Exogenous application of phytoprotectants in legumes against environmental stress - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 180

under NaCl-induced stress suggested that Put treatment
may partially ameliorate the adverse effects of sodium
and chloride ions. In P. vulgaris Put treatment improved
the growth of salt-stressed seedlings due to partial inhi-
bition of amylase and protease enzymes, and increased
the total content of nucleic acids and photosynthetic
pigments. The same author also observed changes in
protein banding patterns that suggested that a defence-
response gene could be activated by Put treatment
(Zeid, 2004). Jiménez-Bremont et al. (2006) suggested
that PA could alleviate salt stress in P. vulgaris by prompt-
ing Pro accumulation. Since the metabolic pathways
involved in Pro and PA biosynthesis require glutamate,
ornithine and arginine as precursors, these pathways
are probably well coordinated. They also observed differ-
ential responses of PA in salt-sensitive and -tolerant
cultivars. When sensitive plants were subjected to salt
stress (150 mM) in the presence of PAs, the content of
Pro decreased in relation to controls with PAs and NaCl
alone, whereas such a decrease did not occur in resis-
tant plants (Jiménez-Bremont et al., 2006). In V. sinensis ,
Alsokari (2011) observed the protective effect of Spm
on some physiological aspects under salt stress (50%
seawater from the Red Sea). Salt stress negatively
affected most of the physiological and biochemical
parameters in plants. Plants irrigated with seawater
exhibited reductions in chl a , chl b , carotenoids, carbo-
hydrates, protein, and Spd and Spm levels as well as
amylase activity. Salt stress also decreased different yield
attributes and seed yield of bean. In contrast, salt caused
increases in Pro, K + , Na + and Put concentrations, and in
POD activity. Importantly, exogenous Spm application
(0.3 mM) mitigated the deleterious effects of salinity
stress on growth and yield by enhancing the physiologi-
cal and yield attributes of plants (Alsokari, 2011).
Exogenous Put could also alleviate HT stress (affected by
late sowing) in P. vulgaris (Ibrahim et al., 2012). Upon
exposure to HT, the plants exhibited significant reduc-
tions in height, branches per plant, number of leaves
per plant, fresh weight and dry matter of plants and
content of chl. However, foliar spray of Put (200 mg/L)
alleviated the harmful effects of HT stress in the late-
sown plants, which indicated the protective role of
PA in heat stress tolerance (Ibrahim et al., 2012).
Radhakrishnan and Lee (2013) observed that exoge-
nous Spm-induced changes in antioxidant metabolism
and ABA levels could ameliorate the effects of osmotic
stress in soybean. When soybean plants were exposed

to osmotic stress (9% PEG) at the flowering stage, the
fresh weight of pods and seeds and the protein content
were decreased significantly. However, exogenous
application of Spm (0.1 mM) induced the enhancement
of pod and seed fresh weight and protein content under
osmotic stress conditions. Osmotic stress also reduced
the enzymatic activities of antioxidant enzymes in the
pod, which resulted in higher lipid peroxidation (MDA).
In contrast, exogenous Spm application could upregu-
late the activities of antioxidant enzymes and maintain a
lower level of the MDA, which indicated the role of Spm
in antioxidant defence in soybean (Radhakrishnan &
Lee, 2013).

11.4.4 antioxidants
11.4.4.1 Glutathione
Glutathione (GSH) is a water-soluble non-protein thiol
compound that serves a broad range of biochemical
functions in almost all cell organelles (Foyer & Noctor,
2003). GSH can protect plants from different abiotic
stresses due to its dynamic biochemical properties like
high water solubility, relative stability, capacity to form
mercaptide bonds with metals and reactivity with
selected electrophiles (Gill et al., 2013a) (Figure 11.3). It
is a vital component of the antioxidant defence system,
playing crucial roles in cellular redox homeostasis and
stress signalling (Wu et al., 2011; Chen et al., 2012).
Glutathione has a special role in the elimination of
metal toxicity due to its role in the activity of phyto-
chelatin (PC) synthesis (Figure 11.3).
Pretreatment of Vigna cutjang with l -cysteine and GSH
produced resistance against water deficit stress by
modulating the H 2 O 2 and ascorbic acid contents. Water
stress (−0.5, −1.0, −1.5 MPa) increased glycolate oxidase
activity and H 2 O 2 and Pro contents in V. cutjang seed-
lings, and resulted in decreased leaf water potential and
relative water content, catalase activity, and ascorbic
acid and protein contents. Pretreatment with l -cysteine
and reduced glutathione (10 −3 M) decreased glycolate
oxidase activity, H 2 O 2 content, ascorbic acid oxidase
activity and Pro content and also slightly improved the
water status of leaves stressed (−1.0 MPa) for 2 days
(Mukharjee & Choudhuri, 1983). It was proposed that
Phaseolus vulgaris seedlings prevented damage due to HT
stress (38-39 °C, 2 h followed by exposure to 45-48 °C,
8 h) by enhancing GSH and AsA contents, and the activ-
ities of β-amylase, acid phosphatase and guaiacol-specific
peroxidase (Babu & Devaraj, 2008). Mung bean ( V. radiata