Muhammad Fahad Ansari12IEEM14

1. Plant nutrition
lecture # 6
Muhammad Fahad
Ansari
12IEEM14

2. PLANT NUTRITION
Section A: Nutritional Requirements of Plants
1. The chemical composition of plants provides clues to their nutritional
requirements
2. Plants require nine macronutrients and at least eight micronutrients
3. The symptoms of a mineral deficiency depend on the function and mobility
of the element
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

3. Introduction
• Every organism is an open system
connected to its environment by a
continuous exchange of energy and
materials.
– In the energy flow and chemical cycling that
keep an ecosystem alive, plants and other
photosynthetic autotrophs perform the key step
of transforming inorganic compounds into
organic ones.
– At the same time, a plant needs sunlight as its
energy source for photosynthesis and raw
materials, such as CO2 and inorganic ions, to
synthesize organic molecules.
– The root and publishing as systems
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4. 1. The chemical composition of plants
provides clues to their nutritional
requirements
• Early ideas about plant nutrition were not
entirely correct and included:
– Aristotle’s hypothesis that soil provided the
substance for plant growth
– van Helmont’s conclusion from his experiments
that plants grow mainly from water
– Hale’s postulate that plants are nourished mostly
by air.
• Plants do extract minerals from the soil.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

5. • Mineral nutrients are essential chemical
elements absorbed from soil in the form of
inorganic ions.
– For example, plants acquire nitrogen mainly in
the form of nitrate ions (NO3-).
• However, only a small fraction of the water
entering a plant contributes to organic
molecules.
– Over 90% is lost by transpiration.
– Most of the water retained by a plant functions
as a solvent, provides most of the mass for cell
elongation, and helps maintain the form of soft
tissues by keeping cells turgid.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

6. • By weight, the bulk of the organic material
of a plant is derived not from water or soil
minerals, but from the CO2 assimilated
from the atmosphere.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

7. • The uptake of nutrients
occurs at both the roots
and the leaves.
– Roots, through
mycorrhizae
and root hairs, absorb
water
and minerals from the
soil.
– Carbon dioxide diffuses
into
leaves from the
surrounding publishing as Benjamin Cummings
Fig. 37.1
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8. • Roots are able to absorb minerals
somewhat selectively, enabling the plant to
accumulate essential elements that may be
present in low concentrations in the soil.
– However, the minerals in a plant reflect the
composition of the soil in which the plant is
growing.
– Therefore, some of the elements in a plant are
merely present, while others are essential.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

9. 2. Plants require nine macronutrients
and at least eight micronutrients
• A particular chemical element is considered
an essential nutrient if it is required for a
plant to grow from a seed and complete the
life cycle.
– Hydroponic cultures have identified 17 elements
that are essential nutrients in all plants and a few
other elements that are essential to certain
groups of plants.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

10. • Hydroponic culture can determine which
mineral elements are actually essential
nutrients.
– Plants are grown in solutions of various
minerals dissolved in known concentrations.
– If the absence of a
particular mineral, such
as potassium, causes a
plant to become abnormal
in appearance when
compared to controls
grown in a complete
mineral medium, then
that element is essential.
Fig. 37.2

11. • Elements required by plants in relatively
large quantities are macronutrients.
– There are nine macronutrients in all, including
the six major ingredients in organic
compounds: carbon, oxygen, hydrogen,
nitrogen, sulfur, and phosphorus.
– The other three are potassium, calcium, and
magnesium.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

12. • Elements that plants need in very small
amounts are micronutrients.
– The eight micronutrients are iron, chlorine, copper,
zinc, manganese, molybdenum, boron, and nickel.
– Most of these function as cofactors of enzymatic
reactions.
– For example, iron is a metallic component in
cytochromes, proteins that function in the electron
transfer chains of chloroplasts and mitochondria.
– While the requirement for these micronutrients is so
modest (only one atom of molybdenum for every 16
million hydrogen atoms in dry materials), a
deficiency of a micronutrient can weaken or kill a
plant.

13. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

14. 3. The symptoms of a mineral
deficiency depend on the function and
mobility of the element
• The symptoms of a mineral deficiency
depend partly on the function of that nutrient
in the plant.
– For example, a magnesium deficiency, an
ingredient of chlorophyll, causes yellowing of the
leaves, or chlorosis.
Fig. 37.3
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

15. • The relationship between a mineral
deficiency and its symptoms can be less
direct.
– For example, chlorosis can also be caused by
iron deficiency because iron is a required
cofactor in chlorophyll synthesis.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

16. • Mineral deficiency symptoms depend also
on the mobility of the nutrient within the
plant.
– If a nutrient moves about freely from one part of
a plant to another, then symptoms of the
deficiency will appear first in older organs.
• Young, growing tissues have more “drawing power”
than old tissues for nutrients in short supply.
• For example, a shortage of magnesium will lead to
chlorosis first in older leaves.
– If a nutrient is relatively immobile, then a
deficiency will affect young parts of the plant
first.
• Older tissue may have adequate supplies which they
retain during periods of shortage.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

17. • The symptoms of a mineral deficiency are
often distinctive enough for a plant
physiologist or farmer to diagnose its
cause.
– This can be confirmed by analyzing the mineral
content of the plant and the soil.
– Deficiencies of nitrogen, potassium, and
phosphorus are the most common problems.
– Shortages of micronutrients are less common
and tend to be geographically localized
because of differences in soil composition.
• The amount of micronutrient needed to correct a
deficiency is usually quite small, but an overdose
can be toxic to plants.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

18. • One way to ensure optimal mineral
nutrition is to grow plants hydroponically on
nutrient solutions that can be precisely
regulated.
– This technique is practiced commercially, but
the requirements for labor and equipment
make it relatively expensive compared with
growing crops in soil.
Fig. 37.4
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

19. • Mineral deficiencies are not limited to
terrestrial ecosystems, nor are they unique
to plants among photosynthetic organisms.
– For example, populations of planktonic algae in
the southern oceans are restrained by
deficiencies of iron in seawater.
• In a limited trial in the relatively unproductive seas
between Tasmania and Antarctica, researchers
demonstrated that dispersing small amounts of iron
produced large algal blooms that pulled carbon
dioxide out of the air.
• Seeding the oceans with iron may help slow the
increase in carbon dioxide levels in the atmosphere,
but it may also cause unanticipated environmental
effects.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

20. 1.Plant Nutrients
 Macronutrients
 Micronutrients

21. 1. Essential Nutrietns of Plants
Chemical Atomic Ionic forms Approximate dry
Element symbol weight Absorbed by plants ____ concentration_____
Mccronutrients
Nitrogen N 14.01 NO3-, NH4+ 4.0 %
Phosphorus P 30.98 PO43-, HPO42-, H2PO4- 0.5 %
Potassium K 39.10 K+ 4.0 %
Magnesium Mg 24.32 Mg2+ 0.5 %
Sulfur S 32.07 SO42- 0.5 %
Calcium Ca 40.08 Ca2+ 1.0 %
Micronutrients
Iron Fe 55.85 Fe2+, Fe3+ 200 ppm
Manganese Mn 54.94 Mn2+ 200 ppm
Zinc Zn 65.38 Zn2+ 30 ppm
Copper Cu 63.54 Cu2+ 10 ppm
Boron B 10.82 BO32-, B4O72- 60 ppm
Molybdenum Mo 95.95 MoO42- 2 ppm
Chlorine Cl 35.46 Cl- 3000 ppm
Essential But Not Applied
Carbon C 12.01 CO2 40 %
Hydrogen H 1.01 H2O 6%
Oxygen O 16.00 O2, H2O 40 %
________________________________________________________________
Plant tissues also contain other elements (Na, Se, Co, Si, Rb, Sr, F, I) which are not
needed for the normal growth and development.

22. 2. Macronutrients
a. Nitrogen (N)
1) Soil Nitrogen Cycle

23. A. Nitrogen (N)
1) Soil Nitrogen Cycle
a) Nitrogen Fixation
-Transformation of atmospheric N to nitrogen forms available to
plants
- Mediated by N-fixing bacteria:
Rhizobium (symbiotic) found in legumes (bean, soybean)
Azotobacter (non-symbiotic bacteria)
b) Soil Nitrification
- Decomposition of organic matter into ammonium and nitrate
- Mediated by ammonifying and nitrifying bacteria
Ammonifying bacteria Nitrifying bacteria
(Actinomycetes) (Nitrosomonas) (Nitrobacter)
Plant residue → NH4+ → NO2 → NO3-
(Protein, aa, etc) Ammonium Nitrite Nitrate

24. 2) N Functions in Plants
- Component of proteins, enzymes, amino acids, nucleic acids, chlorophyll
- C/N ratio (Carbohydrate: Nitrogen ratio)
High C/N ratio → Plants become more reproductive
Low C/N ratio → Plants become more vegetative
- Transamination
NO3- → NH2 → Glutamic acid → Other amino acids (a.a.) → Protein
Enzymes
- Essential for fast growth, green color
3) Deficiency and Toxicity Symptoms
Deficiency: - Reduced growth
- Yellowing of old leaves
Toxicity (excess): - Shoot elongation
- Dark leaves, succulence
4) Fertilizers
- Ammonium nitrate (NH4NO3)
Calcium nitrate [Ca(NO3)2]
Potassium nitrate (KNO3)
Urea [CO(NH2)2]
- Most plants prefer 50:50 NH4+ : NO3-
NH4+-form of N → lowers soil pH
NO3--form of N → raises soil pH
- Organic fertilizers (manure, plant residue) – slow acting

25. Nitrogen (N) Deficiency Symptoms
Yellowing of mature lower leaves- nitrogen
is highly mobile in plants

26. B. Phosphorus (P)
1) Soil Relations
- Mineral apatite [Ca5F(PO4)3]
- Relatively stable in soil
- Has a low mobility (top dressing not effective)
2) Plant Functions
- Component of nucleic acid (DNA, RNA), phospholipids, coenzymes,
high-energy phosphate bonds (ADP, ATP)
- Seeds are high in P
3) Deficiency and Toxicity
- P is mobile in plant tissues (Deficiency occurs in older leaves)
- Deficiency: dark, purplish color on older leaves
- Excess P: causes deficiency symptoms of Zn, Cu, Fe, Mn
4) Fertilizers
- Superphosphates (may contain F)
Single superphosphate (8.6% P): CaH4(PO4)2
Triple superphosphate (20% P): CaH4(PO4)2
- Ammonium phosphate: (NH4)2PO4, NH4HPO4
- Bone meal
- Available forms: PO43-, HPO42-, H2PO4-
P absorption influenced by pH

27. Influence of pH on different forms of phosphorus (P)

28. C. Potassium (K)
1) Soil Relations
- Present in large amounts in mineral soil
- Low in organic soils
2) Plant Functions
- Activator of many enzymes
- Regulation of water movement across membranes and through stomata
(Guard cell functions)
3) Deficiency and Toxicity
- Deficiency: Leaf margin necrosis and browning
Older leaves are more affected
- Toxicity: Leaf tip and marginal necrosis
4) Fertilizers
- Potassium chloride (KCl)- murate of potash
- Potassium sulfate (K2SO4)
- Potassium nitrate (KNO3)

29. Leaf Margin Necrosis in Poinsettia
Potassium (K) Deficiency

30. Macronutrients N, P, K Deficiencies
Leaf Lettuce
Control

31. Macronutrient Deficiencies
Beans

32. D. Calcium (Ca)
1) Soil Relations
- Present in large quantities in earth’s surface (~1% in US top soils)
- Influences availability of other ions from soil
2) Plant Functions
- Component of cell wall
- Involved in cell membrane function
- Largely present as calcium pectate in meddle lamela
Calcium pectate is immobile in plant tissues
3) Deficiency and Toxicity
- Deficiency symptoms in young leaves and new shoots (Ca is immobile)
Stunted growth, leaf distortion, necrotic spots, shoot tip death
Blossom-end rot in tomato
- No Ca toxicity symptoms have been observed
4) Fertilizers
- Agricultural meal (finely ground CaCO3·MgCO3)
- Lime (CaCO3), Gypsum (CaSO4)
- Superphosphate
- Bone meal-organic P source

33. Blossom End Rot of Tomato
Calcium Deficiency
Right-Hydroponic tomatoes grown in the greenhouse, Left-Blossom end
rot of tomato fruits induced by calcium (Ca++) deficiency

34. Influence of Calcium on Root Induction
on Rose Cuttings

35. E. Sulfur (S)
1) Soil Relations
- Present in mineral pyrite (FeS2, fool’s gold), sulfides (S-mineral complex),
sulfates (involving SO4-2)
- Mostly contained in organic matter
- Acid rain provides sulfur
2) Plant Functions
- Component of amino acids (methionine, cysteine)
- Constituent of coenzymes and vitamins
- Responsible for pungency and flavbor (onion, garlic, mustard)
3) Deficiency and Toxicity
- Deficiency: light green or yellowing on new growth (S is immobile)
- Toxicity: not commonly seen
4) Fertilizers
- Gypsum (CaSO4)
- Magnesium sulfate (MgSO4)
- Ammonium sulfate [(NH4)2SO4]
- Elemental sulfur (S)

36. F. Magnesium (Mg)
1) Soil Relations
- Present in soil as an exchangeable cation (Mg2+)
- Similar to Ca2+ as a cation
2) Plant Functions
- Core component of chlorophyll molecule
- Catalyst for certain enzyme activity
3) Deficiency and Toxicity
- Deficiency: Interveinal chlorosis on mature leaves
(Mg is highly mobile)
- Excess: Causes deficiency symptoms of Ca, K
4) Fertilizers
- Dolomite (mixture of CaCO3·MgCO3)
- Epsom salt (MgSO4)
- Magnesium nitrate [Mg(NO3)2]
- Magnesium sulfate (MgSO4)

37. Magnesium (Mg) Deficiency on Poinsettia
Interveinal Chlorosis on Mature Leaves

38. Micronutrients
• Micronutrient elements
– Iron (Fe)
– Manganese (Mn)
– Boron (B)
– Zinc (Zn)
– Molybdenum (Mo)
– Copper (Cu)
– Chlorine (Cl)
• Usually supplied by irrigation water and soil
• Deficiency and toxicity occur at pH extremes

39. Influence of pH on Nutrient Availability

40. 3. Micronutrients
A. Iron (Fe)
- Component of cytochromes (needed for photosynthesis)
- Essential for N fixation (nitrate reductase) and respiration
- Deficiency
Symptom: Interveinal chlorosis on new growth
Fe is immobile
Iron chlorosis develops when soil pH is high
Remedy for iron chlorosis:
1) Use iron chelates
FeEDTA (Fe 330) – Stable at pH < 7.0
FeEDDHA (Fe 138) – Stable even when pH > 7.0
2) Lower soil pH
Iron is in more useful form (Fe2+)

41. Iron (Fe) Deficiency Symptoms
1 2
3 4
A B
1-Piggyback Plant, 2- Petunia, 3-Silver Maple,
4-Rose (A-normal, B-Fe-deficient)

42. Iron Chelates

43. Iron (Fe) Absorption by Plants

44. B. Manganese (Mn)
- Required for chlorophyll synthesis, O2 evolution during photoshynthesis
- Activates some enzyme systems
- Deficiency: Mottled chlorsis between main veins of new leaves
(Mn is immobile), similar to Fe chlorosis
- Toxicity: Chlorosis on new growth with small, numerous dark spots
Deficiency occurs at high pH
Toxicity occurs at low pH
- Fertilizers: Manganese sulfate (MnSO4)
Mn EDTA (chelate) for high pH soils
C. Boron (B)
- Involved in carbohydrate metabolism
- Essential for flowering, pollen germination, N metabolism
- Deficiency: New growth distorted and malformed, flowering and fruitset
depressed, roots tubers distorted
- Toxicity: Twig die back, fruit splitting, leaf edge burns
- Fertilizers: Borax (Na2B4O710H2O), calcium borate (NaB4O7 4H2O)
D. Zinc (Zn)
- Involved in protein synthesis, IAA synthesis
- Deficiency: (occurs in calcarious soil and high pH)
Growth suppression, reduced internode lengths, rosetting,
interveinal chlorosis on young leaves (Zn is immobile in tissues)
- Toxicity: (occurs at low pH) Growth reduction, leaf chlorosis

45. Micronutrient Toxicity on Seed Geranium
B
Cu
Fe
Mn
Mo
Zn
Cont 0.25 0.5 1 2 3 4 5 6
Concentration (mM)

46. E. Molybdenum (Mo)
- Required for nitrate reductase activity, vitamin synthesis
Nitrate reductase
NO3 -
————————————— NH2
Mo
Root-nodule bacteria also requires Mo
- Deficiency: Pale green, cupped young leaves (Mo is immobile)
Strap leafe in broad leaf plants
Occurs at low pH
- Toxicity: Chlorosis with orange color pigmentation
- Fertilizer: Sodium molybdate
F. Copper (Cu)
- Essential component of several enzymes of chlorophyll synthesis, carbohydrate
metabolism
- Deficiency: Rosette or ‘witch’s broom’
- Toxicity: Chlorosis
- Fertilizers: Copper sulfate (CuSO4)
G. Chlorine (Cl)
- Involved for photosynthetic oxygen revolution
- Deficiency: Normally not existing (Only experimentally induced)
- Toxicity: Leaf margin chlorosis, necrosis on all leaves
- Fertilizer: Never applied
(Cl- is ubiquitous!)

47. Molybdenum Deficiency on Poinsettia