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Biology IB HL - 9.4 Plant Reproduction Part 3

Biology20 CardsCreated about 1 month ago

This deck covers key concepts of plant reproduction, focusing on the role of phytochromes, photoperiodism, and the classification of plants based on flowering in response to light and dark periods.

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What is the sepal?

Outer covering which protects the flower when in bud
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Key Terms

Term
Definition
What is the sepal?
Outer covering which protects the flower when in bud
What is the peduncle?
The stalk of the flower
What is the purpose of flowering?
The purpose of flowering is to enable the plant to sexually reproduce via pollination, fertilisation and seed dispersal
What 2 types of flowering plants are there? (depending on when they bloom)
Some plants bloom in long day conditions (summer), whereas other plants bloom in short day conditions (autumn / winter)
What is the critical factor responsible for flowering?
The critical factor responsible for flowering is the length of light and dark periods, which is detected by phytochromes
What are phytochromes?
Phytochromes are leaf pigments which are used by the plant to detect periods of light and darkness
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Biology IB HL - 9.4 Plant Reproduction Part 3
TermDefinition
What is the sepal?
Outer covering which protects the flower when in bud
What is the peduncle?
The stalk of the flower
What is the purpose of flowering?
The purpose of flowering is to enable the plant to sexually reproduce via pollination, fertilisation and seed dispersal
What 2 types of flowering plants are there? (depending on when they bloom)
Some plants bloom in long day conditions (summer), whereas other plants bloom in short day conditions (autumn / winter)
What is the critical factor responsible for flowering?
The critical factor responsible for flowering is the length of light and dark periods, which is detected by phytochromes
What are phytochromes?
Phytochromes are leaf pigments which are used by the plant to detect periods of light and darkness
What is photoperiodism?
Phytochromes are leaf pigments which are used by the plant to detect periods of light and darkness
What are the 2 forms of phytochromes?
Pr -inactive form | Pfr - active form
When is the inactive form of phytochrome converted?
The inactive form of phytochrome (Pr) is converted into the active form when it absorbs red light (~660 nm)
When is the active form of phytochrome broken down?
The active form of phytochrome (Pfr) is broken down into the inactive form when it absorbs far red light (~725 nm)
Can the active form of phytochrome be converted into the inactive form?
YES | the active form will gradually revert to the inactive form in the absence of light (darkness reversion)
Which form of phytochrome is predominant during the day? Why?
Because sunlight contains more red light than moonlight, the active form is predominant during the day
Which form of phytochrome is predominant during the night? Why?
as the active form is reverted in darkness, the inactive form is predominant during the night
How can plants be classified into long/short day plants?
Plants can be classed as short-day or long-day plants, however the critical factor in determining their activity is NIGHT LENGTH
When do short-day plants flower? (length…)
Short-day plants flower when the days are short – hence require the night period to exceed a critical length
How does phytochrome play a role in short-day plants?
In short-day plants, Pfr INHIBITS flowering and hence flowering requires low levels of Pfr (i.e. resulting from long night
When do long-day plants flower? (length…)
Long-day plants flower when the days are long – hence require the night period to be less than a critical length
How does phytochrome play a role in long-day plants?
In long-day plants, Pfr activates flowering and hence flowering requires high levels of Pfr (i.e. resulting from short nights)
How can horticulturalists manipulate flowering?
Horticulturalists can manipulate the flowering of short-day and long-day plants by controlling the exposure of light
What must be uninterrupted/maintained to control plant flowering?
The critical night length required for a flowering response must be uninterrupted in order to be effective