giftidentity.blogg.se - Example of binary fission

Definitive or secondary nucleus : 2 Polar nuclei fuse in central cell – form diploid nucleus.ġ0. Antipodal cells : 3 cells at chalazal end.ĩ. Synergids with filiform apparatus – guides pollen tube towards egg.Ĩ.

Egg apparatus : 3 nuclei at micropylar end.ħ.

One from each pole moves towards centre – polar nucleiĥ.

3rd mitosis-4 nuclei formed at each pole.

2nd mitosis-2 nuclei formed at each pole.

1st mitosis -2 nuclei which migrate to opposite poles.

Functional megaspore – First cell of female gametophyte.

Upper 3 degenerate but lower one is functional, By meiosis → Linear tetrad of 4 megaspores (n).Ĥ. Megaspore mother cell is situated in nucellus towards micropylar end.ģ. Process of formation of haploid megaspores from Megaspore Mother Cell (MMC) which is diploid (2n).Ģ. Oval, elongated, multicellular 7 celled structure.ġ.

Female gametophyte or embryo sac remains embedded in nucellus.

Integuments : Outer and inner two protective coverings.

Nucellus : Parenchymatous tissue that forms body of ovule.

Anatropous ovule : Curved ovule, where micropyle is near stalk.

Funiculus : Stalk by which ovule is attached to placenta.

Structure of Anatropous ovule (Most common type)

Pollen grains are lodged on stigma of pistil.

Pollen grains are shed in either two celled stage or three celled stage.

Either occur in pollen grain or in pollen tube.ģ.

Second mitotic division → In generative cell → equal cells First mitotic division → 2 unequal cells →Ģ.

Pollen grain (n) is first cell of gametophyte.ġ.

It lasts for few minutes (Grasses, Wheat, Rice) to months (Members of Rosaceae, Solanaceae, Fabaceae, Leguminosae).

Depends on environment factors – Temperature and humidity.

Pollen Viability : It is the ability of pollen grain to germinate and develop male gametophyte.

Presence of thin areas germ pores for emergence of pollen tubeĥ.

Composed of non- biodegradable sporopollenin.

Pollen grain – Non-motile with single nucleus.ģ. Process of formation of Microspores by meiosis from MMC - Microspore Mother CellĢ.

From archesporial cell primary parietal cell forms anther wall and sporogenous cell forms sporogenous tissue.ġ.

When microspores develop wall around it then it is known as pollen grain.

Haploid (n) microspores separate from tetrad.

Microsporangium contains microspore mother cells (2n) which undergo meiosis to form microspore tetrad.Outer epidermis (Protective) followed by fibrous endothecium, thin walled middle layers and tapetum innermost nutritive layer. Anther wall is outer layer and microsporangium has sporogenous tissue.Mature anther has anther wall and microsporangium.Heterogeneity appears with formation of archesporial cell.Monothecous (Having single lobe) → Bisporangiate (Having two pollen sacs).Usually dithecous (Having two lobes) → tetrasporangiate (Having four pollen sacs).Gametes ← within flower ← Reduced structure ← gametophyte

Diploid sporophyte is dominant plant body → Meiosis → Haploid spores → Sexual reproduction – Two major events –Ĩ. Flowers, specialized reproductive structure producing haploid gametes-ħ. Variations are useful for survival and evolution of species.Ħ. Production of genetically different offspring.ĥ. In higher plants, flowering indicates beginning of reproductive phase.Ĥ. Involves fusion of two compatible gametes (male and female).ģ. Micropropagation - Modern method to get plants from tissue culture.A small amount of plant tissue is carefully and aseptically grown to get plantlets.Joining of two plant parts stock and scion.New plants are identical to parent plant.Artificial methods useful in agriculture and horticulture.Reproduction with vegetative plant parts.Inheritance of genes of parent by progeny. Production of genetically identical progeny, i. Fusion of two compatible gametes or sex cell is not involved.Ģ. TWo types – Asexual reproduction and Sexual reproduction.ġ.To maintain continuity of life, organisms produce offspring showing similar characters.Essential Process related to continuity of species.Reproduction is production of young ones like parents.Maharashtra State Board 12th Biology Notes Chapter 1 Reproduction in Lower and Higher Plants By going through these Maharashtra State Board 12th Science Biology Notes Chapter 1 Reproduction in Lower and Higher Plants students can recall all the concepts quickly.