Assertion: Flooding rapidly depletes available oxygen in the soil and often causes abnormal growth in roots.
Reason: Hormone levels change in flooded plants with a decrease in ethylene levels and an increase of gibberellins and cytokinins.

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

1. If both the assertion and the reason are true and the reason is a correct explanation of the assertion
2. If both the assertion and reason are true but the reason is not a correct explanation of the assertion
3. If the assertion is true but the reason is false
4. If both the assertion and reason are false

Assertion: Deciduous plants are common in areas that periodically experience severe drought.
Reason: In a broad sense, annual plants conserve water when conditions are unfavorable simple by going into dormancy as seeds.

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

In which of the following, all three are macronutrients?
1. Iron, copper, molybdenum
2. Molybdenum, magnesium, manganese
3. Nitrogen, magnesium, phosphorus
4. Boron, zinc, manganese

During biological nitrogen fixation, inactivation of nitrogenase by oxygen poisoning is prevented by
1. leghaemoglobin
2. xanthophyll
3. carotene
4. cytochrome

Deficiency symptoms of nitrogen and potassium are visible first in

The first stable product of fixation of atmospheric nitrogen in leguminous plants is
1. ${\mathrm{NO}}_2^{-}$
2. ammonia
3. ${\mathrm{NO}}_3^{-}$
4. glutamate

A nitrogen fixing microbe associated with Azolla in rice fields is
1. Spirulina
2. Anabaena
3. Frankia
4. Tolypothrix

Nitrifying bacteria
1. convert free nitrogen to nitrogen compounds
2. convert proteins into ammonia
3. reduce nitrates to free nitrogen
4. oxidize ammonia to nitrates

An organism used as a biofertilizer for raising soyabean crop is
1. Azospirillum
2. Rhizobium
3. Nostoc
4. Azotobacter

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