Question

Plants adapted to low light intensity have

• A. Larger photosynthetic unit size than the sun plants
• B. Higher rate of $CO_2$ fixation than the sun plants
• C. More extended root system
• D. Leaves modified into spines

Answer 1

The Correct Option is A

Plants adapted to low light intensity have distinct features that help them maximize their photosynthetic efficiency in environments where sunlight is scarce. One such adaptation is having a larger photosynthetic unit size.

Here's the reasoning behind why this is the most effective adaptation among the given options:

1. Photosynthetic Unit Size: Plants adapted to low light conditions increase their photosynthetic unit size, meaning they have more chlorophyll molecules associated with each photosystem. This adaptation enhances their ability to capture more light energy, albeit low, thus maintaining efficient photosynthesis. The larger unit size compensates for the lower light intensity by maximizing the amount of light energy captured.
2. Other Options Justification:
   • Higher rate of CO_2 fixation than the sun plants: Typically, sun plants have a higher rate of CO_2 fixation due to higher light availability. Shade plants cannot surpass this rate due to their adaptation to low light.
   • More extended root system: An extended root system is more related to adaptations for water and nutrient uptake rather than light availability.
   • Leaves modified into spines: Leaf modification into spines is an adaptation seen in xerophytic plants (desert plants) for conserving water, not in plants adapted to low light conditions.

Conclusion: Among the given options, Larger photosynthetic unit size than the sun plants is the correct adaptation for plants in low light conditions, as it directly relates to increasing the photosynthetic efficiency under limited light availability. This adaptation enables shade plants to survive and grow by optimizing the light they do receive.