Biology: Sexual Reproduction in Flowering Plants

A comprehensive set of vocabulary flashcards covering the morphology, structures, and processes of sexual reproduction in flowering plants, including key terminology from microsporogenesis to seed formation and apomixis.

Panchanan Maheshwari

A distinguished Indian botanist ($1904-1966$) who specialized in embryology and tissue culture, and led the development of the first NCERT Biology textbooks in $1964$.

Androecium

The male reproductive organ of a flower consisting of a whorl of stamens.

Gynoecium

The female reproductive organ of a flower which may consist of one or more pistils.

Filament

The long and slender stalk that forms one of the two parts of a typical stamen.

Anther

The terminal, generally bilobed part of a stamen where pollen is produced; typically dithecous in angiosperms.

Microsporangia

Four structures located at the corners of a tetragonal anther that develop into pollen sacs and are packed with pollen grains.

Microsporangium Wall Layers

The four layers surrounding a microsporangium: the epidermis, endothecium, middle layers, and the tapetum.

Tapetum

The innermost wall layer of the microsporangium that nourishes the developing pollen grains and typically contains dense cytoplasm and more than one nucleus.

Sporogenous Tissue

A group of compactly arranged homogenous cells occupying the center of each microsporangium when the anther is young.

Microsporogenesis

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

Exine

The hard outer layer of a pollen grain made up of sporopollenin, one of the most resistant organic materials known.

Germ Pores

Apertures on the pollen grain exine where sporopollenin is absent and through which the pollen tube emerges.

Intine

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

Vegetative Cell

The larger of the two cells in a mature pollen grain which has abundant food reserves and a large irregularly shaped nucleus.

Generative Cell

The smaller, spindle-shaped cell that floats in the cytoplasm of the vegetative cell and divides to give rise to two male gametes.

Parthenium (Carrot Grass)

A plant that entered India as a contaminant with imported wheat and is a common cause of pollen allergy.

Pollen Banks

Facilities where pollen grains are stored for years in liquid nitrogen at $-1960C$ for use in crop breeding programmes.

Syncarpous

A multicarpellary gynoecium in which the pistils are fused together, such as in Papaver.

Apocarpous

A multicarpellary gynoecium in which the pistils are free, such as in Michelia.

Hilum

The region of the ovule that represents the junction between the body of the ovule and the funicle.

Nucellus

A mass of cells enclosed within the integuments of an ovule that contains abundant reserve food materials.

Megasporogenesis

The process of formation of megaspores from the megaspore mother cell (MMC).

Monosporic Development

The formation of an embryo sac from a single functional megaspore, a process common in the majority of flowering plants.

Filiform Apparatus

Special cellular thickenings at the micropylar tip of synergids that guide the pollen tube into the synergid.

Antipodals

The three cells located at the chalazal end of a mature embryo sac.

Autogamy

A type of pollination where pollen grains are transferred from the anther to the stigma of the same flower.

Cleistogamous Flowers

Flowers that do not open at all, ensuring autogamy even in the absence of pollinators.

Geitonogamy

The transfer of pollen grains from the anther to the stigma of another flower on the same plant.

Xenogamy

The transfer of pollen grains from an anther to the stigma of a different plant, bringing genetically different types of pollen.

Emasculation

The removal of anthers from a bisexual flower bud using forceps to prevent self-pollination in artificial hybridization.

Double Fertilisation

A phenomenon unique to angiosperms involving two fusions: syngamy (forming a zygote) and triple fusion (forming a primary endosperm nucleus).

Free-nuclear Endosperm

A stage of endosperm development where the primary endosperm nucleus (PEN) undergoes successive nuclear divisions without immediate cell wall formation.

Scutellum

The single cotyledon of the grass family, situated laterally to the embryonal axis.

Coleorrhiza

An undifferentiated sheath that encloses the radicle and root cap in a monocotyledonous embryo.

Coleoptile

A hollow foliar structure that encloses the shoot apex and leaf primordia in a monocotyledonous embryo.

Albuminous Seeds

Seeds that retain a part of the endosperm because it is not completely used up during embryo development (e.g., wheat, maize, castor).

Perisperm

The residual, persistent nucellus found in certain seeds such as black pepper and beet.

False Fruits

Fruits in which the thalamus contributes to formation alongside the ovary, such as in apple, strawberry, and cashew.

Parthenocarpic Fruits

Fruits that develop without fertilisation and are consequently seedless, such as the banana.

Apomixis

A form of asexual reproduction that mimics sexual reproduction by producing seeds without fertilisation.

Polyembryony

The occurrence of more than one embryo in a single seed, which is common in Citrus and Mango varieties.