Agriculture Reference
In-Depth Information
areas since the plant can tolerate high tissue concentrations of Zn without suffer-
ing adverse physiological effects, and can produce a significant amount of biomass
while sequestrating high concentrations of this metal. Other species that belong to
the
Atriplex
genus, such as
Atriplex halimus
, have already been studied for their
level of resistance to heavy metals (Cd, Zn, Pb). These species have been recom-
mended as a promising species for the phytoremediation of heavy-metal contami-
nated areas based on their high biomass production, deep root systems and ability to
tolerate high concentrations of toxic elements (Lutts et al.
2004
; Lefèvre et al.
2009
;
Manousaki and Kalogerakis
2009
). Precipitation of heavy-metal with oxalate and/
or its excretion into trichomes and increased synthesis of glycine betaine may con-
tribute to the tolerance of
A. halimus
. Among the heavy metals frequently present
in contaminated soils, mercury is arguably of the greatest environmental and public
health concern.
A. conodocarpa
proved to be the most suitable candidates for mer-
cury phytoextraction because of its ability to translocate mercury from roots to the
above-ground tissues (Lomonte et al.
2010
). Vickerman et al. (
2002
) evaluated 30
Atriplex
lines for potential habitat improvement and phytoremediation of selenium
contaminated sites.
A. patula
was found to be one of the top selenium accumula-
tors and grew well in saline soil.
A. atacamensis Phil
has been proposed as possible
candidates for phytoremediation of Ar (Vromman et al.
2011
).
Atriplex
Species Forage Production
The main limitations to animal production in the arid and semi-arid regions, is the
scarcity of green forage. The use of native or introduced halophytes for livestock
production is an important issue in many semi-arid and arid areas. Several halo-
phytes plants have been used as fodder crops under saline conditions in order to
produce green forage during the dry season (El Shaer
2010
). These include planting
perennial salt marsh plant species, mainly
Atriplex
species, in numerous regions. In
several experiments, the Mediterranean
Atriplex
species has been the most success-
ful shrub species in terms of establishment and productivity. Research conducted in
north-east Morocco showed an average production of 920 Kg DM/ha (1,000 plants/
ha density), with variations from 406 to 2,140 Kg DM/ha depending on the spe-
cies studied.
A. vesicaria
,
A. semibaccata
,
A. nummularia
and
A. paludosa
scored
the high levels of production. Other reports indicate that forage production from a
2-year old
Atriplex
plantation was 5 t under 150 and 200 mm rainfall.
The pastoral value of fodder shrubs depends not only upon their biomass but
also upon their nutritive value and their palatability and digestibility (Salem et al.
2012
). The low concentrations of metabolizable energy and high concentrations of
soluble salt in herbage of
Atriplex
species as well as the presence of anti-nutritional
compounds, including tannins, flavonoids, oxalate tends to reduce fodder palatabil-
ity and feed intake of sheep and goats. Several methods have been devised to lessen
adverse effects of phenols and to alleviate deleterious effects of sodium chloride
found in tree and shrub fodder foliages. These include treatment with alkalis such
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