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Micronutrients and beneficial elements in horticultural crops between critical aspects and new opportunities for the production and quality Processes at the soil/root interface involved in plant nutrient acquisition Prof. Stefano Cesco [email protected]
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Micronutrients and beneficial elements in horticultural ... · horticultural crops between critical aspects and new opportunities for the production and quality Processes at the soil/root

Sep 22, 2018

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Page 1: Micronutrients and beneficial elements in horticultural ... · horticultural crops between critical aspects and new opportunities for the production and quality Processes at the soil/root

Micronutrients and beneficial elements in horticultural crops between critical aspects and new opportunities for the production

and quality

Processes at the soil/root interface involved in plant nutrient acquisition

Prof. Stefano Cesco

[email protected]

Page 2: Micronutrients and beneficial elements in horticultural ... · horticultural crops between critical aspects and new opportunities for the production and quality Processes at the soil/root

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

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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

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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

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Iron

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IRON

General

Fe is the second most abundant metal in the earth’s crust after Al

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

Fe is normally found in most soils being the fourth most abundant

element in the lithosphere

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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)

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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)

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Acquisition mechanism in dicots

Strategy I

Apoplasm Symplasm

H+ ATP

ADP H+

Fe(III)-chelate NADH

Fe(II) NAD+

Fe(II) Fe(II)

AHA2

IRT1

FRO2

Fe

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+ Fe - Fe

Fe(III)-chelate reductase activity [nmol Fe(II) gpf

-1h-1]

64 2388

16-day-old Cucumber plants

Fe Acquisition mechanism in dicots

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IRON

General

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

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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 short- or 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

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Heme Proteins

Iron-containing Constituents of Redox Systems

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

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Heme Proteins

Iron-containing Constituents of Redox Systems

• 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

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.

catalase and peroxidases

Catalase facilitates detoxification of H2O2 to water and O2 according to the reaction:

Peroxidases catalyse the following reactions

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Heme Proteins

Iron-containing Constituents of Redox Systems

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

The formation of H2O2 is catalysed by the oxidation of NADH at the plasma membrane/cell wall interface

Taiz-Zeiger - Plant Physiology

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Heme Proteins

Iron-containing Constituents of Redox Systems

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

In response to Fe deficiency, red clover releases high amounts of phenolics which contribute to utilization and remobilization of root apolastic Fe

https://dl.sciencesocieties.org/publications/books/abstracts/sssabookseries/micronutrientsi2/145?access=0&view=article

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Fe-S Proteins

Iron-containing Constituents of Redox Systems

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

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

https://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb1/part2/redox.htm

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Nitrogen Assimilation Ammonium Assimilation

Two isoforms of GOGAT. One form accepts electrons from reduced ferredoxin (from photosystem I) the other from NADPH from respiration

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

Glutamate synthase (GOGAT)

Buchanan-Gruissem-Jones – Biochemistry &MBP

Fe-S Proteins

Iron-containing Constituents of Redox Systems

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Fe-S Proteins

Iron-containing Constituents of Redox Systems

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

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Fe-S Proteins

Iron-containing Constituents of Redox Systems

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)

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

Taiz-Zeiger - Plant Physiology

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Other Fe-requiring Enzymes

Iron-containing Constituents of Redox Systems

Along the ethylene biosynthetic pathway, in the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene, a two-step one-electron oxidation takes place, catalysed by Fe(II)

ethylene formation is very low in Fe-deficient cells and is restored immediately upon resupply of Fe, without the involvement of protein synthesis

Ethylene biosynthetic pathway and the Yang cycle

Taiz-Zeiger - Plant Physiology

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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

In the thylakoid membranes, about 20 Fe atoms are directly involved in the electron transport chain

Taiz-Zeiger - Plant Physiology

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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

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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

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)

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

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

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Solubilità delle specie ioniche del ferro in equilibrio con ossidi di ferro in relazione alle esigenze di alcune colture

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)

Availability in the soil

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Solubilità delle specie ioniche del ferro in equilibrio con ossidi di ferro in relazione alle esigenze di alcue colture

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)

Availability in the soil

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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

Symptoms

http://www.omafra.gov.on.ca/IPM/english/apples/plant-nutrition/iron.html

http://county.wsu.edu/chelan-douglas/agriculture/treefruit/Pages/Irrigation_and_Iron_Chlorois_in_Orchards.aspx

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• Occurs on young leaves • Green veins with the leaf appearing light

yellowish to white in color • Small fruit

http://www.crec.ifas.ufl.edu/extension/greening/ndccg.shtml

Citrus

Fe deficiency

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http://www.todayshomeowner.com/how-to-treat-iron-deficiency-in-plants/ Grapevine

http://www.peuke.de/Assets/images/k-vineleaf-chlorot.jpg

http://djsgrowers.blogspot.it/2012/04/grapevine-nutritonal-problems-what-to.html

http://www.wineland.co.za/technical/a-guide-to-grapevine-abnormalities-in-south-africa-nutrient-element-deficiencies-and-toxicities-part-7

Fe deficiency

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http://ucanr.edu/sites/fruitreport/Nutrition_-_Fertilization/Individual_Nutrients/Iron_Chlorosis/

Peach tree with Fe chlorosis New growth on tree with severe Fe chlorosis

Fe chlorosis - closeup of plum leaf Plum tree with almost white leaves from Fe chlorosis

Plum leaves with Fe chlorosis symptoms

Plum plants

Peach plants Fe deficiency

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Symptoms Fe deficiency

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Fe deficiency Symptoms

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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)

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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

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

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/Iron-III--edta-complex/

http://www.lookchem.com/cas-195/19529-38-5.html

http://www.lookchem.com/Sodium-ferric-EDDHA/

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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

Fe Fertilizers

http://www.smart-fertilizer.com/articles/iron

http://www.relabdenhaan.com/UserData/Documents/E3EDD30F9F6B45EEB3C2000656C7CC6F.pdf

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Acquisition mechanism in dicots

Strategy I

Apoplasm Symplasm

H+ ATP

ADP H+

Fe(III)-chelate NADH

Fe(II) NAD+

Fe(II) Fe(II)

AHA2

IRT1

FRO2

Fe

Affinity of the Enzyme for the substrate

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A wheat root and surrounding soil, the rhizosphere, and root hairs extending into a pore space

Australian Government, Grain Research and Development Corporation, GRDC for growers, issue 40, June 2002

Fe-Microbial Siderophores

Fe-Phytosiderophores

Fe-Organic acids

Fe-Phenolic compounds

Fe-WEHS

Use efficiency of Fe sources

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Use efficiency of Fe sources

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Use efficiency of Fe sources

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Use efficiency of Fe sources

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Nutrient Interactions

Can be the Fe-deficiency responses

limited by other environmental

factors?

Other Nutrients?

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Nutrient Interactions

Nitrogen

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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)

Nitrogen acquisition

nitrate content : - external 1-4 mM - internal 5-30 mM

Nitrate uptake

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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)

Nitrogen acquisition

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

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Nitrogen Assimilation

Overview of N uptake and N assimilation in plants

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Nitrogen Assimilation

Buchanan-Gruissem-Jones – Biochemistry &MBP

Overview of N uptake and N assimilation in plants

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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 two-electron 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

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Interaction between nitrate and iron nutrition

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Interaction between nitrate and iron nutrition

Fe versus N

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Fe versus N

Nitrate accumulation in leaves

-Fe

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Accumulo di Nitrati nelle foglie

-Fe

Fe versus N

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Fe versus N

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mm

olN

O3-

g-1

roo

t F

W h

-1 ‘Gala’ cv ‘Eurion’ cv

BC

B

A

B

A A A

B B

CC

LATS gene

Rel

ativ

e g

ene

exp

ress

ion

LATS gene

LATS gene (coding for a low-affinity nitrate transporter)

Fe versus N

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0

1

2

3

4

5‘Gala’ cv ‘Eurion’ cv

A

C

B

A

C

AB

Rel

ativ

e g

ene

exp

ress

ion

NR gene

NR gene (coding for an nitrate reductase)

Fe versus N

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-Fe

Fe versus N

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Interaction between nitrate and iron nutrition

N versus Fe

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+4mM NO3- +10µM Fe -NO3

- +10µM Fe

+4mM NO3- +0.5µM Fe -NO3

- and -Fe +4mM NO3

-

+4mM NO3- +1µM FeWEHS

+4mM NO3- +10µM Fe

7 days 5 days Up to 24 hours

The nitrate deprivation for 5 days strongly decreased the Fe-chelate reductase activity and nitrate uptake capacity of cucumber roots

Interactions between nitrate and iron nutrition in cucumber

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Effects of N and Fe supply on Fe(III)-reduction capacity by roots of cucumber plants grown with () or without () 10µMFe supply

+Fe-WEHS

+Fe-WEHS

+Nitrate

+Ammonium

N versus Fe Nitrate supply

Recovery of the Fe(III)-chelate reductase activity dependent on nitrogen supply

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+Fe-WEHS

+Fe-WEHS

+Nitrate

+Ammonium

N versus Fe Ammonium supply

Effects of N and Fe supply on Fe(III)-reduction capacity by roots of cucumber plants grown with () or without () 10µMFe supply

Recovery of the Fe(III)-chelate reductase activity dependent on nitrogen supply

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Effect of root exposure to nitrate on 59Fe2+ uptake rate by cucumber roots

+Fe-WEHS +Nitrate

No effect of N application on Fe2+

uptake

A progressive increase in 59Fe accumulation in the plant tissues

N versus Fe

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Acquisition mechanism in dicots

Strategy I

Apoplasm Symplasm

H+ ATP

ADP H+

Fe(III)-chelate NADH

Fe(II) NAD+

Fe(II) Fe(II)

AHA2

IRT1

FRO2

Fe

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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

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Nutrient Interactions

Sulphur

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Interaction between sulphur and iron nutrition

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Interaction between sulfur and iron nutrition

S versus Fe

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S versus Fe

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S versus Fe

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S versus Fe

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S versus Fe

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S versus Fe

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S versus Fe

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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

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Interaction between sulfur and nitrogen nutrition

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http://ca.wikipedia.org/wiki/Fitxer:Spinacia_oleracea_Breedblad_scherpzaad.jpg

S versus N

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http://ca.wikipedia.org/wiki/Fitxer:Spinacia_oleracea_Breedblad_scherpzaad.jpg

Accumulation of nitrate in leavess

S versus N

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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

S versus N

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Fe

S

NO3-

Relevant for the use efficiency of Fe-sources

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Fe

S

NO3-

Relevant for the use efficiency of nutrients

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Iron

Use efficiency of Fe sources

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http://www.smart-fertilizer.com/articles/iron

http://www.relabdenhaan.com/UserData/Documents/E3EDD30F9F6B45EEB3C2000656C7CC6F.pdf

Use efficiency of Fe sources

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Use efficiency of Fe sources

nutrient solution

soil conditions with unlimited Cu2+

soil conditions with limited (normal) Cu2+

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Use efficiency of Fe sources

nutrient solution

soil conditions with unlimited Cu2+

soil conditions with limited (normal) Cu2+

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+Fe -Fe

Control Fe-WEHS Fe-EDTA

Use efficiency of Fe sources

Buffered at pH 7.5

Control Fe-WEHS Fe-citrate

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Use efficiency of Fe sources

Fe allocation in aerial tissues

http://elements.geoscienceworld.org/content/5/6/375/F2.large.jpg

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59Fe-PS

59Fe-WEHS

5th day 1th day

Zanin et al., 2014, submitted

Biofortification

Use efficiency of Fe sources

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Use efficiency of Fe sources

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Experiment of intercropping in field (peanut/maize)

(Zuo et al., 2000)

Use efficiency of Fe sources

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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)

PS

FeIII-hydroxide

FeIII-PS

FeII

FeIII-PS

FeIII-PS

2 1 3 FeIII-PS

Root Responses to Fe Deficiency

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Control Fe-chelate

Intercropping

Faenza, Ravenna, Italy, 2006

A.D. Rombolà Fe applications

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http://www.ersa.fvg.it/tematiche/colture-erbacee/cerealicoltura/frumento-tenero/frumento-tenero-2006-2007

Biofortificazione

Use efficiency of Fe sources

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Biofortificazione

Use efficiency of Fe sources

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Nutrient Interactions

Can be the Fe-deficiency responses affected by other

environmental factors?

Other Elements?

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Nutrient Interactions

Silicon

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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

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Silicon

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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?

Silicon

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Genotypes Valerianella (Valerianella locusta Laterr.) Cultivar: Gala

Growth system Hydroponic system

Nutritive solution composition Control + 30 mM Si (applied as Na2SiO3)

Novel strategies meeting the needs of the fresh-cut vegetable sector - STAYFRESH

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Silicon

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Silicon

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Silicon

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Silicon

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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

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Silicon

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Fe

S

NO3-

Very relevant aspect for the use efficiency of nutrients in the soil

Si

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biofortification of ready-to-eat salads

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Nickel

biofortification of ready-to-eat salads

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Analisi al Sincrotrone2D Scanning µ-XRF

Ni Fe

Piante di cetriolo allevate in soluzione idroponica preparata con sali di grado analitico

Zanin et al., 2011

1. in biological systems the preferred oxidation state Ni2+ (NiII), but it can also exist in Ni(I) and Ni(III) redox states

2. forms stable complexes (with histidine, cysteine and citrate, and in Ni-enzymes it is coordinated to various ligands

3. involved in the function of at least nine proteins of which urease and the Ni-urease accessory protein are the most relevant

4. Ni concentration in plants grown on uncontaminated soil ranges from 0.05 to 5.0 µg g-1 dw

5. 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).

6. Ni deficiency also: marked enhancement in plant senescence and reduction in tissue Fe concentrations

Nickel

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Nickel

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Selenium

biofortification of ready-to-eat salads

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The chemistry of selenium (Se) has features in common with sulphur

Selenium is present in soil in small amounts (typically ranging from 0.01 to 2 mg kg-1)

Selenium

like sulphur, can exist in the -2 (selenide Se2-), 0 (elemental selenium), +4 (selenite SeO3

2-) and +6 (selenate SeO4

2-) oxidation states

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

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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

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Environmental conditions

10

15

20

25

30

35

40

45

50

0.00 12.00 0.00 12.00 0.00 12.00 0.00 12.00 0.00

Aria Soluzione nutritiva

15 °C 19 °C 24 °C

Novel strategies meeting the needs of the fresh-cut vegetable sector - STAYFRESH

Cortella et al., Applied Thermal Engineering, In press

Nutritive solution Air

Yield (g m-2)

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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 Bari Roberto Terzano

Free University of Bolzano: Tanja Mimmo, Massimo Tagliavini, Matteo Mario Scampicchio e Stefano Cesco

University of Belgrade: Miroslav Nikolic

University of Hohenheim Volker Römheld

Ricerca eseguita con contributi dei progetti: Regione Friuli Venezia-Giulia LR/26-2005 Unibz TN5056 AGER – STAYFRESH (2010 2370)

University of Bologna Adamo D Rombolà

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Thanks for your attention