Problem 185 - Objective Biology for NEET

Question

When flowering is either quantitatively or qualitatively dependent or exposure to low temperature it is called \(\quad\) phenomenon. (a) Photoperiodism (b) Thermoperiodism (c) Vernalization (d) Dormancy

Step-by-Step Solution

Answer

(c) Vernalization

Step 1: Analyze the Definition

The initial stage of the problem-solving process is to understand the definition provided. The phenomenon described is dependent on exposure to low temperature, i.e., the flowering of the plant is affected by cold weather conditions.

Step 2: Match Terms with Definition

The next step is to match the available options with the definition. (a) Photoperiodism relates to the effect of length of day or night on plant processes. (b) Thermoperiodism refers to the regulation of physiological processes by seasonal variations in temperature. (d) Dormancy refers to a period in an organism's life cycle when growth, development, and physical activity are temporarily stopped.

Step 3: Identifying The Correct Term

Considering the interpretation of the definition and corresponding terms, the correct answer is (c) Vernalization. Vernalization refers to the hastening of plant flowering and/or seeding by chilling treatments.

Key Concepts

Photoperiodism

Photoperiodism is an essential plant process that relies on the changing lengths of day and night. This adaptation helps plants determine the appropriate time for activities such as flowering, seed germination, and even leaf fall. The variation in daylight has a significant influence as many plants use it as a cue to adjust to seasonal changes.

To understand photoperiodism better, consider plants like chrysanthemums and poinsettias, which are classic examples of short-day plants. They need longer nights and shorter days to trigger flowering. On the other hand, long-day plants like spinach prefer more daylight hours before they start blossoming.

• Short-day plants: Flower when nights are long.
• Long-day plants: Flower when nights are short.
• Day-neutral plants: Flower regardless of the night length.

Thermoperiodism

Thermoperiodism involves the influence of temperature variations over the seasons on plant growth and development. Plants are highly sensitive to temperature changes, which often signal the start of germination, flowering, and other physiological activities.

The difference in day and night temperatures can affect how plants perform, impacting their nutrient uptake and overall vitality. For example, some plants need a gradual increase in temperatures from cool to warm to initiate blooming. This sensitivity can be crucial for plants in regions with distinct seasonal changes.

Thermoperiodism typically ensures that plants can time their flowering and seed production to coexist with favorable environmental conditions, enhancing their chances for survival and reproduction. By responding to these temperature cues, plants can optimize their growth cycles for the climate they inhabit.

Dormancy

Dormancy is an intriguing survival strategy that allows plants and some animals to pause normal activity when conditions are not favorable. In this state, plants can withstand extremes in temperature, drought, or cold spells without sustaining damage. This period of suspended growth helps them conserve energy until circumstances improve.

In plants, dormancy occurs in different forms. Seeds often enter a dormant state until conditions are right for germination. Similarly, deciduous trees shed leaves and enter dormancy during winter. This is achieved through hormonal changes that regulate their biological clock, ensuring they emerge from dormancy when environmental threats subside.

• Dormancy helps survive adverse conditions.
• Seeds remain dormant until conditions favor germination.
• Increases survival during extreme weather.