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Selenium in Plants ADVS 5860/RLR 5860 March 2, 2010 T. Zane Davis

Selenium in Plants - USDA · General Selenium Information Selenium is an essential nutrient for animals Deficiencies cause: Immune system dysfunction White Muscle Disease

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Selenium in Plants

ADVS 5860/RLR 5860March 2, 2010T. Zane Davis

History

1295 Marco Polo in China 1857 Fort Randall in Nebraska (… inflammation,

swelling and suppuration of the sheath, tenderness and inflammation of the feet, followed by suppuration at the point where the hoof joins the skin,, the hoof, in a meature, detaching itself, and a new one forming in its place…accompanied by loss of manes and tails…)

1907 and 1908- 15,000 sheep died in Medicine Bow, Wyoming

General Selenium Information

Selenium is an essential nutrient for animals

Deficiencies cause: Immune system dysfunction White Muscle Disease Reproductive dysfunction

Narrow window between deficiency and toxicity < 0.1 ppm in forages may cause deficiency > 5ppm in forages may cause toxicity

Selenium Distribution

Black- low Se (<0.05 ppm)

White- variable Se (0.1 ppm)

Black dots- Se Accumulators (>50 ppm)

Oxidation States of Selenium

Se+6 Selenate- Na2SeO4, SeO3, H2SeO4

Se+4 Selenite- Na2SeO3, SeO2, H2SeO3

Se0 Elemental Selenium Se-2 Selenide compounds

Se2-

SeO32-SeO4

2- SeCys

SeMet Se-containing proteins

GSH β-lyase

utilizationexcretion

methylatedmetabolites

Se-P, SeCystRNA

selenoproteins

UGA codon

Trimethylselenonium-urineDMDSe, DMSe-respiratory

Selenium Accumulation

Plants accumulate SOLUBLE selenium from the soil Insoluble elemental selenium and selenides are NOT

bioavailable to plants

Selenium Indicator Plants

Facultative Selenium Accumulators

Passive Selenium Accumulators

Selenium Indicator Plants

Referred to as OBLIGATE species These species appear to require high selenium

Concentrations range form 1,000 to >13,000 ppm

Specific indicators Astragalus sp. (>20 different species) Xylorrhiza sp. (asters) Oonopsis sp. (goldenweed) Stanleya sp. (prince’s plume)

Astragaluspraelongus

Astragalus bisulcatus

Xylorrhiza glabriusculaStanleya pinnata

Facultative Selenium Accumulators

Accumulate selenium when grown on high selenium soil Do not require selenium for growth

Can grow just as well on low selenium soils

Specific plants Aster sp. Atriplex sp. (saltbush) Sideranthus sp. Machaeranthera sp. (tansy asters) Grindelia sp. (gumweed)

Grindelia squarrosa

Passive Selenium Accumulators

Most other plant species

High soluble soil selenium can be toxic to some plants

Plants that have caused toxicosis Numerous grasses Cereal Grains Numerous weeds Etc.

Selenium content of plants

Selenium Indicator Plants Up to and in excess of 10,000 ppm

Facultative Selenium Accumulators < 0.1 ppm to few thousand ppm

Passive Selenium Accumulators < 0.1 ppm to a few hundred ppm

Form of Selenium in Plants Most Forages are Primarily Organic (> 80 to 98%)

Selenomethionine Selenocysteine Derivatives of the two above Absorbed into animals via amino acid uptake channels

Selenium Accumulator Plants Selenate and Se-methylselenocysteine Absorbed into animals via mineral uptake proteins Absorbed into animal via amino acid uptake channels?

Selenium in sheep liver

6.73

3.98

0.96

0.24

2.09

5.07

10.80

2.20

0.21

8.87

y = 2.7846x - 2.9243R2 = 0.9882

y = 1.6x - 2.003R2 = 0.9385

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0 1 2 3 4

amount of selenium given orally(in mg Se/kg BW)

Se co

ncen

tratio

n in

live

r (we

t wt.

basis

) (p

pm)

sodium seleniteSeMetLinear (SeMet)Linear (sodium selenite)

Inorganic vs. Organic

Selenium concentration in serum of sheep dosed with various selenocompounds

0 20 40 60 80 100 120 140 160

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Control MeSeCys Selenate SeMet Woody Aster

Conc

entr

atio

n (p

pm)

Time (hrs)

Selenium concentration in whole blood of sheep dosed with various selenocompounds

Time (hrs)

0 20 40 60 80 100 120 140 160

Conc

entra

tion

(ppm

)

0

1

2

3

4

5

6

7

ControlMeSeCysSelenateSeMetWoody Aster

Selenium Toxicity

Acute > 0.5 to 1 mg Se/kg BW by injection 1 to >10 mg Se/kg BW by ingestion

Chronic > 5 ppm Se in the total diet

Acute Selenium Poisoning Usually Obligate or Facultative Accumulators Clinical signs develop in a few hours to 1 day

Garlic like smell to the breath Anorexia Depression Dyspnea Recumbence Coma Death

Death usually occurs within a few hours of signs

Chronic Selenium Poisoning Occurs after weeks of high selenium forage intake (> 5 to <

150 ppm)

Once called “alkali disease” due to its association with alkaline soils

Clinical Signs Dullness Hair loss Lameness Hoof and Joint Abnormalities Anemia Death due to starvation

??“Blind Staggers” – wandering, paralysis, dyspnea, death ??

Pathology Myocardial Necrosis

Pulmonary Hemorrhage and Edema

Passive Congestion

+/- enteritis

+/- systemic hemorrhage

Hoof/joint lesions (chronic)

Emaciation (chronic)

Possible Mechanisms of Selenium Toxicity

1. Substitution of selenium for sulfur. 2. Reaction between selenite and glutathione

consumes or depletes cellular-free and protein-bound thiol levels.

3. Free radicals such as superoxide anions may be produced by the reactions of certain forms of Se with tissue thiols, causing oxidative injuries to tissues.

Selenium Interactions

High selenium can cause deficiencies in other essential nutrients Copper Iron Zinc

Sample Testing Liver Kidney Heart

Rumen or Stomach Content

Forages

Water

Other Plant Minerals

Sulfur Can cause polioencephalomalacia Can cause copper deficiency Can cause selenium deficiency

Molybdenum Causes copper deficiency

Selenium suspected in cattle deaths near ID mineBy JOHN MILLER - Associated Press WriterPublished: 08/14/09BOISE, Idaho — Eighteen cattle likely died of selenium poisoning near a southeastern Idaho phosphate mine, the latest livestock deaths in a region rich in phosphates where a legacy of pollution has killed horses and hundreds of sheep since the 1990s. The cattle died around Aug. 5 near the defunct Lanes Creek Mine. Fertilizer-maker J.R. Simplot Co. controls the mineral rights here, but says it's never actively mined the site. The dead cattle's livers showed high levels of selenium, a naturally occurring mineral unearthed with phosphate ore that contaminates groundwater and plants.

Chemotype A Chemotype B

MLA

No MLA

400 500 600 700 8000

20

40

60

80

100

Rel

ativ

e A

bund

ance

508.3

609.2

482.3

552.3 578.3 683.3

564.3

404.2 468.3753.3

400 500 600 700 8000

20

40

60

80

100

Rel

ativ

e A

bund

ance

508.3

609.2

482.3

552.3 578.3 683.3

564.3

404.2 468.3753.3

400 500 600 700 800m/z

0

20

40

60

80

100

Rel

ativ

e A

bund

ance

508.2

609.2

482.3

468.3

578.2552.3446.2 564.2

428.2 641.1

Electrospray mass spectra from samples representing each chemotype

of D. occidentaleDeltaline

MLA No MLA

Lanes Creek mine site…

Site # Plant Se Conc. (ppm)

4 Alfalfa 291.34

4 Burnet 94.384 Clover 15.73

7 Burnet 316.31

7 Grass 291.34

7 Yarrow 232.037 Timothy 114.26

8 Aster 4360.48

8 Aster 4063.00

8 Aster 4059.51

8 Wheatgrass 182.03

8 Clover 155.638 Brome 155.49

9 Aster 941.49

11 Alfalfa 1.13

12 Clover 28.53

12 Aster 12.68

12 Water (in pond) 0.00512 Water (below outlet) 0.005

13 Erigeron 1.6613 Aster 1.53

Alfalfa = 291.34 ppm SeBurnet = 94.38 ppm SeClover = 15.73 ppm Se

Site # Plant Se Conc. (ppm)

4 Alfalfa 291.34

4 Burnet 94.384 Clover 15.73

7 Burnet 316.31

7 Grass 291.34

7 Yarrow 232.037 Timothy 114.26

8 Aster 4360.48

8 Aster 4063.00

8 Aster 4059.51

8 Wheatgrass 182.03

8 Clover 155.638 Brome 155.49

9 Aster 941.49

11 Alfalfa 1.13

12 Clover 28.53

12 Aster 12.68

12 Water (in pond) 0.00512 Water (below outlet) 0.005

13 Erigeron 1.6613 Aster 1.53

Site # Plant Se Conc. (ppm)

4 Alfalfa 291.34

4 Burnet 94.384 Clover 15.73

7 Burnet 316.31

7 Grass 291.34

7 Yarrow 232.037 Timothy 114.26

8 Aster 4360.48

8 Aster 4063.00

8 Aster 4059.51

8 Wheatgrass 182.03

8 Clover 155.638 Brome 155.49

9 Aster 941.49

11 Alfalfa 1.13

12 Clover 28.53

12 Aster 12.68

12 Water (in pond) 0.00512 Water (below outlet) 0.005

13 Erigeron 1.6613 Aster 1.53

Western Aster (Aster ascendens)

Tissue Se concentrations of steers that died from grazing Se-accumulator plants

Steer IDTissue (8/3/09)

Se conc. (ppm)

Normal Se conc. (ppm)

F54 Lung 0.760 ~0.2

F54 Kidney 3.530 ~1.0

F35 Lung 1.984 ~0.2

F35 Kidney 3.286 ~1.0

F35 Liver 8.983 0.25 - 0.50

F118 Lung 1.236 ~0.2

F118 Kidney 1.859 ~1.0

F118 Heart 1.883 ~0.2

Average whole blood and serum selenium concentrations of steers poisoned on woody aster

Time (days)

0 20 40 60 80 100 120 140 160

Se c

once

ntra

tion

(ppm

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

Whole bloodSerum

Normal range of selenium in bovine whole blood = 0.20 to 1.20 ppm Normal range of selenium in bovine serum = 0.08 to 0.30 ppm

Average selenium concentration in liver of steers poisoned on woody aster

Time (days)

0 20 40 60 80 100 120 140 160

Se c

once

ntra

tion

(ppm

)

0.0

0.8

1.6

2.4

3.2

4.0

4.8

5.6

6.4

7.2

8.0

8.8

9.6

10.4

11.2

12.0

Liver

Normal range of selenium in bovine liver = 0.25 to 0.50 ppm

Average selenium concentration in muscle of steers poisoned on woody aster

Time (days)

0 20 40 60 80 100 120 140 160

Se c

once

ntra

tion

(ppm

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Muscle

Normal range of selenium in bovine muscle = 0.07 to 0.15 ppm

Questions

???????

Assigned Reading: pp 305-317 in A Guide to Plant Poisoning of Animals in North America