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Title: PowerPoint Sunusu


1
BIO-543 Plant Stress Physiology
2
Plant Stress Physiology interacts with genetical
engineering to identify and characterize target
plant traits
Identify Genes
Structural Genomics
Transgenic Development
Better Varieties, New Traits Markets
Germplasm
Plant stress physiology
crop varieties with good genes
Functional Genomics
Breeding Enhancement
Learn what genes do
3
BIO-543 Plant Stress Physiology
  • Reactions of plants to environmental stress
    factors
  • Importance of stress factors in global crop
    production
  • Gene expression in response to stress and
    development of transgenic plants with elevated
    stress tolerance
  • Adaptation of photosynthetic apparatus to stress
    conditions
  • Drought, salinity, high light, heat, low
    temperature, freezing, mineral nutrient
    deficiency, heavy metal toxicity, root responses
    to mineral deficiencies and toxicities,
    phytoremediation, responses to plant pathogens,
    flooding/oxygen deficiency
  • A special attention will be given to synthesis
    and detoxification of oxygen free radicals and
    oxidative cell damage under stress conditions

4
Plant Stress Physiology   Importance of Stress
Factors in Global Crop Production   Plant
Response to Stress Factors   Soil
Acidity -Aluminum Toxicity -Metal
Toxicity -…related Phosphorus Deficiency   Drought
and Salinity -Water deficiency -Salinity -Sodicit
y/alkalinity
5
Mineral Nutrient Deficiency -Macronutrients -Micro
nutrients   Extreme Temperatures -Low
temperature/freezing -High temperatures/heat   Flo
oding/O2 Deficiency Diseases
6
BITTER FACTS OF REAL LIFE WHAT HAPPENES OUT OF
TEST TUBES?
7
Source FAO, 1998
8
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9
Agricultural productivity is decreasing globally
due to enhanced soil degradation
  • Erosion
  • Nutrient depletion
  • Water scarcity/global warming
  • Acidity
  • Salinization
  • Depletion of organic matter
  • Poor drainage
  • Central America and Sub-Saharan Africa are the
    most affected parts of the world

10
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11
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12
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13
Many factors determine how plants respond to
environmental stress
14
Plant resistance to environmental stresses can
involve tolerating the stressful condition or
avoiding them. Some resistance mechanisms are
constitutive and are active before exposure to
stress. After stress recognition, the signal is
communicated within cells/throughout plant,
resulting in altered gene expression at cellular
level and plant response to stress in the form of
a physiological and/or developmental event.
15
Aluminium Toxicity and Acid Soils
16
Third most abundant element in the earths crust
Al toxicity is an important stress factor to
agricultural productivity worldwide
At soil pH values below 5, Al3 solubilizes into
the soil solution
30 - 40 worlds arable soils are acidic
Al3 inhibits root growth and function
17
Al Toxicity and Soil Acidity are Closely Related
Stress Factors
In strong acid soils (pHlt5.0) ?Al3 becomes
soluble ?Al3 undergoes hydrolysis
18
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19
Changes in Al Species in Soil as Affected by pH
20
- ideal pH for plant growth is 6.5
- acid soils pH lt 5.5
Factors causing soil acidification
  • high rainfall
  • leaching of basic cations
  • soil acidification also due to
  • disturbance in N cycle
  • acid rains

21
Nitrogen transformation and soil acidification
Topsoil
22
Change in soil pH as response to form of nitrogen
supply
23
Nitrate leaching and soil acidification
Topsoil
Fertiliser nitrate
NO3-
24
Soil pH change under red clover and ryegrass
during a 14-month growth period
Ryegrass
Soil pH
Clover
Number of cuts
Mengel Steffens (1982)
25
Major constraints to plant growth on acid mineral
soils
1. H toxicity (pH lt 4.0)
2. Al toxicity (pH 4.0-5.0)
  • Mn toxicity (pH 5.0-5.5)  

4. Cation deficiency Mg, Ca and sometimes K
5. Anion deficiency P and Mo
6. Inhibition of root growth and water uptake
26
Total area of acidic soils in the world 3.777
to 3.950 billion ha approximately 30 of the
total ice-free land area on this planet
27
Spread of acid soils in the world
World Acid land (x109 ha) of total
Africa 0.66 22
Europe 0.39 37
Aus / NZ 0.24 30
Near East 0.005 1
28
Spread of acidic topsoil and subsoil in the world
billions of ha
World Acid topsoil Acid subsoil
Slight (5.5-6.5) 1.25 0.5
Moderate (4.5-5.5) 1.54 1.38
High (3.5-4.5) 0.98 0.95
Extremely acid (lt3.5) 0.15 0.01
Total 3.92 2.92
29
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30
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31
Value of crops grown on acid soils (1990 data)
Crops Million ha Billion US
Roots tubers 36 48
Tree crops 33 26
Cereals 95 22
Sugarcane 12 17
Legumes 36 8
Fruits vegetables 1 8
Total 213 129
Von Uexkull Mutert 1995. Plant and Soil
1711-15 .
32
ALUMINUM TOXICITY IN HIGHER PLANTS
Al3 is the major toxic species
Dramatic inhibition of root growth, occurring
within minutes
ATLAS
Root apex must be exposed to Al to inhibit root
growth
10 cm
0
5
20
50
µM Al3
Root apex is the site of toxicity
Genetic variation in Al tolerance has led to
identification of adaptive mechanisms for plant
growth on acidic Al-toxic soils
SCOUT
Plants grown for 4 days
33
Lime
Acid soils
Non-acid soils
Al3
Clay ? Clay 3 CO2
Al3
Rengel Z (2002) Encyclopedia of Soil Science
34
Effect of liming 2.5 t lime/ha in 1984, barley
photographed in 2000 Wongan Hills, W. Australia
Lime
-Lime
35
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36
Lime
Acid soils
Non-acid soils
Al3
Clay ? Clay 3 CO2
Al3
Rengel Z (2002) Encyclopedia of Soil Science
37
Variability for Al Tolerance in Crop Species
  • Variation for Al tolerance exists between
    species
  • - in the cereals rye gt wheat gt barley
  • Variation for Al tolerance exists within species
  • - range can be broad and continuous

38
Excess Al3
  • Normal Growth
  • Exclusion of Al and/or intrinsic Al tolerance
  • Root exudation of organic acids (citrate, malate)
  • Reduced Growth
  • Inhibition of nutrient uptake
  • Disturbance of cellular functions

39
Differential Al Tolerance Within/Between Cereal
Crops
Root Growth (mm) Relative Root
Length -Al Al
( of control)
Wheat Atlas 32 35
111 Scout 39 8
21 Barley Dayton 39
4 9 2 days
at 5 uM Al3
40

41
Aluminum Accumulation in Maize Root Apices
Total Al 222 µM Al3 activity 39 µM
42
Al3 accumulation in Al sensitive (left) and
tolerant (right) barley cultivars
Dayton
Harlan Hybrid
Root Tip Hematoxylin Staining The absence of
the color in root tips treated by hematoxylin
indicates that these plants either exclude or
bind aluminum in complexes that are unavailable
to hematoxylin. The method has been used
extensively for quick evaluation of and screening
for aluminum tolerance.
43
Aluminum Accumulation in Wheat Root Apices
44
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45
ALUMINIUM TOLERANCE
  • Detoxification of Al by chelation with organic
    acids released from the root apex

Malate2- Al3 Al-malate1
46
Organic Acid Release an Al Tolerance Mechanism
? Al-citrate and Al-malate complexes are not
taken up by roots
? Al tolerant maize/wheat exclude Al only from
root apex
? Exogenously added citrate and malate
ameliorate Al toxicity
47
Mechanism of Al3 tolerance in Plants
Al-tolerant
Al-sensitive
Al3
Al3
Al3
Al3
Al3
Al3
Al3
Al3
Al3
Al3
Malate2- and K efflux from the root apices of
tolerant genotype
Al3
Al3
Al3
48
ROOT EXUDATES AND Al TOLERANCE
  • Malate Release
  • Wheat
  • Delhaize et al (1993) Plant Physiol 103 695
  • Ryan et al (1995) Planta 196 103
  • Huang et al (1996) Plant Physiol 110 561
  • Citrate Release
  • Snapbean Miyasaka et al (1991) Plant Physiol 96
    737
  • Maize Pellet et al (1995) Planta 196 788
  • Cassia tora (1997) Plant Cell Physiol 38 1019
  • Oxalate Release
  • Buckwheat Ma JF et al (1997) nature 390 569
  • Taro Ma Z and Miyasaka (1998) Plant Physiol 118
    861
  • Phosphate release
  • Maize and wheat Pellet et al (1995) Planta 196
    788 and Pellet et al (1996) Plant Physiol 112 591

49
Relationship between malate exudation and Al
resistance in wheat genotypes (n36)
r2 0.84
É
É
3
É
É
É
É
Malate exudation, nmol/apex
2
É
É
É
É
É
É
É
É
É
1
É
É
É
É
É
É
É
É
É
É
É
É
É
É
É
É
É
É
0
É
É
0
20
40
60
80
100
Relative root length in 10 µM Al
Ryan et al. (1995)
50
Ameliorative effect of exogenously added malate
Genotype ES3
10 µM malate
20 µM malate
3 µM Al
3 µM Al 5 µM malate
3 µM Al 10 µM malate
3 µM Al 20 µM malate
0
25
50
75
100
125
Relative root length,
Ryan et al. (1995)
51
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52
Aluminum-Induced Malate Efflux in Wheat (n8)
53
Reduced Al Tolerance in Chinese Spring
Ditelosomic Lines is Associated With Altered
Malate Exudation (Al treatment 25 µM)
Relative Root Growth
Malate Efflux ( of
control) (pmol root-1h-1) Ch.
Spring 80 7 515 44 Dt4DS 16 3 44
7 Dt5AL 32 8 121 14 Dt7AL 31 11 191 15
Source Papernik et al., 1998
54
Root Citrate Efflux in Al Tolerant and Sensitive
Barley
55
Al Accumulation in Al Sensitive and Tolerant
Barley Cultivars
Harlan Hybrid
Dayton
56
Root Al Tolerance in Wheat NILs and Parents
120
Atlas 66
Century
100
Century-T
Chisholm
Chisholm-T
80
Relative root growth ( of control)
60
40
20
0
0
5
10
15
20
25
30
35
m
Al concentration (
M)
57
Al-Induced Root Malate Exudation
3
Atlas 66
Century
Century-T
Chisholm
Chisholm-T
2
Malate efflux (nmoles root -1 h-1)
1
0
0
5
10
15
20
25
30
35
m
Al concentration (
M)
58
ChT
CeT
Ce
A
Ch
59
EXUDATION IS LOCALIZED
Citrate
Malate
0.5
0.4
0.3
nmoles/h/root
0.2
0.1
0
0.5
0.4
0.3
nmoles/h/root
0.2
0.1
0
-Al
Al
-Al
Al
60

Predicted Organic Acid Concentrations in the
Wheat Rhizosphere

61
Citrate Release
10
8
6
citrate nM/root/h
4
2
0
0
10
20
30
40
50
segment cut from root tip mm
62
Evidence in Support of Al-Induced Organic Acid
Release as an Al Tolerance Mechanism
  • Addition of malate or citrate to Al-toxic
    solutions ameliorates Al toxicity
  • Al-malate/Al-citrate complexes are not absorbed
    by roots
  • Rapid release is consistent with time frame of
    observed tolerance differences
  • Tolerance and malate release are both specific
    for Al
  • Recent evidence for an Al-gated anion channel in
    the plasma membrane of root apical cells from ET3
  • Over-expression of bacterial citrate synthase
    gene in tobacco and papaya results in increased
    root citrate efflux and significant increase in
    Al tolerance

63

Model for Organic Acid Detoxification of Al in
the Rhizosphere
Root
Soil
Microbial decomposition
Dissolution
Malate efflux
Solid phase Al
Al3 in soil solution

Sorption
Sorption to anion exchange sites
64

Al3 Induced Organic Acid Efflux Via an Al-Gated
PM Anion Channel
Cytoplasm
Apoplasm
(pH 7.0)
(pH 4.0-4.5)
2-
Malate
3-
Citrate
3
Al binding to
organic acid channel
channel
3
Al binding to PM
opening

unknown PM receptor)
3
Al uptake
Al-species ?
65
Al- INDUCED ORGANIC ACID EXUDATION IN
WHEAT
AND
CORN
1.5
Tolerant
Malic Acid (µmoles flask -1)
0.5
Sensitive
0
100
200
Al added (µM)
66
CSb transformant
Control
Control and CSb transformant (citrate-overproducin
g transformant containing a vector with a CS
coding sequence) papaya plants after 30 days of
culture in the presence of 300 µM Al.
de la Fuente et al., 1997 Science, 276 5318,
1566-1568
67
Level of citrate and citrate efflux in roots of
transgenic 35S and control tobacco plants
de la Fuente et al., 1997 Science, 276 5318,
1566-1568 ,
68
Root growth inhibition of 35S-CSb and control
tobacco lines by different concentrations
de la Fuente et al., 1997 Science, 276 5318,
1566-1568 ,
69
Growth of tobacco CSb and control lines
germinated in Al-containing media (A) Control
plants germinated in media with or without 300 µM
Al, (B and C) Control (B) and CSb-18 (C) plants
germinated in media containing 0, 75, 300, and
1000 µM Al, (D and E) CSb-4 and CSb-18 1-week-old
seedlings germinated in 200 µM Al. (H)
Segregation of Al-tolerance phenotype in the
CSb-18 T1 progeny in medium containing 300 µM Al
(pH 4.3) arrows indicate susceptible seedlings.
(F, G, I, and J) Hematoxylin staining of root
hairs and root tips of 7-day-old seedlings
treated for 1 hour with 100 µM Al (F) and (I)
are control and (G) and (J) CSb-18 seedlings.
de la Fuente et al., 1997 Science, 276 5318,
1566-1568
70
Nature Biotechnology 18, 450 - 453 (2000)
71
Growth and productivity of CSb tobacco plants
subjected to different P treatments.
Transgenic (CSb-4 and CSb-18) and control (1522)
plants were grown in a sterile low-P, alkaline
soil with or without application of P.
Nature Biotechnology 18, 450 - 453 (2000)
72
Transgenic (CSb-4 and CSb-18) and control (1522)
plants were grown in MS nutrient media (pH 8.0)
with or without application of 1 mM of citric
acid. Soluble and insoluble sources of phosphate
were adjusted to 1 mM.
Nature Biotechnology 18, 450 - 453 (2000)
Effect of citrate on the biomass accumulation of
tobacco plants grown in media containing an
insoluble source of phosphate.
73
P level in leaves of CSb and control lines.
Total content of phosphorus in shoots of control
and CSb-4 and -18 lines grown at two levels (22
and 44 p.p.m.)
74
Al-activated efflux of citrate from whole roots
of tobacco. Tobacco (cv Wisconsin 38) plants were
grown for 11 d in full nutrients, then
transferred to either control solution (-Al
0.2 mM CaCl2, pH 4.3) or Al solution (Al 50 µM
Al, 0.2 mM CaCl2, pH 4.3)
Delhaize et al., 2001 Plant Physiol, 2001
2059-2067
75
A Al-activated efflux of citrate from various
root segments of tobacco B the effect of Al
concentration (0-50 µM) on citrate exuded over
9 h by 6-mm root apices.
Delhaize et al., 2001 Plant Physiol, 2001
2059-2067
76
Citrate concentrations of roots from various
transgenic lines expressed as a percent of
control lines. Citrate concentrations for P502
(control for PA lines) ranged from 0.29  0.01 mM
to 0.56  0.11 mM and was 0.30  0.04 mM for
CM1522 (control for CSb lines).
Delhaize et al., 2001 Plant Physiol, 2001
2059-2067
77
Delhaize et al., 2001 Plant Physiol, 2001
2059-2067
78
Al tolerance of selected transgenic lines of
tobacco
The transgenic tobacco (Nicotiana tabacum cv
Xanthia) lines CM1522 (control) and CSb18. P502
(control for PA lines)
Delhaize et al., 2001 Plant Physiol, 2001
2059-2067
79
Activity levels of citrate synthase in different
lines of A. thaliana including wild-type (WT
solid bar), null plants (pseudo-wild type N
shaded bar) and DcCS transgenic plants (T open
bar).
Koyama et al., Plant and Cell Physiology, 2000,
41 1030-1037
80
Relationship between in vitro CS activity and the
amount of citrate excreted from roots of A.
thaliana
Koyama et al., Plant and Cell Physiology, 2000,
41 1030-1037
81
Growth comparison of transgenic (T7) and wild
type A. thaliana. Plants were grown for 4 weeks
on a typical Japanese acidic soil with a range of
P-levels (0.050.25 g NaH2PO4/100 g soil) in the
presence of 0.25 g CaCO3.
Koyama et al., Plant and Cell Physiology, 2000,
41 1030-1037
82
Citrate excretion in a carrot (Daucus carota L.)
mutant cell line IPG (insoluble phosphate grower)
HPLC analysis of organic acids released from IPG
cells. IPG cells were grown for 7 d with
Al-phosphate (2 mM) as a sole phosphate source
Ohno et al., Plant and Cell Physiology, 2003, 44
156-162
83
Time course of citrate excretion from IPG (filled
circle) and wild-type (open square) cells. Both
cell lines were incubated in a medium containing
colloidal Al-phosphate (2 mM Pi 4 mM Al) at
pH 5.6
Ohno et al., Plant and Cell Physiology, 2003, 44
156-162
84
Biochemical detection of lipid peroxidation and
other events caused by aluminum in pea roots. Pea
seedlings were treated with (?) or without (?)
10 µM aluminum in 100 µM CaCl2 (pH 4.75) for
24 h. The root apex was sectioned in 5-mm
intervals from the tip (0 mm) toward the basal
region (25 mm). Each section was analyzed for
aluminum content (A), lipid peroxidation (B),
callose content (C), or the loss of plasma
membrane integrity
85
Dose dependent (0-20 µM Al) changes in lipid
peroxidation and other events caused by high
aluminum stress in pea roots
86
Time dependent changes in lipid peroxidation and
other events caused by high aluminum stress in
pea roots treated with (?) or without (?) 10 µM
aluminum in 100 µM CaCl2 (pH 4.75) for up to 24 h
Plant Physiol, January 2001, Vol. 125, pp. 199-20
87
Histochemical detection of lipid peroxidation and
other events caused by aluminum in pea roots. Pea
seedlings were treated with (left) or without
(right) 10 µM aluminum in 100 µM CaCl2 (pH 4.75)
for 24 h. The roots were stained with either
hematoxylin (A, aluminum accumulation), Schiff's
reagent (B, lipid peroxidation), aniline blue (C,
callose production), or Evans blue (D, the loss
of plasma membrane integrity
Plant Physiol, January 2001, Vol. 125, pp. 199-20
88
  • Commonly secreted organic acids that detoxify
    aluminium (Al) in wheat (cv. Scout 66).
  • Root elongation during 20 h exposure to Al
  • Al accumulation (pink/blue color) stained by
    Eriochome cyanine dye. The absence of colour
    indicates that the organic acid has chelated the
    Al and prevented its accumulation in the root
    apices

Ma et al., 2001, Trends Plant Sci., 6273-278
89
Models for the aluminium (Al)-stimulated
secretion of organic acid anions (OA) from plant
roots. For Pattern I-type responses (1) Al3
interacts directly with the channel protein to
trigger its opening (2) Al3 interacts with a
specific receptor (R) on the membrane surface or
with the membrane itself to initiate a
secondary-messenger cascade that then activates
the channel or (3) Al3 enters the cytoplasm and
activates the channel. The Al-activated efflux
from maize probably occurs by mechanism (1) In
the Pattern II response, Al interacts with the
cell, perhaps via a receptor protein (R) on the
plasma membrane, to activate the transcription of
genes that encode proteins involved with the
metabolism of organic acids or their transport
across the plasma membrane.
Ma et al., 2001, Trends Plant Sci., 6273-278
90
pH
4.5 6.5 8.5
91
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92
Ma et al., 2001, Trends Plant Sci., 6273-278
Colours of Hydrangea sepals with different
concentrations of aluminium (Al). Hydrangea was
grown in a nutrient solution with or without Al,
or in a soil amended with or without Al. The blue
colour of Hydrangea sepals is due to the
formation of a complex between delphinidin
3-glucoside, Al and 3-caffeoylquinic acid. The Al
concentration in the sepals from pink to blue is
51, 106, 640, 804 and 3959 mg Al kg-1 dry weight,
respectively.
93
Uptake and distribution of various aluminium (Al)
forms in the Al-accumulating plant, buckwheat
(Fagopyrum esculentum).
Ma et al., 2001, Trends Plant Sci., 6273-278
94
Heavy Metal Stress in Plants
95
Heavy Metal Abundance in Nature
  • Heavy metals are natural elements
  • Elements with specific weight gt5 g cm-3 are
    generally accepted as heavy metals e.g. Zn (7.1),
    Cr (7.2), Cd (8.6), Ni (8.7), Co (8.9), Cu (8.9),
    Mo (10.2), Pb (11.4), Hg (13.5)
  • Al (2.7) is a light metal..!

96
Heavy Metal (HM) Abundance in Nature
  • Concentration depends on soil parent material and
    human activity (anthropogenic sources )
  • Can be highly toxic to biological systems when
    their availability is high (i.e. availability is
    more important than total amount of HMs)
  • Anthropogenic HM sources can be more dangerous
    very long time is required for binding to
    soils/sediments/basins and get stabilized

97
For Plants to Take Up Metals
Metals should be in available form in the growth
media (i.e. dissolved in soil solution)
Plants must have unique metal uptake mechanisms
(e.g. release of metal chelating root exudates,
organic acids, H )
98
Main Soil Factors Affecting Metal Availability to
Plants
  • Water content, pH, CEC (cation exchange capacity
    clay content, organic matter)
  • Low pH increases metal (Men) availability by
    displacement of Men by H from the negatively
    charged clay surfaces
  • High CEC means a higher possibility to bind to
    negatively charged surfaces (i.e. clay minerals
    and organic matter)
  • General principle higher organic matter, CEC,
    clay content and pH means more firmly binding of
    Men (i.e. lower availability to plant roots)

99
Metal Uptake by Roots
  • Diffusion metals can diffuse towards roots along
    a concentration gradient formed by depletion of
    that metal due to continuous active uptake of
    roots
  • Root Interception displacement of soil volume by
    the root volume during growth
  • Mass Flow transport of metals by mass flow of
    soil solution (driving source transpiration and
    soil water potential)

100
Path of Heavy Metal Uptake by Roots
To Shoot
Stabilization on root cell walls
Free metal cation in soil solution
Apoplastic transport
Casparian strip
Root apoplast
Men
stele
Transport across root cells
101
Possible Mechanisms of HM Tolerance in Plants
?Binding to cell wall ?Restricted influx through
plasma membrane ?Active efflux ?Compartmentation
in vacuole ?Chelation at the cell wall-plasma
membrane interface ?Chelation in the cytoplasm
102
Biosynthesis of Glutathione and Phytochelatins
103
Heavy metal (e.g. Pb) induced generation of ROS
and subsequent antioxidative responses in plants
Ascorbate-Glutathione Cycle
104
Superoxide dismutases (SODs) are antioxidant
metalloenzymes catalysing the dismutation of
superoxide radical, O2
SOD
It is generally accepted that in all SODs the
metal ion (M) catalyses dismutation of the
superoxide radical through a cyclic
oxidationreduction mechanism

105
The Mn-SOD
O2.- generation and NBT reduction test
106
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107
Cysteine, glutathione, phytochelatin and cadmium
concentration in apical (0-10 cm) maize roots
exposed to 0 or 3 µM Cd2 for 24h
108
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109
Source Managing cadmium in potatoes for quality
produce (CSIRO 1996)
110
Nutrient Deficiency Stress in Plants
111
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112
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113
Copenhagen Consensus
Micronutrient Malnutrition is among 3-most
critical problems facing the world, currently a
statement made by a panel of worldwide
distinguished economists including Nobel
laureates
Source http//www.copenhagenconsensus.com
114
Zinc Deficiency Stress
115
Zn Deficiency a Global Nutritional Problem
Australia gt10 mio ha Turkey 14 mio
ha Bangladesh 2 mio ha China 30 mio
ha India 90 mio ha
Source White and Zasoski, 1999 Field Crops
Res., 6011-26 Eyüpoglu et al., 1994 Soil
Fertilizer Res. Inst. Reports
116
Geographic distribution of severe- (red areas)
and moderate- (green areas) Zn deficient soils of
the world
(Alloway, 2001)
117
Zinc deficiency as global nutritional problem in
human beings
Zinc deficiency
Courtesy of Dr. J.Veenemans, Wageningen University
118
Soil factors affecting availability of Zn to roots
  • high CaCO3
  • high pH
  • clay soils
  • low organic matter
  • low soil moisture
  • high Fe and Al oxides

SOIL
Zn
Zn
Enhanced Zn adsorption and precipitation
Zn
Zn
Limited Zn uptake
Zn
Decreased Zn desorption
Zn
Zn
119
Functions of Zn
  • Zn forms tatrahedral complexes with N-, O- and S-
    ligands
  • Zn has both functional (catalytic) and structural
    role in enzymes
  • Zn is an essential nutrient virtually for all
    living organisms and is a co-factor for more than
    300 enzymes, representing over 50 different
    enzyme classes

120
  • Catalytic Function (e.g. carb. anhydrase, carb.
    peptidase) Zn is coordinated to four ligands
    (three AA and one H2O)
  • Structural Function (e.g. alcohol dehydrogenase,
    proteins involved in DNA repl. and gene
    expression) structural Zn atoms are coordinated
    to S-groups of four cystine residues

121
Carbonic anhydrase (180 kDa) -consists of six
sub units with six Zn atoms -localized in
chloroplasts and cytoplasm -required for an
efficient photosynthesis by catalyzing the
hydration of CO2 -activity is absent at severe Zn
deficiency
122
Under Zn deficiency Cu/Zn SOD activity is reduced
and ROS generation is enhanced
123
Zn is required for an efficient ROS
detoxification under stress conditions
124
FREE RADICAL DAMAGE TO CRITICAL CELL CONSTITUENTS
O2
h.v.
e-
1O2 O2._ H2O2 OH.
DNA
MEMBRANE
PROTEIN
CHLOROPHYLL
S-H
S-H
SS
SS
LIPID PEROXIDATION
MUTATION
CHLOROSIS
PROTEIN DAMAGE
CELL DEATH
125
Zn is required in DNA and RNA metabolism Zn
finger proteins function in transcription/transla
tion and thus gene expression
126
Zn finger protein Zat12 plays an important role
in abiotic stress signaling in Arabidopsis
Source Davletova et al, 2005 Plant Physiology
139 847856
127
Arabidopsis plants expressing luciferase under
the control of the Zat12 promoter in response to
different environmental stresses
Source Davletova et al, 2005 Plant Physiology
139 847856
128
Zinc is essential in carbohydrate metabolism
129
Under Zn deficiency auxin metabolism is altered
due to reduced synthesis and enhanced oxidation
of IAA
130
Zn deficiency specifically alters root P uptake
and translocation of P to shoots
131
Mechanisms affecting expression of a higher Zn
efficiency
  • Uptake (H-ATPase, release of LMW componds and
    phytosiderophores)
  • Root to shoot translocation
  • Remobilization (or retranslocation)
  • Internal utilization
  • Remobilization to grain (i.e. Zn
    biofortification)

132
Growth of maize as affected by seed Zn treatment
Seed Zn Treatment
Untreated
Courtesy of Dr. Kevin Moran
Farming for Health, Oslo, Oct.-2005
133
Durum wheat extremely sensitive to Zn deficiency
Durum Wheat
Rye
Triticale
Bread Wheat
-Zn
Differences in Tolerance to Zinc Deficieny among
Cereal Species
Zn
-Zn
(DTPA-Zn 0.09 mg kg-1 soil)
Source Cakmak et al., 1997 Plant and Soil
134
Effect of soil Zn application on grain yield of
Gerek in different locations of Central Anatolia
having different levels of DTPA-Zn
135
Zinc and Healthy Plant growth
Leaf Zn concentration should be around 25-40 mg
kg-1 to ensure healthy growth and better yield
136
When Zn is deficient in soil or plant
Zn
Leaf Zn 32 ppm
-Zn
Leaf Zn 9 ppm
137
When Zn is deficient in soil or plant
Zn
-Zn
Grain Zn 35 mg kg-1
Grain Zn 12 mg kg-1
138
Foliar Application of Zn on Barley Field
139
severity of Zn deficiency in wheat
Source Cakmak and Braun, 1999 In Application
Physiology in Wheat Breeding, CIMMYT
140
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141
durum wheatltoatltbread wheatltbarleylttriticaleltrye
adaptation to Zn-deficient soil
142
Greenhouse-Screening for Tolerance to Zn
deficiency
143
Rye shows an exceptionally high Zn efficiency
(Zn efficiency better growth/yield under Zn
deficiency)
RYE
RYE
WHEAT
Growth of rye in a Zn-deficient wheat field
144
Resistance to Pests and Diseases
Improving Abiotic Stress Tolerance
SEED ZINC
Improving Human Nutrition
Decreasing Seeding Rate
Better Seedling Vigour
145
Increase in Seed Zn Content Improves Growth
of Wheat on a Zinc-Deficient Soil in Central
Anatolia
0.36 ?g Zn seed-1
1.47 ?g Zn seed-1
0.80 ?g Zn seed-1
Source Yilmaz et al., 1998, J. Plant Nutr.
146
Genotypes with very high Zn content are generally
resistant to diseases (especially root diseases)
and abiotic stress factors such as heat/drought
and low temperature stress (resistance to winter
killing) Better Seedling Vigor
and Vitality Seeding rate on Zn-deficient soils
in Turkey can be lowered greatly causing a
benefit of 50 million USD a year due to better
seedling vigor
147
Zn concentration and Cu-Zn/SOD activity in leaves
of durum wheat, bread wheat and rye grown in
Zn-deficient soil
Zn 6.1 ppm SOD 430 U
Zn 6.4 ppm SOD 695 U
Zn 7.1 ppm SOD 781 U
BREAD WHEAT
RYE
DURUM WHEAT
-Zn
Source Cakmak et al., 1997 J. Plant Physiol.
148
Mineral Nutrition Photooxidative Damage
149
Mineral Nutrition and Photooxidative Damage
Mineral nutrients, by playing a major role in
utilization of absorbed light energy and in
maintenance of photosynthetic carbon metabolism,
protect crop plants from photooxidative damage
150
Generally, under nutrient deficient conditions
  • Photosynthesis is impaired by primary or
    secondary effects of nutrient deprivation
  • ROS production during photosynthetic electron
    transport is enhanced (dissipation of absorbed
    light is impaired)
  • NADPH-oxidizing enzyme reactions are activated
    which facilitates membrane damage and chlorophyll
    degradation
  • Antioxidative defence mechanisms are activated
  • Photooxidation and photoinhibition of
    photosynthesis is enhanced
  • Plants become photosensitive and show light
    induced chlorosis/necrosis
  • Nutritional status can determine survival of
    plants under environmental stress conditions such
    as drought, chilling, and high light intensity.

151
  • ROS is mainly produced in chloroplasts and
    mitochondria
  • Superoxide radical (O2 )
  • Hydrogen peroxide (H2O2)
  • Singlet oxygen (1O2)
  • Hydroxyl radical (OH)
  • Production of ROS is enhanced when plants are
    exposed to environmental stress
  • Drought
  • Chilling
  • Nutrient deficiency
  • Salinity
  • UV Radiation

152
  • Under normal conditions, up to 20 of the total
    photosynthetic electron flux is transferred to
    molecular O2, forming O2 and other ROS species
  • Plants are evolved to overcome this inevitable
    situation by their enzymatic and non-enzymatic
    defense mechanisms (e.g. SOD, enzymes and
    anti-oxidants of the ascorbate-glutathione
    pathway)

153
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154
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155
Subcellular localization of antioxidants and
protective enzymes in a typical plant
cell (adapted from Polle and Junkermann, 1994).
156
Source Bashir et al., 2007. Plant Mol Biol
65277284
157
  • Among mineral nutrients nitrogen (N) plays a
    major role in utilization of absorbed light
    energy and maintaining photosynthetic carbon
    metabolism.
  • In N-deficient leaves an excess of non-utilized
    light energy can be expected leading to high risk
    for occurrence of photo-oxidative damage.

158

Effect of varied nitrogen supply on
photosynthetic characteristics in C. album
leaves grown at high light
Kato et al., 2003, Plant Cell Physiol. 44318-325
159
To avoid occurrence of photooxidative damage in
response to excess light energy, thylakoid
membranes has a protective mechanism by which
excess energy is dissipated as heat.
Dissipation of excess light energy is
associated with enhanced formation of xanthophyll
pigment zeaxanthin
160
Xanthophyll Cycle Composition in Relation to Leaf
N of Fuji/M.26 Trees at Noon Under an Incident
PFD of 1500 µmol m-2 s-1
300
240
180
Z or V (mmol mol Chl-1)
Zeaxanthin (Z)
120
60
Violaxanthin (V)
0
4
5
1
2
3
Leaf N (g m-2)
Verhoeben et al., Plant Physiol. 1997, 113
817-824
161
Use of Absorbed Light Energy for Photosynthesis
Low N
High N
Photochemistry
Dissipation
Dissipation
36
Photochemistry
64
37
63
Verhoeben et al., Plant Physiol. 1997, 113
817-824
162
  • N is greatly needed for efficient use of absorbed
    light energy in photosynthetic CO2 fixation.
  • Adequate N nutrition is of great importance for
    plants exposed to environmental stress factors
    such as drought, chilling, salinity etc.
  • Adverse effects of environmental stresses (e.g.,
    chilling) on plant growth could be more dramatic
    under low N supply

163
Effect of Increasing Nitrogen Supply on Lipid
Peroxidation at Normal and Low Temperature in
Lemon
-3.5 oC
24 oC
Nitrogen Supply
S. Eker, unpublished results
164
Effect of Increasing Nitrogen Supply on Catalase
at Normal and Low Temperature in Lemon
24 oC
-3.5 oC
S. Eker, unpublished Results
Nitrogen Supply
165
Under low temperature conditions an improved
nitrogen nutrition is needed for better
maintenance of photosynthesis and protection
against photo-oxidative damage
166
ACCUMULATION OF TOXIC FREE RADICALS IN
Zn-DEFICIENT PLANTS ZINC-DEFICIENCY INDUCED FREE
RADICAL GENERATION (ESR-SIGNALS) IN COTTON ROOTS
PLANT AGES (days) 14 18
22
Zn
-Zn
Cakmak and Marschner, 1988 J. Experimental
Botany, 391449-1460
167
  • Zn and B deficiencies affect photosynthetic
    activities of plants in various ways.
  • Both micronutrients exert marked influences on
    photosynthetic CO2 fixation and translocation of
    photosynthates.
  • Any disturbance in the adequate supply of plants
    with Zn and B is, therefore, potentially capable
    of inducing photooxidative damage

168
Effect of different light intensities on shoot
growth of Zn-deficient bean plants
ZINC-DEFICIENT PLANTS ARE HIGHLY
PHOTO-SENSITIVE Increases in light intensity
rapidly cause development of chlorosis and
necrosis in Zn-deficient plants
169
Primary leaves of Zn-deficient bean plants grown
at different light intensities
490 µmol m-2 s-1
80 µmol m-2 s-1
230 µmol m-2 s-1
170
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171
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172
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173
Growth of Citrus Trees on a Zn-Deficient Soil
South
North
174
O2.- - Production in Leaf Disks
Unpublished results
175
DEFENSE AGAINST RADICAL DAMAGE (e.g. ascorbic
acid, glutathione, glutathione reductase)
CELL DAMAGE
B
-B
1O2 , H2O2
PHOTOACTIVATION
-B
PHENOLS
QUINONES
PHENOL OXIDATION
O2.-
H2O2
B
O2
Semiquinones
Cakmak and Romheld,1997 Plant and Soil
176
O2 - Generating NADPH - Oxidase
Activity of NADPH-oxidizing enzymes play an
important role in generation of superoxide
radical production under drought, chilling, Zn
deficiency, UV light, wounding, pathogenic
infection, etc.
NADPH
e-
Flavin ox
Flavin red
O2
O2
CELL DAMAGE
177
High light-induced damage in B-deficient plants
Low light
Low light
High light
High light
Sufficient B Supply
Deficient B Supply
178
Photooxidative damage to membrane and chlorophyll
can be expected in B-deficient leaves as a result
of enhanced photogeneration of toxic oxygen free
radicals caused by impaired utilization of light
energy in photosynthesis
Shaded
Un-shaded
179
Changes in antioxidants (ascorbate and nonprotein
SH-compounds) in bean plants grown with
sufficient and deficient Mg supply under
different light intensities
Plant Physiol. 1992 98, 1222-1227
180
Changes in antioxidative enzyme activities in
bean plants grown with sufficient and deficient
Mg supply under different light intensities
Plant Physiol. 1992 98, 1222-1227
181
Activities of antioxidative enzymes in shaded or
non-shaded bean leaves grown under sufficient and
deficient Mg supply
Plant Physiol. 1992 98, 1222-1227
182
PQ-induced chlorophyll degradation in Mg
sufficient and deficient bean leaves
Plant Cell Environment 15, 955-960
183
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184
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185
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186
  • Mineral nutrients supplied at adequate levels
    are essentially required for maintaining
    photosynthetic activities and utilization of
    light energy in CO2 fixation.
  • Improving mineral nutrition of plants is,
    therefore, a major contributing factor to the
    protection of plants from photo-oxidative damage
  • Photo-oxidative damage is an important
    contributing factor in development of mineral
    nutrient deficient symptoms on leaves

187
  • Improving mineral nutritional status of plants
    under marginal environmental conditions is
    indispensable for sustaining survival and high
    yield.
  • Impairment in mineral nutritional status of
    plants exacerbates adverse effects of
    environmental stress factors on plant performance
    by stimulating photo-oxidative damage

188
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