ISSN 10214437, Russian Journal of Plant Physiology, 2016, Vol. 63, No. 1, pp. 172–179. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © E.V. Dubrovskaya, N.N. Pozdnyakova, A.Yu. Muratova, O.V. Turkovskaya, 2016, published in Fiziologiya Rastenii, 2016, Vol. 63, No. 1, pp. 180–187.
Polycyclic aromatic hydrocarbons (PAHs) belong
to a group of persistent organic substances that were
recognized by the Stockholm Convention as the most
dangerous pollutants . For terrestrial plants, toxic
concentration of PAH is rather high (100–1000 mg/kg
and more) and comparable to their solubility .
Possible fate of PAHs in the environment depends
not only on physicochemical processes but also on
microbial degradation. As a result, various derivatives
are produced that can interact with surrounding biotic
and abiotic molecules and travel along food chains
exerting a negative influence on a wide range of living
organisms. Degradation of organic pollutants in a
contaminated soil does not always correlate with a
decrease in its toxicity. In some cases, arising metabo
lites are more toxic and easily available to plants than
starting molecules .
One of the most efficient ways of bioremediation is
employment of plantmicrobial associations. Earlier,
we isolated and described a rhizosphere strain
P221 (IBPPM 383) destructing PAHs and
stimulating growth of a number of plants including
alfalfa and sorghum exposed to environmental pollu
tion with phenanthrene. These plants associated with
the bacterium form a basis for a technique we worked
out for phytoremediation of the soils contaminated
with oil hydrocarbons, including PAHs .
Pathways of microbial degradation of certain repre
sentatives of PAHs are thoroughly investigated; they
differ depending on taxonomic belonging of microor
ganisms [5, 6]. For instance, rhizobacterial strain
P221 can break down phenanthrene with
formation of 9,10dihydro9,10dihydroxyphenan
threne; 9,10phenanthrenequinone; 1hydroxy2
naphthoic; 2,2diphenic; and salicylic acids , as
well as fluorene with production of 9fluorenone. As
regards ecological toxicology, toxicity of the soil
decontaminated with strain
P221 is very
important, because arising intermediates can be more
toxic than starting molecules.
Effect of oil pollutants on plant development was
described in numerous papers [2, 8]. Their influence
was estimated by different parameters: the rate of seed
germination ; rooting and the rate of transpiration
; and changes in plant morphology, chloroplast
functions and content of chlorophyll in the leaves .
There also exists a method of direct biological testing
designed for determination of soil toxicity and based
on the estimation of seed germinating capacity and
development of root system in contaminated soil .
This method is widely used, because it does not require
special equipment and makes it possible to obtain the
Changes in Phytotoxicity of Polycyclic Aromatic Hydrocarbons
in the Course of Microbial Degradation
E. V. Dubrovskaya, N. N. Pozdnyakova, A. Yu. Muratova, and O. V. Turkovskaya
Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences,
pr. Entuziastov 13, Saratov, 410049 Russia
Received May 21, 2015
—Phytotoxicity of six polycyclic aromatic hydrocarbons (PAHs) and their 16 oxidized derivatives
that may be microbial metabolites arising in the course of PAH degradation was determined using an express
test with the seedlings of sorghum (
L. Moench) and alfalfa (
L.). It was shown
that germinating capacity is the least informative characteristic and the most useful parameter is development
of seedlings during 3 days in the presence of compounds under investigation. Among unsubstituted com
pounds, toxicity in respect to seedlings decreased in the series fluorene > phenanthrene > anthracene. Chry
sene, fluoranthene, and pyrene stimulated shoot development. It was found that some of the metabolites pro
duced as a result of microbial degradation of phenanthrene (9,10phenanthrenequinone, 1hydroxy2naph
thoic and benzoic acids) are more toxic for plants than starting PAH molecules. The obtained results are
important for understanding rhizosphere processes associated with phytoremediation technique.
, polycyclic aromatic hydrocarbons (PAH), oxidized derivatives
of PAH, PAH metabolites, germinating capacity, development of seedlings, phytotoxicity
polycyclic aromatic hydrocarbons.