C22 - Plant Reproduction Flashcards
What’s the endosperm?
The food source surrounding the plant embryo.
What is the testa?
The protective layer of the seed / the seed coat.
What are cotyledons?
Seed leaves.
Some fully developed seeds lack endosperms because the cotyledons have absorbed them so the cotyledons act as the food source.
What are gibberellins?
Plant hormones that act as a signalling molecule to break the dormancy of a seed.
After a seed is exposed to water, gibberellin is released which induces the synthesis of amylase. This breaks down starch in the endosperm by hydrolysis into glucose.
What do gibberellins do?
After a seed is exposed to water, gibberellin is released which induces the synthesis of amylase.
This breaks down the starch in the endosperm, by hydrolysis, into glucose.
Where are the male and female gametes found within plants?
Male gametes are found within pollen grains.
Female gametes are found in ovules.
How do plants reproduce?
Pollen from the anthers of one plant must be transferred to the stigma of the other by wind, animals or insects.
What are the components of a plant?
Stigma - part of plant that receives pollen
Style - extension above the ovary holding the stigma
Anther - part of stamen containing pollen
Filament - extension holding the anther
Sepal - part of base of flower enclosing the petals
Petal
Ovary
What 2 environmental factors can plants detect?
Temperature
Day length : night length ratio (known as photoperiods)
What’s photoperiodism?
The response by an organism to synchronise its body with changes in day length.
This is important as change in day lengths indicate seasons and so some plants regulate their flowering accordingly.
What happens during photoperiodism?
Change in day length causes the photoperiod mechanism to occur in leaves by the florigen hormone.
This causes the plant to bud and flower.
What are long day plants?
Plants which flower during late spring when day length is above critical value (>9-16h).
What are short day plants?
Plants which flower when nights are longer and day length is below a critical value (<9-16h).
What are day neutral plants?
Plants that do not respond to day length.
What is nightbreak phenomenon?
For plants with a critical night length, a short flash of light in the middle of the night would make the plant behave as though it had been exposed to a long day.
What’s a phytochrome molecule?
A protein bonded to a non-protein light absorbing pigment molecule.
What 2 types of non-protein light absorbing pigment molecule components exist within plants?
Pr - phytochrome red (absorbs red light)
Pfr-phytochrome far red (absorbs far red light)
How are Pr and Pfr used within plants?
Formation of phytochrome far red results in developmental processes occurring.
Red light is absorbed by phytochrome red which converts it to Pfr for developmental processes.
This however is reversible and reverts back to Pr in the dark.
Back and forth conversions allow the plant to measure day length
How do plants respond to temperature?
A set number of heat units are are required by the plant between developmental stages.
Temperate species must be exposed to low temperatures for an extended period before they can flower, known as vernalisation.
What’s vernalisation?
The cooling of a seed during germination to accelerate flowering when planted.
Some flower after vernalisation without further environmental signals.
What is hermaphroditism?
Having male and female gametes.
Most species of plant are hermaphroditic.
What’s cross pollination?
When pollen from the anther of one flower is transferred to the stigma of another flower.
What’s self pollination?
When pollen from the anther of one flower is transferred to the stigma of another flower on the same plant.
How does fertilisation occur within plants?
The nucleus of the male gamete in the pollen fuses with the nucleus of the female gamete in the ovules.
Each pollen grain grows a pollen tube down into the ovule. One pollen tube reaches the ovule where a nucleus of a male cell joins with the nucleus in the female cell.
