Flower Structure, Pollination, and Fertilisation

Practice vocabulary covering floral anatomy, types of flowers and ovaries, pollination mechanisms, and the process of double fertilisation.

Fertilisation

The fusion of the male and female nuclei in the embryo sac.

Pollen tube

An outgrowth developed by the pollen grain that grows down the style to the embryo sac, carrying male gametes.

Germination of pollen grain

The process where a pollen grain absorbs nutrients from the stigma and develops a pollen tube.

Generative nucleus

A nucleus in the pollen grain that divides by mitosis into $2$ male gamete nuclei.

Tube nucleus

A nucleus that occupies the tip of the growing pollen tube and disintegrates after entering the ovule to give way to the male nuclei.

Micropyle

The opening in an ovule through which the pollen tube enters to penetrate the embryo sac.

Double fertilisation

A unique process in flowering plants where one male nucleus fuses with the egg cell nucleus to form a diploid zygote, and the other fuses with the polar nuclei to form a triploid nucleus.

Endosperm

The tissue developed from the triploid nucleus following double fertilisation.

Superior (hypogynous) ovary

An ovary positioned above the other floral parts on the receptacle.

Inferior (epigynous) ovary

An ovary positioned below the other floral parts, which occur above it.

Perigynous flower

A flower where the receptacle surrounds the carpel, and other floral parts arise around the ovary.

Monocarpous gynoecium

A gynoecium consisting of only $1$ carpel.

Polycarpous gynoecium

A gynoecium consisting of $2$ or more carpels.

Apocarpous gynoecium

A polycarpous gynoecium where the carpels are free and not fused.

Syncarpous gynoecium

A polycarpous gynoecium where the carpels are fused together.

Complete flower

A flower with all floral parts present: calyx, corolla, androecium, and gynoecium.

Unisexual flower

A flower possessing only one type of reproductive part, either male (staminate) or female (pistillate).

Monoecious plant

A plant that bears both male and female flowers on the same individual.

Dioecious plant

A plant species where male and female flowers are borne on separate plants.

Hermaphrodite (bisexual) flower

A flower that contains both male and female reproductive organs.

Actinomorphic (regular) flower

A radially symmetrical flower that can be divided into $2$ similar halves by any vertical section passing through the centre.

Zygomorphic (irregular) flower

A bilaterally symmetrical flower that can be divided into $2$ equal halves in only one particular plane.

Pedicillate flower

A flower that is supported by a stalk called a pedicel.

Inflorescence

A cluster of flowers growing on the same main stalk.

Pollination

The transfer of pollen grains from the anther to the stigma.

Cross-pollination

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

Self-pollination

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

Entomophilous flowers

Flowers adapted for pollination by insects.

Anemophilous flowers

Flowers adapted for pollination by wind.

Calyx

The outermost floral structure made of sepals, which protects the inner parts during bud development.

Corolla

The floral part made of petals, often brightly coloured to attract pollinators.

Androecium

The male part of the flower consisting of one or more stamens.

Gynoecium (pistil)

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