Majority of the nutrients that are essential for the growth and development of plants become available to the roots due to:
1. Microbial actions in the soil
2. Wet deposition from the atmosphere
3. Addition of fertilizers
4. Weathering and breakdown of rocks

To successfully grow a crop in an arid area, the best strategy would be:
1. ensuring an extensive irrigation system
2. using NPK fertilizers liberally
3. selecting crops adapted to arid areas
4. practicing shifting cultivation

A microorganism capable of growing without external sources of fixed nitrogen is called:
1. Diazotroph
2. Auxotroph
3. Prototroph
4. Mixotroph

An agriculture practice based on integration and harmonious mix of environmental health, economic profitability, and social equity is termed as:
1. hydroponics.
2. nutirent fixation.
3. genetic engineering.
4. sustainable agriculture.

Both Rhizobium and Frankia:
1. are symbionts with legumes
2. are symbionts with actinorrhizal plants
3. initiate the formation of root nodules in the symbiont plant
4. are filamentous bacteria

Phytoremediation is:
1. concentrating minerals in rhizosphere.
2. minimizing soil erosion in arid lands.
3. nitrogen fixation by symbiotic bacteria in root nodules.
4. removal of heavy metals from polluted sites.

When nitrates are scarce in the soil where legumes are growing:
I. The plants secrete Nod factors that attract Rhizobia to their root hairs.
II. In turn the bacteria secrete flavonoids that stimulate the infection process in the plant.
1. Both I and II are correct
2. Only I is correct
3. Only II is correct
4. Both I and II are incorrect

The uptake of which of the following by a plant contributes maximum to its dry weight:
1. water and minerals through root hairs.
2. water and minerals through mycorrhizae.
3. carbon dioxide by leaves through stoma.
4. sugars in the root hairs.

All the following regarding bacteroid form of Rhizobium are true except:
1. It is a differentiated symbiotic form of nitrogen fixing Rhizobium
2. It is non-motile and non-reproductive
3. It has a more freely permeable membrane than free living Rhizobium
4. It is larger in size than the free living Rhizobium and spherical in shape

What percentage of the dry weight of a plant is made up of organic molecules?
1. 10%
2. 23%
3. 72%
4. 96%