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Unit: Plant Nutrition
Nutritional Needs of
Plants
Plants and mineral nutrients:
Plants require certain elements in order to grow and stay healthy.
16 Elements essential to plant growth:
Macronutrients:
• Carbon (C)
• Hydrogen (H)
• Oxygen (O)
• Nitrogen (N)
• Phosphorous (P)
• Potassium (K)
• Sulfur (S)
• Calcium (Ca)
• Magnesium (Mg)
•
•
•
•
•
•
Micronutrients:
Chlorine (Cl)
Iron (Fe)
Manganese (Mn)
Boron(B)
Zinc (Z)
Copper (Cu)
• Molybdenum (Mo)
What makes an element essential?
There are 3 established criteria for an “essential element”:
1. The plant cannot complete it’s life cycle without the
element.
2. Action of the element must be specific- no other element
can substitute for it.
3. The element must be directly involved in the nutrition of
the plant.
Macro vs. Micro
• Macronutrients: nutrients required in large
amounts and absorbed from the soil or
hydroponic solution.
• Micronutrients: nutrients required in small
amounts and absorbed from a soil or a
hydroponic solution.
• Does NOT imply importance. All of the essential
nutrients are required for growth and function.
Mobile vs. Immobile
These nutrients are further divided
into the mobile and immobile
nutrients.
Mobile: A plant will always supply
more nutrients to its younger
leaves than its older ones, so
when nutrients are mobile, the lack
of nutrients is first visible on older
leaves.
Immobile: When a nutrient is less
mobile, the younger leaves suffer
because the nutrient does not
move up to them but stays lower in
the older leaves.
Macronutrients
• Carbon (atmosphere)
• Hydrogen (Water)
• Oxygen (atmosphere)
These 3 nutrients make up
95% of a plants fresh
tissue.
Typically not limiting factors
except for:
Drought
Disease
Extreme cold
Poor drainage
N - Nitrogen
• Function: Nitrogen stimulates
growth, increase of fruit
production and gives plants a
healthy green color.
• Toxicity: dark green plant with
restricted root system and fruit
set.
• Deficiency: Mobile. Growth
restricted. Leaves become
light green and yellow then
die.
K - Potassium:
•Function:
Catalyst/activator for enzymes
Encourages vigor/health
•Deficiency: Highly mobile – older
growth
Poor growth, chlorosis, necrosis;
reduced gas exchange
•Toxicity: Hi K may cause Ca, Mg,
Mn, Zn, Fe deficiencies
P - Phosphorus:
•Function: for the energy molecules:
ATP, ADP, AMP
•Deficiency: Very mobile (old growth)
Lower leaf surfaces turn purple
Leaves curl downward
Poor leaf, root, flower development
•Toxicity: Not usually a problem
Ca -Calcium:
•Function:
As an activator of enzymes
Plant strength & vigor
As a “neutralizing” agent
•Deficiency: Immobile (new growth)
Misshapen, poor or no growth
Blossom end rot of fruit
•Toxicity: Not usually a problem
(Mg) Magnesium:
Function:
“heart” of the chlorophyll molecule
Enzyme activator (ATP, DNA, RNA)
•Deficiency: Highly mobile
Older leaf interveinal chlorosis
Upturned leaves
•Toxicity:
Not known
Sulfur:
•Function:
Form “disulfide bonds” that aide in
the folding of proteins and effect
their function
•Deficiency: Moderately mobile
Less chlorophyll  chlorosis and
purplish veins in mid/young leaves
Thin, brittle stems
•Toxicity:
Red. Growth, interveinal chlorosis, leaf burn
Let’s review the macros… (all result in poor growth)
Mobile
Functions
Def. Symptoms
N
Y
protein, RNA, DNA, Chl
chlorosis, necrosis
P
Y
ATP, etc.
purple underleaf
K
Y
Catalyst/activator for enzyme
red. Transpiration
Ca
N
cell walls, enzyme act.
poor “new” growth
blossom end rot in fruit
Mg
Y
Chlorophyll, enzyme act.
Interveinal chl.
brittle upturn leaf
S
Mod
2 amino acids
“mid/new” growth: chlorosis,
purple veins, thin brittle
stems
Micronutrients:
Iron: (Fe)
•Function:
Involved in chlorophyll & protein
synthesis and respiration
•Deficiency: Immobile
New growth interveinal chlorosis
•Toxicity:
If over-apply foliar  necrotic
spots
Manganese: (Mn)
• Function:
Enzyme activator (chl, RNA, DNA)
carbohydrate metab., O2 prod.
• Deficiency: Relatively immobile
Newer growth interveinal chlorosis
Necrotic spots/leaf drop
Upward leaf curl
• Toxicity:
Reduced growth
Hi Mn  Low Fe and interveinal chlorosis
Boron: (B)
• Function:
Related to metabolism of Ca, K
Regulates carbohydrate
Involved in RNA synthesis
•Deficiency: Mobile in leaf; not in
plant
Stems: abnormal/slow growth,
brittle
Shoot/root die back
Young leaves: thick, curled
Low flowering, fruiting; fruit rots
•Toxicity:
Def. sym. + leaf tip
chlorosis/necrosis
Zinc: (Zn)
• Function:
Enzyme activator
Synthesis of proteins, hormones,
RNA, DNA
•Deficiency: Not very mobile
Abnormal and stunted growth
Leaves: interveinal chlorosis,
necrosis
• Toxicity:
Similar to def. symp.
Copper: (Cu)
• Function: (70% of Cu in leaf in chloroplasts)
Chlorophyll synthesis
•Deficiency: Immobile
Leaf stunting, twisting; dark green
Reduced turgor (firmness)
Reduced flowering/fruiting
• Toxicity: Do not use Cu tube/fixtures
Overall stunting; thick, dark roots
Molybdenum: (Mo)
•Function
Involved in carbohydrate
metabolism.
•Deficiency: Mobile
Leaf interveinal chlorosis, mottling,
scorching, inward cupping
Severe: puffy leaf areas & stunting
• Toxicity:
Not usually seen…
Leaves can turn yellow
Chlorine: (Cl)
• Function:
Enzyme activator
Promotes healthy growth of plants
Hi NaCl  stress  flavor, nutrition
• Deficiency: Mobile
Leaf chlorosis then necrosis
Low transpiration, wilting
Plant stunting, die back
•Toxicity: Leaf tip burn.
Let’s review the micros:
** Some are mobile, some are not
** ALL are involved in plant metabolism
Enzyme activators
Parts of enzymes
In electron transfer
As oxygen carriers
Invovled in synthesis/metabolism of proteins, hormones,
RNA/DNA, carbohydrates, chlorophyll, ion balance, etc.
** KEY: mainly move around assisting in reactions, etc.
Therefore, not needed in large amounts for “structure”.
Other nutrients:
Found in some but not all plants; possibly required by those plants
Sodium (Na)
C4 plants
Silicon (Si)
C4 & CAM
Cobolt (Co)
N-fixing bacteria
Vanadium (V)
Essential in green algae; toxic in hp in hi conc
Iodine (I)
Stimulates growth in low conc; toxic in hi conc
Bromine (Br)
Can substitute for Cl
Fluorine (F)
Toxic; some plants accumulate; hi in teas!
Aluminum (Al)
Req’d for tea bush; toxic for most plants
Nickel (Ni)
Maybe req’d for N-fixers; toxic for other plants
Selinium (Se)
In milk vetches; toxic to most plants
Pictures from this presentation can be found at:
www.plantphys.net/_article.php?ch=t&id=289
Plant Physiology online: Chapter 5.1
Visual symptoms of nutrient deficiencies in plants
Dr. Wade Berry, UCLA
Questions?