An element playing important role in nitrogen fixation is
1. molybdenum
2. copper
3. manganese
4. zinc

Which one of the following is not a micronutrient?
1. Molybdenum
2. Magnesium
3. Zinc
4. Boron

The free-living, anaerobic nitrogen-fixer is
1. Beijerinckia
2. Rhodospirillum
3. Rhizobium
4. Azotobacter

A plant requires magnesium for

Farmers in a particular region were concerned that pre-mature yellowing of leaves of a pulse crop might cause decrease in the yield. Which treatment could be most beneficial to obtain maximum seed yield?
1. Frequent irrigation of the crop
2. Treatment of the plants with cytokinins along with a small dose of nitrogenous fertilizer
3. Removal of all yellow leaves and spraying the remaining green leaves with 2, 4, 5 trichlorophenoxy acetic acid
4. Application of iron and magnesium to promote synthesis of chlorophyll

Sulphur is an important nutrient for optimum growth and productivity in:
1. pulse crops
2. cereals
3. fibre crops
4. oilseed crops

If by radiation, all nitrogenase enzymes are inactivated, then there will be no
1. Fixation of atmospheric nitrogen
2. Conversion from nitrate to nitrite in legumes
3. Conversion from ammonium to nitrate in soil
4. Fixation of nitrogen in legumes

Study the cycle shown below and select the option which gives correct words for all the four blanks A, B, C and D:
            

Leguminuous plants are able to fix atmoshpheric nitrogen through the process of symbiotic nitrogen fixation. Which one of the following statement is not correct during this process of nitrogen fixation ?
1. Nodules act as sites for nitrogen fixation
2. The enzyme nitrogenase catalyses the conversion of atmospheric N₂ to NH₃
3. Nitrogenase is insensitive to oxygen
4. Leghamoglobin scavenges oxygen and pinkish in color.

The most abundant intracellular cation is:
1. ${\mathrm{Na}}^{+}$
2. ${\mathrm{Ca}}^{++}$
3. ${\mathrm{H}}^{+}$
4. ${\mathrm{K}}^{+}$