Difference Between Photoperiodism And Vernalisation: Vernalization And Photoperiodism

Introduction To Photoperiodism And Vernalisation

Plants have evolved a high degree of complexity to act against fluctuations in seasons to ensure their survival and propagation. Two prominent modules that cause plants to respond based on external factors include photoperiodism and vernalization. While both of these processes involve some form of perception concerning an external factor followed by regulation over flowering, the two are relatively dissimilar.

What Is Photoperiodism?

Photoperiodism is the response of plants to the relative length of day and night. Plants use specialized photoreceptor proteins, phytochromes and cryptochromes to sense changes in light/dark periods. Based on their response to photoperiod, plants could be classified into three general groups. Photoperiodism, more generally, is considered to be the biological response of plants to the relative length of day and night.

Photoreceptors Involved

Plants make use of specialized photoreceptor proteins known as phytochromes and cryptochromes to perceive changes in light/dark periods.

Types of Plants Based on Photoperiod

Based on their response to photoperiod, plants are categorized into three main groups:

• Long-Day Plants: Those requiring a longer light exposure to induce flowering (LDP).

• Short-Day Plants: Require shorter exposure to light to induce flowering

• Day-Neutral Plants: Flower irrespective of day length

Mechanism Overview

The mechanism of photoperiodic flowering involves the perception of the light/dark signals by photoreceptors, transduction of signals to the leaves and synthesis of a floral stimulus-florigen, followed by its transport to the shoot apical meristem, and induction of flowering genes.

What Is Vernalisation?

Vernalization is the process by which some plants require an extended period of exposure to cold temperatures before they can complete the flowering process. This adaptation enables flowering to take place at the appropriate time. In contrast to photoperiodism, vernalization is a quantitative response, namely, the duration of cold exposure impacts the degree of flowering induction.

Why Vernalisation is Needed

Vernalisation is needed because:

• Prevents premature flowering

• Ensures flowering occurs in favorable seasons

• Common in winter cereals like wheat, barley, rye

Mechanism Overview

In other words, vernalization will be the perception of the cold signal by plants and will have subsequent epigenetic changes in flowering genes. These modifications become fixed and are sustained even following the removal of the cold treatment, allowing flowering under conducive environmental conditions.

Key Differences Between Photoperiodism And Vernalisation

The differences between photoperiodism and vernalisation is given in the table below:

Importance in Agriculture & Ecology

The importance in agriculture and ecology:

• Synchronises flowering with season: Ensures that flowering occurs at the appropriate time of the year, so that conditions are favorable for pollination.

• Used in crop scheduling: Allows farmers to control and predict the time of fruiting and flowering for uniform harvesting.

• Helps extend crop cultivation to new climates: By regulating growth and flowering through hormones, crops can be successfully grown in variable climatic regions.

Photoperiodism vs Vernalisation NEET MCQs (With Answers & Explanations)

Important topics for NEET are:

• Types of Plants based on photoperiodic response

• Long-day plants vs Short-day plants vs Day-neutral plants

• Mechanism of Photoperiodic flowering

Practice Questions for NEET

Q1. Which of the following plants belong to long short Day plants (LSDP)?

1. Hyoscyamus niger

2. Bryophyllum cestrum

3. Oryza sativa

4. Zea mays

Correct answer: 2) Bryophyllum cestrum

Explanation:

Long short Day plants (L-SDP) -

Plants require long photoperiods for floral initiation and short photoperiods for blossoming. When they get more than 12 hours of light per day—typically 14–16 hours—they bloom. Another name for them is short night plants. Plants flower between summer and autumn. Eg. Bryophyllum Cestrum

Hence, the correct answer is Option (2) Bryophyllum cestrum

Q2. Photoperiodism is the

1. Response of plants to the changing environmental conditions

2. Response of plant to the low temperature treatment expressed in the form of flowering

3. Response of plants to the photoperiod expressed in the form of flowering

4. Response of plants to the quality of light expressed in the form of seed germination

Correct answer: 4) Response of plants to the photoperiod expressed in the form of flowering

Explanation:

The response of plants to the photoperiod expressed in the form of flowering is called photoperiodism. Photoperiodism is controlled by photoreceptor proteins like phytochromes and cryptochromes, which sense the duration of light and dark periods. Plants are classified based on their flowering response into short-day, long-day, and day-neutral plants. This mechanism helps plants synchronize their reproductive cycles with favorable environmental conditions.

Hence, the correct answer is option 3 - the response of plants to the photoperiod expressed in the form of flowering.

Q3. Long day plants produces flowers when they exposed to

1. Any duration of light

2. Light period longer than a critical day length

3. Light period longer than 12 hours

4. Light period shorter than a critical day length

Correct answer: 2) Light period longer than a critical day length

Explanation:

The critical photoperiod is the length of time that must be exposed to light for some plants to flower. This varies among species and is important for their reproduction.
Key Terms
Long-Day Plants: These plants need a light period longer than a certain number of hours (the critical photoperiod) to begin flowering. They tend to bloom in late spring or early summer when days are longer.
Examples: Some common long-day plants are:
Spinach
Lettuce
Some Wheat Types
Light exposure past the critical photoperiod causes these plants to begin producing flowering hormones, causing the transition from vegetative growth to flowering. Knowledge of critical photoperiods is critical for agriculture as it determines the timing of planting schedules and crop yields.

Hence, the correct answer is option 2) Light period longer than a critical day length.

Also Read:

• MCQs on Photoperiodism in Plants

• Auxin Biosynthesis

• Factors Affecting Plant Growth

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