Frequently Asked Questions
Free-living nitrogen fixing aerobic bacterium is
A: Rhodospirillum
B: Anabaena
C: Nostoc
D: Beijerinckia
E: Rhizobium
Solution:
Explanation
- The free-living nitrogen-fixing aerobic bacterium is Beijerinckia. It is free-living and can fix nitrogen under aerobic conditions, with the help of the nitrogenase enzyme.
- The nitrogen-fixing bacteria are mostly prokaryotic which can use atmospheric nitrogen and change it into usable forms like ammonia, nitrates, and nitrites.
- Rhodospirillum is a facultative anaerobe, thus, depending upon the availability of oxygen, it can either undergo aerobic respiration or alcoholic fermentation.
- Anabaena is a filamentous bacterium (cyanobacteria), which is free-living or forms a symbiotic association with Azolla (water fern) and has heterocyst cells for nitrogen fixation.
- Nostoc is unicellular cyanobacteria that are found either free-living or live in symbiotic association; for example, coralloid roots of cycas contain symbiotic cyanobacteria Nostoc.
- Rhizobium is a nitrogen-fixing bacteria, commonly found in the root nodules of leguminous plants and fixes nitrogen under anaerobic conditions.
Final Answer
Hence, the correct option is D i.e., Beijerinckia
In Mirabilis the roots are
A: Tuberous
B: Conical
C: Epiphytic
D: Nodulose
Solution:
Explanation
- In Mirabilis the roots are tuberous. Tuberous roots are large, thick, and fleshy, with no definite shape, specialized for storing food.
- So, tuberous roots are thickened secondary roots formed near the base of the root and are common in the plants like dahlia, and sweet potatoes including Mirabilis.
- Conical roots, as the same suggests are conical shaped, stores food e.g., carrot, these are widest at the top and gradually tapers towards the bottom part. Thus, option B is incorrect.
- Epiphytic plants or the epiphytes are the plants that grow on another plant for support only, and are sometimes termed “air plants”. Epiphytes possess epiphytic roots e.g. Orchids.
- Nodulose roots, for example in ginger, are swollen at the apex part, because of the accumulation of food.
Final Answer
Hence, the correct answer is A (Tuberous roots).
Sonora - 64 and Lerma Rojo - 64 were brought to India from Mexico and modified through
A: UV rays
B: X rays
C: beta rays
D: gamma rays
Solution:
Explanation:
- Sonora - 64 and Lerma Rojo - 64 are mutant dwarf varieties of wheat that were developed in Mexico and later are modified through gamma rays to produce a beneficial mutant.
- These varieties are high-yielding and also have other benefits such as resistance to diseases and lodging.
Final Answer: Hence, the correct answer is (D) gamma rays.
Water containing cavities in vascular bundles are found in
A: Sunflower
B: Maize
C: Cycas
D: Pinus
Solution:
Explanation:
Water containing cavities are formed by the disintegration of parenchyma and inner protoxylem vessels.
These cavities are known as lysigenous cavities.
They are only present in monocot plants.
Sunflower is a dicot plant, so it does not have lysigenous cavities.
Maize is a monocot plant, so it does not have lysigenous cavities.
Cycas has two cotyledons but it is not considered a dicot.It also does not have lysigenous cavities.
Pinus are also neither monocots nor dicots.
Final answer:
The correct answer is maize, i.e option (B).
What is cladode
Solution:
Explanation:
Cladodes are also known as phylloclades.
They arise as a green, flattened structure from the stem.
They are the aerial modifications of the stem.
They are photosynthetic in nature and function as leaves.
They have a single internode.
Final answer:
Hence, this is the definition of cladode.
