Ch 9.4 Flashcards
Flowering involves a change in ____ __________ in the _____ _____.
- flowering involves a change in gene expression in the shoot apex.
- stem apical meristem can develop into stem, leaves or flowers
- at different times, different genes are turned on to determine which the meristem will become
What is the switch to flowering a response to?
- the switch to flowering is a response to the length of light and dark periods in many plants (photoperiodism)
- the length of time the plant is continuously in the dark seems to be the true trigger
Types:
- long-day plants (day length >9-16h)
- short-day plants (day length <10-16h)
- day-neutral plants (not responsive to the day length)
What is photoperiodism?
- flowering response due to light
- plants are sensitive to a chemical called phytochrome
- phytochrome exists in two versions which are interconvertible: PR that absorbs red light and PFR that absorbs far red light
- conversion from PR to PFR is fast and occurs during the day, whilst conversion from PFR to PR is slow and occurs during the night
How does phytochrome determine flowering?
- In long day plants (spring/summer bloom), PFR initiates flowering (therefore, when PFR is high, in spring/summer, the flower will bloom)
- In short day plants (late summer/fall bloom), PFR inhibits flowering (therefore, when PFR is low, the flowering is no longer inhibited and the plant flowers.)
List some methods used to induce short-day plants to flower out of season
- manipulate the amount of darkness
- short day plants flower when there are long stretches of night
- cover the greenhouse (blinds) at 6pm to prevent light from reaching the plants
- the long “nights” will initiate flowering
- ie. getting asters to continue blooming through September
List some methods used to induce long-day plants to flower out of season
- manipulate the amount of darkness
- long day plants flower when there are short stretches of night
- flash on a light in the greenhouse in the middle of the night
- the flash of light will trick the plant into responding as though it were a short night and will initiate flowering
- ie. getting roses to continue blooming through the fall and winter
Characteristics of animal pollinated plants
- flowers are colourful and showy
- flowers have a scent
- nectar is produced in the flower
- anther and stigma are low, protected by petals
- pollen is sticky
Characteristics of wind pollinated plants
- flowers are small and often neutral coloured
- no scent
- no nectar
- anther and stigma are held above the petals
- pollen is light
List all the parts of the flower that we need to label
- anther
- filament
- ovary
- ovule
- petal
- receptacle
- sepal
- stigma
- style
What are the three things that the success in plant reproduction relies on?
- pollination
- fertilization
- seed dispersal
List the three steps in reproduction in plants
- Pollination
- Fertilization
- Seed dispersal
Pollination
the transfer of pollen from one plant to the ovule of another plant
a. pollinators gain food in the form of nectar; bright flowers and scent attracts pollinators
b. plant gains a means of transfer of pollen to another plant (ie. wind)
Fertilization
after pollination; the egg is fertilized by the pollen
a. actual joining of sperm with the egg
b. each pollen grain on the stigma grows a tube down the style to the ovary
c. the sperm swim down the tube to fertilize the eggs
d. fertilized egg develops into a seed and the ovary develops into fruit
Seed dispersal
after fertilization; the movement of seeds to another location
a. seeds cannot move themselves
b. seeds need to travel long distances away from their parent plant
- reduces competition between offspring and parent plant
- helps to spread the species
c. depends on the structure of the fruit
- dry and explosive
- fleshy and delicious
- feathery or winged
- covered in hooks
Seed formation
- when ovule is fertilized, a seed develops
- seed contains the embryo plant, a good supply to give it energy when it begins to grow and a protective outer coat to keep it from drying out
- ovary of the plant develops into fruit to protect the seed
