9.4 Reproduction in Plants Cheat Sheet by Arsh.b

Plants can reproduce in a variety of different ways:
- Vegetative propagation
- Spore formations
- Pollen transfer

The transfer of pollen grains from an anther to a stigma.
Many plants possess both male and female structures (monoecious)and can potent­ially self-pollinate.
from an evolut­ionary perspe­ctive, cross-­pol­lin­ation is preferable as it improves genetic diversity.

Fertil­i.s­ation of gametes results in the formation of a seed, which moves away from the parental plant.
Seed dispersal reduces the compet­ition for resources between germin­ating seeds and the parental plant.
There are a variety of seed dispersal mechan­isms, including wind, water, fruits and animals.
Seed structure varies depending on the mechanisms of dispersal employed by the plant.

Cross-­pol­lin­ation involves transf­erring pollen grains from one plant to the ovule of a different plant.

Common pollin­ators include birds, bats and insects.

Phytoc­hromes are leaf pigments which are used by the plant to detect periods of light and darkness.

Phytoc­hromes exist in two forms - an active form and an inactive form, with the active form being P^fr which is formed from the inactive form, P^r at 660nm. P^fr breaks down into P^r at ~725nm, but will also gradually revert to the inactive form in the absence of light.

Only P^fr can cause flowering, however its action differs in certain types of plants.

Short-day plants flower when the days are short – hence require the night period to exceed a critical length, meaning that P^fr inhibits flowering.

Long-day plants require periods of darkness to be less than an uninte­rrupted critical length.

These plants will tradit­ionally not flower during the winter and autumn months when night lengths are long.

Short-day plants require periods of darkness to be greater than an uninte­rrupted critical length.

These plants will tradit­ionally not flower during the summer months when night lengths are short.

Flowers are the reprod­uctive organs of angios­per­mop­hytes and develop from the shoot apex.

The activation of genes respon­sible for flowering is influences by abiotic factors - typically linked to the seasons.

The most common trigger for a change in gene expression is day/night length (photo­per­iod­ism).

Monoecious flowers contain both male and female reprod­uctive struct­ures.

Stamen is the male part of the flower.

Anthers are the pollen producing organs of the flower, with the pollen being the male gamete.
Filaments are the slender stalks that support the anther and make it accessible to pollin­ators.

Support structures in flowers

Petals are brightly coloured modified leaves, which function to attract pollinators.
Sepal is the outer covering that protects the flower when in the bud.
Peduncle is the stalk of the flower.

a small pore in the outer covering of the seed, that allows for the passage of water

the embryonic shoot (also called the epicotyl)

Water

to metabo­lically activate the seed

pH

seeds require a suitable soil pH to sprout

Fire

some seeds will only sprout after exposure to intense heat

Digestion

some seeds require prior animal digestion to erode the seed coat before the seed will sprout

Scarif­ication

seeds are more likely to germinate if the seed coat is weakened from physical damage