GYMNOSPERM= (Gymno = naked + Sperma = seed)
· Gymnosperms are naked seeded plants i.e. those in which the seeds are not enclosed within the fruit but borne by the open carpel called megasporophyll.· These are the intermediate group between the cryptogams and angiosperm.
· Goebel referred to them as “phanerogams without ovary”. So these all are seed plants without ovaries.
· The term gymnosperm was coined by Theophrastus.
· These are called naked seeded vascular plants.
· This is the first group to show the formation of seeds.
· Fruits are not formed due to lack of ovary.
· These are also considered as the link between pteridophytes and angiosperm because primitive gymnosperm possesses ciliated male gametes (which is a characteristic of pteridophyte) but they lack independent gametophytic generation (a characteristic of angiosperm).
Largest gymnosperm: Sequoia gigantia
Smallest gymnosperm: Zamia
· Cycas, Metasequoia and Ginkgo are the living fossils.
· The main plant body is sporophyte; differentiated into root stem and leaves.
· In pinus (or conifers) the root is associated with Fungi (mycorrhiza).
· In Cycas, the stem is unbranched and have a characteristic leaf scar on the stem.
· Conifers are the largest group of gymnosperm.
· Most of the gymnosperms are evergreen shrubs that show xerophytic character.
· Root present– Taproot
· Roots of some gymnosperms have symbiotic relations with Algae (e.g coralloid roots of cycas) or with Fungi (mycorrhizae in pinus)
· Stem – Branched (pinus)
· Vascular tissue in Gymnosperm comprises of
(a) Xylem: Tracheids and xylem parenchyma.
(b) Phloem: Sieve cells and Albuminous cells
· Tracheids are the main conducting tissue and phloem lacks companion cells.
· Cambium is present and secondary growth takes place.
· Vascular bundles in stems are conjoint, collateral and open.
Types of wood in Gymnosperm:
i. Monoxylic Wood: The amount of secondary xylem (wood) is less and parenchyma is present in the large amounts. It is a soft type of wood. e.g. Cycas
ii. Pycnoxylic Wood: The amount of secondary xylem is high and parenchyma is less. It's a compact and hard type of wood. e.g. Pinus.
Gymnosperms are classification into four groups
1. Ginkgophyta: eg. Ginkgo
2. Gnetophyta: eg. Gnetum
3. Cycadophyta: eg. Cycas
4. Coniferophyta: eg. Pinus
· Cycads are also called fossils plants.
Systematic position:
Kingdom: Plantae
Subkingdom: Embryophyta
Phylum: Tracheophyta
Subphylum: Pteropsida
Order: Cyacdales
Family: Cyacadaceae
Genus: Cycas
· It is often called sago palm or palm fern.
· Dioecious (Unisexual)
· Sago is a type of starch extracted from Cycas revoluta.
· Cycas is often called living fossil because it is the oldest member of this group.
· It is the evergreen, xerophytic plant.
· Cycas consists of an unbranched erect stout and palm-like stem with a crown of fern-like pinnately compound leaves arranged spirally around the apex.
· Cycas is dioecious i.e. male and female flowers are born by two separate plants.
· Widely distributed in the tropical regions of the world.
· Sporophytic body is differentiated into root, stem and leaf
A. ROOT
Two types
i. Taproot
ii. Coralloid roots (Corallorhiza)
· Special type of adventitious root resembling like a coral.
· They are Apogeotropic or Aerotropic or Negatively geotropic.
· These roots have nitrogen-fixing blue-green algae (Cyanobacteria) e.g. Anabaena, Nostoc etc.
B. STEM
· Thick, Unbranched, Columnar.
· Contains mucilage canal in the cortical region.
D. Male cone
· Single male cone is present at the top of the male plant.
· Male gametes are motile, top-shaped with multiple bands of cilia.
· Pollen grains of cycas are shed at 3 celled stage.
Note: Pollen grains shed at a 4-celled stage in Pinus and 2-celled stage in Angiosperm
· Largest antherozoids, eggs and ovules are found in cycas.
· Female cone is not organized in cycas, Megasporophylls are loosely arranged at the top of the female plant.
· Archegonia lacks neck canal cells but Egg cells (ventre cell), ventral canal cell and neck cells are present.
· Time interval between pollination and fertilization is 4-5 months.
· No water is required for fertilization.
· Fertilization is Siphnogamous (spermatozoids being carried by pollen tube).
· Spermatiozoids are liberated into the archegonial chamber and the spermatozoids reaches the archegonia with the help of cilia. i.e. fertilization by means of ciliated sperm zoidogamy.
2. Pinus
Systematic position:
Kingdom: Plantae
Subkingdom: Embryophyta
Phylum: Tracheophyta
Subphylum: Pteropsida
Class: Gymnosperm
Order: Coniferales
Family: Pinaceae
Genus: Pinus
· Plant – Monoecious (Bisexual)
· Sporophytic plant body is differentiated into root, stem and leases.
2. STEM:
3. LEAF:
· Foliage leaves are found in dwarf shoots which is commonly called needles.
· Scaly, leaves are found in the long and dwarf shoots.
· Needle and stem of pinus contain resin canal.
· Gymnosperms lack ovary. They were abundant in the Mesozoic era, especially during the Jurassic period.
· They are the dominant vegetation in the cold region of the world where snow rather than water is the source of water.
· They show extreme xerophytic adaptation.
· Plant body is sporophytic which is differentiated into roots, stem and leaves.
· They are the dominant vegetation in the cold region of the world where snow rather than water is the source of water.
· They show extreme xerophytic adaptation.
· Plant body is sporophytic which is differentiated into roots, stem and leaves.
Largest gymnosperm: Sequoia gigantia
Smallest gymnosperm: Zamia
· Cycas, Metasequoia and Ginkgo are the living fossils.
· The main plant body is sporophyte; differentiated into root stem and leaves.
· In pinus (or conifers) the root is associated with Fungi (mycorrhiza).
· In Cycas, the stem is unbranched and have a characteristic leaf scar on the stem.
· Conifers are the largest group of gymnosperm.
· Most of the gymnosperms are evergreen shrubs that show xerophytic character.
· Root present– Taproot
· Roots of some gymnosperms have symbiotic relations with Algae (e.g coralloid roots of cycas) or with Fungi (mycorrhizae in pinus)
· Stem – Branched (pinus)
· Two types of leaves are present in Gymnosperm:
(a) Scaly leaf
(b) Foliage leaf
· Foliage leaves are green, simple, needle-shaped and pinnately compound.
· They help in photosynthesis.
· Scaly leaves are minute, deciduous which help in protection.
· Leaf lacks lateral veins. Hence, lateral conduction of food and nutrients is due to transfusion tissue.
· Leaves have sunken stomata which are covered with thick cuticles.
· Foliage leaves are green, simple, needle-shaped and pinnately compound.
· They help in photosynthesis.
· Scaly leaves are minute, deciduous which help in protection.
· Leaf lacks lateral veins. Hence, lateral conduction of food and nutrients is due to transfusion tissue.
· Leaves have sunken stomata which are covered with thick cuticles.
· Vascular tissue in Gymnosperm comprises of
(a) Xylem: Tracheids and xylem parenchyma.
(b) Phloem: Sieve cells and Albuminous cells
· Tracheids are the main conducting tissue and phloem lacks companion cells.
· Cambium is present and secondary growth takes place.
· Vascular bundles in stems are conjoint, collateral and open.
Types of wood in Gymnosperm:
i. Monoxylic Wood: The amount of secondary xylem (wood) is less and parenchyma is present in the large amounts. It is a soft type of wood. e.g. Cycas
ii. Pycnoxylic Wood: The amount of secondary xylem is high and parenchyma is less. It's a compact and hard type of wood. e.g. Pinus.
· They are heterosporous (production of two types of spores) i.e. microspores and megaspores.
· Megasporangia and microsporangia occur on megasporophylls and microsporophylls respectively which in turn aggregate to form cones. Cones are unisexual or monosporangiate.
Note: Cones are equivalent to flowers of angiosperm.
· Megasporangia and microsporangia occur on megasporophylls and microsporophylls respectively which in turn aggregate to form cones. Cones are unisexual or monosporangiate.
Note: Cones are equivalent to flowers of angiosperm.
A. Male cone
· It is equivalent to the male flower of angiosperm and represented by Microsporophyll (equivalent to the stamen of angiosperm) and Microsporangia (equivalent to pollen grain) are produced inside microsporophyll.
· Female cone (female flower of angiosperm) is represented by Megasporophylls (=carpel) which bears Megasporasporangia (ovules).
· Microsporophylls does not show the distinction between anther and filament.
· It is equivalent to the male flower of angiosperm and represented by Microsporophyll (equivalent to the stamen of angiosperm) and Microsporangia (equivalent to pollen grain) are produced inside microsporophyll.
· Female cone (female flower of angiosperm) is represented by Megasporophylls (=carpel) which bears Megasporasporangia (ovules).
· Microsporophylls does not show the distinction between anther and filament.
· Megasporophyll does not show the distinction between carpel and ovules.
· Ovules are orthotropous and unitegmic.
· Ovules contain archegonium.
· Archegonium lacks neck canal cells.
· Polymbryony (presence of more than one embryo) is common.
· Pollination is Anemophily (wind pollination).
· Male gametes are usually non-motile except Cycas and Ginko which has motile sperms. Double fertilization or triple fusion is absent.
· Endosperm develops from female gametophyte before fertilization hence it is haploid (n) in nature.
· Fertilization is Siphonogamy i.e. via the formation of the pollen tube.
· Double fertilization is absent.
· Polyspermy and polyembryony are common in the seed.
· Endosperm of a gymnosperm is a haploid.
Note: Cycas and Ginko are living fossils. Siphonogamy (formation of pollen tube) is common in gymnosperm which eliminates the dependence on water.
· The number of cotyledons in the seed is two in cycas and more than two in pinus.
· Ovules contain archegonium.
· Archegonium lacks neck canal cells.
· Polymbryony (presence of more than one embryo) is common.
· Pollination is Anemophily (wind pollination).
· Male gametes are usually non-motile except Cycas and Ginko which has motile sperms. Double fertilization or triple fusion is absent.
· Endosperm develops from female gametophyte before fertilization hence it is haploid (n) in nature.
· Fertilization is Siphonogamy i.e. via the formation of the pollen tube.
· Double fertilization is absent.
· Polyspermy and polyembryony are common in the seed.
· Endosperm of a gymnosperm is a haploid.
Note: Cycas and Ginko are living fossils. Siphonogamy (formation of pollen tube) is common in gymnosperm which eliminates the dependence on water.
· The number of cotyledons in the seed is two in cycas and more than two in pinus.
Gymnosperms are classification into four groups
1. Ginkgophyta: eg. Ginkgo
2. Gnetophyta: eg. Gnetum
3. Cycadophyta: eg. Cycas
4. Coniferophyta: eg. Pinus
· Cycads are also called fossils plants.
Life Cycle of Some Gymnosperms
1. Cycas (Sagopalm)Systematic position:
Kingdom: Plantae
Subkingdom: Embryophyta
Phylum: Tracheophyta
Subphylum: Pteropsida
Order: Cyacdales
Family: Cyacadaceae
Genus: Cycas
 |
Fig: Cycas:
External morphology |
· It is often called sago palm or palm fern.
· Dioecious (Unisexual)
· Sago is a type of starch extracted from Cycas revoluta.
· Cycas is often called living fossil because it is the oldest member of this group.
· It is the evergreen, xerophytic plant.
· Cycas consists of an unbranched erect stout and palm-like stem with a crown of fern-like pinnately compound leaves arranged spirally around the apex.
· Cycas is dioecious i.e. male and female flowers are born by two separate plants.
· Widely distributed in the tropical regions of the world.
· Sporophytic body is differentiated into root, stem and leaf
A. ROOT
Two types
i. Taproot
ii. Coralloid roots (Corallorhiza)
· Special type of adventitious root resembling like a coral.
· They are Apogeotropic or Aerotropic or Negatively geotropic.
· These roots have nitrogen-fixing blue-green algae (Cyanobacteria) e.g. Anabaena, Nostoc etc.
B. STEM
· Thick, Unbranched, Columnar.
· Contains mucilage canal in the cortical region.
C. LEAF
· Scale leaf
· Foliage leaf – pinnately compound.
· Scale leaf
· Foliage leaf – pinnately compound.
D. Male cone
· Single male cone is present at the top of the male plant.
· Male gametes are motile, top-shaped with multiple bands of cilia.
· Pollen grains of cycas are shed at 3 celled stage.
Note: Pollen grains shed at a 4-celled stage in Pinus and 2-celled stage in Angiosperm
· Largest antherozoids, eggs and ovules are found in cycas.
· Female cone is not organized in cycas, Megasporophylls are loosely arranged at the top of the female plant.
· Archegonia lacks neck canal cells but Egg cells (ventre cell), ventral canal cell and neck cells are present.
· Time interval between pollination and fertilization is 4-5 months.
· No water is required for fertilization.
· Fertilization is Siphnogamous (spermatozoids being carried by pollen tube).
· Spermatiozoids are liberated into the archegonial chamber and the spermatozoids reaches the archegonia with the help of cilia. i.e. fertilization by means of ciliated sperm zoidogamy.
 |
Fig: Showing L.s of male cone |
Post-Fertilization Changes:
Nucellus – Perisperm
Female Gametophyte – Endosperm
Zygote – Embryo
Integuments – Seed coat (Outer= Testa and Inner= Tegmen)
Ovule – Seed
Nucellus – Perisperm
Female Gametophyte – Endosperm
Zygote – Embryo
Integuments – Seed coat (Outer= Testa and Inner= Tegmen)
Ovule – Seed
2. Pinus
Systematic position:
Kingdom: Plantae
Subkingdom: Embryophyta
Phylum: Tracheophyta
Subphylum: Pteropsida
Class: Gymnosperm
Order: Coniferales
Family: Pinaceae
Genus: Pinus
· Plant – Monoecious (Bisexual)
· Sporophytic plant body is differentiated into root, stem and leases.
1. ROOT:
The mycorrhizal root contains fungi on their cortex (Ascomycetes and Basidiomycetes) helps in the absorption of water and minerals.
2. STEM:
Branched & 2 types
a. Long shoot – branch having unlimited growth.
· Female cone is modified long shoot.
a. Long shoot – branch having unlimited growth.
· Female cone is modified long shoot.
b. Dwarf shoot – branch having limited growth.
· Male cone is modified dwarf shoot.
· Male cone is modified dwarf shoot.
3. LEAF:
· Foliage leaves are found in dwarf shoots which is commonly called needles.
· Scaly, leaves are found in the long and dwarf shoots.
· Needle and stem of pinus contain resin canal.
4. Male Cone
· Found in a cluster behind the apical buds at the bases of new shoots.
· Consists of a number of microsporophylls or stamen
· Each microsporophyll bears two pouch-like microsporangia or pollen sacs.
· Pollen grain has two coats – exine (outer) and intine (inner). The exine forms two wings.
· Male gametes are non-motile.
· Pollen grain of pinus causes allergic fever called Hay fever.
· Found in a cluster behind the apical buds at the bases of new shoots.
· Consists of a number of microsporophylls or stamen
· Each microsporophyll bears two pouch-like microsporangia or pollen sacs.
· Pollen grain has two coats – exine (outer) and intine (inner). The exine forms two wings.
· Male gametes are non-motile.
· Pollen grain of pinus causes allergic fever called Hay fever.
5. Female Cone
· Found in groups of 2-4.
· Single megasporophyll of pinus contains two ovules.
· Each ovule is orthotropous and consists of the central mass of tissue – the nucellus or megasporangium surrounded by a single integument made of three layers.
· Time interval between pollination and fertilization is 12 - 15 months.
· Time interval between cone formation and seed dispersal is 26 months.
· Edible seed of pinus is called chilgoza.
· Found in groups of 2-4.
· Single megasporophyll of pinus contains two ovules.
· Each ovule is orthotropous and consists of the central mass of tissue – the nucellus or megasporangium surrounded by a single integument made of three layers.
· Time interval between pollination and fertilization is 12 - 15 months.
· Time interval between cone formation and seed dispersal is 26 months.
· Edible seed of pinus is called chilgoza.
· Pollination – Anemophily (by wind)
· Pollination drop is mucilage rich sucrose that comes out from the micropyle of the ovule.
· Polyembryony is common in pinus as well as other conifers.
· Many devices to uptake and conserve water like the development of waterproof cuticle, stomata for gaseous exchange etc.
b. Pinus wallichiana (Pinus excelsa)
· Commonly called Blue pine which is with 5 needles.
· Needle or foliage leaves of pinus have a thick waxy cuticle, with sunken stomata.
· Canada balsam used as a mounting agent during the preparation of permanent slides is obtained from Abies balsamea.
· Taxol, an anticancer drug is obtained from the bark of Taxus baccta (Khiote salla)
· Turpentine oil is obtained from the resin of pinus species.
i. Gymnosperm/Dicot: Eustelic
ii. Angiosperm/monocot: Atactostele @MADE (Monocot, Dicot)
3. No of prothallial cells:
In cycas = 1
In pinus = 2
In ephedra = 3
In selaginella = 1
4. Ovule in the ovuliferous scale of:
Pinus = 2
Cycas = 2 - 8
5. Pollen grains are shed in:
a. Cycas = 3 celled stage
b. Pinus = 4 celled stage
c. Ephedra = 5 celled stage
(Hint: Cell stage = Number of prothallial cell + 2)
Selaginella = 13 cell stage
Angiosperm = 2 cell stage (no prothallial cell).
· Pollination drop is mucilage rich sucrose that comes out from the micropyle of the ovule.
· Polyembryony is common in pinus as well as other conifers.
· Many devices to uptake and conserve water like the development of waterproof cuticle, stomata for gaseous exchange etc.
 |
Fig: Showing Life cycle of Pinus. |
Species of Pinus commonly found in Nepal (Pinus longifolia)
a. Pinus roxberghi Khotte salla / Pinus longifolia
· Commonly called chirpine which contains 3 needles.
a. Pinus roxberghi Khotte salla / Pinus longifolia
· Commonly called chirpine which contains 3 needles.
b. Pinus wallichiana (Pinus excelsa)
· Commonly called Blue pine which is with 5 needles.
· Needle or foliage leaves of pinus have a thick waxy cuticle, with sunken stomata.
· Canada balsam used as a mounting agent during the preparation of permanent slides is obtained from Abies balsamea.
· Taxol, an anticancer drug is obtained from the bark of Taxus baccta (Khiote salla)
· Turpentine oil is obtained from the resin of pinus species.
Comparative study of Pinus and Cycas
| Features | Cycas | Pinus |
|---|---|---|
| Plant body | Dioecious | Monoecious |
| stem | Unbranched | Branched |
| Leaf | Large compound | Simple foliage |
| Root | Coralloid | Mycorrhizal |
| Wood | Manoxylic or Softwood | Pycnoxylic or Hardwood. |
| Xylem | Polyxylic | Monoxylic |
| Female strobilus | Absent | Present. |
| Ovule | Orthotropous ovule | Anatropous ovule |
| Fertilization | Zooidogamy | Siphonogamy |
| pollination | At 3-celled stage | At 4-celled stage |
| Germination | Hypogeal | Epigeal |
High Yielding Points of Gymnosperm
1. Types of stele:i. Gymnosperm/Dicot: Eustelic
ii. Angiosperm/monocot: Atactostele @MADE (Monocot, Dicot)
2. The male gamete of Cycas is ciliated (@ c = c) but Pinus and Ephedra are non-ciliated.
3. No of prothallial cells:
In cycas = 1
In pinus = 2
In ephedra = 3
In selaginella = 1
4. Ovule in the ovuliferous scale of:
Pinus = 2
Cycas = 2 - 8
5. Pollen grains are shed in:
a. Cycas = 3 celled stage
b. Pinus = 4 celled stage
c. Ephedra = 5 celled stage
(Hint: Cell stage = Number of prothallial cell + 2)
Selaginella = 13 cell stage
Angiosperm = 2 cell stage (no prothallial cell).
Also, Read Notes of Other Lessons of Botany: