Question of Exercise 1

Plant Growth And Development of Class 11

Xanthium is an example of :


Option 1 LDP

Option 2 SDP

Option 3 DNP

Option 4 None of these

Frequently Asked Questions

Free-living nitrogen fixing aerobic bacterium is

A: Rhodospirillum

B: Anabaena

C: Nostoc

D: Beijerinckia

E: Rhizobium



  • 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



  • 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



  • 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



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



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. 

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