Agriculture Reference
In-Depth Information
activated in the presence of metal ions). The phytochelatin complexes with ions are
formed in the vacuole, thus decreasing the toxic effects of metals. Sulfur-deficient
plants may switch to non-sulfur-based tolerance mechanisms, which often involve
proline. However, phytochelatins appear to be essential for metal
tolerance
(Zagorchev et al.
2013
).
Many studies are indicative of positive effects of NO donors on metal toxicity.
They acted on alleviating manganese (Mn)-induced stress in rice leaves; however,
the effect was reversed by the addition of a NO scavenger (Srivastava and Dubey
2012
). Addition of SNP reversed the inhibitory effect of nickel on the growth of
wheat (
Triticum aestivum
L.) in a dose-dependent manner through increased acti-
vities of antioxidant enzymes and the content of reduced ascorbate and glutathione
(Wang et al.
2010
). A similar paper reported the augmentation of antioxidant
enzymes and suppression of lipid peroxidation due to administration of SNP to
Artemisia annua
stressed by boron and aluminum (Aftab et al.
2012
).
Administration of SNP, a NO donor, efficiently alleviated copper toxicity
effects. The Cu-induced NO in vascular bundles was associated primarily with
the presence of the induced NADPH-diaphorase (NADPH-d) activity. These results
suggested that NOS-like enzyme, but not the nitrate reductase, was the source of
inducible NO generation in roots of
Vicia faba
under Cu stress (Zou et al.
2012
).
9.2.5 Exogenous NO Donors in Plants Tolerance
to Temperature Stress
It is known that plants possess a number of adaptive, avoidance, or acclimation
mechanisms to survive with high-temperature environments. It is believed that the
major tolerance mechanisms are those employing ion transporters, proteins,
osmoprotectants, antioxidants, and factors involved in signaling cascades and
transcriptional control. These mechanisms are activated to offset stress-induced
biochemical and physiological alterations. Genetically, high temperature induced
gene expression and metabolite synthesis that also substantially improve tolerance
(Hasanuzzaman et al.
2013
). SNP administrated in wheat (
T. aestivum
L.) stressed
by high temperature increased activities of antioxidant enzymes and decreased lipid
peroxidation (Bavita et al.
2012
). Similar results were obtained by addition of the
SNP or
S
-nitroso-
N
-acetylpenicillamine (SNAP) on the callus of reed under high
temperature. An increase of activities of antioxidant enzymes was also found
suggesting that NO may act as a signal molecule in defending plant against
oxidative injury caused by heat stress (Siddiqui et al.
2011
).
Exogenous NO (SNP) alleviated heat damage at the reaction center and electron
transport from oxygen-evolving complex (OEC) to encoded peptides of
psbA
gene
(D1 protein) in tall fescue (
Festuca arundinacea
). The results suggest that NO may
improve the recovery process of photosystem II (PSII) by the upregulation of the
transcription of PSII core protein, which leds a different strategy of the protective
