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 Multiple Choice QuestionsMultiple Choice Questions

71.

Heterocysts in Anabaena is helpful in

  • secondary growth

  • nitrogen-fixation

  • ion uptake

  • gaseous exchange


72.

The statement given below are the deficiency symptoms of a certain element. Identify the element with the help of options that follow.

I. Stunted growth

II. Tissue necrosis

III. Curling appear first in young leaves

IV. Premature flower abscission

Choose the correct option

  • magnesium

  • boron

  • calcium

  • nitrogen


73.

The nitrifying bacteria that convert the ammonia to nitrates are

  • Nitrosomonas and Nitrobacter

  • Azotobacter

  • Rhizobium sp.

  • Thiobacillus denitrificans


74.

Insectivorous plant is

  • Cuscuta

  • Drosera

  • Striga

  • None of the above


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75.

Nodules with nitrogen-fixing bacteria are found in

  • cotton

  • gram

  • mustard

  • wheat


76.

Mycorrhiza is an example of

  • endoparasitism

  • decomposers

  • symbiotic relationship

  • ectoparasitism


77.

A metal ion involved in stomatal regulation is :

  • iron

  • potassium

  • zinc

  • magnesium


78.

The plant ash is an indication of :

  • organic matter of plant

  • waste product

  • mineral salts absorbed by plants

  • none of these


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79.

Hydroponics is

  • cultivation of plants in water

  • growth of plants towards water

  • growth of plants away from water

  • soil less cultivation of plants


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80.

When one element is involved in opening and closing of stomata, the other helps to maintain the ribosome  structure. They are

  • Potassium and calcium

  • Phosphorus and sulphur

  • Potassium and magnesium

  • Iron and magnesium

  • Iron and magnesium


C.

Potassium and magnesium

Magnesium is absorbed by plants in the form of divalent Mg2+. It activates the enzymes of respiration, photosynthesis and are involved in the synthesis of DNA and RNA. It is a constituent of the ring structure of chlorophyll and helps to maintain the ribosome structure.

Potassium is absorbed as potassium ion (K+). It helps to maintain an anion-cation balance in cells and is involved in protein synthesis, opening and closing of stomata,
activation of enzymes and in the maintenance of the turgidity of cells.


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