Exogenous application of phytoprotectants in legumes against environmental stress - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 174

activities of peroxidases (POX) and CAT, whereas water
stress increased MDA and Pro levels. Compared to
water-stressed seedlings alone, when seedlings were
supplemented with 0.1 mM ABA under water stress
they showed improved growth parameters, increased
antioxidant enzyme activities and decreased MDA and
Pro levels (Ali et al., 2013). Increased leaf and xylem
ABA concentrations were observed in salt-treated (1,
50, 100 or 200 mM NaCl; 30 days) Medicago citrina ,
which showed higher ion (Na + /Cl − ) compartmentation
and gas exchange parameters compared to M. arborea
(Sibole et al., 2003). High-temperature stress (35/30,
40/35 and 45/40 °C day/night) resulted in oxidative
stress in C. arietinum . Exogenous ABA (2.5 μM) regu-
lated endogenous levels of ABA and osmolytes, reducing
oxidative damage by decreasing MDA and H 2 O 2 levels.
Treatment with ABA also improved the growth of
C. arietinum under HT stress compared to no treatment
(Kumar et al., 2012). Chilling stress (5 °C for 5 or 10 h)
induced significant increases in lipid peroxidation,
membrane leakage and H 2 O 2 level, as well as decreased
activities of CAT, POD and APX in V. radiata seedlings.
Total chl, total carbohydrate, protein and Pro levels
were also decreased by chilling stress. Exogenous ABA
(0.5 and 1 mM) treatments ameliorated the chilling
injuries by enhancing antioxidant enzymes that
reduced lipid peroxidation, membrane leakage and the
H 2 O 2 level. Increaes in total chl, carbohydrates, protein
content and Pro levels were other beneficial effects of
ABA treatment (Saleh, 2007). Under CdCl 2 (1, 3, 5, 7
and 9 μM) stress the adventitious root development of V.
radiata seedlings was inhibited. On the other hand, ABA
(1, 5, 10 and 15 μM) enhanced the number and fresh
weight of adventitious roots by ameliorating the adverse
effects. Exogenous ABA increased indole acetic acid (IAA)
oxidase and phenol levels to a greater extent than the
controls. Cadmium increased oxidative stress by signif-
icantly reducing the activities of SOD, APX, POD and
IAA oxidase, as well as GSH level, but increased AsA
content. But ABA upregulated antioxidative defence
systems towards the alleviation of wounding and
Cd-induced oxidative stress (Li et al., 2014).

(Harper & Balke, 1981), photosynthetic rate, stomatal
conductance, transpiration and glycolysis has also been
examined (Khan et al., 2003). The presence of SA in a
wide range of plant species and its role in basic plant
processes have made SA a potent phytohormone in
responses to environmental stresses (Raskin, 1992;
Yalpani et al., 1994; Senaratna et al., 2000; Alam et al.,
2013; Hasanuzzaman et al., 2014b,c).
Salt stress (67, 134, 202 and 270 mM NaCl) hampered
different growth parameters of V. radiata . But seed
priming with SA (75, 150 and 300 mg/L) alleviated salt
stress effects and improved germination rate, vigour,
root length, shoot length and dry weight (Entesari et al.,
2012). The physiological performace of two mung
bean cultivars, one salt-tolerant (Pusa Vishal) and one
salt-sensitive (T44), was examined under salt stress
(50 mM NaCl) alone or in combination with SA (0.5 mM).
The application of SA increased N and sulphur (S) assim-
ilation, GSH content, and activity of APX and GR. The
SA addition with salinity also restricted Na + and Cl − con-
tents in leaf, and maintained greater efficiencies of PSII,
photosynthetic N-use and water relations. In response
to SA under salt stress, Pusa Vishal performed better
than T44 (Nazar et al., 2011). The positive effects of SA
have also been documented in developing salt tolerance
in faba bean (Azooz, 2009). The ameliorative impact of
salicylic acid (SA) on V. unguiculata L. during water
deficit stress was investigated. Plants were subjected to
water deficit stress (7 days) at the vegetative stage and
reproductive stage, and leaf water potentials (ψw) of
−1.9 MPa and −2.01 MPa were maintained, respectively.
Stress reduced almost all parameters studied. Foliar
applications of SA (3 and 5 mM) increased leaf water
potential by 27%, chl content by 94%, plant biomass
by 75%, nitrate reductase (NR) activity by 7% and Pro
content by 38% in the vegetative stage. Similar but
minor improvements were observed in the reproductive
stage. Stress increased the levels of Pro and the antioxi-
dant vitamin B 12 in the vegetative stage and vitamin C in
the reproductive stage; SA further increased osmolyte
Pro and antioxidants, which maintained better water
potential and growth under stress (Umebese & Bankole,
2013). Seed imbibition following soil drenching with
different levels of SA (0.05, 0.1, 0.5, 1.0 and 5.0 mM) or
acetyl SA improved the tolerance of P. vulgaris against
HT stress (54 °C, 3 h), chilling stress (0 °C) and drought
stress (withholding water for 7 days) as evidenced
by increased plant height, vigour and leaf number,

11.4.1.2 Salicylic acid
The roles of salicylic acid (SA) in seed germination,
growth, flowering and fruit yield are long documented
(Klessig & Malamy, 1994). Its role in fundamental
physiological processes like ion uptake and transport