Exogenous application of phytoprotectants in legumes against environmental stress - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 176

Nonetheless, GA has beneficial effects on both species
under Cd or Pb stresses (Sharaf et al., 2009).

plant growth. Exogenously applied IAA has been docu-
mented to promote growth as well as to alleviate adverse
effects of different abiotic stresses in different plant
species (Chakrabarti & Mukherji, 2003; Ali et al., 2007;
Egamberdieva, 2009).
Salt stress (NaCl at 25, 50, 100 and 200 mM) in Phaseolus
mungo caused significant reductions in germination, seed-
ling growth, root and shoot length, fresh weight and leaf
area. Reductions in protein content and NR activity were
documented at all levels of stresses, but Pro level, free
amino acids, and POD and CAT activities were increased
by salt stresses. Exogenous IAA enhanced salt stress toler-
ance by improving those antioxidant defence processes.
Foliar application of IAA (15 mg/L) to the NaCl-stressed
plants increased the percentage of germination, shoot and
root length, fresh weight, total chl content and dry weight,
and improved yield. IAA also decreased levels of Pro, free
amino acids and total soluble sugar levels, increased NR
activity and modulated CAT activity (Devi et al., 2012).
Drought stress (10% PEG) exerted several adverse effects
on the enzymatic activities of germinated C. arietinum cv.
PBG-1 seedlings. Treatment with IAA (3μM) enhanced
the activities of different metabolic enzymes including
amylase, acid invertase, alkaline invertase, sucrose syn-
thase and sucrose phosphate synthase, improved and
carbohydrate composition. Germination was better in
IAA-supplemented seeds under drought treatment, com-
pared to seeds under drought stress alone (Kaur et al.,
2000). Gangwar et al. (2011) reported that when P. sativum
L. cv. Azad P-1 seedlings were exposed to different levels
of manganese (Mn 50, 100 and 250 μM) their antioxidant
system components were disrupted, including the non-
enzymatic and enzymatic antioxidants, thereby increasing
the oxidative stress (i.e. increased H 2 O 2 and MDA levels).
Indole acetic acid (10 and100 μM) application alleviated
Mn toxicity symptoms by promoting SOD, APX, GR and
DHAR activities; the concentrations of AsA and GSH; and
the ratio of their reduced to oxidized forms. Thus the
oxidative stress was eliminated (Gangwar et al., 2011).
Cadmium exposure inhibited the germination of C. arieti-
num by hampering various attributes. But soaking the
seeds in 4-Cl-IAA (4-chloroindole-3-acetic acid) improved
the RWC, moisture content, and activities of NR and POD.
The combined effects resulted in improvement of the rate
of germination (Ali et al., 2007). Reduced root and shoot
growth, chl, N, phosphorus (P), total sugar, and soluble
protein under Cd stress were ameliorated by 4-Cl-IAA
(10-6 M) in V. radiata seedlings (Mazid et al., 2010).

11.4.1.4 Naphthalene acetic acid
Naphthalene acetic acid (NAA) is a synthetic plant hor-
mone of the auxin family. It is often used in embyogenesis
and in vitro plant regeneration, and for the vegetative
propagation of plants from stem and leaf cuttings.
Application of NAA in plant tissue culture is also common
(Navalón et al., 1997). Exogenous NAA application has
been shown to improve fruit development, quality and
total yield (Stern et al., 2007). Although the information
is sparse, NAA plays effective roles in countering differ-
ent abiotic stresses (Aslam et al., 2010; Kusuma &
Begum, 2013).
The response of C. arietinum to NAA (4.5% a.i.) was
studied under control and reduced moisture levels. Stress
with 50, 65, 80 and 95% available soil moisture depletion
levels was examined with NAA application and without
NAA. With depleted water levels NAA could maintain seed
yield and yield components in chickpeas, indicated by more
pods per plant and seeds per pod, and greater 100-seed
weight, biological yield and seed yield, compared to those
of chickpeas grown in a drought environment without
NAA. Ttreatment with NAA was able to maintain enhanced
performance up to an 80% reduction in water levels
(Aslam et al., 2010). Drought stress had several adverse
effects on G. max var. Nannong 99-6, including reductions
in the rate of biomass production, leaf area, leaf relative
water content, chl content, photosynthesis rate, stomatal
conductance to CO 2 , intercellular CO 2 concentration and
transpiration rate. Pretreatment with NAA alleviated those
adverse effects, and improved physiological adaptation
capability and drought resistance capacity (Peng et al.,
2011). With a view to develop salt-stress-tolerant plants of
A. hypogaea Linn (JL-24), in vitro plant regeneration was
performed under Murashige and Skoog (MS) regeneration
medium with a combination of 2.5 mg/L benzylaminopu-
rine (BAP) and 0.2 mg/L NAA. The NAA-supplemented
medium was good for the development of healthy plants
subjected to different regimes of salt stress; they were found
to be tolerant up to a maximum concentration of 1.0 mg/L
NaCl (Kusuma & Begum, 2013).

11.4.1.5 Indole acetic acid
Indole acetic acid (IAA) is a hormone of auxin group
that stimulates cell elongation and lateral root formation.
It has vital roles in the absorption of minerals and in