lead tolerance of populus alba and clones inoculated with...

Lead Tolerance of Populus alba and Populus nigra Clones Inoculated with Arbuscular Mycorrhizal Fungi in Relation to Physiological Parameters

1. Research Institute of Forests and

Rangelands, Tehran, Iran.

2. Tarbiat Modares University, Tehran, Iran.

3. University of Tehran, Tehran, Iran.

1,2 Azadeh Salehi

2 Masoud Tabari Kouchaksaraei

2 Ebrahim Mohammadi Goltapeh

3 Anoushirvan Shirvany

Introduction

phytoremediation of soils polluted with heavy metals,

which employs plants for this purpose, has received

much consideration as a low-cost and

environmentally friendly method (Komarek et al. 2007;

He et al. 2013).

So, contaminated soils must be forbidden from

agricultural projects and subjected to remediation

processes via afforestation (Bojarczuk and Kieliszewska-

Rokicka, 2010).

entrance of heavy metals to

food chain is dangerous

Tree species belonging to the family Salicaceae are attended as suitable candidates for

phytoremediation of soils polluted with heavy metals due to fast growth, metal tolerance

and ability to accumulate heavy metals (Pulford, Dickinson 2005). 1

Study on Growth Parameters of Poplar

Trees Irrigated with Municipal

Wastewater in South of Tehran-Iran

International Poplar Commission (IPC)

25th Session, Sep 13th to 16th, 2016

Berlin, Germany

Soil microorganisms have a significant impact

in plant tolerance to heavy metal stress (KabataPendias 2004).

The arbuscular mycorrhizal (AM) fungi are a

main portion of soil microbial biomass (Arriagada et al. 2005).

Under natural conditions, AM fungi create

symbiotic associations with the roots of many plants (Smith, Read 1997).

In fact, the symbiosis of plant roots with AM fungi

could improve growth and tolerance of plants to

stress and consequently phytoremediation efficiency (Bissonnette et al. 2010).

2






Berlin, Germany

Plant tolerance to heavy metal stress is an important factor for phytoremediation

of contaminated soils (Zalensy et al. 2005),

and some physiological properties can be used as indicators for tolerance to

contamination, analysis of gas exchange could show plant responses to heavy

metal stress (Pietrini et al., 2003).

In this study the main purposes were:

Investigation on lead tolerance of mycorrhizal and

non-mycorrhizal plants of two poplar colons (Populus

nigra 62/154 and Populus alba 44/9) in relation to

physiological parameters,

Comparison of two poplar colons.

3






Berlin, Germany

The experiment was done as a factorial randomized complete scheme with two factors:

1) mycorrhizal fungus in 4 levels (control, Glomus mosseae, G. intraradices and G. mosseae

+G. intraradices),

2) lead in 4 levels (0, 100, 500 and 1000 ppm),

in a greenhouse for a 6-month growth period.

4






Berlin, Germany

5

Two native AM fungi (isolated from an agricultural and unpolluted soil), propagated on

maize (Zea mays L.) for 4 months on a sterilized soil (Chellappan et al., 2002).

Eventually, the AM fungal inoculum was a mixture of root-soil containing mycorrhizal

root fragments of maize (Zea mays), soil, hyphae and spores.






Berlin, Germany

ربوسکوالر میکوریزآ لوده به سرب توسط صنوبرهای بومی آیرآن همزیست شده با قارچهای آ

گیاه پاالی ی خاکهای آ

6

the cuttings of P. nigra 62/154 and P. alba 44/9

colones were provided from the nursery of Research

Institute of Forests and Rangelands in Karaj-Iran in

February and kept at 4 0C until the start of the

experiment.

These clones commonly used in Iranian poplar

plantations of arid and semi-arid regions.

7

Soil physico and chemical properties used in

this experiment was indicated in Table 1.

A part of the soil was supplemented with

different concentrations of Pb(NO3)2 (equal to

100, 500 and 1000 ppm).

Then,7-L pots were filled with the prepared

soil.






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8

In spring (late March), after removing of the cuttings from cold storage, they

were located overnight under running tap water.






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9

The cuttings were planted in the center of each pot and the fungal inoculum

was posed around each cutting (Each pot received 60 g fungal inoculum).






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10

The prepared pots were put in a greenhouse under natural light, where temperature

was fixed between 15 and 25 0C for one growth cycle.






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11

Physiological parameters were measured during growth cycle (on the fourth and fifth

fully expanded leaves from the apex) using a portable photosynthesis system (ADC

BioScientific, Hoddesdon, UK) (Borghi et al. 2008).






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12

the percentage of root colonization by AM fungi was assessed by the gridline intersect

method (Giovannetti and Mosse, 1980) after clearing and staining of roots using the

standard method of Phillips and Hayman (1970).






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13

Data distribution

Shapiro-Wilks test

SPSS software

Homogeneity of variance

Levene’s test

Since the data exhibited normal distribution, differences

between treatments and between two colons were assessed by

the factorial analysis of variance (ANOVA) and independent-

samples t test, respectively.






Berlin, Germany

Mycorrhizal colonization percentage (M%) of P. nigra and P. alba clones treated with different levels of Pb and AMF.

C: Control; G.m: Glomus mosseae; G.i: G. intraradices; G.m+G.i: G. mosseae + G. intraradices. 14

0

5

10

15

20

25

30

0 100 500 1000

M (%

)

a aaa

A BAA

* *

mg/kg Pb level

*

0

5

10

15

20

25

30

C G.m G.i G.m + G.i

M (%

)

b

aaa

B

A

**

*

Fungi level

a

AB A

*

a a

P. nigra P. alba






Berlin, Germany

0

5

10

15

20

25

C G.m G.i G.m + G.i

M (

%)

of

P. a

lba

0 100 500 1000

e

aa a

de

aa a

e

aab a

f

cdbc

cd

Fungal level

e

aa a

de

aa a

e

aab a

f

cdbc

cd

Fungal level

Two poplar clones reached a greater mycorrhizal colonization when inoculated with

AM fungi than control, suggesting that fungal inoculation could conquer the lack of

natural mycorrhization (Turnau, 1998).

In accordance with our results, in literature, the positive, negative or neutral influences

of soil heavy metals on mycorrhizal colonization, has been reported (Taka`cs et al. 2005;

Lingua et al. 2008; Cicatelli et al. 2010)

Physiological parameters of of P. nigra and P. alba clones treated with different levels of Pb and AMF. C: Control;

G.m: Glomus mosseae; G.i: G. intraradices; G.m+G.i: G. mosseae + G. intraradices; A =

photosynthetic rate; E = transpiration rate; gs = stomatal conductance.

15

0

3

6

9

12

15

18

C G.m G.i G.m + G.i

A(μ

mol

CO

2.m

−2

s−1)

0 100 500 1000P. nigra

**

***

******

**

***

0

1

2

3

4

C G.m G.i G.m + G.i

E (m

mo

l H

2O

.m−

2s−

1)

0 100 500 1000P. nigra

**

******

****

****

0

0.06

0.12

0.18

0.24

0.3

C G.m G.i G.m + G.i

gs

(mm

ol H

2O

.m−

2s−

1)

0 100 500 1000

***

*

P. nigra

C G.m G.i G.m + G.i

0 100 500 1000P. alba

a a a aaaa a aaa

b

a aa a

C G.m G.i G.m + G.i

0 100 500 1000P. alba

aaa

b

aa aaaa aa aa aa

C G.m G.i G.m + G.i

0 100 500 1000P. alba

b

aaaaa aaaaa a aaaa

16

Physiological parameters of P. nigra and P. alba clones treated with different levels of Pb and AMF. C: Control;

G.m: Glomus mosseae; G.i: G. intraradices; G.m+G.i: G. mosseae + G. intraradices; Ci = intercellular

CO2 concentration; WUE = water use efficiency.

0

200

400

600

C G.m G.i G.m + G.i

0 100 500 1000

Ci

(μm

ol.m

ol−

1)

P. nigra

C G.m G.i G.m + G.i

0 100 500 1000P. alba

0

1

2

3

4

5

6

7

C G.m G.i G.m + G.i

0 100 500 1000

WU

E

(μm

ol

CO

2.m

mo

l−1

H2O

)

P. nigra

C G.m G.i G.m + G.i

0 100 500 1000P. alba






Berlin, Germany

in agreement with the results of this study, several physiological responses of poplars

to different heavy metal stress have been reported (Di Baccio et al., 2003; Gu et al, 2007; Pietrini et

al, 2010 and Kang and Chandra, 2015).

In reality, various physiological responses of poplars exposed to heavy metals can be

due to genotype, different growth substrates, plant physiological conditions, type of heavy

metal and time periods of exposure to heavy metals (Borghi et al., 2008; Menon et al., 2007).






Berlin, Germany

In conclusion:

The results of present study demonstrated that in relation to physiological

parameters P. nigra 62/154 clone was more Pb tolerant than P. alba 44/9

clone at least at the dose applied in our experiment.

In contrast, inoculation with mycorrhizal fungi improved physiological

parameters in P. alba 44/9 clone, but the same did not observe in P. nigra

62/154 clone. This suggests that in P. alba 44/9 clone, mycorrhizal

inoculation could improve the tolerance of plants on Pb-polluted soils.

In fact, since the phytoremediation process may be facilitated through

selection of more contaminant-tolerant tree species, therefore the attention to

plant physiological responses in order to choose genotypes suitable for

phytoremediation programs is valuable.

17

Thanks for your

attention

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