Problem 6 - Biology: The Dynamic Science

Question

Which of the following is a process that helps plants utilize nitrogen? a. nitrogen-fixing bacteria synthesizing nitrate b. \(\quad\) ammonifying bacteria using ammonium to produce nitrate c. nitrifying bacteria converting \(\mathrm{NH}_{4}^{+}\) to \(\mathrm{NO}_{3}^{-}\) d. the absorption of \(\mathrm{NH}_{4}+\) by root hairs the absorption of atmospheric \(\mathrm{N}_{2}\) into the xylem

Step-by-Step Solution

Answer

The correct answer is option 'c'. The process that greatly aids plants in utilizing nitrogen is performed by nitrifying bacteria, which convert NH4+ to NO3-.

Step 1: Understanding Nitrogen-Fixing Bacteria

Nitrogen-fixing bacteria play a vital role in converting atmospheric nitrogen (N2) into a form (ammonia NH3) that plants can utilize. It includes bacteria like Rhizobium. However, they do not synthesize nitrate. Therefore, option 'a' is incorrect.

Step 2: Understanding Ammonifying Bacteria

Ammonifying bacteria are responsible for the breakdown of organic material and the release of ammonia (NH4+). This process is also known as ammonification. However, these bacteria do not use ammonium to produce nitrate. So, option 'b' is not correct.

Step 3: Understanding Nitrifying Bacteria

Nitrifying bacteria includes two types of bacteria: Nitrosomonas and Nitrobacter. The Nitrosomonas are responsible for converting ammonia (NH4+) into nitrite (NO2-), while Nitrobacter convert nitrite (NO2-) into nitrate (NO3-). Therefore, they do not convert ammonium directly into nitrate. This makes option 'c' correct.

Step 4: Understanding the process of absorption

Root hairs of plants absorb ammonium (NH4+) from the soil; this is part of the nitrogen cycle. But this process is not the one that mainly helps plants utilize nitrogen. Therefore, option 'd' is not correct.

Step 5: Understanding the absorption of atmospheric N2 into the xylem

The absorption of atmospheric nitrogen (N2) into the xylem doesn't help the plant utilize nitrogen because plants cannot take up atmospheric nitrogen directly as they can't convert it into a usable form. Therefore, this option is not correct.