To fulfill their nitrogen requirements in nutrient-poor soils.
Explanation
Insectivorous (or carnivorous) plants are green plants that possess chlorophyll and are capable of performing photosynthesis to produce carbohydrates. However, they have evolved specific adaptations to survive in environments where the soil is deficient in essential nutrients, particularly nitrogen.
Option Analysis:
- They lack the chlorophyll necessary for photosynthesis. is Incorrect: Insectivorous plants contain chlorophyll and carry out photosynthesis to generate energy and carbon-based food (glucose). They are not non-photosynthetic.
- To fulfill their nitrogen requirements in nutrient-poor soils. is Correct: These plants typically grow in nitrogen-deficient soils, such as bogs or marshes. To fulfill their nitrogen requirements-which are essential for protein synthesis-they trap and digest insects. The insects are broken down by enzymes, and the nitrogenous compounds are absorbed by the plant.
- They lack a root system for water absorption. is Incorrect: Insectivorous plants do possess root systems used for anchoring the plant and absorbing water and minerals from the soil, although the roots may be less developed compared to plants in nutrient-rich soils.
- To obtain carbon dioxide for the dark reaction. is Incorrect: Like other terrestrial plants, insectivorous plants obtain carbon dioxide from the atmosphere through stomata for the dark reaction of photosynthesis.
Key Takeaway:
Insectivorous plants are partial heterotrophs; they are autotrophic regarding their energy and carbon needs (via photosynthesis) but depend on insects for their nitrogen supply due to soil deficiency.