Exogenous application of phytoprotectants in legumes against environmental stress - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 178

reduced the oxidative stress in all cases and improved
physiological adaptation in most of the species under
drought stress; the best response to JA was observed with
Brassica juncea under drought stress. This species showed
fewer deleterious effects than all the other species under
drought stress, which reflects its natural drought toler-
ance capacity.

system so that the oxidative damage was alleviated,
partly due to improvement in photosynthetic parame-
ters (Hayat et al., 2010). Spraying with BRs (25 and
50 mg/L) increased vegetative growth, total yield,
quality of pods and total phenolic acids in the pod of
P. vulgaris under HT stress of 34.7 to 35.2 °C (El-Bassiony
et al., 2012). Gradual increases of Cd toxicity (0, 50, 100
or 150 mM) decreased plant fresh and dry mass, number
of nodules, and their fresh and dry mass in C. arietinum
cv. Uday. This stress also decreased leghaemoglobin,
N and carbohydrate content in the nodules. Increased
Cd levels also gradually reduced the leaf chl content,
and NR and carbonic anhydrase activities. These adverse
effects were overcome by spraying with 0.01 mM
28-homobrassinolide; this spray also regulated the
content of Pro and the activities of CAT, POD and SOD
towards Cd tolerance (Hasan et al., 2008). Exposure of
mung bean plants to Al (1 and 10 mM) in the nutrient
medium caused a sharp reduction in length, and fresh
and dry mass of root and shoot. Aluminium decreased
the activity of carbonic anhydrase, RWC, water use
efficiency, chl content and the rate of photosynthesis.
The activities of antioxidant enzymes (CAT, POD, SOD)
in shoot and root and the Pro content were increased
by Al. Spraying with 10 −8 M 24-epibrassinolide or
28-homobrassinolide improved antioxidant enzyme
activities, Pro content, growth and physiological param-
eters in the absence or presense of Al (Ali et al., 2008).

11.4.1.8 Brassinosteroids
Research with higher plants suggests that brassinosteroids
(BR) are present in most or all parts of the plant and play
crucial roles in many processes like vegetative growth,
floral initiation, and development of flowers and fruits
(Hayat & Ahmad, 2003; Sasse, 2003). Brassinosteroid
metabolism has long been recognized in altering plants'
responses to abiotic stresses, and brassinosteroids confer
stress tolerance via activation of different mechanisms
(Bajguz & Hayat, 2009).
Salt stress exerted several adverse effects on growth,
yield and physiological attributes of P. sativum cv. Climax.
Brassinosteroids alleviated those stress effects in diverse
ways. Compared to the untreated controls, seed treatment
with 24-epibrassinolide (10μM) significantly enhanced
the fresh and dry biomass, seedling height, nodule number
and nodule dry biomass of P. sativum L. cv. Climax.
Photosynthesis rate, stomatal conductance, total chl and
Pro contents were maintained, and activities of antioxi-
dant enzymes like SOD, POD and CAT were enhanced.
Activities of nitrate metabolism enzymes like NR were
also improved by 24-epibrassinolide treatment. All
these might help in achieving higher seed yield, seed
number and seed protein contents (Shahid et al., 2011).
Salinity stress (50-400 mM) inhibited nitrate uptake
and metabolism in C. cajan . Levels of proteins, amino
acids, nitrate, NR of roots and the composition of
xylem sap amino acids were reduced by salt stress. But
exogenous 24-epibrassinolide (10 − 7 M and 0.5 × 10 − 9 M)
increased nitrate uptake and elevated the activity of NR
together with achieving greater levels of free amino
acids and soluble proteins in roots of plants under saline
conditions (Dalio et al., 2013). HT or NaCl stresses, indi-
vidually or in combination, increased electrolyte leakage
and lipid peroxidation, and decreased the membrane
stability index and leaf water potential in V. radiata . High
temperature and NaCl led to a significant decline in
growth, photosynthetic parameters and maximum
quantum yield of PSII. 28-Homobrassinolide improved
photosynthesis, chl fluorescence and the antioxidant

11.4.2 proline and glycine betaine
The accumulation of osmolytes such as Pro is a
well-known adaptive mechanism of plants under osmotic
stress, and it has been suggested that Pro accumulation
can serve as a selection criterion for the tolerance of most
species to stress conditions (Ashraf & Foolad, 2007).
Glycine betaine (GB) is another small water-soluble
organic molecule that can potentially play a protective
role against osmotic stress by protecting plant cells
through osmotic adjustment, protein stabilization, photo-
synthetic apparatus protection and reduction of ROS
(Ashraf & Foolad, 2007).
Hossain et al. (2010) investigated the effect of exoge-
nously applied Pro and GB in defending oxidative stress
in V. radiata seedlings exposed to Cd. Cadmium stress
(1 mM CdCl 2 , 48 h) caused a significant increase in GSH
and GSSG contents, while the AsA content decreased
significantly with a sharp increase in H 2 O 2 and MDA
contents. The activities of APX, GST and GPX increased