Skip to main content
UploadLanguage (EN)Support
BusinessMobileSocial MediaMarketingTechnologyArt & PhotosCareerDesignEducationPresentations & Public SpeakingGovernment & NonprofitHealthcareInternetLawLeadership & ManagementAutomotiveEngineeringSoftwareRecruiting & HRRetailSalesServicesScienceSmall Business & EntrepreneurshipFoodEnvironmentEconomy & FinanceData & AnalyticsInvestor RelationsSportsSpiritualNews & PoliticsTravelSelf ImprovementReal EstateEntertainment & HumorHealth & MedicineDevices & HardwareLifestyle
JB
Uploaded byJasmine Brar
PPTX, PDF19,655 views

Gymnosperms and their economic importance

1. Gymnosperms are woody plants with unbranched stems containing leaf scars. They have either monomorphic or dimorphic leaves. Their roots vary from diarch to polyarch and their wood contains growth rings. 2. They have well-protected foliage leaves with sunken stomata. Their reproductive organs are cones containing microsporophylls and megasporophylls analogous to stamens and carpels. Cones contain naked ovules fertilized by wind-borne pollen. 3. Gymnosperms are economically important as sources of wood, resins, fibers, foods, and medicines. They are used for construction, paper production, and in pharmaceuticals.

Science◦
1 Gymnosperms and their Economic Importance Dr Jasmine Brar Email : drjasmine1807@gmail.com
Stem is erect, unbranched woody. Leaf scars show their characteristics in the stem. Leaves may be monomorphic or dimorphic. Two kinds of dimorphic leaves are: a. Foliage leaves which are evergreen, simple or compound. b. Scale leaves which are minute & deciduous Pinnately compound leaves eg. Cycas; needles in Pinus; Scales in Ephedra 2
Vasculature of roots varies from diarch to polyarch. Vascular bundles in stem are collateral, endarch, open & arranged in rings. Secondary growth is well marked with distinct annual rings but in Cycas, cambium is short lived & hence formation of well developed cortex, pith & parenchyma rays (manoxylic wood). In Pinus, pith & cortex are quite reduced & parenchyma rays are few (pycnoxylic wood) which is densely packed. 3
Foliage leaves are well protected by thick layer of cuticle or waxy layer. Stomata lie in sunken cavities (xerophytic character) Xylem is mesarch (protoxylem develops first in the centre & continues to develop both centrifugally & centripetally) Transfusion tissue (helps in conduction)is the characteristic feature of gymnosperm leaf. Reproductive organs are aggregated to form compact cones or strobili (cones may be either male or female & rarely bisporangiate) 4
Male & female cones are homologus to male & female flowers that bears microsporophylls (stamens) & Megasporophylls (carpels) which are arranged on an elongated axis : thalamus Cones (flowers) are without perianth (except Gnetum & Ephedra where scale like perianth occurs) Female cones are larger than male cones (except Cycas) Male cones are short lived. Microsporophylls are flat In Cycas or peltate in Pinus. Feamle cones are long lived & remain attached to plant for several years for maturity & ripening of seeds. 5
Microsporangia or pollen sacs are borne on abaxial or Morphologically lower surface of microsporophyll. They may be many & grouped in form of sori like ferns. Eg. Cycas & reduced to two in Pinus. Megasporangia or ovules are borne naked on the sporophyll. Ovules are orthotropus & covered by single integument. Integument surrounds nucellus which is differentiated Into outer sarcotesta, inner fleshy sarcotesta & middle stony sclerotesta. 6
Plants are heterosporous & form two types of spores. Gametophytic generation arises by germination of spores & is highly reduced. Male gametophyte has either 1 or 2 prothallial cells: 1 in Cycas & 2 in Pinus. Pollen tube act as haustorium in Cycas & sperm carrier in Pinus. Female gametophyte bears variable number of archegonia. There is no archegonia in Gnetum, Pinus has 2 archegonia while Cycas has many archegonia. 7
Each archegonium has an egg & a venter canal cell. Neck canal cells are absent. Pollination is anemophilous & pollen grains are deposited in pollen chamber where they germinate. Diploid zygote is formed by the fusion of male & female nuclei. Development of zygote is meroblastic where only basal part develops into an embryo, upper part develops into haustoria & middle part forms suspensor. 8
There is development of many embryos in one seed ie. exhibit polyembryony. Embryo is differentiated into roots, stem & leaves. Embryo is endoscopic where plumule is directed away from micropyle & radicle towards the micropyle. Endosperm is food laden tissue & develops before fertilization in gymnosperms. Embryo is developed at the end of long suspensor which is pushed down to endosperm. 9
Food present in nucellus is absorbed by female gametophyte to form endosperm so endosperm is haploid & is formed before fertilization. No double fertilization/triple fusion is there so endosperm is haploid, (n) (triploid, 3n in angiosperms). Except a small part called perisperm, whole of nucellus is crushed. Perisperm persists in the seed in the form of a narrow film or cap. Since, ovary is absent, so seeds are naked & fruits are not formed in gymnosperms. 10
Middle sclerotesta which is stony layer of integument Becomes very hard & give protection to female gametophyte & embryo. Number of cotyledons vary from 1-2 in Cycas to many whorls in Pinus. Seeds may remain dormant for sometime or immediately germinate without any resting period. Radicle of seed grows downward & develops primary tap root while plumule grows upright & develops stem. The stem has unlimited growth, rarely it is limited eg. Welwitschia 11
Sporophytic generation is dominant & independent while gametophytic generation is highly reduced & is dependent. Economic Importance of Gymnosperms Wood: They are most important as source of wood & Constitute major forest wealth. Wood is light coloured, straight grained & light weight. The strongest Indian coniferous wood is used for making Railway slippers is deodar wood obtained from Cedrus Deodara. The heart wood of this tree is resistant to insect/ fungus attacks & has strong scent. 12
Resins: They are derived from conifers by tapping & used in varnishes & paints eg. Copal obtained from Agathis. Rosin: Type of resin obtained as a residue after the distillation of pine oleoresin. It is used in paper sizing, varnish making, enamels & preparation of plasters & ointments. Canada balsam: Abies balsamea This resin does not crystallize on drying & has high refractive index as of glass & used as mounting material for microscopy & cement for lenses in optical work 13
Sandrac : Callitris Used for metal, paper & leather varnish. It is used in modern pharmaceutical as pill varnish. Many essential oils are obtained from coniferous species which are used in perfumery & medicines. Most imp. Oil is turpentine oil which is obtained from Pinus spp. In metallurgy it is used in floatation process for separating minerals from their ores. Oil of Hemlock is obtained from Tsuga canadensis is used as deodorants. 14
Amber (Pinus succinifera) is fossil resin used in making beads & jewellery. Fatty oils: Fleshy outer layer of seeds of Macrozamia, Torreya nucifera, Cephalotaxus drupacea. Gnetum ula also yield oil used for illumination. Paper: Pinus roxburghii, Abies pindrow, Picea smithiana, Cryptomeria japonica supply wood pulp from which paper is made. Food:Very important of starch food. Sago (stem & seeds of Cycas) used as poor man’s food 15
Young shoots of C. pectinata are eaten by tribal people of Assam. Chilgoza (Pinus geradiana) yield edible seeds Strobili of G. gnemon is cooked as vegetable Medicines: Seeds, megasporophylls & bark of Cycas are mixed with coconut oil & applied on sores& wounds. Ephedrine is extracted from E. intermedia, E. geradiana used in treatment of Asthma, hay fever & common cold. 16
Fiber: Bark of Gnetum gnemon & G. latifolium yield fibres of high tensile strength used for making ropes & fishing nets. Poisons: Gnetum latifolium & G. contractum are used as fish poisons. Pollen grains of Cycas circinalis have narcotic properties. Taxus bacata is used as fish poison due to presence of an alkaloid toxin Medicines: Juice from young leaves of Cycas circinalis used to cure stomach disorders, vomiting & skin diseases. 17
Medicines: The seeds of Taxus bacata are used as sedatives. Fuel: The rhizomes of Ephedra gerardiana are used as fuels. The wood & female cones of Pinus insularis are used as fuel. 18
Tanin: The bark of Sequoia sempervirens, Araucaria, Picea, Dacrydium conatins good quality of tannin which is used in tannin industry. Laundary: Starch obtained from Macrozamia seed is used for laundary purposes Perfumes & Scent: Juniperous spp. are burnt as incense in the temples. 19
Funeral wreaths: The leaves of Cycas being strong & leathery & remain green for very long time after being cut from the plant & hence used by Europeans in funeral wreaths. Ornamentals: Many spp. of Cycas are grown in gardens for decorative purposes Thuja plicata, Juniperous, Biota orientals, araucaria Miscellaneous Uses: The leaves of Cycas circinalis are used for making brooms & baskets. Stems of Cycas rumphii are used for making houses in Indonesia 20
Religious Plant: Ginkgo biloba (Maiden hair tree) is grown in temples of China & Japan &is worshipped Healthy Climate: Conifers provide a cool & soothing climate. They are planted in many health resorts & sanatorias where patients go for recreation & treatment. 21
Angiosperms Gymnosperms They may be trees, shrubs & herbs Mostly woody They may be annuals, biennials & perennials Perennials Xylem vessels & companion cells are present (-) except Gnetales Bisexual flowers Unisexual cones Ovules enclosed within ovary wall Ovules are naked Flowers has ovary, style & stigma (-) 22
Angiosperms Gymnosperms Archegonia are absent in female gametophyte (+) except Gnetum Vegetative reproduction is very common (-) except Cycas by bulbils No prothallial cells are formed in germinating male gametophytes (+) Pollination is anemophilous, entomophilous & zoophilous anemophilous Pollen grains fall on stigma, travel through style & reach ovary& ovule Pollen grains directly settle on micropyle during pollination Endosperm formed after fertilization is triploid Endosperm formed before fertilization is haploid 23
Angiosperms Gymnosperms There is no cleavage polyembryony Cleavage polyembryony is present There is no free nuclear division in Angiosperms In zygote Seeds are enclosed in ovary or carpel. Ovary develops into fruits & seeds are enclosed within fruits. Hence name Angiosperms (covered fruits) No ovary is there so seeds remain naked. Hence, name gymnosperms-naked seeds. 24
Manoxylic wood Pycnoxylic wood It is porous, soft & has more broad prenchymatous medullary rays Compact & has narrow medullary rays Commercially useless Great commercial use It is found in Cycadophyta It is found in Coniferophyta Eg. Cycas Eg. Pinus 25
26