Photoperiodism Concepts

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Questions and Answers

What is photoperiodism?

The term used to describe the influence of relative periods of light and darkness on flowering.

How do plants respond to their environment?

By hormones. They don't have a nervous system. They aren't fast responses compared to our nervous system; they are slow but sustained.

What environmental factors do plants respond to?

Light, phototropism, and photoperiodism.

How do plants monitor day length?

Using a photoreceptor known as phytochrome, which absorbs specific wavelengths of light. Signup and view all the answers

What is Pr?

Phytochrome that absorbs red light during the day, specifically at 600nm. Signup and view all the answers

What is Pfr?

Phytochrome that absorbs far red light during the night, specifically at 730nm. Signup and view all the answers

What happens during daylight?

Phytochrome Pr is converted into Pfr quickly. Signup and view all the answers

What happens during night?

Phytochrome Pfr is converted back into Pr slowly. Signup and view all the answers

What is the main form in daylight and why?

Pfr because Pr converts into Pfr very quickly. Signup and view all the answers

What is the main form in darkness and why?

Pr because Pfr has converted into Pr slowly. Signup and view all the answers

Where is the stimulus (light) detected?

In the leaves. Signup and view all the answers

How is flowering in plants initiated?

By the hormone florigen. Signup and view all the answers

Plants flower in response to....

Day length. Signup and view all the answers

What are the three groups that flowering plants can be divided into?

Day neutral plants, long day plants, and short day plants. Signup and view all the answers

What is a day neutral plant?

Flowering is not affected by day length; e.g., cotton, tomato, or cucumber. Signup and view all the answers

What is a long day plant?

Plants that require a longer period of light and a shorter period of darkness, e.g., cabbage, petunia. Signup and view all the answers

What is a short day plant?

Plants that require shorter periods of light and longer periods of darkness, e.g., tobacco, poinsettia. Signup and view all the answers

A short day plant can only flower in the....

Darkness. Signup and view all the answers

A long day plant can only flower in the....

Light. Signup and view all the answers

Study Notes

Photoperiodism

Photoperiodism influences flowering in plants based on relative periods of light and darkness.
Plants use hormones to respond to their environment, lacking a nervous system but exhibiting slow, sustained responses.

Plant Environmental Responses

Light triggers phototropism, where shoots grow towards it.
Photoperiodism allows plants to respond to light and dark periods, influencing flowering.

Monitoring Day Length

Plants monitor day length using photoreceptors called phytochrome.
Phytochrome absorbs specific wavelengths, specifically blue/green light, and exists in two inter-convertible forms: Pr and Pfr.

Phytochrome Forms

Pr (phytochrome absorbing red light at 600nm) is dominant during daylight.
Pfr (phytochrome absorbing far red light at 730nm) is predominant during the night.

Day and Night Phytochrome Dynamics

During the day, Pr converts to Pfr rapidly.
At night, Pfr converts back to Pr slowly, resulting in accumulation of Pr.

Light Detection and Flowering

Light is detected in the leaves, with the stimulus transmitted to buds for flowering.
Flowering is initiated by the hormone florigen.
Day length is crucial for plant flowering responses.

Groups of Flowering Plants

Flowering plants are categorized into three groups:
- Day Neutral Plants: Flowering unaffected by day length (e.g., cotton, tomato, cucumber).
- Long Day Plants: Require longer light periods, shorter darkness (e.g., cabbage, petunia).
- Short Day Plants: Require shorter light periods, longer darkness (e.g., tobacco, poinsettia).

Flowering Conditions

Short day plants can only flower in darkness; interruptions by light prevent flowering.
Long day plants can only flower in light; interruptions by darkness promote flowering.

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Description

This quiz covers key concepts related to photoperiodism, including how plants respond to light and environmental factors affecting their growth. Explore the role of hormones in these responses and understand the influence of light and darkness on flowering. Perfect for students studying plant biology or environmental science.