Problem 182 - Objective Biology for NEET

Question

Plants with no such correlation between exposure to light duration and induction of flower response are called (a) Long day plant (b) Day-neutral plants (c) Short day plant (d) None of these

Step-by-Step Solution

Answer

The correct answer is (b) Day-neutral plants.

Step 1: Understand the Terminology

Long day plants and short day plants are those that require a certain duration of light exposure in a day to induce flower response. In contrast, day-neutral plants do not depend on the duration of light and can bloom regardless of the length of the day.

Step 2: Identify the Correct Answer

With this understanding, it can be concluded that the plants that do not correlate their exposure to light duration and induction of flower response are the Day-neutral plants.

Key Concepts

Long Day Plants

Long day plants, unlike their short day and day-neutral counterparts, have a very special requirement when it comes to blooming. These plants rely on having longer daylight periods in order to trigger flowering. What does this mean exactly? Well, in terms of plant biology, these are plants that flower when the light period exceeds a certain critical threshold.
This threshold varies, but typically long day plants will need more than 12 hours of daylight to start the flowering process.

• Examples: Lettuce, spinach, and certain species of clover are classic examples of long day plants.
• Climate Preference: They are particularly suited to temperate regions, where summer days provide the long daylight exposure these plants thrive on.
• Photoperiodism: This is the process in which the timing of flower formation is influenced by the length of the day (or night). For long day plants, it's the longer days that set the bloom in motion.

Understanding long day plants helps in strategic planting and harvesting, providing insight into how we can best cater to these daylight-centric plants.

Short Day Plants

Short day plants are another fascinating group within the realm of plant photoperiodism. These plants have a different approach to flowering than long day plants. Instead of needing more light, short day plants require longer periods of darkness or shorter days to start blooming.
This means they flower typically when the day length falls below a certain critical duration, often less than 12 hours of daylight.

• Examples: Chrysanthemums, poinsettias, and soybeans tend to be associated with this category.
• Seasonal Timing: They often blossom in late summer, fall, or spring, aligning with naturally shorter days.
• Photoperiod Response: The fundamental signal for these plants is the lengthening of the dark period rather than the daylight.

For gardeners and farmers, recognizing short day plants ensures they can manage crops to align with natural or artificially manipulated cycles in daylight hours.

Day-Neutral Plants

Day-neutral plants are unique in the family of plants governed by photoperiodism because they are not sensitive to light duration for flowering. This lack of sensitivity allows these plants to bloom regardless of how long or short the daylight is throughout the year.
This means they don’t depend on the photoperiod to enter the flowering phase, offering incredible flexibility in terms of their growth cycles.

• Examples: Tomatoes, cucumbers, and some strawberries are prime examples of day-neutral plants.
• Lifestyle Benefits: They can thrive and produce flowers in various climates and seasons since light duration does not trigger flowering.
• Growth Consistency: Being day-neutral enables consistent agricultural production, as these plants remain unaffected by the changing lengths of days and nights.

Recognizing day-neutral plants is particularly useful for commercial growers who aim for a year-round yield without the constraints of seasonal light shifts.