Download Micronutrients and beneficial elements in horticultural crops

Processes at the soil/root interface involved in plant
nutrient acquisition
Micronutrients and beneficial elements in
horticultural crops between critical aspects
and new opportunities for the production
and quality
Prof. Stefano Cesco
[email protected]
Essential mineral element (or mineral nutrient) as proposed by Arnon
and Stout (1939).
1. A given plant must be unable to complete its lifecycle in the
absence of the element
2. The function of the element must not be replaceable by another
element.
3. The element must be directly involved in plant metabolism for
example, as a component of an essential plant constituent such as
an enzyme or it must be required for a distinct metabolic step
such as an enzyme reaction.
According to this strict definition, an element
which alleviates the toxic effects of another
element (e.g., Si for Mn toxicity), or one which
simply replaces another element (e.g., Na for K)
may not be described as essential for plant growth
Micronutrients are defined as substances in
foods that are essential for human health
and are required in small amounts
Micronutrient malnutrition affects about 1/3
of the global population
1. Iron (Fe):
a) availability in soil and metabolic functions,
b) mechanisms for acquisition and use efficiency,
c) interactions with other nutrients such as N and S,
d) possible strategies for biofortification
2. Silicon (Si):
beneficial effect in relation to productivity and to mechanisms
for acquisition of other nutrients
3. Nickel (Ni):
with respect to the acquisition of N and the quality of the
edible product
4. Selenium (Se):
with respect to the acquisition of other nutrients (S and N) and
the quality of the edible product
Iron
General
IRON
Fe is the second most abundant metal in the earth’s crust after Al
Fe is normally found in most soils
being the fourth most abundant
element in the lithosphere
Solubility of Fe is, however, extremely low, especially in aerated
alkaline soils (concentrations of ionic Fe3+ and Fe2+ are below 10-15 M)
Chelates of Fe(III) and occasionally of Fe(II) are therefore the
dominant forms of soluble Fe in soil and nutrient solutions
As a rule, Fe(II) is taken up preferentially compared with Fe(III), but this also
depends on the plant species
Soil availability as a function of pH
Solubility of Fe(III) is very low at neutral pH, and even lower at pH 8,
typical of alkaline soils (30 % of soils worldwide).
http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/iron-chlorosis/
Solubility of inorganic iron species in equilibrium
with iron oxides in well-aerated soils in
comparison to the requirement of soluble iron at
the root surface of various plant species
(Römheld and Marschner, 1986)
Soil availability as a function of pH
Solubility of Fe(III) is very low at neutral pH, and even lower at pH 8,
typical of alkaline soils (30 % of soils worldwide).
http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/iron-chlorosis/
Solubility of inorganic iron species in equilibrium
with iron oxides in well-aerated soils in
comparison to the requirement of soluble iron at
the root surface of various plant species
(Römheld and Marschner, 1986)
Acquisition mechanism in dicots
Strategy I
H+
AHA2
Fe(III)-chelate
Fe(II)
Fe(II)
Apoplasm
FRO2
ATP
ADP
H+
NADH
NAD+
IRT1
Fe(II)
Symplasm
Fe
Fe
Acquisition mechanism in dicots
16-day-old Cucumber plants
+ Fe
- Fe
Fe(III)-chelate reductase activity
[nmol Fe(II) gpf-1h-1]
64
2388
General
IRON
In long-distance transport in the xylem, there is a predominance of
Fe(III) complexes
As a transition element, Fe is characterized by the relative ease by
which it may change its oxidation state:
Fe3+ ↔ Fe2+
and by its ability to form octahedral complexes with various ligands
Depending on the ligand, the redox potential of Fe(II/III) varies widely
General
Due to the high affinity of Fe for various ligands (e.g., organic acids
or inorganic phosphate) ionic Fe3+ or Fe2+ do not play a role in shortor long-distance transport in plants
In aerobic systems many low-molecular-weight iron chelates, and free iron
in particular (either Fe3+ or Fe2+), produce reactive oxygen species (ROS)
such as superoxide radical and hydroxyl radical and related compounds,
These radicals are highly toxic and responsible for peroxidation of
polyunsaturated fatty acids of membrane lipids and proteins
To prevent oxidative cell damage, Fe has to be either tightly bound or incorporated
into structures (e.g., heme and non-heme proteins) which allow controlled reversible
oxidation–reduction reactions
Iron-containing Constituents of Redox Systems
Heme Proteins
The most well known heme proteins are the cytochromes, which contain a
heme Fe–porphyrin complex as a prosthetic group
Role of Fe in the biosynthesis of heme
coenzymes and chlorophyll
Iron-containing Constituents of Redox Systems
Heme Proteins
catalase and peroxidases
• susceptible to low supply of Fe
• under Fe deficiency, the activity of both enzymes rapidly decreases in
plant tissues, particularly catalase in genotypes susceptible to Fe
deficiency, for example tomato
Catalase facilitates detoxification of H2O2 to water and O2 according to
the reaction:
Peroxidases catalyse the following reactions
1. An example of the first type of reaction is the detoxification of H2O2 in chloroplasts
catalysed by ascorbate peroxidase
2. In the second type of reaction, cell wall-bound peroxidases catalyse the polymerization of
phenols to lignin.
Iron-containing Constituents of Redox Systems
Heme Proteins
The alterations in cell wall formation of rhizodermal cells under Fe
deficiency may be related to impaired peroxidase activity
biosynthesis of lignin and suberin
require phenolic compounds and
H2O2 as substrates
Taiz-Zeiger - Plant Physiology
The formation of
H2O2 is catalysed
by the oxidation of
NADH at the plasma
membrane/cell wall
interface
Iron-containing Constituents of Redox Systems
Heme Proteins
In Fe-deficient roots, peroxidase activity is strongly depressed
Consequently, H2O2 production is increased and phenolics are accumulate and
then released at higher rates from the roots
Certain phenolics, such as caffeic acid, are very
effective in chelation and reduction of
inorganic Fe(III), and a component of Strategy
I in Fe acquisition
https://dl.sciencesocieties.org/publications/books/abstracts/sssabookseries/micronutrientsi2/145?access=0&view=article
In response to Fe deficiency, red clover
releases high amounts of phenolics which
contribute to utilization and remobilization
of root apolastic Fe
Iron-containing Constituents of Redox Systems
Fe-S Proteins
Fe is coordinated to the thiol group of cysteine or to
inorganic S as clusters, or to both
The most well-known Fe-S protein is ferredoxin,
which acts as an electron transmitter in a number
of metabolic processes according to the principle
https://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb1
/part2/redox.htm
Due to the involvement of Fe at various steps in nitrate reduction,
positive correlations between Fe supply, ferredoxin concentration
and nitrate reduction are to be expected
Iron-containing Constituents of Redox Systems
Fe-S Proteins
Ammonium Assimilation
Glutamate synthase (GOGAT)
Nitrogen Assimilation
Two isoforms of
GOGAT. One form
accepts electrons
from reduced
ferredoxin (from
photosystem I) the
other from NADPH
from respiration
Buchanan-Gruissem-Jones – Biochemistry &MBP
the ferredoxin-linked GOGAT isoform dominates in leaves, particularly in
the chloroplasts of phloem companion cells in leaf veins , whereas the NADPH
isoform is prevalent in roots
Iron-containing Constituents of Redox Systems
Fe-S Proteins
The isoenzymes of superoxide dismutase (SOD) contain Fe as a metal
component of the prosthetic group (FeSOD)
1. may contain Cu, Zn, Mn or Fe as metal components
2. detoxify superoxide anion free radicals (O2·-) by formation of H2O2
http://textbookofbacteriology.net/nutgro_4.html
Iron-containing Constituents of Redox Systems
Fe-S Proteins
Aconitase is an Fe-S protein which catalyses the isomeration of citrate to
isocitrate in the tricarboxylic acid cycle
1. Fe, as metal component of the prosthetic group,
is required for stability and activity of the
enzyme
2. The Fe cluster of the enzyme is responsible for
the spatial orientation of the substrates (citrate
and isocitrate)
Taiz-Zeiger - Plant Physiology
In Fe-deficient plants,
aconitase activity is lower and
reactions in the tricarboxylic
acid cycle are disturbed
leading to organic acids
accumulation, particularly
citric and malic acid
Similar increases in concentration of organic acids were also found in xylem exudates and leaf apoplasmic fluids of
Fe-deficient plants indicating the Fe transport as stable, water soluble Fe-citrate complexes
Iron-containing Constituents of Redox Systems
Other Fe-requiring Enzymes
Along the ethylene
biosynthetic
pathway, in the
conversion of 1aminocyclopropane1-carboxylic acid
(ACC) to ethylene, a
two-step oneelectron oxidation
takes place,
catalysed by Fe(II)
Ethylene biosynthetic
pathway and the Yang cycle
Taiz-Zeiger - Plant Physiology
ethylene formation is very low in Fe-deficient cells and is restored immediately upon resupply of Fe,
without the involvement of protein synthesis
Chloroplast Development and Photosynthesis
Fe is required for protein synthesis, and the number of ribosomes –
the sites of protein synthesis – decrease in Fe-deficient leaf cells
Decreases in leaf protein content under Fe
deficiency are particularly pronounced for
the Rubisco protein that represents nearly
50% of the chloroplast soluble proteins
Taiz-Zeiger - Plant Physiology
In the thylakoid membranes, about 20 Fe atoms are directly involved in the electron
transport chain
Chloroplast Development and Photosynthesis
Fe-deficient leaves are characterized by low concentrations of starch and
sugars
This is to be expected due to
1. the low concentrations of
chlorophyll and ferredoxin,
2. impairment of
photosynthetic electron
transport
3. the decreased
regeneration of reduced
ferredoxin
4. the low concentration of
Rubisco protein
Localization and Binding State of Fe
When plants are grown under controlled conditions, about 80% of the
Fe is localized in the chloroplasts of rapidly growing leaves, regardless
of Fe nutritional status
With Fe deficiency, a shift in the
distribution of Fe occurs only within the
chloroplasts, whereby the lamellar Fe
concentration increases at the expense
of the stroma Fe
Fe can be stored in the stroma of
plastids as phytoferritin (plant
ferritin). It consists of a hollow
protein shell which can store up to
5,000 atoms of iron as Fe(III)
(Fe content 12–23% dw)
Ferritin is a vital compound in maintenance of
Fe homeostasis and protection against
oxidative damage
it can also be found in the xylem and phloem
Availability in the soil
Solubility of inorganic iron species in equilibrium with iron oxides in well-aerated soils in comparison
to the requirement
soluble iron
at the root
surface
of in
various
plant species
(Römheld
anddi ferro
Solubilità
delleof specie
ioniche
del
ferro
equilibrio
con
ossidi
Marschner, 1986)
in relazione alle esigenze di alcune colture
Availability in the soil
Solubility of inorganic iron species in equilibrium with iron oxides in well-aerated soils in comparison
to the requirement
soluble iron
at the root
surface
of in
various
plant species
(Römheld
anddi ferro
Solubilità
delleof specie
ioniche
del
ferro
equilibrio
con
ossidi
Marschner, 1986)
in relazione alle esigenze di alcue colture
Symptoms
Fe deficiency
• Symptoms appear on the young leaves first,
• Leaves turn yellow between the veins, but the veins will remain green
except in extreme cases
http://www.omafra.gov.on.ca/IPM/english/apples/plant-nutrition/iron.html
http://county.wsu.edu/chelandouglas/agriculture/treefruit/Pages/Irrigation_and_Iron_Chlorois_in_Orchards.
aspx
http://www.crec.ifas.ufl.edu/e
xtension/greening/ndccg.shtml
Citrus
•
•
•
Occurs on young leaves
Green veins with the leaf appearing light
yellowish to white in color
Small fruit
Fe deficiency
http://www.todayshomeowner.com/how-totreat-iron-deficiency-in-plants/
Grapevine
Fe deficiency
http://www.peuke.de/Assets/images/k-vineleaf-chlorot.jpg
http://www.wineland.co.za/technical/a-guide-tograpevine-abnormalities-in-south-africa-nutrientelement-deficiencies-and-toxicities-part-7
http://djsgrowers.blogspot.it/2012/04/grapevine-nutritonal-problems-what-to.html
Fe deficiency
Peach plants
Peach tree with Fe chlorosis
Plum plants
Fe chlorosis - closeup of plum leaf
Plum tree with almost white leaves
from Fe chlorosis
New growth on tree with severe Fe
chlorosis
Plum leaves with Fe chlorosis symptoms
http://ucanr.edu/sites/fruitreport/Nutrition_-_Fertilization/Individual_Nutrients/Iron_Chlorosis/
Symptoms
Fe deficiency
Symptoms
Fe deficiency
Fe Fertilizers
Fe can be applied as ferrous sulfate or in a chelated form
1 Ferrous sulfate (FeSO4) contains about 20% Fe
• It is very cheep and mainly used for foliar spraying.
• Applied to soil, it is often ineffective, especially in pH above 7.0,
because its Fe quickly transforms to Fe3+ and precipitates as one of
the Fe oxides
2 Iron chelates
• compounds that stabilize metal ions (in this case Fe) and protect
them from oxidation and precipitation.
• Fe chelates consist of three components:
a. Fe3+ ions
b. a ligand (such as EDTA, DTPA, EDDHA, amino acids,
humic-fluivic acids, citrate)
c. Sodium (Na+) or ammonium (NH4+) ions
Different chelates hold Fe in different strengths at different pH levels
They also defer in their susceptibility to iron replacement by competitive ions
(For example, at high concentrations, calcium or magnesium ions may replace the chelated metal ion)
Fe Fertilizers
Fe-EDTA:
• Fe chelate stable at pH below 6.0
• Above pH of 6.5, nearly 50% of the Fe is unavailable
• The ligand also has high affinity to calcium, so it is
advised not to use it in calcium-rich soils or water
Therefore this chelate is ineffective in alkaline soils
http://www.lookchem.com/Iron-III--edta-complex/
EDTA is a very stable chelate of micro-elements
other than Fe, even in high pH levels
Fe-DTPA:
• Fe chelate stable in pH levels of up to 7.0
• not susceptible to Fe replacement by calcium
http://www.lookchem.com/cas-195/19529-38-5.html
Fe-EDDHA:
• Fe chelate stable at pH levels as high as 11.0
• it is the most expensive Fe chelate available
http://www.lookchem.com/Sodium-ferric-EDDHA/
Fe Fertilizers
http://www.relabdenhaan.com/UserData/Documents/E3EDD30F9F6B45EEB3C2000656C7CC6F.pdf
http://www.smart-fertilizer.com/articles/iron
In soilless media and hydroponics, pH monitoring of water and media is
relatively easier than in soils. When regular testing is performed, and pH
control is adequate, it is possible to prefer the inexpensive, less stable iron
chelates.
On the other hand, in alkaline soils, where it is difficult to effectively
decrease pH levels, it is advised to use more stable iron chelates, such as
EDDHA
Acquisition mechanism in dicots
Strategy I
Affinity of the Enzyme for the substrate
H+
AHA2
Fe(III)-chelate
Fe(II)
Fe(II)
Apoplasm
FRO2
ATP
ADP
H+
NADH
NAD+
IRT1
Fe(II)
Symplasm
Fe
Use efficiency of Fe sources
Fe-Phytosiderophores
Fe-Microbial Siderophores
Fe-Organic acids
Fe-WEHS
Fe-Phenolic compounds
Australian Government, Grain Research and Development Corporation, GRDC for growers, issue 40, June 2002
A wheat root and surrounding soil, the rhizosphere,
and root hairs extending into a pore space
Use efficiency of Fe sources
Use efficiency of Fe sources
Use efficiency of Fe sources
Nutrient Interactions
Can be the Fedeficiency responses
limited by other
environmental
factors?
Other Nutrients?
Nutrient Interactions
Nitrogen
Nitrogen acquisition
N is mostly acquired by plants in the nitrate (NO3-) and
ammonium (NH4+) forms and for a small part as small organic
molecules (e.g. amino acids, urea)
Nitrate uptake
nitrate content :
- external 1-4 mM
- internal 5-30 mM
Nitrogen acquisition
N is mostly acquired by plants in the nitrate (NO3-) and
ammonium (NH4+) forms and for a small part as small organic
molecules (e.g. amino acids, urea)
Ammonium uptake
AMT1
characterization
in oocytes shows
a high affinity
symport system,
which depends
on the
transmembrane
potential
NH4+ content:
- external 0,1-0,3 mM
- internal
3-7
mM
Nitrogen Assimilation
Overview of N uptake and N
assimilation in plants
Nitrogen Assimilation
Overview of N uptake and N
assimilation in plants
Buchanan-Gruissem-Jones – Biochemistry &MBP
Nitrogen Assimilation
Nitrate Reduction
Nitrate reductase (NR)
A model of the nitrate reductase
dimer, illustrating the three
binding domains. The NADH binds
at the FAD-binding region of each
subunit and initiates a twoelectron transfer from the
carboxyl (C) terminus; Nitrate is
reduced at the molybdenum
complex near the amino terminus
Taiz-Zeiger - Plant Physiology
Nitrite reductase
Model for coupling of photosynthetic
electron flow, via ferredoxin, to the
reduction of nitrite by nitrite
reductase. The enzyme contains two
prosthetic groups, Fe4S4 and heme,
which participate in the reduction of
nitrite to ammonium
Interaction between nitrate and iron nutrition
Interaction between nitrate and iron nutrition
Fe versus N
Fe versus N
Nitrate accumulation in leaves
-Fe
Fe versus N
Accumulo di Nitrati nelle foglie
-Fe
Fe versus N
‘Gala’ cv
‘Eurion’ cv
A
B B
C
B
Relative gene expression
mmolNO3- g-1 root FW h-1
Fe versus N
LATS gene
A
A
A
C
LATS gene (coding for a lowaffinity nitrate transporter)
Relative gene expression
Fe versus N
5
NR gene cv
‘Gala’
‘Eurion’ cv
A
4
B
3
C
AB
A
C
2
1
0
NR gene (coding for an nitrate reductase)
Fe versus N
-Fe
Interaction between nitrate and iron nutrition
N versus Fe
Interactions between nitrate and iron nutrition in cucumber
7 days
+4mM NO3- +10µM Fe
+4mM NO3- +0.5µM Fe
5 days
-NO3- +10µM Fe
-NO3- and -Fe
Up to 24 hours
+4mM NO3- +10µM Fe
+4mM NO3+4mM NO3- +1µM FeWEHS
The nitrate deprivation for 5 days strongly
decreased the Fe-chelate reductase activity
and nitrate uptake capacity of cucumber roots
N versus Fe
Nitrate supply
+Nitrate
+Fe-WEHS
Effects of N and Fe supply on Fe(III)reduction capacity by roots of cucumber
plants grown with () or without ()
10µMFe supply
+Ammonium
+Fe-WEHS
Recovery of the Fe(III)-chelate
reductase activity dependent on
nitrogen supply
N versus Fe
Ammonium supply
+Nitrate
+Fe-WEHS
Effects of N and Fe supply on Fe(III)reduction capacity by roots of cucumber
plants grown with () or without ()
10µMFe supply
+Ammonium
+Fe-WEHS
Recovery of the Fe(III)-chelate
reductase activity dependent on
nitrogen supply
N versus Fe
+Nitrate
+Fe-WEHS
Effect of root exposure to
nitrate on 59Fe2+ uptake rate by
cucumber roots
No effect of N
application on Fe2+
uptake
A progressive increase in
the plant tissues
59Fe
accumulation in
Acquisition mechanism in dicots
Strategy I
H+
AHA2
Fe(III)-chelate
Fe(II)
Fe(II)
Apoplasm
FRO2
ATP
ADP
H+
NADH
NAD+
IRT1
Fe(II)
Symplasm
Fe
These results show that
1. an inadequate Fe supply can limit the acquisition of
nitrate, whereas
2. nitrate supply can affect Fe uptake by influencing the
development and maintenance of a high Fe(III)-chelate
reducing capacity
Nutrient Interactions
Sulphur
Interaction between sulphur and iron nutrition
Interaction between sulfur and iron nutrition
S versus Fe
S versus Fe
S versus Fe
S versus Fe
S versus Fe
S versus Fe
S versus Fe
These results show that S deficiency could limit the
capacity of tomato plants to cope with Fe-shortage by
preventing
1. the induction of the Fe(III)-chelate reductase and
2. limiting the activity and expression of the Fe2+
transporter
Interaction between sulfur and nitrogen nutrition
S versus N
http://ca.wikipedia.org/wiki/Fitxer:Spinacia_oleracea_Breedblad_scherpzaad.jpg
S versus N
http://ca.wikipedia.org/wiki/Fitxer:Spinacia_oleracea_Breedblad_scherpzaad.jpg
Accumulation of nitrate in leavess
S versus N
1. An adequate supply of S is important for a rapidly
growing leaf crop
2. In young leaves of S-deficient plants nitrate content
rises steeply without signs of flattering out
3. Nitrate levels could reach the threshold where the crop
is unusaleable for human dietary consideration
Pb with nitrate uptake but also for the N metabolism
Fe
NO3-
S
Relevant for the use efficiency of Fe-sources
Fe
NO3-
S
Relevant for the use efficiency of nutrients
Iron
Use efficiency of Fe sources
Use efficiency of Fe sources
http://www.relabdenhaan.com/UserData/Documents/E3EDD30F9F6B45EEB3C2000656C7CC6F.pdf
http://www.smart-fertilizer.com/articles/iron
Use efficiency of Fe sources
nutrient solution
soil conditions with unlimited Cu2+
soil conditions with limited (normal) Cu2+
Use efficiency of Fe sources
nutrient solution
soil conditions with unlimited Cu2+
soil conditions with limited (normal) Cu2+
Use efficiency of Fe sources
+Fe
Buffered at
pH 7.5
-Fe
Control
Control
Fe-WEHS
Fe-WEHS
Fe-citrate
Fe-EDTA
Use efficiency of Fe sources
Fe allocation in aerial
tissues
http://elements.geoscienceworld.org/content/5/6/375/F2.large.jpg
Zanin et al., 2014, submitted
Use efficiency of Fe sources
1th day
5th day
59Fe-PS
59Fe-WEHS
Biofortification
Use efficiency of Fe sources
Use efficiency of Fe sources
Experiment of intercropping in field
(peanut/maize)
(Zuo et al., 2000)
Root Responses to Fe Deficiency
FeII
FeIII-PS
FeIII-PS
1
3
PS
2 FeIII-PS
FeIII-PS
FeIII-hydroxide
Schematic presentation of the proposed role of PS on Fe nutrition of intercropped plants
(1, release of PS; 2, traslocator of FeIII-PS; 3 pm-reductase)
Fe applications
A.D. Rombolà
Faenza, Ravenna, Italy, 2006
Intercropping
Control
Fe-chelate
Use efficiency of Fe sources
http://www.ersa.fvg.it/tematiche/colture-erbacee/cerealicoltura/frumento-tenero/frumento-tenero-2006-2007
Biofortificazione
Use efficiency of Fe sources
Biofortificazione
Nutrient Interactions
Can be the Fedeficiency responses
affected by other
environmental
factors?
Other Elements?
Nutrient Interactions
Silicon
Silicon
SILICON
1. the second most abundant element in the
earth’s crust;
2. In soil solution at pH below 9.0, the
prevailing form is monosilicic acid, Si(OH)4,
an uncharged form, with a solubility in
water (at 25°C) of ~2 mM (equivalent to 56
mg Si L-1)
3. All plants grown in soil will contain some Si
in their tissues, however, the Si
concentration in the shoots varies
considerably among plant species
4. Plant roots take up Si in the form of silicic
acid (Si(OH)4). There are three different
modes for Si uptake; active, passive and
rejective uptake, depending on plant species
Silicon
Silicon
The waterproofing of the
tanks and the absence of
soil particles severely limit
the presence of Si in
hydroponic solutions
Can be the
addition of Si to
the NS a benefit
for the corn
salad production
in floating
system?
Novel strategies meeting the needs of the
fresh-cut vegetable sector - STAYFRESH
Genotypes
Valerianella (Valerianella locusta Laterr.)
Cultivar: Gala
Growth system
Hydroponic system
Nutritive solution
composition
Control + 30 mM Si (applied as Na2SiO3)
Silicon
Silicon
Silicon
Silicon
Silicon
The role of Si in alleviation of Fe deficiency
chlorosis includes an increase of the
apoplastic Fe pool in the roots, and an
enhancement of Fe mobilization in the roots
due to Si-mediated biosynthesis of Fe
chelating compounds
Silicon
Fe
Si
NO3-
S
Very relevant aspect for the use efficiency of nutrients
in the soil
biofortification of ready-to-eat salads
biofortification of ready-to-eat salads
Nickel
Nickel
1.
2.
3.
4.
5.
6.
in biological systems the preferred
oxidation state Ni2+ (NiII), but it can also
exist in Ni(I) and Ni(III) redox states
forms stable complexes (with histidine,
cysteine and citrate, and in Ni-enzymes it
is coordinated to various ligands
involved in the function of at least nine
proteins of which urease and the Niurease accessory protein are the most
relevant
Ni concentration in plants grown on
uncontaminated soil ranges from 0.05 to
5.0 µg g-1 dw
The clearest agronomic responses to Ni
have been observed when N is supplied as
urea or by N2fixation (without Ni,
accumulation of urea, severe necrosis of
the leaf tips, reduced growth rate).
Ni deficiency also: marked enhancement in
plant senescence and reduction in tissue
Fe concentrations
Piante di cetriolo
allevate in soluzione
idroponica preparata
con sali di grado
analitico
Analisi al Sincrotrone2D
Scanning µ-XRF
Fe Ni
Zanin et al., 2011
Nickel
biofortification of ready-to-eat salads
Selenium
Selenium
The chemistry of selenium (Se) has features in common with
sulphur
like sulphur, can exist in the
-2 (selenide Se2-),
0 (elemental selenium),
+4 (selenite SeO32-) and
+6 (selenate SeO42-) oxidation states
Selenium is present in soil in small amounts (typically ranging from
0.01 to 2 mg kg-1)
Selenium is an essential micronutrient for animals, but the essentiality has not
been established for higher plants
Deficiency of Se in humans is common; it has been estimated that between
0.5 and 1 billion people worldwide may have insufficient intake of Se
Because plant-based foods are an important source of Se to humans and domestic
animals, it is important to understand how to increase plants intake
Novel strategies meeting the needs of the
fresh-cut vegetable sector - STAYFRESH
yeast and fungal SUL, plant SULTR families
• Selenate is a chemical analogue of sulphate
• they compete for the same transporters during root uptake and, thus,
selenate uptake can be strongly decreased by high sulphate supply
• the affinity constants (Km) for sulphate and selenate uptake into barley
roots were found to be similar, 19 and 15 μM, respectively
• Selenate also competitively inhibits sulphate uptake from nutrient
solutions
Novel strategies meeting the needs of the
fresh-cut vegetable sector - STAYFRESH
Environmental conditions
50
45
15 °C
40
35
30
25
20
15
10
0.00
12.00
0.00
12.00
Air
Aria
0.00 12.00 0.00
Nutritive solution
Soluzione
nutritiva
12.00
0.00
Yield (g m-2)
Cortella et al., Applied Thermal Engineering, In press
19 °C
24 °C
Free University of Bolzano:
Tanja Mimmo, Massimo Tagliavini, Matteo Mario Scampicchio e Stefano Cesco
University of Bari
Roberto Terzano
University of Viterbo:
Stefania Astolfi e Sabrina Zuchi
University of Udine:
Nicola Tomasi, Stefano Gottardi, Giovanni Cortella, Roberto Pinton, Luisa Dalla Costa e
Lara Manzocco
University of Belgrade:
Miroslav Nikolic
Ricerca eseguita con contributi dei progetti:
Regione Friuli Venezia-Giulia LR/26-2005
Unibz TN5056
AGER – STAYFRESH (2010 2370)
University of Hohenheim
Volker Römheld
University of Bologna
Adamo D Rombolà
Thanks for your attention