetic leaves at the, apices of the dwarf shoot and scaly leaves on the surface of long and dwarf shoots. In ie, Ginkgo, the green, triangular petiolated leaves are with open, dichotomous venation and, } are borne on long shoot while scaly leaves arise on dwarf shoot. In Taxus leaves are, shortly petiolate, broadly liner with entire margin and spinuous apex. Only single midyein is present. In Gnetum the leaves are petiolate, ovate to elliptic with entire margin and, acute apex. The venation is reticulate. These leaves resemble dicotyledonous leaves., , 6. TS. of root shows radial vascular bundles with diarch to tetrach and exarch xylem, alternating with phloem. Resin ducts may be present in the xylem. In the mycorrhizal, roots the hyphae of mycorrhizae are seen in the cortex (Pinus)., 7. The cortex is not as large and extensive as found in cycadophytes. In pinus inner, cortex shows resin ducts. In Ginkgo, entire cortex and pith show mucilage ducts. In Taxus, and Gnetum both resin ducts and mucilage ducts are absent. The stele is eustelic., | Vascular bundles are arranged in the form of ting with pith in the centre. Vascular |, bundles are conjoint, collateral and open with endarch xylem. The secondary growth is, due to formation of successive cambial rings. The wood is Pycnoxylic, i.e. more compact, and with less soft tissue., , 8. T.S. of Taxus and Gnetum leaves shows that their Mesophyll is differentiated into, dorsally palisade and ventrally spongy tissue. Hence these leaves are dorsiventral. There, is single vascular bundle in the midrib. The stomata are present only on lower epidermis, and are sunken. However, in Pinus the leaves are needle-like and triangular. In T.S., their, mesophyll shows armed palisade tissue while in the midrib there are two vascular, bundles. Stomata are sunken. Resin ducts are present in the mesophyll., , , , , , , , , , , , , , , , , 9. Sexual reproduction is oogamous. The plants are monoecious (Pinus) or }, dioecious (Taxus, Gnetum, Ginkgo)., , 10. In Taxus, the male cones are borne singly while in Pinus they are borne in clusters., , Tn both the plants the male cones are borne on the branches of unlimited growth and each, , male cone consists of central axis on which many microsporophylls are spirally arranged., , In Taxus, microsporophylls form a globose head and 5 to 9 pendent microsporangia are, , arranged on each microsporophyll. In pinus, male cones have elongated central axis and, , } microrosporophylls are arranged spirally on it. Each microsporophyll contains two, microsporangia on its abaxial side. In Gnetum, male strobilus is of advanced nature. It /, shows a slender axis on which there are successive whorls of staminate flowers. Each, flower shows perianth and stamen. The latter shows a stalk and two unilocular, sporangia. Ginkgo shows male strobilus with spirally arranged Microsporophylls, each, showing two pendent microsporangia. In pinus mature pollen grains (male, gametophytes) are 3-celled and winged. In Taxus, Ginkgo and Gnetum mature pollen grain, are 3-celled but not winged., , 11. In Pinus and Gnetum, the female reproductive organs are aggregated to form, female cones while in Taxus and Ginkgo, they do not form female cones. In pinus, the, female cone shows a central axis on which bract scales and ovuliferous scales are, arranged spirally and alternately. Each ovuliferous scale shows two ovules. In Taxus a, Vegetative shoot bears a primary bud called primary axis and a secondary bud called, Secondary axis. The primary axis is short and abortive while the secondary axis, ferminates into a single ovule. In Ginkgo, female plant produces number of peduncles, each having two apical ovules of which one is abortive. In Gnetwim, female strobilus is of, @dvanced nature. It shows a slender axis on which whorls of female flowers are, successively produced. Each flower shows perianth enclosing single ovule., , | 12. The structure of ovule is more or less similar in all the members of coniferophytes., , has 3 layered, but single integument with a micropyle. It encloses nucellus and female, netophyte. The latter shows 3 to 4 highly reduced archegonia, However, ovule of

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256, , 22°, , , , , , A New Course in Botany (S.Y.B,Se,) (Semalll GV), , Gnetum shows characters, which are more like that of angiosperms, e.g. the ovule shows, two integuments, the female gametophytes shows only potential eggs but archegonia are, , absent, , 13. The pollination is by wind i.e. anemophilous and fertilization is siphonogamous,:, The endosperm is haploid as its formation begins before fertilization. Cotyledons are two, to many. Pinus shows polyembryony. The germination is hypogeal., 14, In all the genera of Coniferophytes, development of gametophytes is endogenous,, CLASSIFICATION OF CONIFEROPHYTES, Chamberlain divided the group Gymnosperms into two classes, viz Cycadophytes, and Coniferophytes. The latter is further divided into four orders, viz., Cordaitales,, Ginkgoales, Coniferales and Gnetales., , , , Coniferophytes | i), , | ii), , Tall plants with profusely branched stem,, , , , , , Leaves are simple., , , , iii) | Stem is with narrow pith and cortex., , , , iv), , Wood is pycnoxylic (compact wood with less, Peete], , , , bai, , Male sporophylls form simple compact cones; but the, female sporophylls form compound cones as the, sporophylls being borne on shoots coming from the, axil of bracts., , , , The ovule shows single integument (except in, Gnetales)., , , , | All the members are extinct now. They were widely, known from carboniferous where the plants formed, , world’s first greatest forests, became extinct in, jurassic,, , , , , , , , , , , , iii) |The leave, , ‘Tall plants with slender, branched stem,, 's were spirally arranged, with different, | shapes and with parallel venation., The stem showed monopodial habit,, The plants are monoecious or dioecious. The strobili, | Were unisexual and formed compound fructifications,, Male appendages bore 4 to 6 terminal micros, , , , , , , , , , , , , , , , , , , , , , , , , , , , jporangia, , , , , , , , , , : | Ginkgoales i), , , , , , , , , , , , , , , , , , , , _| their apices,, , , , , , and female appendages bore 1 to 4 ovules., The nucell inte, other., , lus and integument were free from each, , , , Examples : Cordaites. Dorycordaites, aie, , Tall trees with excurrent habit,, Plants have tap root system which deeplw penemarcc|, pen ve tap root system which deeply penetrates, The leaves are fan-shaped and, The venation is open dichotomous,, Leaves arise singly along the terminal branches, in the |, , a of which buds are Present which grow into short, shoots which also bear a dense cluster of leaves at, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , The plants are dioecious, Inflorescence, that bears microsporan;, , : is catkinlike |, giophores with 2, , to 12 pendent, , , , , , , , , , |, , Order, , r, , |, , ayer)

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| viii), , , , vii), , PRR 257, , , , Ovules arise in groups from the apices of axillary |, branches. eee ea, The mature seeds are produced in large number, large, and fleshy., , , , Coniferales, , , , , , , , i), , ix) | Example : Ginkgo (living fo, wus gotlyine eee, , , , , , Plants are woody perennials distributed in temperate |, regions and at high altitudes of tropics, , The tap ‘root system is mostly associated with |, mycorrhiza which may be ectotrophic or endotrophic, , , , , , , , , , , , , , Usually lower branches are longer and upper, branches are shorter giving cone-like appearance., Branches are of two types, viz., dwarf shoots and long, shoots., , , , , , , , Leaves are of two types,, leaves., , 7, scaly leaves and foliage, , , , , , , , Strobili are unisexual. Male cones are compact,, with microsporophylls spirally arranged on the, central axis and bear two or more abaxial, microsporangia. However, female strobili | are, compound, consisting of central axis on which bract, scales are spirally arranged. In the axils of the bract, scales, ovuliferous scales arise which bear two or more, , , , , , adaxial ovules., , , , , , Pollen grains are winged or not winged but are wind, pollinated with non-motile male gametes. Embryo is, di or polycotyledonous., , , , , , , , is, Araucari, , , , Examples: Pinus, Taxus, Cupre, , , , , , Order, , Gnetales, , The plants are xerophytic shrubs or with dwarf, woody stem or woody climbers (lianas), sometimes, tall woody trees, Stem is usually branched., , , , , , The tap root system is deeply penetrating to reach the |, water table. In some plants it is replaced by, adventitious root system. 5, , The leaves are opposite, long woody with parallel, , venation, or opposite scaly or opposite, large, ovate, with reticulate venation resembling dicot leaves., , , , iv), , Mucilage ducts or resin canals are absent. Vessels are, present., , , , v), , Plants are dioecious with compound male and female |, strobili. |, , , , vi), , The ovule has two integuments with the inner one is, elongated to form micropylar tube. |, , , , vii), , | Embryo is dicotyledonous., , , , , , , , viii), , Examples: Ephedra, Welwitschia (both are living fossils, , , , , , , , now), Gnetum., , , , , , , , i

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A New Course in Botany (S.Y.B.Se-) (Sem & Ty, , E OF CONIFEROPHYTES, , of plants spread all over the, Jevations in the tropics. An, sented here., , 32°92", , ECONOMIC IMPORTANC, an economically important group, and at higher & i, axa of coniferophytes is pre, , , , The gymnosperms are :, world, primarily in the temperate ee, account of economic importance of various, , Wood - cht coloured and light-weighted,, The coniferous wood is generally selena Peat ee where sent pe, It has a softer texture than the angiospermic wood. Leo “Abies is used in the-EOunm, durability are not required. The wood of various sP co janks, boards, Cobia, board of musical instruments, carving, Pe ee Pe ilor, being non-odOroWayt™, furniture making, interior furnishing etc. The wood ° ducts, The wood of Agathis ig, especially suitable for boxes for keeping dairy products: io hi , 3 Pete ing ction, boats, wooden machinery, in, comparatively stronger and is used in building construction, heavy and hence iia, battery separators, for flooring etc. The wood of Araucaria is hea’ yi stant to wht, making doors, bus chassis, carpentary etc. The wood of Callitris is resistl® © WV aot, owing to the presence of phenol and other chemicals. Hence, it is us 4 ne, construction and furniture. The wood of Cedrus is in great demand as it te Mig durable,, oily, sweet scented and generally without resin ducts. The cedar tree was oe io of, God” by the ancients as its wood was used as roof beams in all the sacred temples of, Egypt. Tt was also used for making mummy cases, coffins etc. C. deodara, the “deodar’ is, one of the most important timbers of North India. It is considered as the strongest among, the Indian conifers, about as strong as teak. The seasoned wood is resistant to insect pests, due to presence of oil. It is used for making doors, poles, furniture, beams, ceilings,, columns, carriages, wagons boats, etc. Cryptomeria japonica yields a coarse grained, fragrant, strong, durable, easy to work wood. The wood is employed for building, construction, paneling, furniture, etc. The bark is used for roofing. The wood of, Cunninghamia is light but durable and used in mats, box-making and coffins. The bark is, used for roofing. The wood of Cupressus is very durable, resistant to insect pests, odorous, and resinous. It is used for building constructions, railway sleepers, aircraft manufacture,, furniture etc. It is also burnt as incense in temples. It is considered as the most durable, coniferous wood in India. It has an advantage over deodar that it does not exude oil and, thus could be painted and polished. The heavy durable wood of Juniperus, Pinus, Sequoia,, Taxodium and Taxus, is used for building construction, railway sleepers, furniture glass, house construction, poles, masts etc. while the wood of Podocarpus, being light, is used for, indoor work. P. totara is the only soft wood, which is resistant to mine borer. Hence, it is, valuable for dock and sea work, as well as bridges and ship building., , , , , , , , Resins, , Resins are plant exudates, which make the wood resistant to decay. Conifers are, , amongst the major resin yielder of the world. The resins are insoluble in water but soluble, in organic solvents. The resin of superior grade is used in varnishes, enamels, plasters, medicines, and ointments. The resin of inferior grade goes in the manufactures of yellow, laundry soap, printing ink, oil cloth, insulators, oil and grease, insecticides, adhesive, Plastics, disinfectants and shoe polish. Metals such as lead and magnesium to aldehyde, modified resin, are much valued as paint drier ;, , : An oleoresin is a mixture of rosin and essential oil. Rosin is a gum while essential oil, is turpentine. A pine tree yields only oleoresin from which rosin could be separated b, , distillation. The gum, which is strongly adhesive, is used for special qualit ae hi 4, plasters. The turpentine on the other hand is used in varnishes, Titho hi 4 vail, histology (in stains), veterinary medicines, as a solvent, in stains removers enamel, , lubricants, waxes, polishes, crayons, insecticides, soaps, disinfectants and Cac a, ___Copal belongs to the group of hard resins, wh a, important and most valued copal is ‘Kauri copal’, australis. Copal is either in fossilized form or i, , ‘ich has very little essential oil. The most, obtained from the ‘kauri pine’ — Agathis, in fresh form. Fossilized copal is found, , , , , , , , , , | obtain, fatty 0, M, emulsi, used ai, paint., Paper, Ce, Writing, Kraft, roxburs, Paper,, produc, wo, Food, PT, tom 7, essen, Manuf,, binkgo,, eel, pts, “a, "ebro, , }