Revision: Reproduction in Lower and Higher Plants Biology HSC Science (General) 12th Standard Board Exam Maharashtra State Board

Reproduction is the process of formation of new individuals by sexual or asexual means, which can repeat the process in their own turn.

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Formation of new organism of same species by earlier existing organism is called as reproduction.

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Reproduction is a biological process that results in the formation of new individuals of the same kind, though usually with slight genetic, structural and physiological variations.

A mode of reproduction where a new organism is formed from a part of the parent body without involving gametes.

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The process of forming a new organism from an organism of the same species without the involvement of gametes is called asexual reproduction.

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When offspring is produced by a single parent by the formation of specialised asexual reproductive structures by the parent body, the reproduction is asexual.

Binary fission is an asexual reproduction process in single-celled organisms where a parent cell divides into two genetically identical daughter cells through coordinated nuclear and cytoplasmic division.

Simple binary fission is an asexual reproduction process in which a single Amoeba cell divides along a randomly oriented plane to form two genetically identical daughter cells.

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When a unicellular organism divides into two identical daughter cells in any plane, due to lack of definite shape, it is called simple binary fission.

Example: Amoeba

When a unicellular organism divides across the transverse (horizontal) axis, it is called transverse binary fission.

Example: Paramecium

When a unicellular organism divides along the longitudinal (vertical) axis, it is called longitudinal binary fission.

Example: Euglena

The process by which Amoeba withdraws its pseudopodia and forms a hard, protective, three-layered cyst around its body during unfavourable conditions is called encystation.

The small daughter cells formed when each daughter nucleus produced during multiple fission in Amoeba gets surrounded by a small amount of cytoplasm are called amoebulae or pseudopodiospores.

When an Amoeba forms a protective covering around itself during adverse conditions and stops movement, it is called a cyst.

The process of multiple fission occurring in the oocyst of Plasmodium inside the mosquito is called sporogony.

The daughter individuals formed as a result of sporogony in Plasmodium are called sporozoites.

The end products of multiple fission that are enclosed in a hard, resistant covering are called spores.

When a single organism divides into many daughter cells by forming multiple nuclei followed by cytoplasmic division, it is called multiple fission.

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The mode of asexual reproduction in which a single parent organism divides to produce many daughter organisms at the same time is called multiple fission.

The type of multiple fission in which the parent Amoeba forms a cyst and releases many daughter individuals on return of favourable conditions is called sporulation.

In unicellular organisms like yeast, when a small bud forms on the parent cell, gets a nucleus, grows, and separates to become a new cell, it is called budding.

When the body of a multicellular organism breaks into two or more fragments, and each fragment grows into a new individual, it is called fragmentation.

Example: Ulothrix, Spirogyra, etc

Non-motile asexual spores produced externally and not inside a sporangium in many fungi are called conidia or conidiospores.

Spores that possess flagella and are capable of movement in water are called motile spores or zoospores.

A special reproductive structure formed by simple plants and fungi that germinates directly to form a new individual is called a spore.

Non-motile spores with a typical cell wall and without flagella are called aplanospores.

Asexual spores produced inside a sporangium are called sporangiospores.

Spores that lack flagella and are incapable of movement are called non-motile spores.

Reproduction in plants, in which a new plant can arise from a vegetative part such as a root, stem, or leaf without the help of any reproductive organ, is called vegetative propagation.

The process in which a new plant develops from a vegetative part (stem, root, or leaf) of the parent plant under suitable conditions is called natural vegetative propagation.

The method of plant reproduction in which a part of the mother plant is detached and grown independently to produce a new plant with identical characters is called artificial vegetative propagation.

A mode of reproduction involving the fusion of male and female gametes (sperm and egg) to form a zygote that develops into a new organism.

The period of growth and development before an organism becomes sexually mature is called the juvenile phase.

Individual members of the perianth are called tepals.

When calyx and corolla are not differentiated, the floral envelope is called the perianth.

A circular arrangement of floral organs at the same level on the thalamus is called a whorl.

The swollen terminal part of the pedicel on which all floral whorls are arranged is called the thalamus or receptacle.

A modified, compressed reproductive shoot of angiosperms bearing sepals, petals, stamens, and carpels, meant for sexual reproduction, is called a flower.

A compact mass formed when all microspores within a pollen sac remain united as a single structure is called a pollinium.

The process of formation of microspores from the sporogenous tissue is said to be microsporogenesis.

When microspores of a tetrad do not separate and remain attached together in groups, they are called compound pollen grains.

A yellowish, sticky, oily substance covering the exine of insect-pollinated pollen grains is called pollenkitt.

The study of external morphology of mature pollen grain is called palynology.

The protective wall or covering of a pollen grain is called the sporoderm.

The region where the exine is absent and through which the pollen tube emerges is called a germ pore.

The structure in flowering plants that develops into a seed after fertilization is called the ovule.

Transfer of pollen grains from the anther to the stigma of a flower is called pollination.

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Pollination is the transfer of pollen grains from the anther of a flower to the stigma of the same flower or of another flower of usually the same species.

When pollen grains from the anther are transferred to the stigma of the same flower, it is known as autogamy.

When pollination occurs between flowers on two different plants of the same species, it is called cross-pollination.

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Transfer of pollen grains from the anther of a flower from one plant to the stigma of the flower on another plant is called cross-pollination

When pollens of a flower pollinate any other flower present on the same plant, it is said to be geitonogamy

Transfer of pollen grains through wind is known as anemophily.

When pollination of flowers occurs below water, it is said to be hypo-hydrophily.

When pollination of flowers occurs at the surface of water, it is called epi-hydrophily. 

Transfer of pollen grains through water is known as hydrophily.

Transfer of pollen grains through the agency of insects is known as entomophily.

Transfer of pollen grains by birds is known as ornithophily.

Transfer of pollen grains by bats is known as chiropteriphily.

Transfer of pollen grains by snails and slugs is known as malacophily.

Union of a male gamete with the egg cell to form a zygote is called fertilization.

The recognition and acceptance or rejection of pollen by the pistil, from pollen deposition on the stigma to pollen tube entry into the ovule, is called pollen–pistil interaction.

The controlled crossing of selected male and female parent plants to produce genetically superior offspring is called artificial hybridization.

Union of the second male gamete with two polar nuclei to form endosperm, along with fertilization, is called double fertilization.

Endosperm is a nutritive tissue formed after fertilisation in flowering plants. It is usually triploid and provides food to the developing embryo.

The embryo is the young developing plant formed from the zygote after fertilisation. It develops at the micropylar end of the embryo sac.

Apomixis is the production of seeds without fertilisation and is a form of asexual reproduction that mimics sexual reproduction.

The process of fruit formation without fertilisation is called parthenocarpy.

It is the condition in which fruit is developed without the process of fertilization. It occurs naturally in some varieties of Pineapple, Banana, Papaya, etc.

Presence of more than one embryo within a single seed is called polyembryony.

Apomixis is a type of asexual reproduction that mimics sexual reproduction, i.e., the production of seeds without pollination and fertilization.

The transfer of pollen grains through water as a medium for pollination is called as hydrophily.

Pollination that occurs below the surface of water where pollen grains sink and reach the stigma is called as hypohydrophily.

Pollination in which pollen grains float on the surface of water and reach the stigma is called as epihydrophily.

Pollination carried out with the help of living organisms is called as biotic pollination.

Pollination carried out with the help of insects is called as entomophily.

Pollination carried out with the help of birds is called as ornithophily.

Pollination carried out with the help of bats is called as chiropterophily.

The yellow, sticky substance present on pollen grains that helps in adhesion to insect body is called as pollenkit.

The formation of an embryo-like structure directly from a gametophytic organ or cell without fertilisation is called as apogamy.

The development of a diploid gametophyte from a diploid sporophytic cell without undergoing meiosis is called as apospory (e.g., Orange, Mango).

The development of fruit from the ovary without fertilisation, resulting in a seedless fruit, is called as parthenocarpy.

The process of development of zygote into an embryo is called embryogenesis.

The process in which each microspore mother cell undergoes meiosis to form a tetrad of haploid microspores (pollen grains) is called as microsporogenesis.

A temporary state of metabolic arrest that enables organisms to survive adverse environmental conditions is called as dormancy.

The process of formation of haploid megaspores from a diploid megaspore mother cell (MMC) in the nucellus of ovule is called as megasporogenesis.

• Meaning - Reproduction is the production of young ones similar to their parents. It is an essential biological process for the continuation of the species and continuity of life.
• Two Types - All methods of reproduction fall into two categories: Asexual Reproduction and Sexual Reproduction.
• Asexual Reproduction - New individuals are produced without the fusion of gametes. Offspring are genetically identical to the parent (clones).
• Sexual Reproduction - Involves the fusion of male and female gametes, resulting in offspring with genetic variation from both parents.

• Meaning - Asexual reproduction involves only one parent, produces no fusion of gametes, and results in offspring that are genetically identical to the parent, called clones.
• Modes of Asexual Reproduction - Common methods include Binary Fission (Amoeba, Paramoecium), Fragmentation (Spirogyra), Budding (Yeast, Protosiphon), Spore Formation/Zoospores (Chlamydomonas), Conidia (Penicillium), and Gemmules (Marchantia).
• In Plants - Asexual reproduction in plants is called Vegetative Propagation. It can be Natural or Artificial (e.g., cutting, grafting, tissue culture).
• In Animals — Common in lower animals only. Does not involve meiosis or gamete formation. Lower animals reproduce asexually by budding and gemmule formation.
• Key Feature — Since only one parent is involved and no fusion occurs, all offspring are morphologically and genetically identical (clones) to the parent.

• Sexual reproduction involves the formation and fusion of male and female gametes (amphimixis) to form a zygote, with gamete formation by meiosis.
• It occurs in two phases: juvenile phase (no reproduction) and reproductive phase (sex organs active), regulated by hormones.
• It includes three main events: pre-fertilisation (gamete formation and transfer), fertilisation (fusion of gametes), and post-fertilisation (zygote and embryogenesis).
• Sexual reproduction produces genetic variation due to meiosis, recombination, and fertilisation, which is important for evolution.
• Primary sex organs (testes, ovaries) produce gametes, and organisms may be seasonal or continuous breeders depending on the reproduction pattern.

• A typical anther is dithecous and tetrasporangiate, having two lobes, each with two microsporangia (pollen sacs).
• Microsporangia contain sporogenous tissue, which develops into microspore mother cells that form pollen grains.
• The anther wall has four layers: epidermis, endothecium, middle layers, and tapetum.
• The tapetum provides nutrition to developing pollen, and microspore mother cells undergo meiosis to form haploid microspores.
• During anther dehiscence, the endothecium helps in rupture at the stomium, releasing pollen grains for pollination.

• Microsporogenesis is the process in which pollen mother cells (PMC) undergo meiosis to form haploid microspores (pollen grains).
• Each PMC divides meiotically to produce a tetrad of four haploid microspores.
• Microspores separate at maturity and develop into pollen grains.
• A pollen grain has a two-layered wall called sporoderm: outer exine and inner intine.
• Exine is made of sporopollenin, a tough and resistant substance, and contains germ pores for pollen tube growth.
• Intine is the inner layer made of cellulose and pectin.
• Pollen viability (ability to germinate) depends on temperature and humidity; it is short (about 30 minutes) in crops like rice and wheat but can last for months in some plant families.

• Pollen grains act as male gametophytes and are usually spherical, measuring about 25–50 μm in diameter.
• Each pollen grain has a two-layered wall (sporoderm) consisting of a thick outer exine and a thin inner intine.
• The exine contains sporopollenin, which makes pollen grains highly resistant and helps in their fossil preservation.
• Germ pores are present where the exine is absent; dicots usually have three pores, while monocots have one pore.
• The intine protrudes through the germ pore during germination to form the pollen tube.
• In insect-pollinated plants, pollen grains are coated with pollenkitt, which aids in insect attraction and pollination.
• Pollen viability varies widely, lasting minutes in cereals and months in some dicots; pollen can be preserved at –196°C in pollen banks.
• After release, the pollen grain divides into a vegetative cell and a generative cell, and the generative cell later forms two male gametes.

• The ovule is an integumented megasporangium present inside the ovary and is attached to the placenta by a stalk called the funicle.
• The nucellus is the central part containing reserve food, surrounded by one or two integuments for protection.
• The integuments leave a small opening called the micropyle at the apex, while the basal region is called the chalaza, and the attachment point is the hilum.
• The ovule is commonly anatropous, and contains an embryo sac (female gametophyte) with structures like egg cell, synergids, and polar nuclei.
• During development, the ovule arises from the placenta, and integuments grow around the nucellus to form a mature ovule.

• Pollen-pistil interaction is the series of events from pollen landing on the stigma to fertilisation.
• The pistil recognises compatible pollen and rejects incompatible or foreign pollen using specific proteins.
• Compatible pollen germinates on the stigma and forms a pollen tube by absorbing nutrients.
• The pollen tube grows through the style and reaches the ovule, entering through a synergid in the embryo sac.
• The pollen tube releases male gametes, enabling fertilisation and seed formation.

• Endosperm is a nutritive tissue formed from the triploid primary endosperm nucleus (PEN) after fertilisation.
• The PEN undergoes repeated mitotic divisions, and the embryo and endosperm develop simultaneously inside the ovule.
• Other cells of the embryo sac degenerate, while endosperm formation provides nourishment to the developing embryo.
• Nuclear type is the most common; divisions occur without wall formation initially, forming free nuclei, and walls develop later.
• Cellular type shows immediate wall formation after each division, making it cellular from the beginning.
• Helobial type is intermediate; first division forms two unequal cells (micropylar and chalazal), followed by nuclear divisions and later wall formation.

• Embryogenesis is the process of development of the zygote into an embryo, which begins after fertilisation and some endosperm formation.
• The embryo develops at the micropylar end of the embryo sac.
• The zygote divides to form a two-celled proembryo: a terminal (embryonal) cell and a basal (suspensor) cell.
• The suspensor pushes the developing embryo into the endosperm and helps in nutrient supply, while the embryonal cell forms the main embryo.
• The embryo passes through stages like the octant and heart-shaped stage, forming structures such as cotyledons, plumule, radicle, and hypocotyl.
• In monocots, a single cotyledon (scutellum) is present with protective sheaths, the coleoptile (plumule) and coleorhiza (radicle), while in dicots, two cotyledons are formed.

• Polyembryony is the formation of more than one embryo in a single seed, leading to multiple seedlings.
• It was first observed by Leeuwenhoek in Citrus (orange) seeds.
• Polyembryony can occur due to development from the zygote or other tissues like the nucellus and integuments.
• Types include true polyembryony (embryos in the same embryo sac) and false polyembryony (embryos in different embryo sacs).
• Cleavage polyembryony occurs when the zygote splits into many parts, while adventive polyembryony occurs from nucellus or integument cells.
• It is important in horticulture and increases chances of survival by producing multiple seedlings.

• Anatropous ovule is the most common ovule in angiosperms, where the ovule is inverted so that the micropyle lies close to the funiculus.
• The ovule is attached to the placenta by a stalk called funiculus, and the point of attachment is known as hilum.
• The central tissue of the ovule is nucellus, which is usually surrounded by two integuments (outer and inner).
• The ovule has a micropyle at the apex, chalaza at the base, and an embryo sac embedded in the nucellus.

• Seed development begins after fertilization; the fertilized ovule develops into a seed, and the integuments form the seed coat (testa and tegmen).
• Seeds may be endospermic (albuminous) with endosperm present (e.g., maize, coconut) or non-endospermic (exalbuminous) where endosperm is absorbed by the embryo (e.g., pea, bean).
• The micropyle persists as a small pore in the seed coat and helps in the entry of water and oxygen during germination.
• Fruit development is triggered by hormones from developing seeds; the ovary transforms into the fruit and the ovary wall becomes the pericarp.
• Seeds and fruits protect the embryo, store or supply food, aid in dispersal, and help in the continuation and distribution of plant species.

• Anther is usually dithecous and tetrasporangiate, having two lobes with four pollen sacs in total.
• In the immature anther, hypodermal cells differentiate into archesporial cells, initiating anther development.
• The archesporial cell divides to form sporogenous tissue (gives rise to microspore tetrads) and parietal cells (form anther wall layers).
• The mature anther wall has four layers: epidermis (protective), endothecium (helps in dehiscence), middle layers (degenerate), and tapetum (nutritive layer).