In plants with nitrogen fixing bacteria (such as alfalfa or soybeans), the presence of oxygen will poison the bacterium. Which of the following acts as a natural defense against oxygen toxicity by scavenging free oxygen in these systems?

1. Hemoglobin	2. Myoglobin
3. Leghemoglobin	4. Methemoglobin

Identify a free living anaerobic nitrogen fixing microbe:

Conversion of ammonium to nitrate during nitrogen cycle is called as:
1. Nitrogen assimilation
2. Denitrification
3. Nitrification
4. Nitratification

A microbially facilitated process of dissimilatory nitrate reduction that may ultimately produce molecular nitrogen (${\mathrm{N}}_2$) through a series of intermediate gaseous nitrogen oxide products is called as:

For biological fixation of one molecule of nitrogen into two molecules of ammonia, the number of ATP molecules needed is:

In plants, ammonia reacts with alpha ketoglutaric acid to form glutamic acid in a process called as:

Name the amino acid from which 17 other amino acids are formed by transamination in plants?

If you have carefully read the role of macronutrients in your NCERT, you should be able to tell the name of the mineral that plays an important role in several carbon dioxide transfers catalyzed by carboxylase enzymes. The mineral is:
1. Magnesium
2. Sulfur
3. Iron
4. Calcium

Primary macronutrients are heavily used by plants. Based on your understanding of role of macronutrients , section 12.2.2, NCERT, can you predict which of the following may be a secondary macronutrient for plants?
1. Nitrogen
2. Phosphorus
3. Potassium
4. Calcium

Which one of the following statements can best explain the term critical concentration of an essential element?
1. Essential element concentration below which plant growth is retarded.
2. Essential element concentration below which plant growth becomes stunted.
3. Essential element concentration below which plant remains in the vegetative phase.
4. None of the above