The common nitrogen-fixer in paddy fields is

(1) Frankia

(2) Rhizobium

(3) Azospirillum

(4) Oscillatoria

Which of the following bacteria reduce nitrate in soil into nitrogen?

1. Nitrobacter

2. Thiobacillus

3. Nitrococcus

4. Nitrosomonas

A free living aerobic soil bacterium capable of
fixing nitrogen is
1. Azotobacter

2. Clostridium

3. Rhizobium

4. Streptococcus

Thiobacillus is a group of bacteria helpful in carrying out:

1. Denitrification

2. Nitrogen fixation

3. Chemoautotrophic fixation

4. Nitrification

A plant requires magnesium (Mg) for:

1. holding cells together

2. protein synthesis

3. chlorophyll synthesis

4. cell wall development

Which of the following is responsible for biological nitrogen fixation?

1. Nif gene

2. Nitrogenase

3. Both 1. and 2.

4. RNA synthetase

Which of the following is a non-symbiotic nitrogen fixer organism?

1. VAM

2. Azotobacter

3. Anabaena

4. Rhizobium

Which of the following is a flowering plant with nodules containing filamentous nitrogen-fixing microorganism?

1. Casuarina equisetifolia

2. Crotolaria juncea

3. Cycas revoluta

4. Cicer arietinum

Manganese is required in:
1. nucleic acid synthesis
2. plant cell wall formation
3. photolysis of water during photosynthesis
4. chlorophyll synthesis