9.4 Reproduction in plants Flashcards
What is the vegetative phase?
This is the phase when a young plant germinates and grows roots stems and leaves. This can last for weeks months or years until a trigger causes the plant to change into the reproductive phase and produce flowers.
What is needed for a plant to go from the vegetative phase to the reproductive phase?
Flowering involves a change in gene expression in the shoot apex.
- Change in the length of the dark period
- Change in temperature
LONG DAY PLANTS
The active form of the pigment phytochrome leads to the transcription of a flowering time (FT gene). The FT mRNA is then transported in the phloem to the shoot apical meristem where it is translated into FT protein. The FT protein binds to a transcription factor. This interaction leads to the activation of many flowering genes which transform the leaf-producing apical meristem into a reproductive meristem.
What are short day plants?
They flower when the dark period becomes longer. SO THEY FLOWER IN WINTER
What are long day plants?
They flower when the dark period becomes shorter. SO THEY FLOWER IN SUMMER
How do long day plants enter the reproductive phase?
The active form of the pigment phytochrome leads to the transcription of the FT gene. The FT mRNA then is transported to the shoot apex in the phloem and there it is translated into FT protein which binds to a transcription factor. This interaction leads to the activation of many flowering genes which transform the leaf producing apical meristem into a reproductive meristem.
How does a plant enter the reproductive phase? Full
IT IS THE LENGTH OF DARKNESS THAT DETERMINES IT
A pigment was discovered in leaves that plants use to measure the length of dark periods. It is called phytochrome and is unusual as it can switch between two forms P-r and P -rf.
When P-r absorbs red light of wavelength 660nm it is converted into P-fr.
When P-fr absorbs far red light of wavelength 730nm it is converted into P-r but this is of little importance because sunlight contains more 660 than 730 anyway so it is normally converted to P-fr.
What is important is that Pr is more stable than P-fr and so in darkness P-fr gradually turns into Pr
P-fr is the active form that receptors can bind to. So in long day plants the night is short and so there is more P-fr because there was not enough time overnight for it all to turn to Pr. These P-fr then promote transcription of genes needed for flowering.
Short day plans P-fr inhibits the receptor and so whenever there are short nights and there is still lots of P-fr the flower does not flower. However at the end of a long night there has been lots of P-fr changed to P-r and there is not enough to inhibit it, and so the plant flowers.
How do long day plants flower?
Long day - short night - not much P-r, so the receptors pick up the P-fr and that promotes transcription of genes needed for flowering.
A pigment was discovered in leaves that plants use to measure the length of dark periods. It is called phytochrome and is unusual as it can switch between two forms P-r and P -rf.
When P-r absorbs red light of wavelength 660nm it is converted into P-fr.
When P-fr absorbs far red light of wavelength 730nm it is converted into P-r but this is of little importance because sunlight contains more 660 than 730 anyway so it is normally converted to P-fr.
What is important is that Pr is more stable than P-fr and so in darkness P-fr gradually turns into Pr
P-fr is the active form that receptors can bind to. So in long day plants the night is short and so there is more P-fr because there was not enough time overnight for it all to turn to Pr. These P-fr then promote transcription of genes needed for flowering.
How do short day plants flower?
Short day - long night, lots of P-r formed, so the P-fr is no longer inhibiting the receptors so flowers.
A pigment was discovered in leaves that plants use to measure the length of dark periods. It is called phytochrome and is unusual as it can switch between two forms P-r and P -rf.
When P-r absorbs red light of wavelength 660nm it is converted into P-fr.
When P-fr absorbs far red light of wavelength 730nm it is converted into P-r but this is of little importance because sunlight contains more 660 than 730 anyway so it is normally converted to P-fr.
What is important is that Pr is more stable than P-fr and so in darkness P-fr gradually turns into Pr
Short day plans P-fr inhibits the receptor and so whenever there are short nights and there is still lots of P-fr the flower does not flower. However at the end of a long night there has been lots of P-fr changed to P-r and there is not enough to inhibit it, and so the plant flowers.
How can we induce plants to flower out of season?
Growers can manipulate the length of the days and nights to force flowering.
Draw an animal pollinated flower?
Ones with flowers, bright colours.
Ovary - in the broad bit of the stem
Sepal - bit of green hard leaf that the flower buds from
Filament - stand that holds the pollen on
Anther - pollen pocket
Style - long bit in the middle of the flower
Stigma - top of the long bit in the middle of the flower.
How do most flowering plants sexually reproduce?
They use a mutualistic relationship between flowers and animals.
Sexual reproduction in flowering plants depends on the transfer of pollen from the stamen to a stigma of another plant. Pollen is transferred between plants via a number of strategies including wind and less commonly water but most commonly via animals known as pollinators. Examples of pollinators include birds, bats and insects such as butterflies and bees. Pollinators gain food in the form of nectar and the plant gains a means to transfer pollen to another plant.
How do plants reproduce?
Enter the flowering phase
Pollination
Fertilisation
Seed dispersal
What is fertilisation?
From each pollen grain on the stigma a tube grows down the style to the ovary. The pollen tube carries male games to fertilise the ovary. The ovary is located inside a small rounded structure called an ovule.
The fertilised ovule develops into a seed and the ovary develops into a fruit.
What is seed dispersal?
Seeds need to travel long distances from their parent plants in order to reduce competition between offspring and parent, and in order to spread the species.
How do we protect extinction?
Because plants rely so heavily on pollinators, and pollinators rely so heavily on flowering plants to survive humans have realised in order to protect individual organisms you need to protect the entire ecosystem.
