Photoperiodism and Vernalisation
Day-length classes of plants and the cold requirement for flowering. (Biology › Plant Growth and Development, NEET UG syllabus.)
What is Photoperiodism and Vernalisation?
The physiological response of plants to the relative lengths of day and night, primarily influencing flowering.
Key points
- Define photoperiodism and vernalisation.
- Classify plants based on their photoperiodic response (SDP, LDP, DNP) with relevant examples.
- Explain the concept of critical photoperiod and its significance.
- Describe the mechanism of photoperiodic perception, including the role of phytochrome (Pr and Pfr).
Common exam trap
Confusing critical photoperiod with absolute day length; it's a threshold for flowering.
Definitions
- Term
Photoperiodism
- Meaning
The physiological response of plants to the relative lengths of day and night, primarily influencing flowering.
- Term
Vernalisation
- Meaning
The process by which plants require a period of low temperature (cold treatment) to induce or accelerate flowering.
- Term
Critical Photoperiod
- Meaning
The specific duration of light or darkness that must be exceeded or not exceeded for a plant to flower.
- Term
Phytochrome
- Meaning
A blue-green photoreceptor pigment in plants that exists in two interconvertible forms (Pr and Pfr) and plays a crucial role in perceiving light and dark periods.
- Term
Florigen
- Meaning
A hypothetical hormone believed to be produced in leaves under appropriate photoperiodic conditions and transported to the shoot apex to induce flowering.
- Term
Vernalin
- Meaning
A hypothetical hormone believed to be produced in response to cold treatment, which then induces flowering.
Learning objectives
Define photoperiodism and vernalisation.
Classify plants based on their photoperiodic response (SDP, LDP, DNP) with relevant examples.
Explain the concept of critical photoperiod and its significance.
Describe the mechanism of photoperiodic perception, including the role of phytochrome (Pr and Pfr).
Explain the significance of vernalisation in plant development and its agricultural applications.
Identify the site of perception for both photoperiodism and vernalisation.
Discuss the hormonal control (florigen, vernalin, gibberellins) related to these processes.
Prerequisites
Basic understanding of plant anatomy (leaves, meristems).
Knowledge of major plant hormones and their general functions.
Fundamental concepts of plant physiology.
Common mistakes
Confusing critical photoperiod with absolute day length; it's a threshold for flowering.
Believing Short-Day Plants (SDPs) need short days; they actually require a long, continuous night period.
Believing Long-Day Plants (LDPs) need long days; they actually require a short, continuous night period.
Misunderstanding the active form of phytochrome (Pfr) and its role in SDPs vs. LDPs.
Not knowing the distinct sites of perception: leaves for photoperiodism and apical meristems for vernalisation.
Keywords
Photoperiodism
Vernalisation
Short-Day Plants (SDP)
Long-Day Plants (LDP)
Day-Neutral Plants (DNP)
Critical Photoperiod
Phytochrome
Pr
Pfr
Florigen
Vernalin
Gibberellins
Flowering
Cold Treatment
Apical Meristem
Leaves
Devernalisation
Practice preview
Which of the following is an example of a short-day plant?…
easy
Vernalisation refers to the promotion of flowering by:…
easy
In long-day plants, the active form of phytochrome (Pfr) generally:…
medium