Sexual Reproduction in Flowering Plants

Flashcards covering key vocabulary and concepts related to sexual reproduction in flowering plants.

Reproduction

A vital process for species survival, enabling the continuation of species through asexual or sexual means.

Sexual Reproduction

Mode of reproduction that enhances survival advantage by creating new genetic variants.

Panchanan Maheshwari

A distinguished Indian botanist (1904-1966) known for his work on embryological aspects and tissue culture.

Embryology in Taxonomy

The use of embryological characters in the classification of organisms.

Tissue Culture

The artificial culture of immature embryos, now a landmark in science.

Flowers

Objects of aesthetic, ornamental, social, religious, and cultural value, and also morphological and embryological marvels and the sites of sexual reproduction.

Floriculture

The cultivation of flowers.

Floral Primordium

The initial stage of flower development in a plant.

Androecium

The whorl of stamens representing the male reproductive organ in a flower.

Gynoecium

The female reproductive organ in a flower.

Stamen

Consists of the filament (the stalk) and the anther (terminal structure), representing the male reproductive organ.

Anther

The bilobed structure at the end of the stamen containing the pollen.

Theca

Each lobe of an anther having two theca, making it dithecous.

Microsporangia

Four-sided structure consisting of four microsporangia located at the corners, two in each lobe which further develop into pollen sac.

Tapetum

The innermost wall layer of the microsporangium, which nourishes the developing pollen grains.

Sporogenous Tissue

Compactly arranged homogenous cells that occupy the center of each microsporangium.

Microspore Tetrads

Cluster of four cells formed from meiotic divisions of sporogenous tissue.

Microsporogenesis

The process of formation of microspores from a pollen mother cell (PMC) through meiosis.

Pollen Grain

Represents the male gametophytes in flowering plants.

Exine

The hard outer layer of a pollen grain made of sporopollenin.

Sporopollenin

One of the most resistant organic materials known, found in the exine of pollen grains.

Germ Pores

Apertures on pollen grain exine where sporopollenin is absent.

Intine

The inner wall of the pollen grain made up of cellulose and pectin.

Vegetative Cell

Larger cell in a pollen grain, has abundant food reserve and a large irregularly shaped nucleus.

Generative Cell

Small, spindle-shaped cell that floats in the cytoplasm of the vegetative cell which divides mitotically to give rise to two male gametes.

Allergens (Pollen)

Pollen grains causing severe allergies and bronchial afflictions like asthma and bronchitis.

Pistil

The female reproductive part of the flower, consisting of the stigma, style, and ovary.

Monocarpellary

Gynoecium consisting of a single pistil.

Multicarpellary

Gynoecium having more than one pistil.

Syncarpous

Pistils are fused together.

Apocarpous

Pistils are free.

Stigma

Serves as landing platform for pollen grains.

Style

The elongated slender part beneath the stigma.

Ovary

The basal bulged part of the pistil.

Ovarian Cavity (Locule)

The cavity inside the ovary.

Placenta

Located inside the ovarian cavity.

Megasporangia (Ovules)

Arise from the placenta inside the ovarian cavity.

Funicle

A stalk by means of which ovule is attached to the placenta.

Hilum

The junction between ovule and funicle.

Integuments

One or two protective envelopes of the ovule.

Micropyle

Small opening at the tip of the ovule, where integuments are absent.

Chalaza

Represents the basal part of the ovule, opposite the micropylar end.

Nucellus

Mass of cells enclosed within the integuments, containing abundant reserve food materials.

Embryo Sac

Female gametophyte located in the nucellus.

Megasporogenesis

The process of formation of megaspores from the megaspore mother cell.

Megaspore Mother Cell (MMC)

A large cell containing dense cytoplasm and a prominent nucleus.

Monosporic Development

Embryo sac formation from a single megaspore.

Polar Nuclei

Two nuclei situated below the egg apparatus in the large central cell.

Egg Apparatus

Three cells grouped together at the micropylar end consists of two synergids and one egg cell.

Synergids

Have special cellular thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes.

Filiform Apparatus

Cellular thickenings at the micropylar tip of synergids.

Antipodals

Three cells are at the chalazal end.

Pollination

Transfer of pollen grains from the anther to the stigma of a pistil.

Autogamy

Pollination achieved within the same flower.

Chasmogamous Flowers

Flowers are similar to flowers of other species with exposed anthers and stigma.

Cleistogamous Flowers

Flowers which do not open at all.

Geitonogamy

Transfer of pollen grains from the anther to the stigma of another flower of the same plant.

Xenogamy

Transfer of pollen grains from anther to the stigma of a different plant.

Wind Pollination

Pollen grains are light and non-sticky so that they can be transported in wind currents.

Water Pollination

Limited to about 30 genera, mostly monocotyledons.

Hermaphrodite Flowers

Majority of flowering plants produce hermaphrodite flowers and pollen grains are likely to come in contact with the stigma of the same flower.

Inbreeding Depression

Continued self-pollination result in inbreeding depression.

Self-Incompatibility

A genetic mechanism that prevents self-pollen (from the same flower or other flowers of the same plant) from fertilising the ovules.

Unisexual Flowers

Production of this prevents self-pollination.

Monoecious

Male and female flowers are present on the same plant prevents autogamy but not geitonogamy (castor and maize).

Dioecy

Male and female flowers are present on different plants prevents both autogamy and geitonogamy (papaya).

Pollen-Pistil Interaction

Dynamic process involving pollen recognition followed by promotion or inhibition of the pollen.

Artificial Hybridisation

One of the major approach of crop improvement programme.

Emasculation

Removal of anthers from the flower bud before the anther dehisces using a pair of forceps is necessary if the female parent bears bisexual flowers.

Bagging

Emasculated flowers have to be covered with a bag of suitable size, generally made up of butter paper, to prevent contamination of its stigma with unwanted pollen.

Double Fertilisation

Syngamy and triple fusion take place in an embryo sac.

Syngamy

One of the male gametes moves towards the egg cell and fuses with its nucleus.

Triple Fusion

Other male gamete moves towards the two polar nuclei located in the central cell and fuses with them.

Primary Endosperm Nucleus (PEN)

Formed when the other male gamete moves towards the two polar nuclei located in the central cell and fuses with them called triple fusion.

Free-Nuclear Endosperm

PEN undergoes successive nuclear divisions to give rise to free nuclei.

Scutellum

Cotyledon in the grass family situated towards one side (lateral) of the embryonal axis.

Coleorrhiza

Radical and root cap enclosed in an undifferentiated sheath.

Coleoptile

Epicotyl has a shoot apex and a few leaf primordia enclosed in a hollow foliar structure.

Non-Albuminous Seeds

No residual endosperm as it is completely consumed during embryo development.

Albuminous Seeds

Retain a part of endosperm as it is not completely used up during embryo development.

Perisperm

Residual, persistent nucellus (black pepper and beet).

Parthenocarpic Fruits

Fruits develop without fertilisation.

Apomixis

A special mechanism to produce seeds without fertilisation, a form of asexual reproduction that mimics sexual reproduction.

Polyembryony

Occurrence of more than one embryo in a seed.