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ICAR JRF Soil and Plant Nutrition — practice questions — page 2

Explore 44 free Soil and Plant Nutrition questions in ICAR JRF Plant Sciences. Open each question or exercise to read its content, reference answers and available explanation.

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Soil and Plant Nutrition questions and exercises with answers

Showing questions 31–44 of 44.

Why can plants not use atmospheric dinitrogen directly?Read the answer and worked solution →Biological nitrogen fixation is carried out exclusively by which organisms?Read the answer and worked solution →Biological processes contribute what share of the nitrogen used in agriculture?Read the answer and worked solution →Which enzyme reduces atmospheric nitrogen to ammonia inside a root nodule?Read the answer and worked solution →Soil bacteria that form nodules on legume roots are collectively called what?Read the answer and worked solution →Through mycorrhization, which nutrients does the plant mainly obtain?Read the answer and worked solution →What share of the total carbon accessed by plants can mycorrhizal fungi obtain?Read the answer and worked solution →Endomycorrhizae are found in the roots of what proportion of terrestrial plants?Read the answer and worked solution →Which term describes a parasitic plant that is fully photosynthetic and uses its host only for water and minerals?Read the answer and worked solution →About how many species of parasitic plants are there?Read the answer and worked solution →How do most saprophytic plants actually obtain their food?Read the answer and worked solution →In a lichen, what does the algal partner contribute?Read the answer and worked solution →Which two root types does an epiphyte have?Read the answer and worked solution →What do the minerals obtained from trapped insects compensate for in a Venus flytrap?Read the answer and worked solution →

Worked practice questions

Why can plants not use atmospheric dinitrogen directly?

  1. Their roots cannot absorb any gas from soil
  2. They lack the enzymes to convert it usefully
  3. Their stomata are shut whenever nitrogen is high
  4. They can only absorb nitrogen bound to carbon
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Correct answer: B. They lack the enzymes to convert it usefully

1. Atmospheric nitrogen, the diatomic molecule known as dinitrogen, is the largest pool of nitrogen in terrestrial ecosystems. 2. Plants cannot take advantage of it because they lack the enzymes needed to convert it into biologically useful forms. 3. Nitrogen can instead be fixed, meaning converted to ammonia, by biological, physical or chemical processes. 4. The ammonia that results can be transported into plant tissue and built into amino acids and then proteins. 5. Nitrogen matters because it is part of nucleic acids and proteins, so a plant cut off from it cannot grow. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 31 "Soil and Plant Nutrition", section 31.3 Nutritional Adaptations of Plants_

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Biological nitrogen fixation is carried out exclusively by which organisms?

  1. Legume root cells
  2. Mycorrhizal fungi
  3. Soil invertebrates
  4. Prokaryotic microbes
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Correct answer: D. Prokaryotic microbes

1. Biological nitrogen fixation is the conversion of atmospheric nitrogen into ammonia. 2. It is carried out exclusively by prokaryotes, such as soil bacteria or cyanobacteria. 3. The legume itself does not fix nitrogen, it houses the bacteria that do, which is why legume root cells are the trap here. 4. Mycorrhizal fungi are eukaryotes and their role is mineral uptake, chiefly phosphate, rather than nitrogen fixation. 5. Soil invertebrates contribute to soil structure but take no part in fixation. 6. The most important source of this fixation is the symbiotic interaction between soil bacteria and legume plants. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 31 "Soil and Plant Nutrition", section 31.3 Nutritional Adaptations of Plants_

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Biological processes contribute what share of the nitrogen used in agriculture?

  1. 25 percent
  2. 45 percent
  3. 65 percent
  4. 85 percent
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Correct answer: C. 65 percent

1. Nitrogen reaches crops either through biological fixation or through chemical fertiliser. 2. Biological processes contribute 65 percent of the nitrogen used in agriculture. 3. That leaves the remainder to industrial routes, which draw on a nonrenewable resource such as natural gas. 4. So biological fixation is the majority contributor, which rules out the two values below half. 5. Using rhizobia is therefore a natural and environmentally friendly way to fertilise plants. 6. It also leaves some biologically available nitrogen in the soil after the crop, which is why legumes feature in rotations. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 31 "Soil and Plant Nutrition", section 31.3 Nutritional Adaptations of Plants_

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