Plant Nutrition

Plant Nutrition is part of Biology. Below are notes on 12 sub-topics, followed by practice MCQs from State PSC and UPSC papers.

Deficiency Symptoms of Specific Nutrients

• Zinc (Zn) deficiency: Causes White Bud disease, White tip of maize leaves, and 'Little leaf' (e.g., in cotton).
• Potassium (K) deficiency: Leads to yellow leaves with dead spots and petal burn (e.g., in Chrysanthemum).
• Nitrogen (N) deficiency: Results in buttoning in cauliflower, general yellowing, and poor plant growth.

Essential Mineral Elements: Criteria for essentiality and classification

• Criteria for Essentiality (Arnon & Stout, 1939):
• Element is absolutely necessary for normal growth and reproduction.
• Deficiency of the element causes specific symptoms which can only be corrected by supplying that particular element.
• The element must be directly involved in the metabolism of the plant.
• Its function cannot be replaced by any other element.
• Classification of Essential Elements (Based on Quantitative Requirement):
• Macronutrients:
• Required in amounts generally in excess of 10 mmol kg⁻¹ of dry matter.
• Examples: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Sulfur (S).
• Nitrogen (N), Phosphorus (P), and Potassium (K) are primary macronutrients commonly found in fertilizers.
• Micronutrients (Trace Elements):
• Required in amounts generally less than 10 mmol kg⁻¹ of dry matter.
• Examples: Iron (Fe), Manganese (Mn), Copper (Cu), Zinc (Zn), Boron (B), Molybdenum (Mo), Chlorine (Cl), Nickel (Ni).
• Iron (Fe) is a micronutrient.
• General Functions of Essential Elements (in plants):
• Involved in metabolic processes.
• Facilitate energy transformations.
• Influence permeability of cellular membranes.
• Crucial for normal growth and reproduction.

Factors Affecting Nutrient Availability in Soil

• Plants primarily receive their nutrients from the soil.
• Soil pH: Significantly affects the solubility and availability of most nutrients. Alkalinity indicates a soil's or water's buffering capacity and resistance to pH changes.
• Soil Texture: Influences water retention, aeration, and nutrient-holding capacity. Clay loam, silty clay, and silty clay loam are suitable for fish ponds due to good water retention.
• Soil Mineral Composition: Clay minerals (e.g., Kaolinite is dominant in red soil) contribute to Cation Exchange Capacity (CEC), affecting nutrient retention.
• Organic Matter Content: Improves soil structure, water holding capacity, and acts as a reservoir for essential nutrients, slowly releasing them upon decomposition.
• Microbial Activity: Soil microbes (e.g., decomposers, nitrogen-fixing bacteria like Rhizobia, mycorrhizal fungi) facilitate nutrient cycling and absorption by plants.
• Phosphorus is essential for better rhizobial nitrogen fixation.
• Soil Aeration: Adequate oxygen is crucial for root respiration and the activity of beneficial aerobic microbes, impacting nutrient uptake.
• Water Availability: Water acts as the solvent and transport medium for nutrients from the soil to the plant roots.
• Soil Salinity: High salt concentrations can negatively impact water and nutrient uptake by plants. Sugarbeet is a high salt-tolerant crop.

Hydroponics: Principles and applications in nutrient studies

• Hydroponics is a method of growing plants without soil.
• Plants are grown in mineral nutrient solutions dissolved in water.
• It is also known as soil-less culture or soilless agriculture/cultivation.

Macronutrients: Role, uptake, and deficiency symptoms

• Macronutrients: Required in large quantities (>10 mmol/kg dry matter).
• Primary Macronutrients (NPK): Nitrogen (N), Phosphorus (P), Potassium (K).
• Secondary Macronutrients: Calcium (Ca), Magnesium (Mg), Sulfur (S).
• Other Macronutrients (Structural): Carbon (C), Hydrogen (H), Oxygen (O).
• Nitrogen (N):
• Role: Essential for proteins, nucleic acids (DNA/RNA), vitamins, hormones, chlorophyll. Drives overall growth & development.
• Uptake: Primarily as NO3- and NH4+.
• Deficiency: Stunted growth, chlorosis (yellowing) of older leaves. Soil Ndeficiency leads to insectivorous plant adaptations.
• Phosphorus (P):
• Role: Component of cell membranes, nucleic acids, ATP. Crucial for energy transfer, root development.
• Uptake: H2PO4- or HPO4^2-.
• Deficiency: Stunted growth, dark green/purplish coloration of leaves, delayed flowering.
• Potassium (K):
• Role: Regulates stomatal opening/ closing, maintains turgor/water balance, activates over 60 enzymes. Not a structural component of organic molecules.
• Uptake: K+.
• Deficiency: Yellowing/scorching (necrotic spots) along leaf margins, weak stems, increased disease susceptibility.
• Calcium (Ca):
• Role: Component of cell walls (calcium pectate), essential for membrane function, mitotic spindle formation. Immobile in phloem.
• Uptake: Ca2+.
• Deficiency: Necrosis of young leaves/ bud, distorted growth, "blossom end rot" in fruits.
• Magnesium (Mg):
• Role: Central atom in chlorophyll molecule. Activator of many enzymes (respiration, photosynthesis, DNA/RNA synthesis).
• Uptake: Mg2+.
• Deficiency: Interveinal chlorosis (yellowing between veins) of older leaves.
• Sulfur (S):
• Role: Component of amino acids (cysteine, methionine), vitamins (thiamine, biotin), coenzymes (Coenzyme A).
• Uptake: SO4^2-.
• Deficiency: Yellowing of young leaves (immobile in phloem), stunted growth.
• Iron (Fe): (Micronutrient, but crucial for chlorophyll synthesis)
• Role: Essential for chlorophyll formation (though not a structural component), electron transport (cytochromes, ferredoxins).
• Uptake: Fe3+ or Fe2+.
• Deficiency: Interveinal chlorosis of young leaves (immobile).
• Boron (B): (Micronutrient)
• Role: Involved in cell elongation & differentiation, cell wall formation, sugar transport, pollen germination.
• Note: Not primarily responsible for disease resistance as a direct role.

Mechanisms of Mineral Absorption: Active and passive transport

• Mineral absorption in plants occurs via both active and passive transport mechanisms.
• Passive Transport: Movement of ions down a concentration gradient (from higher to lower concentration) without the expenditure of metabolic energy (ATP).
• Active Transport: Movement of ions against a concentration gradient (from lower to higher concentration), requiring metabolic energy (ATP) and specific membrane proteins (pumps).
• Active absorption enables plants to absorb nutrients from a lowly concentrated soil solution and accumulate them in the more concentrated plant sap.
• Most of the water and mineral nutrients absorbed by plant roots are primarily through root hairs, which provide a large surface area.

Metabolism of Phosphorus, Potassium, and Sulphur

• Phosphorus (P): Absorbed as H2PO4- and HPO4^2-. Constituent of cell membranes, nucleic acids (DNA, RNA), nucleotides (ATP, ADP). Essential for energy transfer and phosphorylation reactions.
• Potassium (K): Absorbed as K+. Crucial for opening and closing of stomata, maintaining turgor pressure, activating many enzymes, and maintaining anion-cation balance in cells. Required in meristematic tissues.
• Sulphur (S): Absorbed as SO4^2- (sulphate ion). Constituent of amino acids (cysteine, methionine), and vitamins (thiamine, biotin, Coenzyme A). Gypsum (Calcium Sulphate) is a common source, providing Sulphur to plants.

Micronutrients: Role, uptake, and deficiency symptoms

• Micronutrients (Trace Elements): Required by plants in very small amounts (typically < 10 mmol/kg of dry matter).
• Essential Micronutrients: Iron (Fe), Manganese (Mn), Copper (Cu), Zinc (Zn), Boron (B), Molybdenum (Mo), Chlorine (Cl), Nickel (Ni).
• Macronutrients: Required in larger amounts (e.g., Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Sulfur (S)).
• Magnesium (Mg): A macronutrient; central metal atom of the chlorophyll molecule, essential for photosynthesis.
• Iron (Fe): A micronutrient; required for chlorophyll synthesis and electron transport.
• Zinc (Zn): A micronutrient; essential for enzyme activation and auxin synthesis.
• Sodium (Na): Not universally an essential micronutrient for all plants; essential for some halophytes and C4 plants.
• Oxygen (O), Hydrogen (H): Essential elements, primarily obtained from water (H2O) and atmospheric O2; not classified as macro or micronutrients in the same context as soilderived elements.
• Nitrogen (N): An essential macronutrient.
• Pungency in Garlic: Primarily due to Diallyl disulfide.
• Lycopene: A red pigment found in fruits/ vegetables like tomato.
• Seaweeds: Important natural source of Iodine.

Mineral Toxicity and its effects

• Mineral toxicity occurs when the concentration of an essential element in plant tissues exceeds a critical level, typically causing a 10% reduction in dry weight.
• High mineral concentrations can inhibit enzyme activity, damage cell organelles, interfere with essential nutrient uptake, and induce oxidative stress.
• Common symptoms of mineral toxicity include chlorosis (yellowing), necrosis (tissue death), stunted growth, leaf deformation, and reduced root development.
• Miconia lutescens is a known iron (Fe) metallophyte, demonstrating tolerance and hyperaccumulation capabilities for high concentrations of iron.
• Metallophytes are plant species adapted to grow in soils with elevated concentrations of heavy metals; some are hyperaccumulators and are valuable for phytoremediation.
• Plant mechanisms to cope with mineral toxicity include:
• Exclusion: Preventing uptake of the toxic ion by roots.
• Sequestration: Binding toxic ions to cell wall components or within specific proteins.
• Compartmentalization: Storing toxic ions in vacuoles or other non-metabolic compartments.
• Chelation: Forming complexes with organic acids (e.g., citrate, malate) or phytochelatins to detoxify or transport metals.
• Antioxidant Defense: Producing enzymes (e.g., superoxide dismutase, catalase) to counteract oxidative damage.

Nitrate Assimilation and Ammonification

• Plants primarily absorb Nitrogen as Nitrate (NO₃⁻) and also as Ammonium (NH₄⁺).
• Nitrate Assimilation:
• Process where absorbed Nitrate (NO₃⁻) is reduced to Ammonium (NH₄⁺) within plant cells.
• Nitrate Reductase enzyme catalyzes the reduction of Nitrate (NO₃⁻) to Nitrite (NO₂⁻).
• Nitrite Reductase enzyme catalyzes the reduction of Nitrite (NO₂⁻) to Ammonium (NH₄⁺).
• The resulting Ammonium (NH₄⁺) is rapidly incorporated into amino acids and other organic compounds.
• Ammonification:
• Process of decomposition of dead organic nitrogenous matter (e.g., proteins, nucleic acids from dead plants, animals, and waste products) by diverse soil microorganisms (bacteria, fungi).
• Result: Release of Ammonia (NH₃), which in the soil solution rapidly protonates to form Ammonium ions (NH₄⁺).
• Mineralization:
• Broader process involving the degradation of organic compounds by microorganisms, releasing inorganic nutrients (e.g., NH₄⁺, PO₄³⁻, SO₄²⁻) into the soil.
• Ammonification is a crucial step in the mineralization of organic nitrogen.
• This process makes nutrients available for plant uptake.
• Organic manures (e.g., FYM, compost, vermicompost, neem cake) are sources of organic nitrogen which undergoes ammonification and mineralization, eventually supplying plants with usable inorganic nitrogen forms like Ammonium and Nitrate.

Nitrogen Cycle and Nitrogen Fixation

• Nitrogen Cycle: Converts atmospheric nitrogen (N₂) into usable forms (ammonia, nitrates) and recycles it back to the atmosphere.
• Atmospheric Nitrogen (N₂) is approximately 78% of the atmosphere but is largely unusable by most organisms directly.
• Nitrogen Fixation: Process of converting atmospheric N₂ into ammonia (NH₃).
• Biological Nitrogen Fixation:
• Symbiotic: Rhizobium bacteria reside in root nodules of leguminous plants (e.g., peas, beans, clover), converting N₂ into ammonia (NH₃) for the plant.
• Free-living: Bacteria like Azotobacter, Clostridium, and cyanobacteria (bluegreen algae) like Nostoc, Anabaena fix nitrogen independently in soil or water.
• Atmospheric Nitrogen Fixation: During atmospheric lightning, N₂ is converted into oxides of nitrogen (NOx), which dissolve in rainwater to form nitrates (NO₃⁻) and fall to earth.
• Industrial Nitrogen Fixation: Haber-Bosch process used to produce ammonia for fertilizers.
• Ammonification: Decomposition of organic nitrogenous compounds (e.g., proteins, nucleic acids from dead organisms, waste products) into ammonia (NH₃) or ammonium ions (NH₄⁺) by decomposer bacteria and fungi.
• Nitrification: A two-step aerobic process where ammonia (NH₃) is converted to nitrates (NO₃⁻).
• Step 1: Ammonia (NH₃) is oxidized to Nitrite (NO₂⁻) by nitrifying bacteria like Nitrosomonas and Nitrococcus.
• Step 2: Nitrite (NO₂⁻) is further oxidized to Nitrate (NO₃⁻) by bacteria like Nitrobacter.
• Nitrates (NO₃⁻) are the primary form of nitrogen absorbed by plants from the soil.
• Assimilation: Plants absorb nitrates (NO₃⁻) or ammonium ions (NH₄⁺) and convert them into organic nitrogen compounds like amino acids, proteins, and nucleic acids. Animals obtain nitrogen by consuming plants or other animals.
• Denitrification: An anaerobic process where nitrates (NO₃⁻) in the soil are converted back into gaseous atmospheric nitrogen (N₂) by denitrifying bacteria (e.g., Pseudomonas, Thiobacillus), returning nitrogen to the atmosphere.
• Importance of Nitrogen: It is a vital component of all living organisms, forming part of proteins, nucleic acids (DNA and RNA), ATP, chlorophyll, and enzymes.

Symbiotic Nitrogen Fixation: Nodule formation and biochemistry

• Symbiotic nitrogen fixation involves the conversion of atmospheric nitrogen (N2) into usable forms like ammonia (NH3), nitrites, and nitrates by microorganisms.
• This process primarily occurs in specialized structures called root nodules, formed on the roots of host plants.
• Leguminous plants are the primary hosts for symbiotic nitrogen-fixing bacteria (e.g., Rhizobium).
• Examples of common nitrogen-fixing leguminous plants include: Gram, Pea, Bean (Common Beans), Soybean, Peanut, Alfalfa, Chickpea, Clover, and Moong.
• Some plants, despite being pulses/legumes, show negligible or no significant symbiotic nitrogen fixation; Rajma (Kidney Bean) is a notable example.
• Plants generally not involved in symbiotic nitrogen fixation (in the context of root nodules) include: Paddy (rice), Oats, Amaranth, Purslane (Kulfa), and Spinach.
• More than 90% of all nitrogen fixed by soil microorganisms is converted into ammonia, nitrites, and nitrates.

20. Plant Hormones

Practice MCQs: Plant Nutrition

Deficiency Symptoms of Specific Nutrients

1. Which set of vegetables is underground stem or modified stem of a plant?

   Asked in: UPSC CDS 1 2024

   1. Potato, artichoke, round gourd
   2. Onion, garlic, carrot
   3. Potato, onion, garlic
   4. Potato, garlic, turnip
   Show answer

   Answer: C. Potato, onion, garlic

   Potato, onion, and garlic are examples of vegetables that are modified underground stems adapted for storage or reproduction.

2. White Bud disease in plant is caused by deficiency of

   Asked in: JPSC CS Prelims 2016

   1. Zinc
   2. Copper
   3. Boron
   4. Manganese
   Show answer

   Answer: A. Zinc

   Chlorophyll is the primary pigment responsible for photosynthesis in plants and is the reason why most plant leaves appear green.

3. The green colour of a plant leaf is due to

   Asked in: TOURIST INFORMATION OFFICER(TIO) 2017

   1. chlorophyll
   2. mitochondria
   3. embryonic fluid
   4. photosynthesis
   Show answer

   Answer: A. chlorophyll

   Chlorophyll is the pigment responsible for the green colour of plant leaves and is crucial for photosynthesis. - Zinc is a crucial micronutrient for plant growth, playing vital roles in enzyme systems, protein synthesis, and growth regulation. - Deficiency symptoms often appear in young leaves and meristematic tissues.

4. A plant having yellow leaves with dead spots has the deficiency of

   Asked in: UPSC NDA 2 2016

   1. Potassium
   2. Magnesium
   3. Nitrate
   4. Phosphate
   Show answer

   Answer: A. Potassium

   Potassium (K) is a mobile nutrient in plants. Deficiency symptoms typically appear first in older leaves because the plant translocates potassium to younger, growing tissues. Common symptoms of potassium deficiency include chlorosis (yellowing) along the margins and tips of older leaves, which progresses inwards. As the deficiency worsens, these yellow areas often develop into necrotic spots (dead tissue), giving the appearance of scorched or brown margins and tips.

5. Which of the following is an insectivorous plant?

   Asked in: UPPCS Prelims 2023

   1. Nepenthes
   2. Nelumbo
   3. Nyctanthes
   4. Nicotiana
   Show answer

   Answer: A. Nepenthes

   - Insectivorous plants grow in nutrient-poor soils, especially lacking nitrogen. - They trap insects using various mechanisms, such as pitchers (Nepenthes), sticky traps, snap traps, etc.

6. White tip of maize leaves indicates the deficiency of

   Asked in: UPPSC Upper Mains 2010

   1. Fe
   2. Mn
   3. N
   4. Zn
   Show answer

   Answer: D. Zn

   Nutrient deficiencies cause specific symptoms in plants, which can help identify the missing element.

7. Buttoning in cauliflower is caused due to deficiency of which nutrient ?

   Asked in: Agri. Officer 2020

   1. Potassium
   2. Phosphorus
   3. Nitrogen
   4. Calcium
   Show answer

   Answer: A. Potassium

   Nutrient deficiencies in crops often lead to specific physiological disorders. This question focuses on a specific disorder in cauliflower and its causative nutrient.

8. ‘Little leaf’ of cotton occurs due to the deficiency of which nutrient ?

   Asked in: Agri. Officer 2020

   1. Mn
   2. Zn
   3. B
   4. Ca
   Show answer

   Answer: B. Zn

   This question focuses on micronutrient deficiencies in cotton and their characteristic symptoms, specifically the 'little leaf' disorder.

Essential Mineral Elements: Criteria for essentiality and classification

9. Which one of the following nutrients is *not* available in fertilizers?

   Asked in: UPSC CISF AC EXE 2020

   1. Iron
   2. Nitrogen
   3. Phosphorus
   4. Potassium
   Show answer

   Answer: A. Iron

   While all options are plant nutrients and can be found in fertilizers, Nitrogen, Phosphorus, and Potassium are the primary macronutrients (needed in large quantities) and form the basis of most common fertilizers. Iron is a micronutrient (needed in smaller quantities).

10. With reference to 'earthworms', which of the following statements is/are correct? 1. Earthworms improves soil fertility and are known as farmer's friends. 2. Earthworm has two pair of hearts. Select the correct answer from the code given below : Code :

    Asked in: uppsc 2025 2025

    1. Only 2
    2. Both 1 and 2
    3. Neither 1 nor 2
    4. Only 1
    Show answer

    Answer: D. Only 1

11. This statement is correct. Earthworms play a crucial role in soil aeration, drainage, and nutrient cycling through their burrowing and waste-excreting activities, thus improving soil fertility. They are often referred to as "farmers' friends" due to their beneficial impact on agriculture. 2. This statement is incorrect. An earthworm has not two pairs, but rather four pairs of seminal vesicles, and it possesses five pairs of aortic arches, which are often colloquially referred to as "hearts". So, it has five "hearts" (aortic arches) rather than two pairs. 12. For the below Assertion and Reason, choose the correct alternative : Assertion (A) : Commonly, there are 20 recognized macro and micro inorganic elements in fish body. Reason (R) : Essential functions of inorganic elements are metabolism, bone formation, blood clotting, muscle function, impulse transmission, energy transformation, permeability of cellular membrane, genetic coding & control of reproduction and growth. - Question not attempted

    Asked in: Asst. Fisheries Development Officer 2024

    1. Both (A) and (R) are individually true and (R) is correct explanation of (A).
    2. Both (A) and (R) are individually true, but (R) is not correct explanation of (A).
    3. (A) is true, but (R) is false.
    4. (A) is false, but (R) is true.
    Show answer

    Answer: A. Both (A) and (R) are individually true and (R) is correct explanation of (A).

    Assertion (A) is correct: Fish bodies contain numerous inorganic elements, broadly categorized into macro (major) and micro (trace) elements, essential for various physiological functions. Reason (R) accurately lists the critical roles these inorganic elements play in fish physiology, including metabolism, structural integrity (bone formation), cellular processes, and overall growth and reproduction. These essential functions directly explain why these inorganic elements are recognized as important components of the fish body.

12. Assertion (A) : Mahua oil cake is used for manuring as well as an effective agent for eradication of predatory and weed fishes. Reason (R) : Mahua oil cake contains Rotenone (about 4-6%) which is an effective fish poison. Choose the correct answer : - Question not attempted

    Asked in: Asst. Fisheries Development Officer 2024

    1. Both (A) and (R) are true and (R) is a correct explanation of (A).
    2. Both (A) and (R) are true, but (R) is not a correct explanation of (A).
    3. (A) is true, but (R) is false.
    4. (A) is false, but (R) is true.
    Show answer

    Answer: A. Both (A) and (R) are true and (R) is a correct explanation of (A).

    Assertion (A) is true: Mahua oil cake is indeed used for pond manuring to enhance fertility and productivity, and it also acts as an effective piscicide for removing unwanted predatory and weed fish before stocking. Reason (R) is also true and provides the correct explanation: Mahua oil cake contains rotenone (a naturally occurring compound), which is a potent fish poison. Rotenone disrupts cellular respiration in fish, leading to their death. The presence of rotenone is the direct mechanism by which Mahua oil cake functions as a fish poison, thus explaining its use for eradicating fish.

Factors Affecting Nutrient Availability in Soil

13. Plants receive their nutrients mainly from

    Asked in: BPSC Prelims Exam 67th Re Exam

    1. atmosphere
    2. light
    3. soil
    4. chlorophyll
    Show answer

    Answer: C. soil

    Plants absorb water and dissolved mineral nutrients (such as nitrogen, phosphorus, potassium, etc.) from the soil through their roots. While plants obtain carbon and oxygen from the atmosphere (as CO2 and O2) and energy from light, the essential elements needed for growth and structure (the mineral nutrients) are primarily derived from the soil.

14. Which chemical fertilizer is essential for better rhizobial nitrogen fixation?

    Asked in: GPSC Prelims CSP 2 2024

    1. Calcium
    2. Potassium
    3. Sodium
    4. Phosphorus
    Show answer

    Answer: D. Phosphorus

    - Rhizobium bacteria form a symbiotic relationship with legumes, fixing atmospheric nitrogen into a usable form for the plant. - This nitrogen fixation process is highly energy-intensive, requiring a significant supply of ATP (adenosine triphosphate). - Phosphorus (P) is a key component of ATP and plays a vital role in energy transfer within cells. Adequate phosphorus levels are essential for the metabolic activities of both the host plant and the rhizobia, including nodule formation and the enzymatic processes involved in nitrogen fixation.

15. Plants receive nutrients from

    Asked in: WBPSC CS Prelims 2020

    1. atmosphere
    2. chlorophyll
    3. soil
    4. light
    Show answer

    Answer: C. soil

    Soil is the primary source of mineral nutrients for plants.

16. Which of the following clay mineral is dominant in red soil ?

    Asked in: Agri. Officer 2020

    1. Illite
    2. Smeetite
    3. Mica
    4. Kaolinite
    Show answer

    Answer: D. Kaolinite

    This question tests knowledge of soil science, specifically the mineralogical composition of different soil types, particularly red soils.

17. Parameter that indicates the water's buffering capacity and resistance to pH changes - Question not attempted

    Asked in: Asst. Fisheries Development Officer 2024

    1. Dissolved oxygen
    2. Hardness
    3. Alkalinity
    4. Ammonia
    Show answer

    Answer: C. Alkalinity

    Buffering capacity is the ability of a water body to resist changes in pH.

18. A list of some soil textures is given below: A. Clay loam B. Silty clay C. Sandy clay D. Silty clay loam Which of these are suitable for fish ponds?

    Asked in: Asst. Fisheries Development Officer 2024

    1. A & D
    2. A, B & C
    3. A, B & D
    4. A, B, C & D
    Show answer

    Answer: C. A, B & D

    Soil texture is crucial for fish pond construction. Soils with a high proportion of clay are generally preferred as they offer good water retention, preventing seepage. However, very heavy clay can be problematic for digging and management. A loam or clay loam texture, which is a balanced mixture of sand, silt, and clay, is often considered ideal for fish ponds. Silty clay and silty clay loam also fall into this suitable category.

19. Which is high salt tolerant crop ?

    Asked in: Food Safety Officer 2022

    1. Tomato
    2. Sugarbeet
    3. Beans
    4. Chilli
    Show answer

    Answer: B. Sugarbeet

    Sugarbeet is a high salt-tolerant crop.

Hydroponics: Principles and applications in nutrient studies

20. What is Hydroponics ?

    Asked in: UPPSC Upper Mains 2009

    1. Soil less culture of plants
    2. Grafting of plants
    3. Study of vegetable
    4. Water conservation
    Show answer

    Answer: A. Soil less culture of plants

    In hydroponics, the plant roots are directly exposed to a nutrient-rich water solution or an inert medium (like perlite, vermiculite, rockwool, or coconut coir) that supports the plant and holds moisture, eliminating the need for soil.

21. 'Hydroponics' is

    Asked in: Additional Private Secretary Exam 2017

    1. Waterless agriculture
    2. Waterless forestry
    3. Soil-less agriculture
    4. Soil-less forestry
    Show answer

    Answer: C. Soil-less agriculture

    Hydroponics refers to agriculture that is practiced without the use of soil.

22. The method of growing plants (without the use of soil) usually crops; by using mineral nutrient solutions is known as

    Asked in: Assistant Auditor (Direct) 2021

    1. hydroponics
    2. nutroponics
    3. cropodronincs
    4. extronicology
    Show answer

    Answer: A. hydroponics

    This question defines a specific horticultural or agricultural technique and asks for its correct terminology.

23. Hydroponics is concerned with

    Asked in: Assistant Conservator of Forest (ACF) 2012

    1. Growing plants without soil
    2. Growing plants without water but with atmospheric moisture
    3. The treatment of water with sound
    4. The conservation of water technique
    Show answer

    Answer: A. Growing plants without soil

    Hydroponics allows for precise control over nutrient delivery and water usage, leading to faster growth rates and higher yields in many cases.

24. What is 'Hydroponics' ? A) Grafting a plant B) Growing a plant without soil C) Study of vegetables D) Soil conservation

    Asked in: RO ARO pre 2023

    1. Grafting a plant
    2. Growing a plant without soil
    3. Study of vegetables
    4. Soil conservation
    Show answer

    Answer: B. Growing a plant without soil

    Hydroponics is a method of growing plants without soil, using mineral nutrient solutions in an aqueous solvent. The roots are supported by an inert medium or suspended directly in the nutrient solution.

25. The growing of plants under soil loss conditions, is called

    Asked in: Management Officer Exam 2011

    1. Hydrology
    2. Hydroponics
    3. Aquatics
    4. Terrestrial
    Show answer

    Answer: B. Hydroponics

    Hydroponics is a method of growing plants without soil, by using mineral nutrient solutions in an aqueous solvent.

26. Hydrophonics is

    Asked in: UPPSC ACF RFO gs 2 2021

    1. Aquatic plant culture
    2. Cultivation of crop plants
    3. Soil free cultivation of plants
    4. Growing floating aquatic plants
    Show answer

    Answer: C. Soil free cultivation of plants

    Hydroponics is a soilless cultivation technique where plants are grown using nutrient-rich water solutions.

Macronutrients: Role, uptake, and deficiency symptoms

27. Insectivorous plants grow in soil deficient in

    Asked in: BPSC Prelims Exam 67th Cancelled

    1. water
    2. magnesium
    3. nitrogen
    4. calcium
    Show answer

    Answer: C. nitrogen

    Insectivorous plants are plants that derive some or most of their nutrients from trapping and consuming animals or protozoans, typically insects and other arthropods. They are often found in habitats where the soil is poor, particularly in nitrogen. Such environments include acidic bogs, swamps, and rocky outcrops. These plants supplement their nutrient intake, especially nitrogen, by digesting their prey, which provides the nitrates they cannot obtain adequately from the soil.

28. Which one of the following elements is essential for the formation of chlorophyll in green plants?

    Asked in: UPSC CDS 1 2018

    1. Calcium
    2. Iron
    3. Magnesium
    4. Potassium
    Show answer

    Answer: C. Magnesium

    - Chlorophyll is the primary pigment responsible for absorbing light energy during photosynthesis. - Its unique structure, with a central magnesium atom, is crucial for its function in capturing light. - Deficiency of magnesium in plants leads to chlorosis, a yellowing of leaves, particularly between the veins, due to reduced chlorophyll production.

29. Which of the following is macronutrient in relation to growth of plants?

    Asked in: CGPSC Prelims Exam 2020

    1. Potassium
    2. Zinc
    3. Boron
    4. Chlorine
    Show answer

    Answer: A. Potassium

    Macronutrients are elements required by plants in relatively large quantities. The primary macronutrients are Nitrogen (N), Phosphorus (P), and Potassium (K). Secondary macronutrients include Calcium (Ca), Magnesium (Mg), and Sulfur (S). Micronutrients are required in much smaller amounts, such as Zinc (Zn), Boron (B), and Chlorine (Cl).

30. Which of the following is a macronutrient ?

    Asked in: MPSC CS Prelims 2015

    1. Mg
    2. Mo
    3. Bo
    4. Zn
    Show answer

    Answer: A. Mg

    Macronutrients are elements required by plants in large quantities for growth and development.

31. The three primary soil micro-nutrients are

    Asked in: UPSC CAPF 2013

    1. carbon, oxygen and water
    2. copper, cadmium and carbon
    3. nitrogen, phosphorus and potassium
    4. boron, zinc and magnesium
    Show answer

    Answer: C. nitrogen, phosphorus and potassium

    Plants require various nutrients from the soil for healthy growth. These are broadly classified into macronutrients (needed in larger quantities) and micronutrients (needed in smaller quantities). The three most crucial macronutrients, often called primary nutrients, are Nitrogen (N), Phosphorus (P), and Potassium (K). While the question asks for "micro-nutrients", option C lists the standard "primary" nutrients. Given the options, NPK is the only plausible set of primary nutrients listed.

32. Depending on the requirements, plant nutrients are classified as micronutrients and macronutrients. Which one of the following is an example of a macronutrient?

    Asked in: UPSC CAPF 2022

    1. Manganese
    2. Copper
    3. Magnesium
    4. Chlorine
    Show answer

    Answer: C. Magnesium

    Plant nutrients are classified as macronutrients or micronutrients based on the quantity required by the plant. Macronutrients are needed in relatively large amounts, while micronutrients are needed in very small amounts. The primary macronutrients are Nitrogen (N), Phosphorus (P), and Potassium (K). Secondary macronutrients include Calcium (Ca), Magnesium (Mg), and Sulfur (S). Manganese (Mn), Copper (Cu), and Chlorine (Cl) are classified as micronutrients.

33. The element that is required for the synthesis of chlorophyll is

    Asked in: WBCS Main Paper 4 2023

    1. Mn
    2. Fe
    3. Mg
    4. Mo
    Show answer

    Answer: C. Mg

    Chlorophyll is a pigment found in plants and algae that absorbs light energy for photosynthesis. Its molecular structure includes a porphyrin ring with a magnesium ion at its center.

34. Q116: Which of the following is a tuber?

    Asked in: Asstt. Jailor 2013

    1. Radish
    2. Garlic
    3. Potato
    4. Cucumber
    Show answer

    Answer: C. Potato

    Understanding different types of modified plant structures like tubers, roots, bulbs, and rhizomes is important in biology.

Mechanisms of Mineral Absorption: Active and passive transport

35. Absorption of nutrients from lowly concentrated soil solution compared to plant sap is called as ______

    Asked in: MPSC CS Prelims 2012

    1. Active absorption
    2. Passive absorption
    3. Negative absorption
    4. Positive absorption
    Show answer

    Answer: A. Active absorption

    - Absorption against a concentration gradient requires energy. - Active absorption involves metabolic energy (ATP) expenditure by the plant. - Passive absorption does not require metabolic energy and follows concentration gradients.

36. Most of the water absorbed by roots of plants is through

    Asked in: Additional Private Secretary Exam 2017

    1. Embryonic zone
    2. Growing point
    3. Root hairs
    4. Zone of Elongation
    Show answer

    Answer: C. Root hairs

    Root hairs are the primary structures responsible for the absorption of water by plant roots.

Metabolism of Phosphorus, Potassium, and Sulphur

37. Application of Gypsum provides which of the following elements to the plants ?

    Asked in: UPPSC ACF RFO gs 1 2021

    1. Phosphorus
    2. Sulphur
    3. Magnesium
    4. Iron
    Show answer

    Answer: B. Sulphur

    Understanding the role of soil amendments and the essential nutrients they provide to plants is important for agricultural science and environmental studies.

Micronutrients: Role, uptake, and deficiency symptoms

38. Which one among the following is not a micronutrient for plants ?

    Asked in: UPSC CDS 2 2024

    1. Iron
    2. Manganese
    3. Magnesium
    4. Chlorine
    Show answer

    Answer: C. Magnesium

    Plant nutrients are classified into macronutrients and micronutrients based on the amount required by the plant for healthy growth.

39. Which one of the following is not an essential micronutrient for plants ?

    Asked in: HPPSC HPAS Prelims 2013 · UPPCS Prelims 1996

    1. Boron
    2. Zinc
    3. Sodium
    4. Copper
    Show answer

    Answer: C. Sodium

    Essential nutrients are elements required for a plant to complete its life cycle. Macronutrients (N, P, K, Ca, Mg, S) are needed in relatively large amounts, while micronutrients (Fe, Mn, Zn, Cu, B, Mo, Cl) are needed in smaller amounts. Sodium (Na) is beneficial for many plants, especially those performing C4 photosynthesis or growing in saline conditions, but it is not universally essential for all plant species.

40. Ǔनम्नͧलͨखत में से कौन सा एक पादपों के ͧलए एक आवश्यक सूक्ष्मपोषक नहीं है ?

    Asked in: HPPSC HPAS Prelims 2013

    1. बोरॉन
    2. lजंक
    3. सोlल्डियम
    4. कॉपर (ताम्र)
    Show answer

    Answer: C. सोlल्डियम

    Essential plant nutrients are categorized into macronutrients and micronutrients. Boron, Zinc, and Copper are essential micronutrients, while Sodium is generally not considered essential for most plants.

41. Choose the micronutrient needed for plant growth

    Asked in: TNPSC CS Prelims 2017

    1. Oxygen
    2. Hydrogen
    3. Nitrogen
    4. Zinc
    Show answer

    Answer: D. Zinc

    Plant essential nutrients are classified based on the quantities required by the plant. Macronutrients are needed in relatively large amounts (grams per kg of dry matter). They include Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), and Sulfur (S). Micronutrients (or trace elements) are needed in much smaller amounts (milligrams per kg of dry matter). They include Iron (Fe), Manganese (Mn), Copper (Cu), Zinc (Zn), Boron (B), Molybdenum (Mo), Chlorine (Cl), and sometimes Nickel (Ni). From the options provided: A) Oxygen: Macronutrient (from air/water). B) Hydrogen: Macronutrient (from water). C) Nitrogen: Macronutrient. D) Zinc: Micronutrient.

42. Which one of the following elements is present in the green pigment of leaves ?

    Asked in: UPSC CAPF 2017

    1. Magnesium
    2. Iron
    3. Calcium
    4. Copper
    Show answer

    Answer: A. Magnesium

    - The green pigment in leaves is called chlorophyll. - Chlorophyll molecules are crucial for photosynthesis, the process by which plants convert light energy into chemical energy. - The core structure of the chlorophyll molecule is a porphyrin ring, similar to the heme group in hemoglobin, but with a central magnesium atom coordinating the nitrogen atoms, whereas hemoglobin has iron at its center.

43. Pungency in Garlic is due to

    Asked in: Agri. Officer 2020

    1. Diallyl di sulphide
    2. Allyl-Propyl-di sulphide
    3. Isothioeyanate
    4. Solanin
    Show answer

    Answer: A. Diallyl di sulphide

    The pungency in garlic is due to sulfur-containing organic compounds, with diallyl di sulphide being the primary contributor.

44. Lycopene pigment is found in which of the following fruit or vegetable?

    Asked in: Junior Accountant and TRA 2013

    1. Corn
    2. Blackberries
    3. Tomato
    4. Spinach
    Show answer

    Answer: C. Tomato

    Lycopene is a natural pigment that gives red and pink colors to fruits and vegetables, and it is known for its antioxidant properties.

45. Seaweeds are the important source of

    Asked in: ASSISTANT PROSECUTION OFFICER (PRELIM.) EXAM. 2022

    1. Chlorine
    2. Iodine
    3. Bromine
    4. None of the above
    Show answer

    Answer: B. Iodine

    Seaweeds, which are marine algae, are well-known for being a rich source of various minerals and elements, including iodine. Iodine is essential for the proper functioning of the thyroid gland.

Mineral Toxicity and its effects

46. Which one of the following is a known metallophyte for Fe?

    Asked in: UPSC Geoscientist 2023

    1. Eichhornia crassipes
    2. Miconia lutescens
    3. Astragalus acemosus
    4. Mentha arvensis
    Show answer

    Answer: A. Eichhornia crassipes

    - Metallophytes are plants tolerant of or able to accumulate high levels of heavy metals. - Eichhornia crassipes is a prominent example of a plant used for phytoremediation, including the removal or accumulation of iron. - Miconia species are often associated with nickel accumulation; Astragalus species with selenium accumulation.

Nitrate Assimilation and Ammonification

47. Nitrogen is taken by plants in the form of

    Asked in: JPSC CS Prelims 2021

    1. Chloride
    2. Oxide
    3. Nitrate
    4. Nitric acid
    Show answer

    Answer: C. Nitrate

    - Plants absorb nitrogen mainly as nitrate (NO3-) and ammonium (NH4+) ions from the soil. - These ions are products of nitrogen fixation and nitrification processes in the soil.

48. Which organic manure has high nitrogen content ?

    Asked in: MPSC CS Prelims 2012

    1. FYM
    2. Neem cake
    3. Compost
    4. Vermi compost
    Show answer

    Answer: B. Neem cake

    Neem cake contains nitrogen ranging from 2% to 6%, phosphorus from 0.5% to 1%, and potassium from 1% to 2%. FYM and Compost generally have lower and more variable nutrient content, typically generally richer than FYM and compost but its nitrogen content is also typically in the range of 1-2.5%.

49. The process of degradation of humus by some microorganisms and release of inorganic nutrients is known as

    Asked in: UPSC CISF AC EXE 2024

    1. eutrophication
    2. mineralization
    3. humification
    4. stratification
    Show answer

    Answer: B. mineralization

    Mineralization is the process by which organic matter, such as humus, is decomposed by microorganisms into inorganic nutrients (minerals) like nitrates, phosphates, and sulfates. These inorganic nutrients are then available for uptake by plants.

50. The plants receive Nitrogen in form of

    Asked in: UPPCS Prelims 2016

    1. Nitric oxide
    2. Nitrate
    3. Ammonia
    4. Nitride
    Show answer

    Answer: B. Nitrate

    Nitrogen is a crucial macronutrient required for various plant functions, including the synthesis of amino acids, proteins, nucleic acids, and chlorophyll. It is taken up from the soil solution.

51. Nitrogen is utilized by the plants in the form of:

    Asked in: APPSC Draughtman 2008

    1. Nitrogen peroxide
    2. Free nitrogen
    3. Nitrate
    4. Ammonia
    Show answer

    Answer: C. Nitrate

    Plants primarily absorb nitrogen from the soil in the form of nitrate and ammonium ions, with nitrate being the most readily absorbed form.

52. Plants accepts nitrogen in which form?

    Asked in: RO ARO Mains 2021

    1. Nitrogen gas
    2. Nitrite
    3. Nitrate
    4. Ammonia
    Show answer

    Answer: C. Nitrate

    Nitrogen is an essential nutrient for plant growth, but it must be in an inorganic, ionic form for plants to absorb it through their roots. The conversion of atmospheric nitrogen into these absorbable forms is a crucial process in the nitrogen cycle.

Nitrogen Cycle and Nitrogen Fixation

53. Ǔनम्न कथनों पर ͪवचार कीǔजए : i. नाइǑट्रिͩफके शन एक प्रͩक्रया है ǔजसमें नाइट्रिेट्स का रूपांतरण नाइट्रिोजन में होता है। ii. डिीनाइǑट्रिͩफके शन एक प्रͩक्रया है ǔजसमें नाइट्रिोजन का रूपांतरण नाइट्रिेट्स में होता है। iii. न्यूक्लीक अम्ल (DNA और RNA) में नाइट्रिोजन है। iv. वायुमंडिलीय ǒबजली/तͫड़त के दौरान वायु के अंदर की नाइट्रिोजन का रूपांतरण नाइट्रिोजन के ऑक्साइडि में होता है। v. मूल ͧशंब (root legumes) में नाइट्रिोजन यौͬगकीकरण जीवाणु मौजूद होते हैं। सही कथन का चयन कीǔजए :

    Asked in: HAS Prelims 2021

    1. i, ii, iii और v
    2. ii, iii और v
    3. iii, iv और v
    4. i, ii और iv
    Show answer

    Answer: C. iii, iv और v

    - Statement i: नाइlट्रिlफके शन एक प्रlक्रया है lजसमें नाइट्रिेट्स का रूपांतरण नाइट्रिोजन में होता है। (Nitrification is a process where nitrates are converted to nitrogen.) Incorrect. Nitrification is the conversion of ammonia/ammonium to nitrite (by Nitrosomonas bacteria) and then to nitrate (by Nitrobacter bacteria). The conversion of nitrates to nitrogen gas is called denitrification. - Statement ii: ल्डिीनाइlट्रिlफके शन एक प्रlक्रया है lजसमें नाइट्रिोजन का रूपांतरण नाइट्रिेट्स में होता है। (Denitrification is a process where nitrogen is converted to nitrates.) Incorrect. Denitrification is the process where nitrates (NO₃⁻) are reduced to nitrogen gas (N₂) by denitrifying bacteria, which then returns to the atmosphere. The conversion of atmospheric nitrogen (N₂) into usable forms (like ammonia) is called nitrogen fixation. - Statement iii: न्यूक्लिीक अम्लि (DNA और RNA) में नाइट्रिोजन है। (Nucleic acids (DNA and RNA) contain nitrogen.) Correct. Nitrogen is a fundamental component of the nitrogenous bases (Adenine, Guanine, Cytosine, Thymine, Uracil) which form the building blocks of nucleotides in DNA and RNA. - Statement iv: विायुमंल्डिलिीय lबजलिी/तlड़त के दौरान विायु के अंदर की नाइट्रिोजन का रूपांतरण नाइट्रिोजन के ऑक्साइल्डि में होता है। (During atmospheric lightning/thunder, nitrogen in the air is converted into oxides of nitrogen.) Correct. The high energy from lightning breaks the strong triple bond in atmospheric nitrogen (N₂) and allows it to react with oxygen, forming nitrogen oxides (NOx), which can then dissolve in rain and reach the ground, contributing to nitrogen fixation (abiotic fixation). - Statement v: मूलि lशंब (root legumes) में नाइट्रिोजन यौlगकीकरण जीविाणु मौजूद होते हैं। (Nitrogen-fixing bacteria are present in root legumes.) Correct. Plants belonging to the legume family (Fabaceae) have a symbiotic relationship with nitrogen-fixing bacteria (primarily Rhizobium and Bradyrhizobium) that live in root nodules. These bacteria fix atmospheric nitrogen (N₂) into ammonia (NH₃), which is then converted into organic nitrogen compounds usable by the plant.

54. Consider the following statements:- i. Nitrification is a process in which nitrates are converted to nitrogen. ii. Denitrification is a process in which nitrogen is converted into nitrates. iii. Nucleic acids (DNA and RNA) contain nitrogen. iv. During atmospheric lightening, nitrogen in the air gets converted into oxides of nitrogen. v. Nitrogen fixing bacteria are present in root legumes. Choose the correct statement(s) :

    Asked in: HAS Prelims 2021

    1. i, ii, iii and v
    2. ii, iii and v
    3. iii, iv and v
    4. i, ii and iv
    Show answer

    Answer: C. iii, iv and v

    The nitrogen cycle involves several key processes including nitrogen fixation, nitrification, assimilation, ammonification, and denitrification. Nitrogen is essential for building organic molecules like proteins and nucleic acids.

55. A biological process by which nitrate is converted into nitrogen gas is called

    Asked in: Assistant Town Planner (Pre.) Exam 2023

    1. Nitrification
    2. Oxic
    3. Denitrification
    4. Anoxic
    Show answer

    Answer: C. Denitrification

    Nitrification is the opposite process, where ammonia is converted to nitrites and then to nitrates. Oxic refers to aerobic conditions (presence of oxygen), and anoxic refers to anaerobic conditions (absence of oxygen).

Symbiotic Nitrogen Fixation: Nodule formation and biochemistry

56. Which of the following plant is not helpful in nitrogen fixation ?

    Asked in: CGPSC Prelims Exam 2017

    1. Gram
    2. Pea
    3. Bean
    4. Paddy
    Show answer

    Answer: D. Paddy

    Biological nitrogen fixation is primarily carried out by microorganisms that convert atmospheric nitrogen (N2) into ammonia (NH3). Symbiotic nitrogen fixation occurs when these bacteria live in association with plants, providing the plant with usable nitrogen in exchange for carbohydrates. The most well-known example is the symbiotic relationship between Rhizobium bacteria and leguminous plants, where the bacteria reside in root nodules. A) Gram (Chickpea), B) Pea, and C) Bean are all leguminous plants. They form symbiotic relationships with Rhizobium bacteria in their root nodules, which are highly effective in fixing atmospheric nitrogen. Thus, they are helpful in nitrogen fixation. D) Paddy (Rice) is a cereal crop and not a legume. It does not form root nodules with Rhizobium. While some rice plants can have associative relationships with other nitrogen-fixing bacteria in the rhizosphere or symbiotic relationships with cyanobacteria in flooded conditions, the mechanism and scale of nitrogen fixation are significantly different and generally much less impactful compared to the Rhizobium-legume symbiosis. Therefore, paddy is the plant among the options that is not helpful in nitrogen fixation in the same prominent way as the legumes.

57. More than 90 percent of all nitrogen are fixed as ammonia, nitrites, and nitrates by soil microorganisms. Symbiotic bacteria associated with leguminous plants fix nitrogen by the formation of root nodules. In which of the following plant nitrogen fixation does not occurs?

    Asked in: OPSC CS Prelims 2022

    1. Common Beans
    2. Soybeans
    3. Peanuts
    4. Oats
    Show answer

    Answer: D. Oats

    Common Beans, Soybeans, and Peanuts are all leguminous plants that form symbiotic relationships with nitrogen-fixing bacteria in their root nodules. Oats (Avena sativa) are a cereal grain and a member of the grass family (Poaceae). Grasses generally do not form the classic root nodules with Rhizobium and do not perform symbiotic nitrogen fixation in the same manner as legumes.

58. Which of the following are nitrogen-fixing plants ? Alfalfa 1. Amaranth 2. Chickpea 3. Clover 4. Purslane (Kulfa) 5. Spinach 6. Select the correct answer using the code given below :

    Asked in: UPSC IAS 2022

    1. 1, 3 and 4 only 20. Plant Hormones
    2. 1, 3, 5 and 6 only
    3. 2, 4, 5 and 6 only
    4. 1, 2, 4, 5 and 6
    Show answer

    Answer: A. 1, 3 and 4 only 20. Plant Hormones

    - Nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) or related nitrogenous compounds. In agriculture, this is primarily done by bacteria, notably Rhizobia, which live symbiotically in the root nodules of leguminous plants. - Alfalfa (Medicago sativa) is a legume and fixes nitrogen. - Amaranth (Amaranthus spp.) is not a legume and does not fix nitrogen. - Chickpea (Cicer arietinum) is a legume and fixes nitrogen. - Clover (Trifolium spp.) is a legume and fixes nitrogen. - Purslane (Kulfa) (Portulaca oleracea) is not a legume and does not fix nitrogen. - Spinach (Spinacia oleracea) is not a legume and does not fix nitrogen.

59. Pulse crop which does not fix atmospheric nitrogen is

    Asked in: UPPSC Upper Mains 2009

    1. Gram
    2. Pea
    3. Raj ma
    4. Moong
    Show answer

    Answer: C. Raj ma

    Rajma (Kidney bean, Phaseolus vulgaris) is known for its relatively poor ability to fix atmospheric nitrogen compared to other common Indian pulses like Gram (Cicer arietinum), Pea (Pisum sativum), and Moong (Vigna radiata). While it can form nodules, the nitrogen fixation is often ineffective or insufficient for its needs.