In this IBDP Biology blog post, we will be looking at how flowering is controlled and the factors associated with the plants for this process.
Control of Flowering
Photoperiodism: Process through which the control of flowering is achieved
CRITICAL FACTOR: NIGHT LENGTH
Plants use photoreceptors called phytochromes to determine the length of night and day
Two interconvertible forms of phytochrome:
- Pfr
- Pr
Plants measure the time taken to convert from far-red form (Pfr) to its red form (Pr) as a mesure of "day" but in actuality this conversion takes place at night
Sunlight contains more red light than far red light - in the day most Pr is quickly converted to Pfr
During darkness Pfr is slowly converted back to Pr
Long day plants: A lot of Pr during day which allows for a lot of Pfr to trigger flowering
Short day plants: Pfr binds to inhbiting factor binds to an inhibiting factor
How flowering is controlled in long & short term
- Flowering is affected by light
- Phytochrome exists in two inconvertible forms Pr and Pfr
- Pr (red absorbing) is converted to Pfr in red or day light and the gradual reversion of Pfr to Pr occurs in darkness
- Pfr is the active form in long day plants
- and occurs when day is longer than a critical length
- Enough
Pfr remains in long day plants at the end of short nights to stimulate flowering. Pfr acts as a promoter of flowing in long day plants
- Short day flowers are induced to flower when the days are shorter than a critical value. At the end of
long nights enough Pfr has been converted to Pr to allow flowering to occur. Pfr acts as an inhibitor of flowering in short-day plants
Chrysanthemums can be produced out of flowing season by keeping in greenhouse with blinds
That's all!
References:
- https://www.google.com/url?sa=i&url=http%3A%2F%2Fib.bioninja.com.au%2Fhigher-level%2Ftopic-9-plant-biology%2Funtitled-3%2Fphotoperiodism.html&psig=AOvVaw3BQr5HbvLr7Pbzvj9TO4N3&ust=1627177384357000&source=images&cd=vfe&ved=0CAsQjRxqFwoTCNiy3KLK-vECFQAAAAAdAAAAABAN
- https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.pathwayz.org%2FTree%2FPlain%2FPHYTOCHROME%2BSYSTEM&psig=AOvVaw1zre4sWf_vXPPVVAnsQjZa&ust=1627177566282000&source=images&cd=vfe&ved=0CAsQjRxqFwoTCNDygvrK-vECFQAAAAAdAAAAABAD
Drafted by Venetia (Biology)