Volume 10 - 2008

Phytoremediation is a low cost alternative solution to soil contamination compared with
traditional removal and/or disposal techniques. One of the phytoremediation technologies is
the phytovolatilization, whereby the contaminant is not primarily accumulated in above-ground
tissues, but is instead transformed by the plant into the atmosphere. The detoxification of
highly toxic organmercurial compounds and subsequent volatilization of elemental mercury is
a unique example for the successful phytoremediation based on genetic engineering
approach. For mercury removal techniques we constructed a dicistronic construct containing
the bacterial mercury detoxification genes merA and merB under the control of the
Arabidopsis Actin2 promoter and terminator. The resulted construct was introduced to
Agrobacterium competent cells using heat shock transformation method. In the mean time,
we germinated tobacco (Nicotiana tabacum var. Gold leaf) seeds on MS media and infected
leaf discs of 6-8 weeks tobacco seedlings with Agrobacterium containing Ti plasmid harboring
merA/merB dicistronic construct. The results showed that about 90% of tobacco seedlings
were carrying the mer genes. Tobacco seeds were collected from wild type and transgenic
lines and tested for mercury resistance. The results showed that transgenic plants are
resistant to both Phenyl Mercuric Acetate (PMA) and HgCl2. The root length and dry weight of
wild and transgenic seedlings growing on both media amended with mercury compounds and
media without mercury (control) were scored. The results showed that the root lengths and
dry weight of the transgenic lines are significantly higher by 60 and 17-folds, respectively,
compared to wild type. The results showed clear evidence that the transgenic plants are
resistant to both organic and inorganic mercury compounds and can be used to clean up
mercury contaminated sites.

The trace element analysis of Aleppo pine (Pinus halepensis Mill) as a function of tree
age, was achieved by the tree-ring sampling method, in a polluted region of Attica,
Greece. The elements quantitatively determined for the last 140 years by atomic
spectrophotometry analysis were: Cu, Fe, Zn, Mn and Pb. With the exception of Pb, all
other elements tend to increase for the time period of this study. A very interesting
fluctuation was noted between the years 1920 to 1960-1970, a time coinciding with the
major industrial activity of the area. The decreasing concentration of all elements for the
last few decades may be attributed to the increasing environmental awareness as well as
respective regulations posed by the government and the E.U. The radial distribution of
concentrations in annual tree rings provides adequate information that, in most of the
cases, can be related to the history of the tree and the biological processes interacting on
its growth. Soil, litter, air deposits and water are important nutrient sources contributing
to changes in elemental concentration in the annual rings.