Transcript lecture 14 secondary nutrients

Chapter 13
Plant secondary nutrients
Calcium
Calcium in physiology
Uptake and translocation
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Higher plants often contain appreciable
amounts Ca and generally in the order
of about 5-30 mg Ca/g dry matter
The high Ca2+ concentrations related
with the high Ca2+ levels in media, not
related with the Ca2+ uptake
mechanism of the roots cells.
The uptake rate of Ca2+ is usually lower
than that of K+.
Why ?
Uptake and translocation
This low Ca2+ uptake potential occurs because
Ca2+ can be absorbed only by young root
tips in which the cell walls often are still
unsuberized未木栓化.
The amount of absorbed by the plant
depends on the concentration in the root
medium and is also genetically controlled.
The calcicole(钙生植物)>calcifuge(避钙植物)
Dicotyledons>monocotyledons
This is related with cation exchange capacities
and oxalate content in the tissue.
Uptake and translocation
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Calcium ions are not transported effectively
by the symplast. The typical pathway for
Ca2+ uptake of involves initial movement into
the free space of the root apoplast and then
further movement through apoplastic
pathways.
The movement of Ca2+ in the xylem vessels
can not be explained simply in terms of
mass flow as Ca2+ is absorbed by adjacent
cells and also absorbed to indiffusible anions
in the xylem walls.
The cell wall is as reservoir for supply to
acropetal (向顶的）growing centre.
Uptake and translocation
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In growing plants, Ca2+ is translocated
preferentially towards the shoot apex even
though the transpiration rate here is much
low lower than in the older leaves.
The rate of Ca2+ downward of plant is very
low due to the fact that Ca2+ is transported
in only very small concentration in the
phloem, tissues supplied by the phloem sap
(such as fruit) has less Ca2+ than leaves.
Once it is deposited in older leaves it
cannot be mobilized to the growing tips.
The factors affecting calcium uptake
1. The other cations such as K+ and NH4+
2. Transpiration steam
Calcium transport controlled by humidity
Blossom end rot caused by
drought,
water logged soil,
high salt concentration
poor aeration
low temperature.
The forms of calcium in plant
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Free Ca2+
Absorbed Ca2+ by carboxylic,
phosphorylic(磷酰基) and phenolic
hydroxyl groups.
Precipitated as Ca oxalate, carbonate
and phosphate in vacuoles, or pectins
in cell walls, or phytate in seed.
Calcium ions are also bound to
membranes
Calcium concentration in non ripping Rin and
Normal Rutgers pericarp果皮 tomato tissue at
different stages of fruit development (Poovaiah 1979)
Days after
Soluble Ca, μg Ca/g DM
Bound Ca, μg Ca/g DM
anthesis
rin
Rutgers
rin
Rutgers
40
299
349
530
562
50
412
602
667
246
60
492
622
1357
291
Ca concentrations in various compartments
of fully expended plants cells
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Apoplast 0.1 mol/m3
Vacuole 1mol/m3
Cytosol 1mmol/m3
ER 1 mol/m3
Biological functions
1.
2.
3.
4.
5.
Stability and integrity of biological
membrane and tissues-cross links in cell
wall
Plant growth, such as root tips, growing
points of shoot and storage organs
Cell elongation and cell division
Calcium as second messenger—via
secondary receptor, Calmodulin (钙调
素)and calmodulin-like proteins, regulate
numerous and complex processes.
Pollination(授粉）
The model of CaM function
Calcium deficiency and disorders
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Reduction in growth of meristematic tissues
Deformed and chlorotic and at a more advanced stage
necrosis occurs
The effected tissues become soft due to dissolution of
the cell walls
Brown substances (suberian) occur which accumulate in
intracellular spaces and also in the vascular
Not usual in soil but can occur in artificial medium
Disorder of undersupply of Ca
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Apple: bitter pit苦痘病, cork spot木
栓病, watercore水心病
Tomato, water melon potato and
pepper: blossom-end rot蒂腐病
Celery: blackheart黑心病
Carrot: cavity spot空洞病
Cherry: firmness and cracking硬化
与开裂病
Contributors to Ca deficiency
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Oversupply N
K, NH4+ and Mg2+ compete in uptake
B deficiency
Excessive pruning 修剪
Large fruits
Weather factors: humidity, drought,
Soil factors:
water logged soil,
high salt concentration
poor aeration
low temperature.
lettuce
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Calcium deficiency
Young leaves,
margins distorted
and scorch; may
be followed by
Botrytis infection
Calcium deficiency of beet plant
Hooking of young leaves,
followed by death of growing point
Advanced stage of acute deficiency.
Young leaves fail to expand and die off;
older leaves marginal scorch
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Calcium deficiency (soil acidity complex)
Forking and turning of roots in acid subsoil
layer
Leaf margins slightly pale, curled forward
and scorched
TOMATO STEM Calcium deficiency
Death of growing point and
die-back of main stem
from tip; die-back of
leaves, progressing from
terminal leaflets and of
flower and fruiting trusses.
Dying off of terminal leaflets
and flowers;
leaves purplish brown tinting
Dying back of trusses and
"Blossom End Wilt" of distal fruitlets
Calcium-deficient plants are stunted, having distorted,
cupped leaves and characteristic interveinal chlorosis.
Symptoms appear first on new growth in cucumber plant
-Mg Yellowing and light tan burn on older leaves of
deficient plant (left) compared with a healthy plant
(right).
–Mg Yellowing between the major veins of older
leaves (left) turns to a light tan papery burn (right).
Younger leaves (top) are less affected.
Calcium deficiency of
celery with high potassium
Death of growing point;
bushy habit of growth,
leaves bluish green.
Calcium deficiency with
high sodium
Death of growing point;
growth tall,
vigour greater than with
high potassium,
Leaves medium green.
Diagnosing of Ca deficiency
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What is the history of the block?
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Are Ca related disorders common?
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Weather?
Wet, dry, hot, cool and humid?
Irrigation?
No correlation between leaf and fruit
levels; so tissues test is not reliable.
Remedies to Ca deficiency
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CaCl2 spraying
Rate:
3lb/100gal.
6lb/acre concentrate
Don’t repeat without rain, corrosive
Soil Calcium
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The mean Ca concentration of the earth’s
crust amounts to about 36.4 g/kg.
Under humid conditions, acidification of soil
causes Ca2+ leaching.
Pedogenesis factors成土因素: nitrate,
bicarbonate
Anthropogenic factors人为因素: sulphuric
acid and nitrate
Liming and Calcium in crop nutrition
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pH effect and Ca2+ effect
Improving soil structure
Neutralizes soil acidity
Reduces the level of toxic AI in
soils
Supplies Ca2+ to crops, especially
in acid peat soils (酸性泥炭土）
Liming materials
Liming material
Chalk or limestone 石灰石
Formula
CaCO3
Neutralizing value in CaO
50% CaO
Slake lime 熟石灰
Ca(OH)2
70% CaO
Burnt lime 煅(生)石灰
CaO
85% CaO
Other material bearing Ca
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Gypsum CaSO4
Ca phosphate
Ca Chloride CaCI2
Ca nitrate Ca(NO3)2
Magnesium
Total magnesium in the soil
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The Mg+2 of most soils is generally between
0.05% and 0.5%
The level of Mg in soil depends on soil types and Mg
bearing minerals types, and rate of weathering and
intensity of leaching
a) Mg+2 tends to be lower in coarse textured
soils (sandy soils) and higher in fine textured
soils (soils with a higher clay content)
b) Mg+2 also tends to be higher in arid or
semi-arid areas.
Magnesium fractions in the soil
1. Non exchangeable Mg (largest fraction)
Primary mineral
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Ferromagnesian minerals-easily weather
Biotite(黑云母) 130 g Mg/kg；Serpentine(蛇纹石) 250 g Mg/kg
Hornblende(角闪石) g Mg/kg；Olivine(橄榄石) g 240 g Mg/kg
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Second clay mineral:
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Chlorite(绿泥石) and vermiculite(蛭石)
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Mg carbonate:
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dolomite(白云石) and Mg carbonate
Much of the Mg+2 is easily leached from plant residues. The remainder
is mineralized during the early stages of residue decomposition. Only
about 1% of the total soil Mg is found in the organic matter.
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Magnesium fractions in the soil
2. Exchangeable Mg
Like Ca+2, Mg+2 is an exchangeable ion
that is held on to the exchange sites of
clay and organic matter.
it is about 5% of the total Mg
it is normally constitutes from 4 to 20%
of CEC.
Magnesium fractions in the soil
3. Soluble magnesium
The concentration of Mg+2 in the soil
solution is typically 5-50 ppm, or 1100mol/m3.
Exchange Mg and soluble Mg are an
important source of Mg+2 for plants.
4. Mg associated with organic matter
It is usually small and less than 1% of
total Mg
All the fraction are in equilibrium
Magnesium remove from soil
Leaching
Mg2+ is a divalent cation. It is
sorbed less strongly to the exchange
sites compared to Ca+2, therefore Mg2+
is more easily leached from the soil
compared to Ca2+.
leaching rate are in the order of 2
to 30 kg Mg/ha/yr.
Erosion
Removed by crop harvest
Magnesium availability to the plant
the availability of Mg2+ to the plant is
affected by several factors.
Base saturation
Mg2+ saturation of >10% is required
for adequate availability.
Other cations
(1) High levels of Ca2+, K+, and NH4+ can
all result in a reduction in Mg2+ uptake
(2) NO3-N can cause an increase in Ca2+
uptake
Plant Magnesium
Magnesium content of plants
0.05%-0.7% of dry matter
0.2%-0.25% of dry matter in
mature laves
legumes>cereals
seeds>stem and leaves>roots
Magnesium forms in plants
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70% of total Mg is diffusible and
associated with inorganic and organic
anions such as malate and citrate.
As counter cation of indiffusible
anions such as carboxyl and
phosphoral groups
As Mg phytate in cereals grains
Mg associated with chlorophyll in
leaves
Uptake and translocation
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Magnesium movement to roots
• Mg is primarily supplied to the root by
mass flow.
• Root interception is much lower for Mg2+
compared to Ca2+
Magnesium uptake
1. Mg2+ is taken up by roots in its ionic form.
2. Mg2+ uptake is passive (facilated diffusion).
The concentration of Mg2+ in the soil solution is
higher than the concentration of K+, but the uptake
is lower.
3. The uptake of Mg2+ can be greatly
depressed by an excess of other cation
species, especially of K+ and NH4+
4. Mg2+ uptake of plants is frequently low on
acid soils.
Mg translocation
1. The Mg translocation from roots to the
upper parts can be restricted by K+ and Ca2+
2. Increasing K+ supply affects the Mg2+
concentration of different plant parts organs
in varying extent.
k+ promotes the translocation of Mg2+
towards fruits and storage tissues.
3. Mg is very mobiles in the phloem and can be
translocated from older to younger leaves or
to the apex.
Effect of an increasing K+ supply on the cation concentration
in various organs of the tomato plant (Viro 1973)
Treatment
K
mol K/m3 nutrient solution
Leaves
2
10
20
Roots
2
10
20
Fruits
2
10
20
Na
Ca
Mg
In mg/g dry matter
5.0
33
42
4.0
1.9
1.8
47
42
33
6.1
2.7
1.5
2.0
22
24
3.6
2.5
1.3
39
32
33
3.3
3.1
2.6
16
25
27
1.0
0.7
0.6
0.9
0.8
0.7
0.7
0.8
0.9
Function of magnesium
1. Essential for photosynthesis
It is the central atom in the chlorophyll
molecule. Chlorophyll contains 15-20% of the
Mg in plants.
2. Mg is important for activating enzymes
(ATPase, and Rubsico – enzyme involved in CO2
assimilation)
3. It is essentially for the structure and
conformation of nucleic acids and ribosomal
particles. It is needed by the ribozymes.
So it has a detrimental impact on the
polypeptides synthesis and thus on the protein
formation.
Mg deficiency symptoms
For dicotyl, the main symptom on
many plants is interveinal（脉间）
yellowing or chlorosis.
This means that the area very
near to the veins in the leaf remains
green, while the area between the veins
turns yellow.
In extreme cases the intercostal
(脉间） areas become necrotic.
Mg deficiency symptoms
Leaves may have a withered
appearance (not enough water) and
they may be stiff and brittle (easily
broken). For some plants, the
leaves may fall off early.
The deficiency begins in the
older leaves.
Apple Tree
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Magnesium deficiency
Severe defoliation of
terminal shoots
progressing from base
to tip.
Interveinal chlorosis and necrosis.
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Cabbage Plant
Magnesium
deficiency
• Older leaves
chlorotic
marbling
Calcium deficiency
Older leaves, marginal and
intervenal collapse; young
leaves, cupping and
distortion and scorching of
margins.
Grape
Magnesium
deficiency in
cotton
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Magnesium deficiency
of lettuce
Older leaves chlorotic
marbling
Sugar Beet Plant
Magnesium deficiency
Older leaves severe
intervenal chlorosis and
necrosis.
Intervenal chlorosis,
beginning at tips and
margins and progressing
towards midrib; chlorosis
followed by marginal and
intervenal necrosis.
Mg deficiency of tomato
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TOMATO LEAF
Magnesium deficiency
Central intervenal
chlorosis and green
marginal bands.
Leaves intervenal
chlorosis and necrosis;
fruits show "Green
Back".
Mg deficiency symptoms
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In cereals and monocots in general the
appearance of Mg deficiency is different.
The base of the leaf first shows small dark
green spots of chlorophyll accumulation
which are apparent against the pale yellow
background color of leaves.
In more advanced stages of deficiency the
leaves become more chlorotic and striped.
Necrosis occurs particularly at the tips of
the leaf.
Corn
Magnesium
deficiency in rice
Mg deficiency symptoms
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In grapes a syndrome (综合症) is observed which
is related to Mg nutrition. It is the drying out (干
枯) of the petioles of a grapes. The petioles of the
berries, the main axis of the grape and its
ramification分枝 become necrotic.
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Vine with Mg deficiency on the leaves as well as
vine which have received heavy K fertilizer
application are particularly prone to the drying
out of the grape petioles
The disease very much affects grape yield and
quality.
Conditions of Mg deficiency
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Organic acid soils or sandy soils which
have been given heavy dressing of lime
High concentrations of K+, NH4+ or Ca2+ or
their combination
High purity of fertilizers used
Sugar beet, potato, fruit, and glasshouse
crops.
Exchange Mg is less than 25 mg/kg for all
crops ,and 50 mg/kg for sensitive crops.
Acids rains
Excessive levels of magnesium
1. Not toxic to plants or other
organisms. The excess Mg2+ can
be stored in vacuoles in the plant
cells.
2. High Mg2+ can reduce the uptake
of other ions (for example K+)
Magnesium fertilizer
Mg, g/kg
Magnesian limestone (Mg carbonate)（白云石） 30-120
Applications
Acid soil and regular liming
Ground burnt magnesian lime (MgO)
Kieserite (MgSO4 ·H2 O)
6-200
Acid soil and regular liming
160
Neutral soils
Epsom Salts (MgSO4 ·7H2 O)
Sulphate of potash magnesia (K2 SO4 ·MgSO4 )
96
66
Spraying
Suitable for plant need K and Mg
Magnesite (MgCO3 )（菱镁矿）
270
All soils
Used in horticulture
Magnesium ammonium phosphate
Management of Mg fertilizer
1. Recommendations for applying Mg2+
are the same as for Ca2+.
2. Small amounts of Mg may be applied
in a band of starter fertilizer
3. The application of Mg in combination
with other nutrients such as Si
In areas where the soil is deficient in Mg2+,
the milk cows may develop a disease that is called
“grass tetany”(草强直）staggers
(hypomagnesaemia低镁血） unless Mg2+ is added
to their diet in some other way.
Sulphur
Sulfur in soil
A. Total sulfur in the soil
Range of total S is 0.01%-0.1%
it is similar to soil P content
The concentration of S in the
soil solution is generally 5-20 ppm
in agricultural soils. A concentration
of 3-5 ppm can generally meet the
needs of the plants.
Forms of sulfur
1. Inorganic S
Sulfate (SO42-)
a) This is the form taken up by plants. It
exists in the soil solution and weakly
sorbed to soil. Generally <10% of the S in
the soil is in this form, but drier climates
may have higher amounts.
b) dissolved sulfate and absorbed sulfate
c) In arid conditions calcium sulfate (CaSO4),
magnesium sulfate (MgSO4), and sodium
sulfate (Na2SO4) are common forms of
mineral S.
Forms of sulfur
Sulfides (S2-)
Reduced S, such as H2S or FeS2,
is common in saturated soils or
waterlogged.
Elemental S (S0)
Uncommon in significant amounts
Forms of sulfur
Organic S
a) In most areas 90-95% of the total
amount of S in the soil is found in
organic matter.
The percentage is lower in dry areas
where the amount of gypsum in the soil is
large.
Organic S concentration generally
decreases with soil depth
b) Organic matter typically contains
about 1% S.
Forms of sulfur
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Sulphur in soil organic matter can be
divided into 2 fractions
Carbon bonded S and non carbon bonded S
Non carbon bonded S, such as C-O-S
and C-N-S linkage compound, is reduced to
H2S by treatment with hydriodic acid (氢碘
酸).
Carbon bonded S is reduced ( 还原型
的)and is present in cysteine(半胱氨酸）
and methioine（甲硫氨酸）, which are
readily hydrolyzed by soil sulphatase硫酸酯
酶, so it is rapidly available to plant. But
the mineralization of reduced S in organic
S is very slow.
Sulfur transformations in the soil
1. Mineralization – immobilization
It is same as previously discussed for N
and P. The mineralization of S is very
important for S nutrition in plants.
a) Affected by microbial activity,
temperature, moisture, aeration, pH,
nutrient content
b) The enzyme, sulfatase, is involved in
the mineralization of organic S
Sulfate is released from sulfate esters
Sulfur transformations in the soil
c) Effect of the C:S ratio on
mineralization and immobilization
(1) C:S >400, S immobilization > S
mineralization
(2) C:S = 200 to 400, S immobilization
= S mineralization
(3) C:S < 200, S mineralization > S
immobilization
Sulfur transformations in the soil
2. Adsorption –desorption
a) SO42- can be sorbed on the edges of
oxides and clay similar to PO42-, but the
strength of adsorption is not as great
for HPO42b) Adsorbed SO42- is a labile S pool
It is usually readily available,
replenishes the SO42- in the soil
solution
Sulfur transformations in the soil
Factors affecting strength of adsorption
(1) Sulphate adsorption capacity follows
the order
AI2O3>kaoline>bauxite(矾土）
>peat>limonite（褐铁矿）>haematite(赤
铁矿）>hydrate aluminium（氢氧化铝）
>goethite（针铁矿）
(2) Soil clay content
Soil pH (adsorption greatest in acid soils)
Adsorption of P in an acid soil
O
OH2+
O S
Al
OH2+
O
O
Al
OH2+
OH2+
OH2+
Al
OH2+
Al
O
OH2+
Al
O
OH2
+
O
S
O
Al
OH2+ -HSO4
Sulphate adsorption and special adsorption or ligand exchange
Sulfur transformations in the soil
Oxidation – Reduction
a) S exists in a number of different oxidation states
(from –2 to +6)
b) SO4-2 is the most oxidized form. Plants must
reduce SO4-2 for incorporation into most organic
compounds
c) Microorganisms are involved in the oxidation and
reduction of S in the soil.
d) Reduced inorganic S compounds occur in
anaerobic conditions
Sulfur loss from soil
1. Erosion – erosion results in a loss of
topsoil.
2. Leaching
3. Volatilization
a) Microorganisms can produce
dimethyl sulfide (CH3SCH3).
b) Direct volatilization can also occur
from plant leaves
The Sulfur Cycle
Volatilization
Dry or wet deposition
leaching
Plant Sulfur
Sulfur content of plants
１．S concentration in plants is of the same
order as that of P
２．Plant dry matter usually contains 0.2 –
0.5% S.
Grain crops (such as wheat and corn)
require 5 – 20 kg S/ha.
Forage crops (such as alfalfa) require
10 – 35 kg S/ha.
Sulfur uptake and translocation
1. Most S is taken up by roots as
inorganic SO42- (sulfate).
The process is believed to be
through active uptake, either H+/SO4-2
co-transport or OH-/SO4-2 antiport.
Selenate compete the same
transporter with Sulphate.
2. SO2 and H2S from the atmosphere
can be absorbed by plant leaves.
Sulfur movement in the plant
Sulfur is relatively immobile in the
plant.
It is usually not translocated from
older leaves to younger growing parts.
As a result, deficiencies usually occur
first on upper, younger leaves.
Tripeptide (GSH) of reduced S is an
main long distance transport form of
reduced S and also as an inhibitor of
SO42- uptake by root.
Assimilation of S in plants
1. The assimilation of S in plants begins with the
formation of adenosine phosphosulphate(APS)
２．APS is the universal donor of sulphuryl
groups（磺酰基） for the formation of sulphate
esters. Cysteine（半胱氨酸） is the first stable
product in which S is present in the a reduced
organically bound form
３．The uptake and reduction of sulphate are
regulated
Assimilation of S in plants
焦磷酸基
ATP sulphurylase
ATP磺酸化酶
磺酰基
Assimilation of S in plants
半胱氨酸
载体
乙酰基
丝氨酸
Function of Sulfur in Plants
1. S if required by plants in
relatively large amounts (similar to
P, Ca, Mg, but less than N and K)
2. S is a component of the essential
amino acids cysteine (cystine) and
methionine. These are the building
blocks for proteins. About 90% of
the S in plants in contained in
proteins.
The Amino Acid – Cysteine半胱氨酸
The cysteine is oxidizes when exposed to air to form cystine,
which is two cysteine molecules bound together by S-S bonds.
The Amino Acid with SMethionine甲硫氨酸
Function of Sulfur in Plants
3. Sulfur is important in
proteins because it
forms disulfide bonds
(S—S bonds) that are
very important for
stabilizing the
conformation(构像） of
enzyme protein．It is
also important in the
baking quality of flour
(glutenin)
Function of Sulfur in Plants
４．The oxidation of cysteine to cystine and vice
versa serves as a redox system.
The glutathione has similar reaction.
It in conjunction with an ascorbate（抗坏血酸）
dehydrogenase provides an important mechanism in the
detoxification of oxygen radical (自由基）
S is a component of ferredoxin
An important protein which carries electrons in
photosynthesis, nitrogen fixation, nitrate reduction and
sulfate reduction
Function of Sulfur in Plants
5. S is a component of Coenzyme A (an
enzyme in the production of fatty acids)
and vitamins (biotin, thiamine, B1)
6. S is a component of volatile
compounds in onions as well as plants
that are related to the cabbage family.
７．Phytochelations植物螯合剂
Cd>Pb>Zn>Sb>Ag>Ni>Hg
Sulfur deficiency symptoms
1. S deficiency results an inhibition
in protein synthesis and NO3reduction.
the ratio of organic N to organic S
is considerably higher in S deficiency
tissues.
2. In field crops sulphur deficiency
and nitrogen deficiency are
sometimes difficult to distinguish.
so leaf analysis can be invaluable.
Sulfur deficiency symptoms
3. The growth rate is reduced and delay in
maturity. Plant are rigid( 硬)and brittle（脆）
and stem remain thin. Often the entire
plant is uniformly chlorotic
4. In cruciferae (like cabbage, rape)，S
deficiency symptom appears first in
younger leaves in the form of reddish color
and necrosis beginning at margins. Finally
the entire leaf become necrotic.
5. Corn leaves may have striping.
lettuce
Excessive Levels of Sulfur
1. High SO42- concentration is Not directly
toxic to plants, but can contribute to a
soluble salt problem in saline soils (50mM).
2. High SO2 concentration in the
atmosphere may be toxic to plants.
SO2 toxicity in plants is characterized
by necrotic symptoms in leaves.
acids rain leads to destruction of
epicuticular(表皮） waxes of the needles of
spruce trees .
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Foliar symptoms
often caused by SO2
vary from interveinal
chlorosis (discolouration)
to premature
senescense of leave
Sulfur fertilizer
A. Gypsum
1. (CaSO4·2H2O)
2. 18.6% S
3. mined or a byproduct from the
manufacture of phosphate fertilizer
B. Magnesium sulfate
1. MgSO4·7H2O
2. 13% S
Sulfur fertilizer
C. Potassium magnesium sulfate
1. K2SO4 + 2MgSO4
2. 22% S
D. Sulfur-coated urea
1. 10-20% S
E. Single supersphosphate
1. 13.9% S
Management of S fertilizers



In regions far from the sea and industry, S
deficiency of crops can be common
Reduction of application of sulphate
containing fertilizers combined with
marked reduction in atmospheric SO2
concentration
Required of crops
Cruciferae（十字花科） or brassica (芸薹属）>
cereals
Glucosinolate（硫代葡萄糖苷）
containing cultivars>glucosinolate free ones

The relationships of S and N are of
particularly importance to the S
application.