Final answer:
The process by which plants absorb ammonium and nitrate ions from the soil to make essential compounds such as DNA, amino acids, and proteins involves nitrogen fixation, nitrification, and the interactions with nitrifying and denitrifying bacteria.
Step-by-step explanation:
The process by which plant roots absorb ammonium ions and nitrate ions to synthesize compounds such as DNA, amino acids, and proteins is an integral part of the nitrogen cycle, a critical series of processes involving different forms of nitrogen in the environment. When dead organisms or their wastes decompose, ammonium ions (NH₄⁺) are released into the soil, which plants can directly absorb. Conversely, nitrifying bacteria in the soil convert ammonium into nitrate (NO₃⁻), which is another form that plants can assimilate for their nutritional needs. The absorbed nitrogen is then incorporated into plant tissues and used to produce vital molecules such as nucleotides and proteins, essential for plant growth and development.
Nitrogen fixation is another process, mainly associated with symbiotic relationships between soil bacteria and certain plant roots, such as legumes. This biological process converts atmospheric nitrogen gas (N₂), which is inaccessible to most plants, into a usable form of ammonia (NH₃). The resulting ammonia from nitrogen fixation can be directly assimilated by plants or further processed into nitrate by the action of soil bacteria. Complex interactions with bacteria, such as denitrifying bacteria, can also reverse this process, converting nitrate back to nitrogen gas, a process known as denitrification.
These biological processes are crucial for maintaining the balance of nitrogen in soil, which is indispensable for plant nutrition and the overall health of terrestrial ecosystems. Therefore, the capability of plants to absorb ammonium and nitrate from the soil is foundational for the synthesis of crucial organic molecules and for sustaining life on Earth.