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. ${\mathrm{K}}^{+}$

Assertion: Negatively charged ions in soils are more easily lost by leaching than positively charged ions.
Reason: Soil particles in most productive soils are positively charged.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Assertion: High acidic soils can present problems for plant growth.
Reason: At low pH, aluminum ions toxicity becomes important.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Assertion: In some cases, sodium may be a ninth essential micronutrient.
Reason: Essential micronutrients are needed by the plants only in tiny quantities.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Assertion: Micronutrients function in plants mainly as cofactors.
Reason: Iron is a metallic component of cytochromes.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Assertion: Iron deficiency in plants can cause chlorosis.
Reason: Iron is a component of chlorophyll.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false