Environmental and Economical Opportunities for the Valorisation of the Genus Atriplex: New Insights - Crop Improvement: New Approaches and Modern Techniques - page 439

resistant to osmotic stress induced by 15 % PEG, and mainly accumulates proline in
response to this treatment (Ben Hassine et al. 2008 ). Some Atriplex species grown
under rangeland conditions has leaf ash concentrations of 13-27 % (Welch 1978 ;
Hyder 1981 ; Berrett-Lennard 2002) and Atriplex species grown in saline soils can
have leaf ash concentrations up to 39 % (Malcolm et al. 1988 ). Khan et al. ( 2000 )
reported that A. halimus was more salt-tolerant than A. calotheca and A. nitens ,
when grown at 750 mM NaCl (− 40, − 67 and − 80 % of biomass production) but in-
terestingly, all three species were able to survive at this salt concentration. Recently,
Benzarti et al. ( 2012 ) found that A. portulacoides was able to grow in medium con-
taining 1,000 mM NaCl without displaying salt-induced toxicity symptoms. The
salinity resistance of some Atriplex species is often attributed to the presence of
vesiculated trichomes covering the leaf surface and containing large amounts of
salt (Smaoui et al. 2011 ). These trichomes play a significant role in removing salt
from the the leaf tissues, thereby preventing the accumulation of toxic salts in the
parenchyma and vascular tissues. For many Atriplex species, more than 50 % of the
salt transported to the shoots is excreted via these epidermic trichomes (Belkheiri
and Mulas 2011 ). These attributes have led some workers to suggest that Atriplex
species could be grown to remove salt from the soil (Barrett-Lennard 2002 ).
Atriplex species ( A. canescens ) has been especially recommended for arid zone
restoration projects (Fitzsimmons et al. 1998 ). In a field experiment Chisci et al.
( 2001 ) demonstrated the use of A. halimus in improving physical characteristics of a
clay soil in Italy and to provide environmental protection by controlling runoff and
reducing soil erosion on slopes. Atriplex plant litter can modify the top soil salinity,
along with other soil properties. Maganhotto de Souza Silva et al. ( 2008 ) found that
soils cultivated with A. nummularia and irrigated with saline effluents, in semi-arid
conditions in Brazil, improved their fertility (organic carbon, nitrogen and phospho-
rus contents) and microbiological properties (enzymes activity). Sameni and Solei-
mani ( 2007 ) studied the distribution of salinity and of some soil physico-chemical
properties, observing significant changes in salinity and pH and found that A. num-
mularia may actually facilitate growth of plants under their canopy. The work by
Zucca et al. ( 2011 ) in a study site in Morocco also confirmed that the significant
relationship between soil properties and A. nummularia development can be mostly
observed within the first 10 cm. A. nummularia is one of the most important species
used for the revegetation of degraded land in low rainfall areas. Slavich et al. ( 1999 )
planted A. nummularia as a vegetative cover in a salt affected land in southeast Aus-
tralia. Brown et al. ( 1999 ) showed that A. barclayana could be used as a biofilter to
remove nutrients from saline aquaculture effluents. Gharaibeh et al. ( 2011 ) showed
that amelioration of a calcareous saline sodic soil can be achieved efficiently by
growing A. halimus without applying an amendment. Planting A. halimus reduced
soil sodicity and electrical conductivity considerably to values comparable to that
of gypsum treatments.
The Atriplex species may also be used for wildfire prevention purposes. The
high salt concentration found in its leaves increases their moisture content, which
makes this species behave as a fire retardant in the event of wildfire (Montgomery
and Cheo 1969 ).