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Mineral Nutrition

Element Toxicity Practice Questions

38 free Element Toxicity practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.

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Question 1 of 38 Medium

Toxicity of mineral elements in plants generally occurs when:

  1. A When an element is completely absent
  2. B When an element exceeds its optimum level
  3. C When only micronutrients are available
  4. D When soil pH remains constantly neutral

Correct answer: When an element exceeds its optimum level

Mineral elements are required only within a specific concentration range. Accumulation beyond the optimum level leads to toxicity and metabolic imbalance in plants.

Question 2 of 38 Medium

Which element commonly shows toxicity symptoms when present in excess as a micronutrient?

  1. A Nitrogen excess
  2. B Phosphorus excess
  3. C Boron excess
  4. D Iron excess

Correct answer: Iron excess

Iron is a micronutrient required only in small amounts. Excess iron interferes with metabolic processes and commonly causes toxicity symptoms in plants.

Question 3 of 38 Medium

One of the earliest visible symptoms of mineral toxicity in plants is:

  1. A Faster flowering
  2. B Chlorosis
  3. C Stronger root tips
  4. D Higher transpiration

Correct answer: Chlorosis

Chlorosis, the yellowing of leaves due to impaired chlorophyll synthesis, is a common early symptom of mineral toxicity. It results from interference with pigment production.

Question 4 of 38 Medium

Excess manganese in soil most commonly leads to toxicity by:

  1. A Directly inhibiting photosynthetic reactions
  2. B Reducing uptake of iron and magnesium
  3. C Stimulating nitrogen fixation in roots
  4. D Promoting elongation of root cells

Correct answer: Reducing uptake of iron and magnesium

High manganese concentrations reduce uptake of iron and magnesium through ionic antagonism. This causes nutritional imbalance and characteristic toxicity symptoms.

Question 5 of 38 Medium

Which of the following elements is toxic to plants even at very low concentrations?

  1. A Potassium
  2. B Calcium
  3. C Cadmium
  4. D Sulphur

Correct answer: Cadmium

Cadmium is a heavy metal with no biological role in plants. Even small amounts can severely disrupt plant metabolism.

Question 6 of 38 Medium

Soil pollution mainly affects mineral nutrition of plants by:

  1. A Increasing availability of all nutrients
  2. B Altering nutrient balance and uptake
  3. C Improving soil aeration
  4. D Enhancing nitrogen fixation

Correct answer: Altering nutrient balance and uptake

Soil pollution disturbs nutrient availability and absorption. Toxic substances interfere with root function and ion uptake.

Question 7 of 38 Medium

Which industrial pollutant commonly leads to heavy metal toxicity in soil?

  1. A Sulfur dioxide gas
  2. B Carbon monoxide gas
  3. C Lead from industrial waste
  4. D Ozone from smog

Correct answer: Lead from industrial waste

Lead is a heavy metal released from industrial processes and vehicular emissions. It accumulates in soil and causes toxicity in plants by disrupting enzymatic and metabolic functions.

Question 8 of 38 Medium

Excess boron in soil primarily affects plants by:

  1. A Reducing enzyme activity
  2. B Enhancing sugar transport
  3. C Increasing leaf expansion
  4. D Improving root nodulation

Correct answer: Reducing enzyme activity

Boron toxicity interferes with enzyme function and cell metabolism. This leads to leaf damage and reduced growth.

Question 9 of 38 Medium

Which symptom is characteristic of heavy metal toxicity in plants?

  1. A Excess flowering
  2. B Leaf necrosis
  3. C Higher chlorophyll
  4. D Faster water uptake

Correct answer: Leaf necrosis

Heavy metal toxicity damages plant tissues and disrupts cellular functions, commonly resulting in necrosis (death of tissue) of leaves.

Question 10 of 38 Medium

Soil polluted with excessive fertilizers may lead to toxicity due to accumulation of:

  1. A Micronutrients only
  2. B Macronutrients only
  3. C Salts and ions
  4. D Organic matter

Correct answer: Salts and ions

Excessive fertilizer use increases salt concentration in soil. This causes ionic imbalance and osmotic stress in plants.

Question 11 of 38 Medium

Which element in excess causes leaf tip and margin burning in plants?

  1. A Nitrogen
  2. B Potassium
  3. C Chlorine
  4. D Magnesium

Correct answer: Chlorine

Chlorine toxicity commonly leads to leaf margin and tip burn. This occurs due to accumulation of chloride ions.

Question 12 of 38 Medium

Toxic levels of aluminium are more common in soils that are:

  1. A Neutral
  2. B Alkaline
  3. C Acidic
  4. D Saline

Correct answer: Acidic

In acidic soils, aluminium becomes more soluble. This increases its uptake and toxicity in plant roots.

Question 13 of 38 Medium

Aluminium toxicity primarily affects which part of the plant?

  1. A Leaves
  2. B Stem
  3. C Roots
  4. D Flowers

Correct answer: Roots

Aluminium toxicity inhibits root growth and function. This reduces water and nutrient absorption.

Question 14 of 38 Medium

Which of the following is a long-term consequence of soil pollution on plant nutrition?

  1. A Temporary wilting
  2. B Reduced soil fertility
  3. C Increased microbial activity
  4. D Improved nutrient cycling

Correct answer: Reduced soil fertility

Soil pollution alters chemical properties of soil. Over time, this leads to reduced fertility and poor crop productivity.

Question 15 of 38 Medium

Which mineral element toxicity can interfere with photosynthesis by damaging chloroplasts?

  1. A Zinc
  2. B Iron
  3. C Copper
  4. D Calcium

Correct answer: Copper

Excess copper damages chloroplast structure and inhibits photosynthesis. It also disrupts enzyme activity.

Question 16 of 38 Medium

The major source of soil pollution affecting mineral nutrition in agricultural fields is:

  1. A Natural weathering of rocks
  2. B Biological nitrogen fixation
  3. C Overuse of agrochemicals
  4. D Periodic crop rotation

Correct answer: Overuse of agrochemicals

Overuse of fertilizers and pesticides introduces toxic substances into the soil. This negatively affects nutrient balance and overall plant health in agricultural fields.

Question 17 of 38 Medium

Which nutrient shows toxicity symptoms similar to deficiency of another nutrient due to antagonism?

  1. A Nitrogen
  2. B Manganese
  3. C Phosphorus
  4. D Calcium

Correct answer: Manganese

Excess manganese interferes with uptake of iron and magnesium through ionic antagonism. This causes symptoms that resemble iron and magnesium deficiencies.

Question 18 of 38 Medium

Toxic accumulation of elements in edible plant parts is a concern mainly because it:

  1. A Reduces transpiration
  2. B Decreases seed size
  3. C Enters the food chain
  4. D Improves crop yield

Correct answer: Enters the food chain

Toxic elements can accumulate in edible plant parts. These toxins enter the food chain and pose health risks to animals and humans.

Question 19 of 38 Medium

Which practice helps reduce the impact of soil toxicity on plants?

  1. A Increasing irrigation frequency
  2. B Balanced fertilizer application
  3. C Continuous monocropping
  4. D Excess pesticide use

Correct answer: Balanced fertilizer application

Balanced fertilizer application prevents excess accumulation of minerals. This helps maintain optimal nutrient levels and avoids toxicity.

Question 20 of 38 Medium

Overall, toxicity of elements highlights the importance of:

  1. A Maximum nutrient supply
  2. B Minimum nutrient use
  3. C Elimination of micronutrients
  4. D Optimum nutrient concentration

Correct answer: Optimum nutrient concentration

Both deficiency and excess of nutrients are harmful to plants. Healthy growth depends on maintaining nutrients within an optimum concentration range.

Question 21 of 38 Medium

Which element in excess commonly causes leaf tip and margin burning?

  1. A Nitrogen
  2. B Potassium
  3. C Chlorine
  4. D Calcium

Correct answer: Chlorine

Excess chlorine can cause leaf tip and margin burning. It affects osmotic balance and cellular integrity.

Question 22 of 38 Medium

Aluminium toxicity is most common in:

  1. A Alkaline soils
  2. B Neutral soils
  3. C Acidic soils
  4. D Saline soils

Correct answer: Acidic soils

Aluminium becomes more soluble and toxic in acidic soils. This affects root development.

Question 23 of 38 Medium

Which of the following is a common source of soil pollution?

  1. A Rainwater
  2. B Excess fertilizers
  3. C Sunlight
  4. D Air movement patterns

Correct answer: Excess fertilizers

Overuse of fertilizers introduces excess nutrients into soil. This leads to toxicity and imbalance.

Question 24 of 38 Medium

Excess boron in soil primarily causes:

  1. A Increased growth
  2. B Leaf necrosis
  3. C Improved photosynthesis
  4. D Root growth

Correct answer: Leaf necrosis

Boron toxicity leads to necrosis of leaf tissues. It affects cell wall structure and metabolism.

Question 25 of 38 Medium

Which element is toxic to plants even at very low concentrations?

  1. A Nitrogen
  2. B Phosphorus
  3. C Mercury
  4. D Calcium

Correct answer: Mercury

Mercury is highly toxic even in trace amounts. It disrupts enzyme activity and cellular processes.

Question 26 of 38 Medium

Which symptom is commonly associated with heavy metal toxicity?

  1. A Rapid growth
  2. B Chlorosis and stunted growth
  3. C Increased flowering
  4. D Enhanced root and shoot growth

Correct answer: Chlorosis and stunted growth

Heavy metal toxicity often causes chlorosis and stunted growth. It interferes with nutrient uptake and metabolism.

Question 27 of 38 Medium

Soil pollution affects plant nutrition mainly by:

  1. A Increasing water availability
  2. B Enhancing photosynthesis
  3. C Reducing temperature
  4. D Disrupting nutrient balance

Correct answer: Disrupting nutrient balance

Polluted soil alters nutrient availability and uptake. This disrupts plant nutrition.

Question 28 of 38 Medium

Which of the following industrial discharges is a common source of heavy metal toxicity?

  1. A Boiler flue gas that is rich in carbon dioxide
  2. B Tannery effluent carrying chromium compounds
  3. C Warm water discharged from a cooling tower
  4. D Sulfur dioxide released while burning coal

Correct answer: Tannery effluent carrying chromium compounds

Heavy metal toxicity comes from effluents that carry the metals themselves. Tannery waste is the classic example — it discharges chromium compounds that build up in soil and water and reach people through crops, fish and drinking water. Carbon dioxide, sulfur dioxide and warm cooling water cause greenhouse warming, acid rain and thermal pollution respectively, but none of them is a heavy metal.

Question 29 of 38 Medium

Excess manganese in soil leads to toxicity by:

  1. A Enhancing photosynthesis
  2. B Increasing root growth
  3. C Improving nutrient uptake efficiency
  4. D Interfering with enzyme activity

Correct answer: Interfering with enzyme activity

Excess manganese disrupts enzyme function. It affects metabolic processes in plants.

Question 30 of 38 Medium

Which nutrient toxicity may mimic deficiency of another nutrient?

  1. A Calcium
  2. B Nitrogen
  3. C Potassium
  4. D Iron ion

Correct answer: Iron ion

Excess iron can interfere with uptake of other nutrients. This creates symptoms similar to deficiency.

Question 31 of 38 Medium

One of the earliest visible symptoms of mineral toxicity is:

  1. A Leaf chlorosis
  2. B Flowering
  3. C Fruit formation
  4. D Seed germination

Correct answer: Leaf chlorosis

Chlorosis is often the first visible symptom. It indicates disruption in chlorophyll synthesis.

Question 32 of 38 Medium

Toxic accumulation of elements in edible plant parts is a concern because it:

  1. A Improves the taste and overall flavor
  2. B Increases plant growth and biomass
  3. C Enhances yield and market value
  4. D Enters food chain and affects health

Correct answer: Enters food chain and affects health

Toxic elements can accumulate in edible parts. This poses health risks when consumed.

Question 33 of 38 Medium

Which of the following helps reduce soil toxicity?

  1. A Crop rotation and soil management
  2. B Excess fertilizer overuse
  3. C Over-irrigation and waterlogging of fields
  4. D Continuous monoculture without crop rotation

Correct answer: Crop rotation and soil management

Proper soil management and crop rotation reduce toxicity. They help maintain nutrient balance.

Question 34 of 38 Medium

Which micronutrient shows toxicity when present in excess?

  1. A Carbon
  2. B Hydrogen
  3. C Oxygen
  4. D Zinc ion

Correct answer: Zinc ion

Zinc is essential in small amounts but toxic in excess. It disrupts enzyme activity.

Question 35 of 38 Medium

Which long-term effect is caused by soil pollution?

  1. A Reduced crop productivity
  2. B Improved fertility
  3. C Enhanced nutrient uptake rate
  4. D Increased biodiversity

Correct answer: Reduced crop productivity

Soil pollution reduces fertility and crop yield. It affects plant growth and health.

Question 36 of 38 Medium

Which of the following best explains mineral toxicity?

  1. A Excess accumulation interfering with metabolism
  2. B Lack of essential nutrients in the growing medium
  3. C Balanced nutrition supporting normal plant growth
  4. D Normal growth under standard soil conditions

Correct answer: Excess accumulation interfering with metabolism

Mineral toxicity occurs when excess nutrients interfere with metabolic processes. It disrupts normal growth.

Question 37 of 38 Medium

Excess fertilizers can lead to toxicity due to accumulation of:

  1. A Salts and nutrients
  2. B Water
  3. C Oxygen
  4. D Carbon dioxide buildup

Correct answer: Salts and nutrients

Excess fertilizers increase salt concentration in soil. This leads to osmotic stress and toxicity.

Question 38 of 38 Medium

Which process is most affected by heavy metal toxicity in plants?

  1. A Photosynthesis
  2. B Respiration
  3. C Transpiration rate
  4. D Growth only

Correct answer: Photosynthesis

Heavy metals damage chloroplasts and enzymes. This directly affects photosynthesis.

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