This document discusses using legume-microbe symbioses for phytoremediation of heavy metal polluted soils. Legumes form symbiotic relationships with arbuscular mycorrhizal fungi, plant growth-promoting rhizobacteria, and endophytic microorganisms which help the plants grow in contaminated soils. Mono-inoculation or combined inoculation with different microorganisms can increase legume growth and uptake of heavy metals. However, accelerated heavy metal uptake may cause toxic effects or inhibit plant growth. The interactions between heavy metal tolerance of symbiotic plant and microbe partners needs to be better understood.

1. Use of legume-microbe symbioses for
phytoremediation of heavy metal
polluted soils: Advantages and
potential problems

2. 2
Introduction about topic
▰Phytoremediation
▰Heavy metals polluted soils
▰Use of legumes
▰Advantages of using legumes
▰Potential problems

3. “Love the nature and
nature will Love You
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4. “
4

5. Requirements for phytoremediation
 High growth rate
 More biomass production
 Easily cultivated
 Hyperaccumulators and metallophytes
 Can form symbiotic relationships
5

6. Legumes
▰ Belong to family fabaceae
▰ form symbiosis
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7. Associations of legumes with other
microbes
▰AMF
▰PGPR
▰Endophytic microorganism
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8. AMF PGPR
8

9. ▰Efficiently used in
phytoremediation
of HM pollutes
sites
Benefits of using legumes
▰ Revegetation and
phytostabilization
of mine soils
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10. 10

11. Why legumes form symbiosis?
▰Their growth
depends on plant
microbe
interaction
▰Symbiotrophic
organisms
possess
mechanism for
tolerance
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12. EFFECTS OF SYMBIOTROPHIC
MICROORGANISMS ON LEGUMES IN
THE PRESENCE OF HMS
▰Mono-
Inoculations with
Different Types of
Microorganisms
▰Combined
Inoculations with
Different Types of
Microorganisms
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13. Mono-Inoculations with Different
Types of Microorganisms
1. AMF
▰ ecologically safe
and efficient
biological
instrument
▰ better growth and
uptake of
phosphorus
▰ stimulation of
nodule formation
▰ high
photosynthetic
activity
Legume species used:
▰ Cicer arietinum
▰ Lens culinaris
▰ Pisum sativum
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14. AMF role
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15. Mono-Inoculations with Different Types of
Microorganisms
2. PGPR
▰ Counteract
negative effects
of HMs
▰ Stimulate
production of
phytohormones
▰ Microbially-
mediated
biogeochemical
processes
▰ Reduce HM
solubility
▰ Mobilization of
HM
Legume species used:
▰Phaseolus vulgaris
▰ Pisum sativum,
▰ Trifolium repens
▰ Vigna radiate
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17. Endophytic micro organisms
(mostly bacteria)
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18. Combined Inoculations with Different Types
of Microorganisms
▰exert multiple effects on plants
▰increase their activity and persistence
▰additive and synergistic effects on plant
growth and nutrition
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19. Combined Inoculations with Different Types
of Microorganisms
▰Cultivation of Trifolium repens
▰Co-inoculation with AMF Glomus mosseae
and PGPR Brevibacillus brevis
▰accumulation of nutrient elements and toxic
Cd.
▰Stimulated nodulation on roots
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20. Combined Inoculations with Different Types
of Microorganisms
▰Increased tolerance of plants to stress
▰Stimulated nodulation on roots
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21. CHEMICALLY ASSISTED HM ACCUMULATION
BY LEGUME-MICROBE SYMBIOSES
▰Legume plants are capable of actively
accumulate HMs from polluted soils and
hydroponics
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22. CHEMICALLY ASSISTED HM ACCUMULATION BY
LEGUME-MICROBE SYMBIOSES
▰Cassia fistula accumulated Cr, Cu, Zn
and Mn
▰Medicago sativa actively accumulated
Cd, Cu, Ni and Zn and Cd, Cr and Ni
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23. CHEMICALLY ASSISTED HM ACCUMULATION
BY LEGUME-MICROBE SYMBIOSES
▰Actively accumulate HMs from polluted
But...
accelerated HM uptake may cause:
▰toxic effects
▰inhibit plant growth
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24. INTRASPECIFIC VARIABILITY OF PLANTS IN
THEIR INTERACTIONS WITH MICROORGANISMS
▰Plants significantly differ in their
tolerance to and accumulation of HMs
and intraspecific genetic variation of
these traits exists
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25. INTRASPECIFIC VARIABILITY OF PLANTS IN
THEIR INTERACTIONS WITH MICROORGANISMS
▰Cultivars of Glycine max differed in Zn
and Cd tolerance
▰Cultivars of Phaseolus vulgaris differed
in Zn and Cu tolerance
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26. ▰Experiments showed significant genotypic
variability in Cd tolerance and accumulation of
different HMs (Cd, Cr, Cu, Ni, Pb, Sr and Zn)
among 99 Pisum sativum varieties
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INTRASPECIFIC VARIABILITY OF PLANTS IN
THEIR INTERACTIONS WITH MICROORGANISMS

27. ▰Genetic traits may show negative co
relation between growth parameters
▰Increased energy expenditure for
operation of the mechanisms of metal
tolerance
▰Slower growth and lower biomass
production
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INTRASPECIFIC VARIABILITY OF PLANTS IN
THEIR INTERACTIONS WITH MICROORGANISMS

28. RELATIONSHIPS BETWEEN HM TOLERANCE
OF SYMBIOTIC PARTNERS
▰Nodulation and symbiotic nitrogen
fixation is sensitive to HMs
▰Growth inhibited
▰Resulting in nitrogen deficiency and plant
growth limitation
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29. ▰For example
Symbiotic interaction between Vigna
unguiculata and rhizobia
&
more sensitive to Cu toxicity than both
partners separately
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RELATIONSHIPS BETWEEN HM TOLERANCE
OF SYMBIOTIC PARTNERS

30. So,,, plant genotype is of prime
consideration, because…
▰plants, being on a higher evolution level,
are less tolerant to metal toxicity as
compared to microorganisms
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RELATIONSHIPS BETWEEN HM TOLERANCE
OF SYMBIOTIC PARTNERS

31. PHYTOREMEDIATION WITH GENETICALLY
MODIFIED LEGUMES AND SYMBIOTROPHIC
MICROORGANISMS
▰No natural metalliferous and hyper-
accumulating species
▰Genetically modified plants species are
introduced
via transgenic techniques
&
mutagenesis
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32. ▰Introduction of Arabidopsis
metallothionein genes AtMT1 and
AtMT2
▰To guard cells of Vicia faba
▰Resulted in reduction of the level of
reactive oxygen species and thereby
increased tolerance to supplemented Cd
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PHYTOREMEDIATION WITH GENETICALLY
MODIFIED LEGUMES AND SYMBIOTROPHIC
MICROORGANISMS

33. Advantages of using legumes
▰High potential to form symbioses
▰Short life cycle so faster yield with faster
results of microbe interaction
▰Phytostabilizing ability
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34. Potential problems
▰Required a deep understanding of the
complex interactions in the rhizosphere
involving a number of biological,
biochemical and physico-chemical
processes
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35. ▰Still mostly research is based on pot
experiments
▰Only specific HM stress is observed
▰Not applied to field for practical use
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Potential problems

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