Biology of Sexual Reproduction in Flowering Plants

A comprehensive set of vocabulary flashcards covering the biological processes, structures, and terminology related to sexual reproduction in flowering plants based on the lecture transcript.

Panchanan Maheshwari

A distinguished botanist ($1904-1966$) who established the Department of Botany at the University of Delhi and authored the first NCERT Biology textbooks in $1964$.

Stamen

The male reproductive organ of a flower, consisting of a long stalk called the filament and a terminal bilobed structure called the anther.

Anther

The bilobed, dithecous, and tetragonal structure of a stamen that contains four microsporangia and produces pollen grains.

Microsporangium

A near circular structure in the anther surrounded by four wall layers: the epidermis, endothecium, middle layers, and the tapetum.

Tapetum

The innermost wall layer of the microsporangium that nourishes developing pollen grains and whose cells typically possess dense cytoplasm and multiple nuclei.

Microsporogenesis

The process of formation of microspores from a pollen mother cell ($\text{PMC}$) through meiotic division.

Pollen Grain

The male gametophyte, generally measuring $25-50$ micrometers in diameter, featuring a hard outer exine and a thin inner intine.

Sporopollenin

The highly resistant organic material that makes up the exine of pollen grains, capable of withstanding high temperatures and strong acids or alkali.

Germ Pores

Prominent apertures in the pollen grain exine where sporopollenin is absent and through which the pollen tube emerges.

Vegetative Cell

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

Generative Cell

A small spindle-shaped cell that floats in the cytoplasm of the vegetative cell and divides mitotically to form two male gametes.

Gynoecium

The female reproductive part of the flower, which may be monocarpellary (one pistil) or multicarpellary (multiple pistils).

Syncarpous

A term describing a multicarpellary gynoecium where the pistils are fused together, such as in Papayer.

Apocarpous

A term describing a multicarpellary gynoecium where the pistils are free, such as in Michelia.

Megasporangium (Ovule)

A small structure attached to the placenta by a funicle, containing the nucellus and the embryo sac.

Megasporogenesis

The process of formation of megaspores from the megaspore mother cell ($\text{MMC}$) through meiosis.

Monosporic Development

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

Embryo Sac

The female gametophyte of angiosperms, which at maturity is typically $8$-nucleate but $7$-celled.

Filiform Apparatus

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

Pollination

The mechanism for the transfer of pollen grains shed from the anther to the stigma of a pistil.

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, such as those in Viola or Commelina, 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 the anther to the stigma of a different plant, bringing genetically different pollen to the stigma.

Double Fertilisation

A unique angiosperm event involving syngamy (fusion of one male gamete with the egg) and triple fusion (fusion of the second male gamete with two polar nuclei).

Triple Fusion

The fusion of a haploid male gamete with two haploid polar nuclei to produce a triploid primary endosperm nucleus ($\text{PEN}$).

Endosperm

A triploid tissue formed from the primary endosperm cell ($\text{PEC}$) that provides nutrition to the developing embryo.

Scutellum

The single lateral cotyledon found in the embryos of the grass family.

Coleorrhiza

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

Perisperm

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

False Fruits

Fruits in which the thalamus contributes to formation along with 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, as seen in some Asteraceae and grasses.

Polyembryony

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