Agriculture Reference
In-Depth Information
nutrients and water. Moreover, it induces osmotic stress; the physiological drought,
which typically reduces the growth and photosynthesis in plants (Munns and Tester
2008
). Salinity affects plant growth and development in two ways: through osmotic
stress by reducing the soil water potential leading to limiting the water uptake and
by causing uptake of Na
+
and Cl
−
which have an effect on plant metabolism. The
mechanism by which plants perceive stress signals and relay their transmission to
cellular machinery to trigger adaptive responses is crucial for the improvement of
different strategies to impart stress tolerance in crops (Mantri et al.
2012
).
The different abiotic stress factors result in the production of reactive oxygen
species (ROS) that are extremely reactive and cause damage to biological macro-
molecules like proteins, lipids, carbohydrates and DNA ultimately leading to oxi-
dative stress. The ROS include, superoxide radicals, hydroxyl radical, perhydroxy
radical, alkoxy radicals, hydrogen peroxide and singlet oxygen (Gill and Tuteja
2010
). Under normal growth conditions, the ROS molecules are managed by effi-
cient scavenging machinery consisting of various antioxidative defense mechanisms
(Foyer and Noctor
2005
). The production of ROS and their scavenging needs to be
balanced under normal conditions of growth but, however the equilibrium is dis-
turbed by abiotic stress factors including salinity (Tuteja
2007;
Mantri et al.
2012
).
Volatile Organic Compounds (VOC's) and Their Action
Plants are sessile and have to encounter challenges imposed by other organisms and
with the environment mainly by depending on their chemical repertoire. The signif-
icance of natural products and their metabolic diversity contribute very much to the
survival of the plant kingdom. The biogenic volatile organic compounds (VOCs)
released from a wide range of plants help enable the buildup defense against insects,
fungi, herbivores and environmental changes (Loreto and Schnitzler
2010
; Holo-
painen and Blande
2012
). Plant VOCs are comprised of isoprenoids mainly isoprene
and monoterpenes (Variyar et al.
2010
). The function of isoprenoid compounds dur-
ing environmental stress includes protection of the photosynthetic apparatus, de-
toxification from free radicals and reactive oxygen species (ROS) (Munné-Bosch
and Alegre
2000a
; Spinelli et al.
2011
). Although it has been shown that several
metabolic pathways may be involved in building up the defense, antioxidant route is
believed to be the common mechanism (Vickers et al.
2009a
). The identification of
genes in the biosynthetic pathway and transcriptomic profiling has enabled ways to
manipulate the synthesis of isoprenoid compounds. Since chloroplasts are the sites
of isoprene synthesis a possible relation may occur between isoprene production
and environmental stresses affecting the photosynthetic apparatus (Velikova
2008
;
Loyola et al.
2012
). It should thus be of interest to investigate isoprene synthesis in
plants in relation to environmental chemistry. The emission of VOCs contributes to
an appreciable quantity of photosynthetic carbon fixation under stress conditions,
and hence VOCs could also play a significant role in the carbon exchange between
the biosphere and the atmosphere (Guenther et al.
2011
). Significant research prog-
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