Sexual Reproduction in Flowering Plants – Core Vocabulary

Key vocabulary covering structures, processes and adaptations involved in sexual reproduction of flowering plants, suitable for exam revision.

Sexual Reproduction

Process that produces offspring by fusion of male and female gametes, generating genetic variation.

Flower

Reproductive organ of angiosperms that bears androecium (stamens) and gynoecium (pistils).

Stamen

Male reproductive unit of a flower, consisting of a filament and anther.

Anther

Terminal, usually bilobed, dithecous part of stamen that houses microsporangia.

Microsporangium

Pollen sac inside anther where microspores (pollen grains) develop.

Sporogenous Tissue

Central group of cells in microsporangium that gives rise to pollen mother cells.

Pollen Mother Cell (PMC)

Diploid cell in sporogenous tissue that undergoes meiosis to form microspore tetrads.

Microsporogenesis

Meiotic formation of haploid microspores from pollen mother cells.

Pollen Grain

Male gametophyte consisting of exine, intine, vegetative cell and generative cell(s).

Exine

Hard outer wall of pollen grain made of sporopollenin; bears germ pores.

Intine

Inner wall of pollen grain composed of cellulose and pectin.

Sporopollenin

Highly resistant biopolymer forming exine, enabling fossil preservation of pollen.

Germ Pore

Aperture in exine lacking sporopollenin through which pollen tube emerges.

Tapetum

Innermost nutritive layer of anther wall that supports developing pollen; often binucleate.

Pistil (Carpel)

Female reproductive unit consisting of stigma, style and ovary.

Stigma

Pollen-receptive surface at tip of pistil.

Style

Slender stalk of pistil connecting stigma to ovary.

Ovary

Basal, swollen part of pistil containing ovules; develops into fruit.

Ovule (Megasporangium)

Structure inside ovary that develops into seed after fertilisation.

Integument

Protective envelope(s) around nucellus; become seed coat after fertilisation.

Micropyle

Small opening in integuments through which pollen tube enters ovule.

Chalaza

Basal region of ovule opposite micropyle; point where integuments and nucellus meet.

Funicle

Stalk attaching ovule to placenta.

Hilum

Junction point between funicle and body of ovule or seed.

Nucellus

Central, food-rich tissue of ovule containing megaspore mother cell.

Megaspore Mother Cell (MMC)

Diploid cell in nucellus that undergoes meiosis to form four megaspores.

Megasporogenesis

Meiotic formation of megaspores from the megaspore mother cell.

Embryo Sac

Female gametophyte of angiosperms, typically 7-celled, 8-nucleate.

Synergid

One of two cells of egg apparatus aiding pollen tube entry; contains filiform apparatus.

Egg Cell

Female gamete located in embryo sac ready for syngamy.

Polar Nuclei

Two centrally located haploid nuclei that fuse with a male gamete during triple fusion.

Antipodals

Three cells at chalazal end of embryo sac with nutritive/support functions.

Filiform Apparatus

Thickened region at micropylar end of synergids guiding pollen tube.

Autogamy

Self-pollination within the same flower.

Geitonogamy

Transfer of pollen between different flowers of the same plant.

Xenogamy

Cross-pollination between flowers of different plants.

Chasmogamous Flower

Flower that opens exposing anthers and stigma.

Cleistogamous Flower

Never-opening flower that ensures obligatory self-pollination.

Wind Pollination (Anemophily)

Abiotic transfer of pollen via air currents; requires light, dry pollen and feathery stigma.

Water Pollination (Hydrophily)

Abiotic transfer of pollen by water currents, rare in angiosperms (e.g., Vallisneria).

Biotic Pollination

Pollen transfer mediated by animals such as insects, birds or bats.

Self-Incompatibility

Genetic mechanism preventing self-pollen from fertilising ovules.

Outbreeding Devices

Structural or temporal traits that discourage self-pollination and promote cross-pollination.

Pollen-Pistil Interaction

Recognition processes between pollen and pistil leading to acceptance or rejection.

Pollen Tube

Structure emerging from pollen grain that delivers male gametes to embryo sac.

Double Fertilisation

Characteristic angiosperm event involving syngamy and triple fusion in same embryo sac.

Syngamy

Fusion of one male gamete with egg cell forming diploid zygote.

Triple Fusion

Fusion of second male gamete with two polar nuclei forming triploid primary endosperm nucleus.

Primary Endosperm Nucleus (PEN)

Triploid nucleus that initiates endosperm formation.

Endosperm

Triploid nutritive tissue formed after fertilisation; may be free-nuclear or cellular.

Zygote

Diploid cell resulting from syngamy; develops into embryo.

Embryogeny

Sequential development of zygote into mature embryo.

Hypocotyl

Region of embryonic axis below cotyledon insertion, ending in radicle.

Epicotyl

Region of embryonic axis above cotyledon insertion, bearing plumule.

Scutellum

Single cotyledon of grass (monocot) embryo.

Coleoptile

Protective sheath enclosing plumule in monocot embryo.

Coleorrhiza

Sheath covering radicle and root cap in monocot embryo.

Albuminous Seed

Seed that retains part of endosperm at maturity (e.g., maize).

Non-Albuminous Seed

Seed in which endosperm is completely consumed during embryo development (e.g., pea).

Perisperm

Residual, persistent nucellus in some mature seeds (e.g., black pepper).

Pericarp

Fruit wall formed from ovary wall after fertilisation.

False Fruit

Fruit derived from ovary plus other floral parts (e.g., apple, strawberry).

Parthenocarpy

Development of fruit without fertilisation, resulting in seedless fruits.

Apomixis

Formation of seeds without fertilisation, producing clonal progeny.

Polyembryony

Occurrence of multiple embryos within a single seed.

Emasculation

Removal of anthers from bisexual flower to prevent self-pollination in hybridisation.

Bagging

Covering of emasculated or unisexual flowers to avoid unwanted pollen contamination.

Pollen Bank

Cryogenic storage (-196 °C) of viable pollen for long-term breeding use.