11 Questions
What type of plants will flower only under long-day conditions and never under unsuitable photoperiodic cycle conditions?
Absolute long-day plants
Which type of plants can flower under short-day conditions or inappropriate photoperiods, although flowering may be delayed?
Facultative short-day plants
What type of plants have flowering that is promoted by short-day conditions, but can still flower under inappropriate photoperiods?
Facultative short-day plants
Which type of plants require a specific photoperiod for flowering, whereas flowering is delayed under other conditions?
Absolute short-day plants
What type of plants have flowering that is promoted by long-day conditions, but can still flower under inappropriate photoperiods?
Facultative long-day plants
What is the name of the hormone-like substance that controls flowering and other plant responses?
Phytochrome
Which of the following chemical substances inhibits flowering?
Maleic hydrazide
What is the name of the common herbicide that can cause floral induction?
2,4-Dichlorophenoxyacetic acid
Which of the following statements is true about gibberellic acid?
It promotes flowering in long-day plants but inhibits flowering in short-day plants
What is the year in which phytochrome was finally isolated, identified, and named?
1959
Which of the following chemical substances can cause floral induction at certain concentrations?
All of the above
Study Notes
Types of Photoperiodic Plants
- Facultative long-day plants: Flowering is promoted by long-day conditions, but they can still flower under short-day conditions, although flowering is delayed.
- Facultative short-day plants: Flowering is promoted by short-day conditions, but they can still flower under long-day conditions, although flowering is delayed.
Absolute Photoperiodic Plants
- Absolute long-day plants: Flowering absolutely depends on long-day conditions, and they never flower under unsuitable photoperiodic cycle conditions.
- Absolute short-day plants: Flowering absolutely depends on short-day conditions, and they never flower under unsuitable photoperiodic cycle conditions.
Hormonal Control of Flowering
- Flowering is controlled by several hormone-like substances, not just one.
Phytochrome and Light Response
- Phytochrome is a light-receptive component that controls various plant responses, including seed germination, bud dormancy, stem elongation, and petiole development.
- Phytochrome was isolated, identified, and named in 1959.
- Light responses are similar across different plant sections, indicating a common mechanism.
Chemical Stimuli and Floral Induction
- Certain natural and synthetic chemical substances can cause floral induction.
- Examples of auxin-like compounds that induce flowering include indoleacetic acid, naphthaleneacetic acid, and 2,4-dichlorophenoxyacetic acid (2,4-D).
- Gibberellic acid can promote flowering in long-day plants under short-day conditions, but inhibits flowering in short-day plants under the same conditions.
- Other substances that induce flowering or increase flower production include cytokinins, ethylene, acetylene, ethylene chlorohydrin, and 2,3,5-triodobenzoic acid.
- Maleic hydrazide inhibits flowering.
This quiz covers the different types of plant responses to day length, including facultative and absolute long-day and short-day plants. Understand the effects of photoperiodism on plant flowering and growth.
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