By going through these CBSE Class 12 Biology Notes Chapter 2 Sexual Reproduction in Flowering Plants, students can recall all the concepts quickly.

Sexual Reproduction in Flowering Plants Notes Class 12 Biology Chapter 2

→ Reproduction is the process of continuous production of offsprings. It is an important way of multiplication and perpetuation of species.

→ Modes of reproduction in plants can be broadly classified into two groups:

  1. asexual reproduction,
  2. sexual reproduction.

→ Asexual reproduction or Apomixis only takes place with a single parent. It does not involve the formation of sex organs, meiosis and fusion of gametes.

→ Regeneration of a whole new plant from vegetative parts of the plant is called vegetative reproduction. Its unique features of plants and can be natural or induced.

→ Runners, rhizomes, bulbs, corns and tubers are means of propagation.

→ Cutting, layering, grafting and micropropagation are artificial means of vegetative propagation. These are used for commer¬cially important plants.

→ A population of genetically identical plants derived from an individual is called a clone.

→ Plants that have lost the capacity to produce seeds e.g. banana, reproduce vegetatively.

→ Grafting is the technique used to improve the varieties of plants.

→ The flower and floral parts are the organs of sexual reproduction in angiosperms.

→ Sexual reproduction involves meiosis and the fusion of gametes.

→ The flower is a modified shoot with whorls of reproductive leaves – sepals, petals, stamens and carpels. Stamen and carpel are essential floral parts; sepals and petals are non-essential floral parts.

→ The calyx is the whorl of sepals. It is green in colour and protects the other parts of the bud. It prevents rapid transpiration.

→ Corolla is the whorl of petals. It is generally coloured, attractive and fragrant. It helps in pollination by attracting pollinators.

→ The androecium is the whorl of stamens. Stamen is made up of filament and anther. Anthers are bilobed and contain microsporangia (pollensac). Microsporangia produce a large number of pollen grains.

→ Gynoecium or pistil is the whorl of carpels. It consists of ovary, style and stigma.

→ Flowers that contain both stamen and pistil are called bisexual or hermaphrodite.

→ Stigma receives pollen grains, style provides the way to the ovary, the ovary is basal swollen part of gynoecium which contains ovules.

→ The ovule is an integument megasporangium where meiosis occurs and a megaspore is formed. It develops into an 8 nuclei embryosac.

→ Placentation is the manner in which the placenta is distributed. In the placenta, ovules are suspended.

→ The 8 nuclei of the monosporic embryo sac (e.g.Polygonum) are arranged such that a mature female gametophyte or embryosac contains: Two synergids, a single egg, a single secondary nucleus(2n) and three antipodals.,

→ Mature pollen grains are liberated from dehisced anthers. They are at a two-celled stage. The exine of pollen grains is made up of sporopollenin.

→ Pollination is the transfer of pollen grains to the stigma of the flower.

→ When the pollen grains are transferred from another to the stigma of the same flower it is called self-pollination. It occurs by autogamy and geitonogamy.

→ When pollen grains are transferred from the anther to the stigma of the flower of another plant it is termed cross-pollination. It takes place by the wind, water, insects, animals, bats and birds.

→ Allogamy represents cross-pollination where genetic recombination is ensured.

→ The pollen grains deposited on the stigma, after mutual recognition, absorb water and germinate and form a pollen tube.

→ Pollen tube traverses through stigma and style and reaches the ovary. It enters the ovule through micropyle, enters into embryo sac and releases two male gametes.

→ Siphonogamy is the carrying of male gametes to the egg through a pollen tube. It occurs in angiosperms.

→ Angiosperms exhibit double fertilization.

→ During fertilization, one male gamete fuses with the egg to form a diploid zygote in embryosac.

→ Second male gamete fuses with two polar nuclei to give rise to triploid primary endosperm nucleus inside embryosac.

→ After the process of fertilization, the ovule develops into a seed. The diploid zygote develops an embryo and the triploid primary endosperm nucleus forms an endosperm.

→ The ovary matures into a fruit.

→ The size, shape and colours of fruits and seeds vary enormously.

→ In a mature seed, the reserve food material is stored for embryo development and sustenance. In non-endospermic seeds, seeds are stored in cotyledons and in endospermic seeds, seeds are stored in endosperm.

→ The integuments of the ovule are transformed into seed coats.

→ All seeds have certain common features: an embryo, stored food and protective coverings.

→ Seeds are the principal means of the perpetuation of the species.

→ The embryo is differentiated into radicle, plumule and cotyledons. Dicot embryos have two cotyledons and monocot embryos have single terminal cotyledon.

→ A true fruit derived from the ovary consists of seeds and a pericarp. The pericarp is three layered-epicarp, mesocarp and endocarp.

→ Seed may remain dormant for some time before germination and growing into a new plant.

→ Amphimixis: The normal sexual reproduction is called

→ amphimixis. It involves meiosis and the fusion of haploid gametes.

→ Apomixis: It is the substitution of usual sexual reproduction which does not involve meiosis and syngamy.

→ Autogamy: Autõgamy results when a flower is pollinated by its own pollen.

→ Apogamy: It is the phenomenon in which an embryo is formed from any cell of embryosac (except egg) without fertilization.

→ Automixis: It is the fusion of nuclei derived both from the same zygote and from the same meiosis.

→ Aleurone layer: It is a layer of aleurone grains (protein grains) present on the outer surface of seeds and of maizë etc.

→ Coleoptile: The covering sheath of plumule in monocots.

→ Coleorhiza: The protective sheath of radicle in monocots.

→ Callus: The mass of undifferentiated cells formed in a culture medium.

→ Gootee: The process of air layering practised in lichi, promo- gran dates.

→ Grafting: Process of combining characters -of two related plants having vascular cambium.

→ Monogamy: The process of entry of pollen tube into ovule through integuments for fertilization.

→ Non-recurrent apomixis: The kind of apomixis in which the haploid egg or any other cell of haploid embryo sac develops an embryo without fertilization.

→ Polliniurn: Pollen grains contained in a pollen sac remain united in a single grain mass called pollinium.

→ Placentation: Arrangement and distribution of placenta within the ovary.

→ ParthenogeneSis: The kind of uniparental sexual reproduction in which an embryo is formed from an unfertilized egg.

→ PolyembryoflY: The phenomenon of formation of more than one embryo per ovule.

→ Pseudogamy: The phenomenon where pollination is needed for the development of apomictic embryò.

→ Scutellum: Single cotyledon of maize grain.

→ Siphonogamy: The process of carrying male gametes in the vicinity of female gamete by pollen tube.

→ Tapetum: The nutritive layer of cells around pollen sacs in anther.

→ Vivipary: The germination of seed within fruit while still attached to parent wall.

→ Viability: The ability of seeds to retain the power of germination.