PRESENTATION OF GYMNOSPERM
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This document provides an overview of the classification of gymnosperms by different researchers over time. It discusses the key characteristics of modern gymnosperms and describes the four orders that living gymnosperms are commonly grouped into: Cycadales, Ginkgoales, Coniferales, and Gnetales. For each order, it highlights some representative genera and provides details on morphological features. The classification schemes of various scientists who studied gymnosperms, such as Bentham and Hooker, Engler, Coulter and Chamberlain, are summarized. Diagrams of their classification systems are also included.
![EWING CHRISTIAN
COLLEGE
[AN AUTONOMOUS COLLEGE OF ALLAHABAD UNIVERSITY]
M.Sc previous year
First Semester](https://image.slidesharecdn.com/1d790066-9981-4027-b10a-5ff4e4c37b6a-160927165922/85/PRESENTATION-OF-GYMNOSPERM-1-320.jpg)
![• The trees are branched,woody and perennial.
• The leaves are dimorphic scaly and foliar.
• Tap root system mostly associated with fungi
[mycorrhizal association]
• Reproductive structures are formed on leaves which
arrange to form cones male and female cones are
formed sepratly.
• Pollen grains are wind spread and embryo formed is di
to polycotylednous](https://image.slidesharecdn.com/1d790066-9981-4027-b10a-5ff4e4c37b6a-160927165922/85/PRESENTATION-OF-GYMNOSPERM-20-320.jpg)
PRESENTATION OF GYMNOSPERM
- 1. EWING CHRISTIAN COLLEGE [AN AUTONOMOUS COLLEGE OF ALLAHABAD UNIVERSITY] M.Sc previous year First Semester
- 2. Classification of GYMNOSPERM By- CHETNA SHUKLA
- 3. Introduction • Gymnosperms are woody seed-bearing plants differing from the other group of seed plants. • The term "gymnosperm" comes from word gymnospermos, meaning "naked seeds", after the unenclosed condition of theirseeds (called ovules in their unfertilized state). • There are between 700 and 900 extant* or currently living species of Gymnosperms. • They grow in xerophytic conditions and posses xerophytic adaptations. • Gymnosperms are heterosporous which means that they produce different male and female spores. The microspores develop into pollen grainsand the megasporesare in an ovule
- 4. • . • Male and female reproductive structures are borne on sporophylls, scales, or comparable structures • Most of them are trees and some are shrubs. There are no herbs.. • They have monopodial growth represented by one main axis. As the axis grows taller it increases in diameter due to secondary growth. Stem branches are of two types: 1. Long shoots or branchesof unlimited growth. 2. Dwarf shoots or branchesof limited growth. • The plants possess well-developed tap root system. In some cases the roots are symbiotically associated with algae (coralloid roots of Cycas) or with fungi (mycorrhizal roots of Pinus).
- 5. Classification • Gymnosperms include a number of fossil and living forms. They include the primitive members of the Spermophyta (seed- bearing plants) and form a link between the Pteridophyta on the one hand and the angiosperms on the other. Various attempts have been made by different workers to classify the Gymnosperms. • One of the earliest attempts was made by Bentham and Hooker (1866-1883), when they divided seed bearing plants into Dicots, Gymnosperms and Monocots. Gymnosperms were further divided into Cycadaceae, Gnetaceae and Coniferae. Engler (1885) divided Gymnosperms into seven groups as follows: 1. Cycadofilicales 2. Cycadales 3. Bennittitales 4. Cordaitales 5. Ginkgoales 6. Coniferales 7. Gnetales
- 6. • Coulter and Chamberlain (1917) adapted Engler’s system with slight modifications and divided gymnosperms into seven orders: Cycadofilicales, Cycadales, Bennittitales, Cordaitales, Coniferales, Ginkgoales and Gnetales. He further divided order Coniferales into two families (Pinaceae and Taxaceae) and six sub-families as follows: • Orders Families Sub-families • Cycadofilicales • Cycadales • Bennittitales • Cordaitales • Coniferales Pinaceae Abietineae, Taxodineae, Cupressineae , • Araucarineae • Taxaceae Taxineae, Podocarpineae • Ginkgoales • Gnetales
- 7. • Depending upon the composition of wood, Seward (1919) divided gymnosperms into two classes: i) Manoxylic with loose textured and porous wood, and ii) Pycnoxylic with compact wood. Orders Cycadales, Cycadeoidales and Cycadofilicales were included in the former whereas, the latter included the orders Cordaitales, Ginkgoales, Coniferales and Gnetales. • Prof. Birbal Sahni (1920) classified gymnosperms into two divisions depending upon the axial or foliar origin of the ovules. These are: i) Stachyspermae – in which the ovules arise on the axial organs, and ii) Phyllospermae – in which the ovules are borne on leaves. Stachyspermae was further divided into four orders and Phyllospermae into three orders as follows:
- 8. • Divisions Orders • Stachyspermae Cordaitales, Coniferales • Ginkgoales, Gnetales • Gymnosperms Phyllospermae Cycadofilicales, Bennittitales • Cycadales • Chamberlain (1934) however, divided the gymnosperms into two large groups A. Cycadophyta and B. Coniferophyta. • In the Cycadophyta, sporophylls are in cones. • They include three orders: • Cycadofilicales (Pteridospermae)-extinct • Bennettitales (Cycadeoideales)-extinct • Cycadales-Mesozoic to present day. • The Coniferophyta is divided into four orders: • Ginkgoales-Palaeozoic to present day. • Cordaitales-extinct • Coniferales-Palaeozoic to present day • Gnetales-Recent.
- 9. • Raizada and Sahni (1938) have summarized the classification of gymnosperms as follows: • Cycadophytes: • Pteridospermae (Cycadofilicales)-Carboniferous. Extinct. • Cycadeoideales (Bennettitales)-Mesozoic. Extinct. • Cycadales-Mesozoic to present day. • Pentoxylales: Jurassic • Coniferophytes: • Cordaitales-Palaeozoic. Exinct • Ginkgoales-Palaeozoic to present day. • Coniferales-Palaeozoic-Mesozoic to present day • Gnetales-Recent.
- 10. • Chamberlain (1935) classified gymnosperms into: • • Gymnosperms with profusely branched trunks, leaves simple (needle-like, scale-like or laminate), stems with small pith and cortex. Secondary xylem cylinder massive and less parenchymatous (pycnoxylic wood). The group includes extinct as well as extant orders like Gymnosperms with fern-like pinnatifid leaves, weakly branched large globose or columnar trunks, having large conspicuously developed pith and cortical zones in stem. Secondary xylem cylinder small, composed mainly of tracheids and abundant parenchyma (manoxylic wood). Group well represented in fossil record. The only surviving representatives are the modern cycads. Orders 1. Cycadofilicales 2. Bennettitales 3. Cycadales Orders: 1. Cordaitales 2. Voltziales 3. Coniferales 4. Ginkgoales 5. Gnetales ConiferophytesCycadophytes Gymnosperms
- 11. • In 1957 prof. D.D PANT gave the modification of Arnold`s classification and gave the following system.. Cycadophyta Chlamydospermophyta Conifrophyta CLASS-1- Pteridospermopsida Orders- Lygniopteridales Medullosales Glossopteridales Peltaspermales Corystospermales Caytoniales CLASS-2- Cycadopsida Orders- Cycadales CLASS-3- Pentaxylopsida Orders- Pentoxylales CLASS-4- Bennettitopsida Orders- Bennettitales CLASS-1- Gnetopsida ORDERS- Gnetales Welwitschiales CLASS-1- Coniferopsida Orders- Corditales Coniferales Ginkgoales CLASS-2- Ephedropsida Orders- Ephedrales CLASS-3- Czekanowskiales Orders- Czekanowskiales CLASS-4- Taxopsida Orders- Taxales
- 12. • Kramer & Green (see Kubitzki, 1990) have classified the Division Gymnosperms into two Subdivision as • follows:- • Cycadophytina Coniferophytina Classes- Cycadatae Order- Cycadales Families- 1.Stangeriaceae 2.Boweniaceae 3.Cycadaceae 4.Zamiaceae Classes- Gnetatae Orders- Gnetales Families- 1.Ephedrac eae 2.Gnetacea e 3.Welwitsc hiaceae Classes- Ginkgoatae Order- Ginkgoales Families- 1.Ginkgoace ae Classes- Pinatae Order- Pinales (Coniferales) Families- 1. Taxaceae 2.Cephalotaxaceae 3.Phyllocladaceae 4. Podocarpaceae 5. Araucariaceae 6. Sciadopityaceae 7. Taxodiaceae 8.Cupressaceae 9. Pinaceae
- 13. Flow charts showing classification by different workers:-
- 16. • The modern gymnosperms are commonly grouped under four orders: • 1. Cycadales; • 2. Ginkgoales; • 3. Coniferales and • 4. Gnetales • The Cycadales and the Ginkgoales include living members which have a long, fossil history and can be regarded as ‘living fossils’. Ginkgoales in the past (early Mesozoic) were represented by widely distributed group of plants, but now the order is represented by a single species Ginkgo biloba. • The Coniferales from the most conspicuous order of the living gymnosperms and include the plants like Pinus, Cedrus, Abies, Juniperus, Cupressus, Biota, etc. • The Gnetales are represented by three living genera, e.g., Gnetum, Ephedra and Welwitschia.
- 18. •
- 20. • The trees are branched,woody and perennial. • The leaves are dimorphic scaly and foliar. • Tap root system mostly associated with fungi [mycorrhizal association] • Reproductive structures are formed on leaves which arrange to form cones male and female cones are formed sepratly. • Pollen grains are wind spread and embryo formed is di to polycotylednous
- 21. The Largest and the Oldest Plants are both Conifers • Bristlecone pines of the California White Mountains are the oldest Giant Sequoias of the California Sierras are the largest
- 22. Earth" - General Sherman - Sequoia National Forest, CA 2200 years old , 275 feet tall , 30 feet in diameter at the base. 119.3 miles of 1X12 planks
- 23. There are seven living families of Conifers Norfolk Island Pines Junipers and Cedars Yew Sequoias and Redwoods Pines, Fir Spruce Five of the most familiar
- 24. • The division coniferophyta contain following 7-families. • PINACEAE • It is composed of 10 genera Cedrus, Pinus, Cathaya, Tsuga,Abies etc. • Tall and well branched trees. • Posses dwarf and long shoot dwarf shoot posses scaly and needle like foliar leaves.
- 26. Taxodiaceae • Comparises evergreen or deciduous trees and plant parts are mostly spirally arranged. • Both male and female cones are arranged on same plants. • Contain ovuliferous scales with 2 to 9 ovules on each. • Pollen grains are wingless and lack prothalial cells. • Seeds may be winged or wingless or irregular in shape. • Consist of…. Taxodium, Sequoia, Sequoiadendron, Taiwania, Cunninghamia etc.
- 28. Cupressaceae • The family comparises evergreen much branched trees or shrubs. • The plant parts are arranged opposite decussate or in whorls of 3 or 4. • Juvenile leaves may be linear adenate or adpressed completely hiding the stem. • Leaves may be glandular and grooved. • Male and female cones occur on same plant. • There are nearly 22 genera some are.. Tetraclinis, Juniperus, Callitris, Thuja etc
- 29. THUJA
- 30. Podocarpaceae • Leaves are extreamly variable. • True leaves are small,scale like and are replaced by phylloclades. • Phylloclades are flattened much branched with fiabelliform. • Male and female cones are seprate solitary axile or terminal. • It consist of 7 genera some are .. Podocarpus, Dacrydium,etc
- 32. Araucariaceae • Evergreen and highly resinous trees. • Leaves are small,stiff,awl-like or large and leatherhy. • Plant may be monoecious or dioecious. • Pollen grain are wingless with multiple persistant prothalial cells. • It consist of 2 genera …Araucaria, Agathis .
- 33. Cephalotaxaceae • Cephalotaxaceae is a monogenic family with only one genera Cephalotaxus. • Named such due to shape of male cone from the greek word “kephale” means head. • Male cones are present in globose heads. • Shrubs or small yew like dioecious plants. • Male trees posses unbranched shoot. • Leaves are more or less same size ,falcate,subacute,base round,and whitish beneath.
- 35. Taxaceae • These are much branched evergreen woody shrub or small,rarely large trees. • The leaves are simple,linear and small and sre spirally arranged. • The wood is pycnoxylic. • Plant is dioecious with male strobilus consist of a cone axis. • The family is represented by 5 living genera…. Amentotaxus, Torreya,Taxus,Psedotaxus,Austrotaxus.
- 37. 2 Cycadophyta
- 39. CYCADOPHYTA • Rarely branched trunks with soft pithy wood. • Plants are dioceous in nature with compound leaves. • Microsporangia (Male gametophyte) grows within the ovule. • Male gametes are multicilliated and motile. • Motile sperm released after several months, sometimes after the seed has fallen.
- 40. Cycads Appeared on Earth 250 MYA • Reached their greatest abundance and diversity during the Jurassic • Declined sharply during the Cretaceous radiation of the angiosperms.
- 41. Cycad Stems • Columnar • Little branching • Not very woody
- 42. Certain roots in Cycads grow toward the soil surface Corraloid Roots
- 43. A Closer Look at Coralloid Roots • Grow upward near soil surface • Branch to form masses • Root cortex inhabited by Cyanobacteria (carry out nitrogen fixation)
- 44. Cycads produce pollen and seeds in cones • Cones develop at apex of stem
- 45. All Cycads are Dioecious • Individual plants produce either pollen cones or seed cones Cycas revoluta Pollen Cone Seed Cone
- 47. Ginkgophytes – Ginkgo • Extensive fossil record but…only 1 living species: Ginkgo biloba! •Highly branched tree withwell developed wood. •Deciduous, fan-shaped leaves with dichotomous venation. •Dioecious: male and female trees -male: “cone” with lateral stalks bearing microsporangia -female: no cone, axis with 2 ovules (outer integument layer fleshy) •motile sperm (ancestral
- 48. Ginkgo – Vegetative Characteristics
- 50. Ginkgo Stems • Extensive branching • Very woody
- 51. Ginkgo Stems long shoot spur shoot
- 52. All Ginkgo trees are Dioecious • Individual plants produce either pollen “cones” or seed “cones” • Produced on spur shoots C
- 53. Ginkgo produces a seed with a fleshy seed coat • Seed Coat contains Butyric Acid • Seed Coat is not edible
- 58. Ephedra is a desert shrub
- 59. Gnetum is a tropical vine or small tree
- 60. Welwitschia is a bizarre plant of an extremely arid environment
- 61. Welwitschia produces only two adult leaves Welwitschia forms a short stem and deep tap root
- 62. Thank You