· Reproduction is the prime characteristic of the living being.
· It is necessary for the continuity of species.
· Types of reproduction:
A) Asexual Reproduction.
B) Sexual Reproduction
A) Asexual Reproduction:
· In asexual reproduction, offspring are produced by single parents without the fusion of gamete.
· Formation of new plants from vegetative parts (somatic cells) without meiosis and fertilization.
· The produced offspring are genetically identical to their parents, thus called clones.
· Cell divisions involved are only mitotic.
· It occurs from vegetative parts of plants such as roots, stems, and leaves thus called vegetative propagation.
· Only method of reproduction in plants that do not flower naturally like; sugarcane, banana, pineapple etc.
· Individual obtained by cloning= Ramet.
B) Sexual Reproduction
· Sexual reproduction involves the process of production of offspring by fusion of male and female gametes.
· Gametes are formed and fertilization takes place.
· The offsprings are genetically non-identical to parents.
· Has the main role in evolution.
1. Various Vegetative propagation in Plants
· Production of new species without fertilization
· Reproduction takes place through vegetative or somatic parts of the plant in those where flowers normally do not occur.
· The detachable plant part that functions in vegetative propagation is called vegetative propagule.
· It's of large importance for the preservation of good qualities of the plant.
It is of two types:
1. Natural Vegetative Reproduction:
- Reproduction occurs naturally in perennial plants under suitable conditions.
- Takes place by following methods: Root, Stem, Bulbils, Leaf
1. Natural Vegetative Reproduction:
- Reproduction occurs naturally in perennial plants under suitable conditions.
- Takes place by following methods: Root, Stem, Bulbils, Leaf
I) Root:
- Roots of some plants develop adventitious buds (radical buds) on them, which on separation gives rise to new plants.
Eg; Dalbergia, guava, poplar, rose, etc.
- Some tuberous adventitious roots besides containing adventitious buds contain sufficient quantities of food,
- Some tuberous adventitious roots besides containing adventitious buds contain sufficient quantities of food,
Eg: Dhalia, Asparagus and sweet potato.
- If sown in the soil, these roots produce several leafy shoots known as slips that develop their own roots.
- If sown in the soil, these roots produce several leafy shoots known as slips that develop their own roots.
II) Stem:
A) Underground stem:
· Are means of perennation or survival during unfavourable periods.
a) Suckers:
a) Suckers:
· Short underground stem branches that arise at the base of the aerial shoot, grow into aerial branches and develop adventitious roots.
· When suckers separate, they give rise to a new plant.
Eg; Mint, Chrysanthemum, Rose, Banana
Eg; Mint, Chrysanthemum, Rose, Banana
b) Rhizomes:
- Thickened prostrate, underground stem storing food for perennation.
- Piece of Rhizome containing bud can give rise to a new plant.
Eg: Banana, Ginger, Turmeric.
c) Corms:
- Swollen unbranched underground stem which is also called the condensed form of Rhizome.
- Bear many buds in the axils of scale leaf present in the nodes. Under favourable conditions, these buds produce new plants using the food stored in the corm. Each new shoot store the food at the base and produce a new corm.
Eg; Colocasia, Freesia, Crocus, Amorphophallus, Gladiolud etc.
d) Bulb:
- Underground condensed disc-shaped shoot with numerous buds.
- Have a number of buds which on separation gives rise to the new plant.
Eg: Garlic, Onion.
· Though onion can be propagated by this method, seeds are more economic.
Note: Onion has contractile roots and its edible part is fleshy leaves.
Note: Onion has contractile roots and its edible part is fleshy leaves.
e) Tubers:
- Swollen end of the underground stem for storing food.
- Bears a number of nodes called eyes with buds. Each piece containing one or more eyes can give rise to the new plant. If the whole tuber is sown, only terminal buds sprouts due to apical dominance.
Eg; Selaginella, Marsilea, potato etc.
B) Sub-aerial stems:
- Creeping and rooted stems.
- Multiply rapidly by vegetative propagation.
i) Runners:
- Narrow green horizontal prostrate stems develop at the base of the crown.
- Have distinct nodes and long internodes.
- Breaking of runner gives new plant.
Eg: Cynodon(dubo), Centella.
- Creeping and rooted stems.
- Multiply rapidly by vegetative propagation.
i) Runners:
- Narrow green horizontal prostrate stems develop at the base of the crown.
- Have distinct nodes and long internodes.
- Breaking of runner gives new plant.
Eg: Cynodon(dubo), Centella.
ii) Stolon:
- Grows laterally from the base of the stem and runs horizontally.
Eg; Wild strawberry.
- Grows laterally from the base of the stem and runs horizontally.
Eg; Wild strawberry.
iii) Offsets:
- One internode long runner that occurs in aquatic plants.
Eg; Eichornia(Water hyacinth), Pistia (water lettuce)
C) Aerial stem:
- Each Segment of the joint phylloclade of opuntia and some cacti have several buds, and stored food and water can form a new plant.
- Sugarcane is propagated from a piece of a stem with one or more nodes having bud.
- Each Segment of the joint phylloclade of opuntia and some cacti have several buds, and stored food and water can form a new plant.
- Sugarcane is propagated from a piece of a stem with one or more nodes having bud.
III) Bulbils:
- Modified multicellular flora or vegetative fleshy buds are called bulbils.
- When sheds from the plant, develop into a new plant.
Eg; bulbil arising in the axil leaves.
Eg; Lily Dioscorea or wild yam, on the inflorescence axis
Eg; Garlic, Agave) over swollen root
Eg; Oxalis and adjacent to the fruit
Eg; Pineapple
- In Agava, they remain attached to the floral axis.
- In Dioscorea bulbils are axillary.
- In Agava, they remain attached to the floral axis.
- In Dioscorea bulbils are axillary.
IV) Leaves:
- Not so common.
- Some leaves produce adventitious buds
- Not so common.
- Some leaves produce adventitious buds
Eg; Bryophyllum, Begonia, Walking fern (Adiantum caudatum), Kalanchoe.
- Fleshy leaves of Bryophyllum on their notches bear adventitious bud.
- In Adiantum, tips of leaves on touching the ground can produce bud.
- Fleshy leaves of Bryophyllum on their notches bear adventitious bud.
- In Adiantum, tips of leaves on touching the ground can produce bud.
2. Artificial Vegetative Reproduction:
· Used by horticulturists to multiply economically important plants.
· It is applicable for:
i) Quick production of new plants, formation of seeds etc.
ii) Combining the qualities of two varieties.
· Used by horticulturists to multiply economically important plants.
· It is applicable for:
i) Quick production of new plants, formation of seeds etc.
ii) Combining the qualities of two varieties.
Some Artificial Methods of Reproduction are:
a) Cutting:
· Cutting is putting a piece of stem, leaf or root with at least one bud.
· Stem cutting is more common. Stem cutting is done in an old stem about 20-30 cm in length.
· Stem cutting is generally used in Rose, Sugarcane, Duranta, Citrus, China rose, Bougainvillea, etc.
· Sansevieria (snake plant) is propagated by leaf cutting.
· Root cuttings are used in blackberry, apple, lemon and raspberry.
· Success depends on the capacity of formation of adventitious roots and so growth hormone-like Auxin (IAA) are applied in very dilute quantities to the lower end of the stem to hasten root formation.
a) Cutting:
· Cutting is putting a piece of stem, leaf or root with at least one bud.
· Stem cutting is more common. Stem cutting is done in an old stem about 20-30 cm in length.
· Stem cutting is generally used in Rose, Sugarcane, Duranta, Citrus, China rose, Bougainvillea, etc.
· Sansevieria (snake plant) is propagated by leaf cutting.
· Root cuttings are used in blackberry, apple, lemon and raspberry.
· Success depends on the capacity of formation of adventitious roots and so growth hormone-like Auxin (IAA) are applied in very dilute quantities to the lower end of the stem to hasten root formation.
b) Layering
· Development of roots on a stem before detaching it from the parent plant for propagation.
· 2 types:
a. air layering (in the air: gottee),
b. mould layering (by bending the branch close to the ground)
c) Grafting
· A shoot or a part of the plant (scion) is inserted into
another plant (stock) so as to be nourished by it and united with it.
· For successful grafting, the union of cambium is necessary.
· Grafting is not possible in monocot stems as they lack cambium.
· Grafting is common in Mango, Citrus, apples etc.
d) Micropropagation:
· Obtaining a large no of plantlets by cutting shoot tips or any other part of the plant by tissue culture method.
· Embryoids are the non-zygotic embryo developed through tissue culture.
· Tissues in the shoot apical meristem are widely used in tissue culture as they are virus-free.
· Callus – its mass of undifferentiated tissue.
· Clone is a population of genetically identical plants derived from an individual. They are the products of vegetative propagation.
· Commonly sugarcane, Rose, and Bougainvillea are propagated by stem Cutting.
Special Note:
· Dry-freeze storage of germplasm is called cryobiology.
· Virus-free plant is obtained by micro-propagation.
· Shoot-tip culture is used to obtain the virus-free plants.
· Budding: Type of grafting in which the scion is a single vegetative bud with a stem peeling having cambium. Eg; Rose, apple, plum etc.
· Dry-freeze storage of germplasm is called cryobiology.
· Virus-free plant is obtained by micro-propagation.
· Shoot-tip culture is used to obtain the virus-free plants.
· Budding: Type of grafting in which the scion is a single vegetative bud with a stem peeling having cambium. Eg; Rose, apple, plum etc.
· Nucellus culture: Genetically uniform and disease-free clones have been produced by nucellus culture. Eg; in citrus, mango etc.
· Protoplast culture is the development in the field of tissue culture.
· Most important use of protoplast culture is somatic hybridization or the production of somatic hybrids.
· Nitrogen fixation gene “nif” can be introduced into non-legumes by protoplast culture.
Chloroplast + nif → Nitroplast.
· Tissue culture is based on the concept of totipotency. i.e. each and every plant cell has an inherent capacity to develop into a complete plant.
· Concept of Totipotency was given by Haberlandt and its practice aspect was shown by the Steward when he developed from a single cell of wild carrot root.
· Endosperm culture is used for triploid plant production,
· Best method for haploid production is pollen culture.
· Triploids are usually seed sterile or triploids are associated with seedless, so these may be explained for the seedless nature of fruits.
· As triploids are usually seeded sterile so undesirable for plants where seeds are commercial products.
· Protoplast culture is the development in the field of tissue culture.
· Most important use of protoplast culture is somatic hybridization or the production of somatic hybrids.
· Nitrogen fixation gene “nif” can be introduced into non-legumes by protoplast culture.
Chloroplast + nif → Nitroplast.
· Tissue culture is based on the concept of totipotency. i.e. each and every plant cell has an inherent capacity to develop into a complete plant.
· Concept of Totipotency was given by Haberlandt and its practice aspect was shown by the Steward when he developed from a single cell of wild carrot root.
· Endosperm culture is used for triploid plant production,
· Best method for haploid production is pollen culture.
· Triploids are usually seed sterile or triploids are associated with seedless, so these may be explained for the seedless nature of fruits.
· As triploids are usually seeded sterile so undesirable for plants where seeds are commercial products.
Sexual Reproduction (Embryology of Angiosperm):
Involves two steps:i) Sporogenesis (Micro and mega-sporogenesis)
ii) Gametogenesis (Micro and mega-gametogenesis)
· Typical anther is Tetrasporangiate, Bithecous i.e. with four microsporangia
· Anther with only two microsporangia (Monothecous) eg. Malvaceae
· In each lobe archesporial cell differentiated to form the archesporium of the anther.
i. Epidermis – the outermost layer of anther wall
ii. Endothecium- Hygroscopic layer below the epidermis which helps in dehiscence of anther and hence the spores are dispersed.
iii. Wall layers (middle layers)– one to three-layered structure that degenerates soon.
iv. Tapetum
- Innermost, nutritive layer of anther wall
- Secretes enzymes and hormones necessary for pollen grains.
- Tapetal cells are multinucleate or coenocytic at maturity.
- Ubish bodies or spheroids (granular structures) are present in the tapetum
Microsporogenesis
- A process of forming pollen grains (microspores) inside a pollen sac (Microsporangium)
- Primary sporogenous → Micropyle mother cell, Pollen mother cell
- Pollen mother cell (2n) on Meiosis → Pollen grains cells (n) or Microspores [Reductional division]
Microgametogenesis
· Process of forming male gametophyte from pollen grains (microspores)
· Pollen grain → Mitosis → Vegetative Nucleus (Tube nucleus) & Generative Nucleus (Divides to give male gamete)
· Pollen grain → Mitosis → Vegetative Nucleus (Tube nucleus) & Generative Nucleus (Divides to give male gamete)
· Study of the pollen grain is palynology
· Pollen grain → Exine (outer) bears germ pore & Intine (inner)
· Pollen grain → Exine (outer) bears germ pore & Intine (inner)
· Chiefly composed of sporopollenin
Note: sporopollenin: most resisting material
 |
| Fig: Ovule |
 |
| Female gametophyte |
· Each ovule (megasporangium) is attached to the placenta by a short stalk-like structure called a funicle.
· Hilum is the point of attachment of the body of the ovule to the stalk or funicle.
· Funicle continues beyond the hilum alongside the body of the ovule forming a short ridge called raphe through which food is carried to the nucellus.
· Chalaza is the junction of integument and nucellus.
· Nucellus is the main body of the ovule, which is surrounded by two coats.
· Micropyle – small opening left at the apex of the integuments.
· Large oval cell lying embedded in the nucellus towards the micropyle is called the embryo–sac (i.e, sac-bearing embryo)
Megasporogenesis
· Process of forming megaspores inside megasporangium or ovule.
· Megaspore mother cell divides meiotically and forms four megaspores.
· Out of four megaspores three become degenerate and only one becomes functional.
· Functional megaspore always lies towards the chalazal end or away from the micropyle
· Process of forming megaspores inside megasporangium or ovule.
· Megaspore mother cell divides meiotically and forms four megaspores.
· Out of four megaspores three become degenerate and only one becomes functional.
· Functional megaspore always lies towards the chalazal end or away from the micropyle
· Process of forming female gametophyte or embryo sac from functional megaspore.
· In a mature embryo sac, a group of three cells (2 egg cells and one synergid) surrounded by a very thin wall is seen lying towards the micropyle which is known as the egg apparatus.
· Filiform apparatus is found in synergids
· Egg cell on fertilization gives rise to the embryo and synergids get degenerated.
· Antipodal cells (3 cells) lie towards the chalazal end.
· Definitive nucleus or secondary nucleus is the fusion product of two polar nuclei.
· Double fertilization is the process of fusion of the secondary nucleus (2n) with the male gamete (n).
· Double fertilization was discovered by Nawaschin in Lilium and Fritillaria can be represented as
· Secondary nucleus (2n) + male gamete (n) = primary endosperm (3n) = Triple fusion (By Nawachin)
· Typical angiosperms embryo sac at the time of fertilization is 7-celled and eight nucleated.
· Embryo sac is called the monosporic polygonal type.
· All the cells in the embryo sac are haploid except the polar nucleus (2n)
 |
| Fig: Showing formation of Female gametophyte (Embryo sac) |
Various Types of Ovules
i. Orthotropous or Atropous
· It's an erect ovule in which the micropyle, chalaza and funicle lie in the same vertical line.
· Common in Gymnosperms
i. Orthotropous or Atropous
· It's an erect ovule in which the micropyle, chalaza and funicle lie in the same vertical line.
· Common in Gymnosperms
ii. Anatropous (ana- Backwards or up)
· It's an inverted ovule in which the body of the ovule lies parallel to the funicle
· This is the common type of ovule found in Angiosperms.
Note: A for A
iii. Hemianatropous (Transverse ovules)
· Body of the ovule (integument and nucellus) lies at a right angle to the funicle.
Eg. Ranunculus
iv. Campylotropous ovule (Curved)
· Curved oule
· Common in legumes, mustard, radish
v. Unitegmic ovule
· Ovule with single integument
· Common in gymnosperms.
· Common in gymnosperms.
vi. Bitegmic ovule
· Ovule with two integuments.
· Common in Angiosperm.
· Common in Angiosperm.
vii. Ategmic ovule
· Ovules without any integument
Eg. Loranthaceae and Santalaceae
Pollination
· Transfer of pollen grains from the anther to the stigmaTwo types of Pollination are:
i. Self-pollination
· Transfer of pollen grains from the anther to the stigma of the same or genetically, similar flowers.
· Flowers are generally small, inconspicuous colourless odourless and nectarless.
· External agent is not necessary for pollination.
Methods of Self-Pollination
i. Homogamy: Anthers and stigma of a bisexual flower mature simultaneously,.
ii. Bisexuality: male and female parts are borne within the same flower.
iii. Cleistogamy (closed flowers)
· Bisexual flower which is always closed.
· Generally accompanied by geocarpy, when the fruits are formed underground.
· Bisexual flower which is always closed.
· Generally accompanied by geocarpy, when the fruits are formed underground.
Eg. Risum sativum, Commelina (Underground flower)
· Chasmogamous flower – flower opens at maturity.
· Cleistogamous flower – closed flowers.
· Chasmocleistogamous – Both open and closed flowers.
· Cleistogamous flower – closed flowers.
· Chasmocleistogamous – Both open and closed flowers.
Advantage of Self-Pollination:
· Preserve parental characters indefinitely, therefore, a useful variety once evolved in a homozygous form can be preserved.
· Helps in maintaining pure lines for experimental hybridization.
· More economical
· The plant does not consume more energy in the production of a large number of pollen grains.
· Preserve parental characters indefinitely, therefore, a useful variety once evolved in a homozygous form can be preserved.
· Helps in maintaining pure lines for experimental hybridization.
· More economical
· The plant does not consume more energy in the production of a large number of pollen grains.
Disadvantages of Self-Pollination:
· Useful characters cannot be introduced by this method.
· The immunity of the race towards infection decreases and ultimately the race becomes susceptible to many diseases.
· Do not cause variability.
· The immunity of the race towards infection decreases and ultimately the race becomes susceptible to many diseases.
· Do not cause variability.
ii. Cross-Pollination:
· Pollination between two different flowers.
a. Xenogamy or allogamy (Xenos – strange, gamos – marriage)
· Pollination between two flowers of different plants.
b. Geitonogamy
· Pollination between two different flowers.
a. Xenogamy or allogamy (Xenos – strange, gamos – marriage)
· Pollination between two flowers of different plants.
b. Geitonogamy
· pollination between the different flowers of the same plant.
· It is often called genetically self-pollination and functional cross-pollination.
· It is often called genetically self-pollination and functional cross-pollination.
Adaptations:
a. Unisexuality or dicliny (gr. Di-two, kline – bed)
· Unisexual flower either male or female that ensures cross-pollination eg. Mulberry, Maize, Papaya.
b. Self-sterility or self-compatibility:
· Pollen grains of a flower are incapable of completing growth on the stigma of the same flowers due to mutual inhibition eg. Potato, and orchids.
c. Dichogamy:
· Bisexual flower in which anther and stigma mature at different times.
a. Unisexuality or dicliny (gr. Di-two, kline – bed)
· Unisexual flower either male or female that ensures cross-pollination eg. Mulberry, Maize, Papaya.
b. Self-sterility or self-compatibility:
· Pollen grains of a flower are incapable of completing growth on the stigma of the same flowers due to mutual inhibition eg. Potato, and orchids.
c. Dichogamy:
· Bisexual flower in which anther and stigma mature at different times.
Two types.
i. Protandry – Anther matures earlier than the stigma
ii. Protogyny – Stigma matures earlier than anther.
d. Heterostyly:
· Occurrence of flowers having a variable length of styles and stamens. Eg. Flower of prime Rose (primula)
i. Protandry – Anther matures earlier than the stigma
ii. Protogyny – Stigma matures earlier than anther.
d. Heterostyly:
· Occurrence of flowers having a variable length of styles and stamens. Eg. Flower of prime Rose (primula)
e. Herkogamy:
· Flower has natural barriers in between anthers and stigma that prevent self-pollination. Eg. Calotropis.
· In calotropis pollen grains are stored in a sac-like structure called pollinium.
· Flower has natural barriers in between anthers and stigma that prevent self-pollination. Eg. Calotropis.
· In calotropis pollen grains are stored in a sac-like structure called pollinium.
· Primula shows dichogamy and herkogamy both
Advantages of Cross-Pollination:
· Can produce new and useful variety.
· It increases the adaptability of varieties towards the new environment.
· Usually large and more vigorous seeds are produced.
· Can produce new and useful variety.
· It increases the adaptability of varieties towards the new environment.
· Usually large and more vigorous seeds are produced.
· The phenomenon of hybrid vigour can also be observed in this method.
Disadvantages of Cross-Pollination:
· Less economical
· Need an agent for pollination
· Some good characteristics are likely to be spoiled.
· Need an agent for pollination
· Some good characteristics are likely to be spoiled.
Agent or Medium for Pollination:
· Wind-pollinated flowers often have a single ovule.
· Gun powder mechanism of pollination is found in Urtica.
· Wind-pollinated flowers often have a single ovule.
· Gun powder mechanism of pollination is found in Urtica.
1. Wind.
· Wind pollination is called Anemophily
· In wind-pollinated flowers, non-essential floral organs are either absent or reduced.
· This makes the flower small inconspicuous and devoid of colour, nectar and smell.
Adaptation:
· Pollen grains are small, light or dusty and can be blown to a long distance.
· Pollen grains are small, light or dusty and can be blown to a long distance.
· Stigma are sticky, hairy and feathery to increase surface area for catching pollen grains. e.g. Maize. Oak, Gramineae (grasses) etc.
2. Pollination by animals: Zoophily
(a) Insect
· Pollination by insects is entomophily.
· Entomophilous flowers are coloured with scent and nectar. E.g. Salvia (pollination by Honey bees.)
· Pollination by birds is ornithophily.
· Sunbirds and Humming birds are common bird pollinators.
· Ornithophilous flowers have bright colours (especially red and orange) and their floral parts are leathery to support the weight of the birds. e.g. Bombax
· Chiropterophily: Pollination by bats.
· Pollination by birds is ornithophily.
· Sunbirds and Humming birds are common bird pollinators.
· Ornithophilous flowers have bright colours (especially red and orange) and their floral parts are leathery to support the weight of the birds. e.g. Bombax
· Chiropterophily: Pollination by bats.
· Bat-pollinated flowers are large, and stout, with a strong odour, abundant nectar and pollen grains. Eg. Anthocephalus.
· Malacophily: Pollination by snails. e.g. Arisaema snake or cobra plant
· Ophiophily – pollination by snakes
· Malacophily: Pollination by snails. e.g. Arisaema snake or cobra plant
· Ophiophily – pollination by snakes
2. Water:
· Pollination by water is Hydrophily (hydro – Water, philein – To love)
· Water-pollinated flowers are small and inconspicuous.
· The stigmas are long and sticky in order to catch the pollen grains.
Two types
a. Hypohydrophily: Occurs below the surface of the water. Eg. Ceratophyllum, Zostera
b. Epihydrophily: occurs over the surface of water Eg. Vallisneria. (Tape grass)
Two types
a. Hypohydrophily: Occurs below the surface of the water. Eg. Ceratophyllum, Zostera
b. Epihydrophily: occurs over the surface of water Eg. Vallisneria. (Tape grass)
Fertilization
· Fusion of gametes.· Process of fertilization was discovered by Strasburger.
· Germ pores are found in pollen grains through which pollen tube comes out, growth of pollen tube is regulated by Ca++, Boron sugar complex.
· Pollen grain is with tube nucleus and generative nucleus which forms Two male gametes.
· Of these two male gametes one fuses with the egg–cell (n) and forms a zygote while the other fuses with the definitive nucleus or secondary nucleus (2n) to form the endosperm (3n). Thus this fusion is called triple fusion or double fertilization.
· Endosperm of angiosperm is usually triploid (3n) while that of gymnosperm is haploid (n) [Endosperm in gymnosperm represents female gametophyte].
· 1st fusion is called fertilization or syngamy and the second fusion is called triple fusion.
· Process of double fertilization was discovered by Nawaschin in Lilium and Fritillaria.
· Double fertilization is common in angiosperm and absent in gymnosperm.
· Porogamic fertilization: pollen tube enters the ovule through the micropyle.
· Chalazogamic fertilization: Pollen tube enters the ovule through the Chalazal region.
· Mesogamic fertilization: Pollen tube enters the ovule through the integument.
· Zygote is often called oospore (2n)
· Withering and shedding of the corolla is an indication of failure in fertilization
· Development of fruit without fertilization is called parthenocarpy
· Chalazogamic fertilization: Pollen tube enters the ovule through the Chalazal region.
· Mesogamic fertilization: Pollen tube enters the ovule through the integument.
· Zygote is often called oospore (2n)
· Withering and shedding of the corolla is an indication of failure in fertilization
· Development of fruit without fertilization is called parthenocarpy
· Parthenocarpic fruit are usually seedless. e.g. Banana, grapes. Papaya.
· Development of zygote without fertilization is parthenogenesis.
· Development of zygote without fertilization is parthenogenesis.
Post-fertilization changes:
- Ovary – Fruit
- Ovule – Seed
- Outer integument – Testa
- Inner integument – Tegmen
- Egg cell – Embryo
- Polar nuclei – endosperm
- Nucellus – Perisperm
- Synergids and antipodal cells – Degenerate.
Embryo development:
· Zygote forms an embryo by mitotic cell division.
· Zygote forms an embryo by mitotic cell division.
· Basal cell divides in one direction to form suspensors which help in food absorption for the growing embryo
· Position of the plumule is in between two cotyledons in the dicot embryo but it is present on the lateral side in the monocot embryo.
· In a monocot embryo, the basal cell doesn't divide and forms one cell suspensor.
· Covering of radical is called coleorhiza
· In Loranthus (monocot embryo has 2-6 cotyledons)
· Covering of plumule is coleoptile
· In monocot, the cotyledon is also called scutellum
· Endosperm is triploid in Angiosperm, haploid in gymnosperm and absent in other plants in angiosperm
· Endosperm is reduced in dicots except for Ricinus (castor oil plant) and it is well developed in monocots except for orchids.
· Polyembryony: Development of more than one embryo in the same seed. Common in pinus and citrus.
· Amphimixis: the fertilization of male and female gamete.
· Apomixis: Development without fertilization or fusion of gametes
· Position of the plumule is in between two cotyledons in the dicot embryo but it is present on the lateral side in the monocot embryo.
· In a monocot embryo, the basal cell doesn't divide and forms one cell suspensor.
· Covering of radical is called coleorhiza
· In Loranthus (monocot embryo has 2-6 cotyledons)
· Covering of plumule is coleoptile
· In monocot, the cotyledon is also called scutellum
· Endosperm is triploid in Angiosperm, haploid in gymnosperm and absent in other plants in angiosperm
· Endosperm is reduced in dicots except for Ricinus (castor oil plant) and it is well developed in monocots except for orchids.
· Polyembryony: Development of more than one embryo in the same seed. Common in pinus and citrus.
· Amphimixis: the fertilization of male and female gamete.
· Apomixis: Development without fertilization or fusion of gametes
Endospermic seed (Albuminous seed):
· Those seeds in which food material is stored in endosperm.
· It is common in monocots (wheat, maize, rice barley, etc)
· In albuminous seed, food is stored in endosperm.
· Those seeds in which food material is stored in endosperm.
· It is common in monocots (wheat, maize, rice barley, etc)
· In albuminous seed, food is stored in endosperm.
Exalbuminous seeds (Non – Endospermic seeds)
· Food material is stored in the cotyledons.
· In exalbuminous seed food is stored in the cotyledons
· Common in dicots (gram, pea, mango etc.)
· Dicot seed is with two cotyledons, the shoot apex is the medial outer seed coat testa and the coat is the inner tegmen.
· Food material is stored in the cotyledons.
· In exalbuminous seed food is stored in the cotyledons
· Common in dicots (gram, pea, mango etc.)
· Dicot seed is with two cotyledons, the shoot apex is the medial outer seed coat testa and the coat is the inner tegmen.
Seed germination
· 1st step in the life of the plant
· Water, oxygen and a suitable temperature are necessary for seed germination
· 1st step in the life of the plant
· Water, oxygen and a suitable temperature are necessary for seed germination
Hypogeal Germination
· Cotyledons remain below the ground.
· Elongation of epicotyl.
· Common in monocots, also in pea and gram
· Cotyledons remain below the ground.
· Elongation of epicotyl.
· Common in monocots, also in pea and gram
Epigeal Germination
· Cotyledons are pushed above the soil
· Elongation of hypocotyls.
· Common in dicots except for pea and gram.
· During seed germination radicles come out first of all from the seed.
· Cotyledons are pushed above the soil
· Elongation of hypocotyls.
· Common in dicots except for pea and gram.
· During seed germination radicles come out first of all from the seed.
Viviparity
· Seed germination inside the fruit while it is still attached to the parent plant.
· It is the adaptation for Mangrove plants (halophytes: salt-loving plants) Eg. Rhizophora.
· Seed germination inside the fruit while it is still attached to the parent plant.
· It is the adaptation for Mangrove plants (halophytes: salt-loving plants) Eg. Rhizophora.
Important Calculative Question:
1. Number of chromosomes in root cells (or leaf cells or stem cells or somatic cells) is 24, what will be the number of chromosomes in:a) Nucellus
b) Integuments
Solution: No. of chromosomes in root cells is 24.
i.e 2n = 24 (sporophyte) so the number of chromosomes in different tissue are:
a) Nucellus = 2n = 24
b) Integuments = 2n = 24
c) Megaspore mother cell = 2n = 24
d) Endosperm (the result of triple fusion) = 3n = 36
e) Synergids(part of gametophyte) = n = 12
f) Antipodals(part of gametophyte):n = 12
g) Secondary nucleus( formed by fusion of 2 polar nucleus) = 2n = 24.
h) Pollens(formed after meiosis) = n = 12
i) Megaspore(formed after meiosis) = n = 12.
2. If the haploid number of chromosomes is 6, then what will be the number of chromosomes in:
a) Nucellus
3. If the number of chromosomes in the endosperm is 30, what will be the number of chromosomes in the nucellus?
Solution: No. of the chromosome is the endosperm, i.e, 3n = 30
So, No. of chromosome in nucellus = 2n = 20
4. How many meiotic divisions are necessary for the formation of 100 pollen grains?
Solution: As 4 pollen grains are produced by reductional division or meiotic division of one pollen mother cell, so meiotic division of 25 PMC is necessary to form 100 pollen grains.
Hence, No. of meiotic divisions necessary for the formation of 100 pollens = 25 as (n/4), n = Number of pollens.
5. How many meiotic divisions are required for the formation of 100 Megaspore?
Solution: No. of meiotic division needed for the formation of 100 megaspore = 100 (as by meiotic division of a megaspore mother cell, 4 megaspores are produced out of which 3 degenerate and only one survives)
6. If the development is normal and there is complete success of pollination and fertilization, then how many meiotic divisions are needed for 100 zygote formation?
Solution: For the formation of 100 zygotes, 100 male gametes and 100 female gametes (eggs) are required. 100 male gametes are developed from 100 microspores (from 25 meiotic divisions) and 100 eggs are developed from 100 megaspores (from 100 meiotic divisions).
Hence, No. of meiotic division needed for 100 zygotes formation= 25+100= 125
Note: Shortcut: No. of meiotic division = n + n/4 = 5n/4, where n = no of the zygote. So here, n = 100 so No. of meiotic division = 5*100/4 = 125.
7. How many meiotic divisions are needed for the formation of 100 grains in wheat?
Solution: No.of meiotic division = 5n/4 (n = no. of grains) = 5.*00/4 = 125
8. How many meiotic divisions are necessary for 100 seed formation in the family Cyperaceae?
Solution: There is an exception in the family Cyperaceae in microsporogenesis i.e out of 4 microspores formed after reductional division of microspore mother cell. 3 degenerates and only one survives (same as in the case of megaspores).
Hence No. of meiotic division = 100 + 100 = 200 or, No. of meiotic division = n + n = 2n = 2*100 = 200 (n = no. of seed)
1. Egg apparatus is situated at the Micropylar end
2. Ubisch bodies are provided by Tapetum
3. Main insects behind entomophily are bees
4. Pollen tube during pollen germination comes out through germ pore
5. Fertilization in which male gametes are carried through a pollen tube is called Siphonogamy
6. Number of meiotic divisions required to produce 400 seeds in a pea plant is 500 (N = 5n/4 where n = 400)
7. Development of sporophytes without fertilization from the vegetative cells of the gametophyte is called Apogamy
8. Commonest nutritive tissue for developing embryos in angiosperms is Endosperm
9. Ovule of angiosperm can be called Megasporangium
10. A true seed is fertilized ovule with an embryo
11. Ovule is inverted, its body is parallel to the funicle, micropyle is near the hilum, then it is called Anatropous
12. The plant part consists of two-generation one within the other is Embryo and another part that consists of three generations is the seed
13. Apospory is the direct formation of gametophyte from the sporophyte.
14. Hay fever is due to wind-borne pollen
15. Clone is a group of individuals got through vegetative propagation
16. Stigmas are large and sticky in the case of hydrophilous while large and feathery in anemophilous flowers.
17. Study of the formation growth and development of the new individual from an egg is Embryology
18. Development of shoot and root in tissue culture is determined by Cytokinin and auxin ratio
19. A unique phenomenon observed in the embryo sac of angiosperms is triple fusion and double fertilization
20. Auxenic culture is a pure culture without contamination
c) Megaspore mother cell
d) Endosperm
e) Synergids
f) Antipodals
g) Secondary nucleus
g) Secondary nucleus
h) Pollen
i) Megaspore
i) Megaspore
Solution: No. of chromosomes in root cells is 24.
i.e 2n = 24 (sporophyte) so the number of chromosomes in different tissue are:
a) Nucellus = 2n = 24
b) Integuments = 2n = 24
c) Megaspore mother cell = 2n = 24
d) Endosperm (the result of triple fusion) = 3n = 36
e) Synergids(part of gametophyte) = n = 12
f) Antipodals(part of gametophyte):n = 12
g) Secondary nucleus( formed by fusion of 2 polar nucleus) = 2n = 24.
h) Pollens(formed after meiosis) = n = 12
i) Megaspore(formed after meiosis) = n = 12.
2. If the haploid number of chromosomes is 6, then what will be the number of chromosomes in:
a) Nucellus
b) Integuments
c) Endosperm
c) Endosperm
d) Synergids
e) Antipodals
Solution: Here, n = 6
So, a number of chromosomes in different tissue:
a) Nucellus = 2n = 12
b) Integuments = 2n = 12
c) Endosperm = 3n = 18
d) Synergids = n = 6
e) Antipodals = n = 6
e) Antipodals
Solution: Here, n = 6
So, a number of chromosomes in different tissue:
a) Nucellus = 2n = 12
b) Integuments = 2n = 12
c) Endosperm = 3n = 18
d) Synergids = n = 6
e) Antipodals = n = 6
3. If the number of chromosomes in the endosperm is 30, what will be the number of chromosomes in the nucellus?
Solution: No. of the chromosome is the endosperm, i.e, 3n = 30
So, No. of chromosome in nucellus = 2n = 20
4. How many meiotic divisions are necessary for the formation of 100 pollen grains?
Solution: As 4 pollen grains are produced by reductional division or meiotic division of one pollen mother cell, so meiotic division of 25 PMC is necessary to form 100 pollen grains.
Hence, No. of meiotic divisions necessary for the formation of 100 pollens = 25 as (n/4), n = Number of pollens.
5. How many meiotic divisions are required for the formation of 100 Megaspore?
Solution: No. of meiotic division needed for the formation of 100 megaspore = 100 (as by meiotic division of a megaspore mother cell, 4 megaspores are produced out of which 3 degenerate and only one survives)
6. If the development is normal and there is complete success of pollination and fertilization, then how many meiotic divisions are needed for 100 zygote formation?
Solution: For the formation of 100 zygotes, 100 male gametes and 100 female gametes (eggs) are required. 100 male gametes are developed from 100 microspores (from 25 meiotic divisions) and 100 eggs are developed from 100 megaspores (from 100 meiotic divisions).
Hence, No. of meiotic division needed for 100 zygotes formation= 25+100= 125
Note: Shortcut: No. of meiotic division = n + n/4 = 5n/4, where n = no of the zygote. So here, n = 100 so No. of meiotic division = 5*100/4 = 125.
7. How many meiotic divisions are needed for the formation of 100 grains in wheat?
Solution: No.of meiotic division = 5n/4 (n = no. of grains) = 5.*00/4 = 125
8. How many meiotic divisions are necessary for 100 seed formation in the family Cyperaceae?
Solution: There is an exception in the family Cyperaceae in microsporogenesis i.e out of 4 microspores formed after reductional division of microspore mother cell. 3 degenerates and only one survives (same as in the case of megaspores).
Hence No. of meiotic division = 100 + 100 = 200 or, No. of meiotic division = n + n = 2n = 2*100 = 200 (n = no. of seed)
High Yielding Points from Reproduction in Flowering Plants
1. Egg apparatus is situated at the Micropylar end2. Ubisch bodies are provided by Tapetum
3. Main insects behind entomophily are bees
4. Pollen tube during pollen germination comes out through germ pore
5. Fertilization in which male gametes are carried through a pollen tube is called Siphonogamy
6. Number of meiotic divisions required to produce 400 seeds in a pea plant is 500 (N = 5n/4 where n = 400)
7. Development of sporophytes without fertilization from the vegetative cells of the gametophyte is called Apogamy
8. Commonest nutritive tissue for developing embryos in angiosperms is Endosperm
9. Ovule of angiosperm can be called Megasporangium
10. A true seed is fertilized ovule with an embryo
11. Ovule is inverted, its body is parallel to the funicle, micropyle is near the hilum, then it is called Anatropous
12. The plant part consists of two-generation one within the other is Embryo and another part that consists of three generations is the seed
13. Apospory is the direct formation of gametophyte from the sporophyte.
14. Hay fever is due to wind-borne pollen
15. Clone is a group of individuals got through vegetative propagation
16. Stigmas are large and sticky in the case of hydrophilous while large and feathery in anemophilous flowers.
17. Study of the formation growth and development of the new individual from an egg is Embryology
18. Development of shoot and root in tissue culture is determined by Cytokinin and auxin ratio
19. A unique phenomenon observed in the embryo sac of angiosperms is triple fusion and double fertilization
20. Auxenic culture is a pure culture without contamination
21. Embryoids formed in tissue culture from pollen grain are due to cellular totipotency
Also, Read Notes of Other Lessons of Botany: