Effect of pesticides on leguminous plants: An overview - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 93

of pesticides in plant samples, such as GC-MS (gas
chromatography-mass spectrometry), GC-NPD (gas
chromatography with nitrogen phosphorus detection),
GLC (gas liquid chromatography) and UHPLC-MS
(ultra-high performance liquid chromatography-mass
spectrometry) (Kaphalia et al., 1990; Jian et al., 2013).

and total biomass content of alfalfa plants was reported
when they were treated separately with DDT, penta-
chlorophenol, methylparathion and bisphenol A (Fox
et al., 2007). The effect of Brominal, Gramoxone,
Afugan, Sumi oil and Selecron was determined on the
nodulation and growth of Glycine max (L.) (Abd-Alla
et al., 2000). Application of Selecron, Brominal, Afugan
and Gramoxone inhibited the growth of Phaseolus vul-
garis L., Vigna sinensis and Lupinus albus L. The chlorophyll
content in leaves and shoots, number of root nodules,
dry weight of whole plant and yield of grains declined
due to imazaquin phototoxicity affecting the growth of
the soybean plants (Alonge, 2000). The legumes tested
with fipronil insecticide showed varied responses; and
this was mainly because the toxic effect of this insecti-
cide depends on both the physiology and genetics of the
plants, which change from species to species (Ahemad &
Khan, 2011b). A decreased concentration of chlorpyri-
fos had a significant effect, which was non-phototoxic
and effective, resulting in increased growth, whereas
high concentration of chlorpyrifos had an inhibitory
effect on growth parameters such as height of the plant,
number of leaves, total area of leaves and biomass of
plant. Similarly, Bashir et al. (2007) noted the effect of
mancozeb on different morphological parameters in
Lens culinaris L. at various developmental stages. They
concluded that at low concentrations of mancozeb, the
morphological parameters increased whereas at high
concentrations a decline was observed. A study of Vigna
radiata L. under chlorpyrifos showed a reduction in
growth parameters with increased concentration,
exhibited as a decline in the leaf number and leaf area,
which could be due to obstruction in translocation of
photosynthates and decline in chlorophyll content
(Parween et al., 2012). Similar results were observed
in bean leaves (Ruano et al., 1988). Under the applica-
tion of dimethoate insecticide the seedlings of cowpea
showed drastic variations in the photosynthetic
machinery and reduced rate of photorespiration hence
increasing the chances of damage, which resulted in
decline of growth and biomass production. Pesticides
showed an adverse effect on synthesis of proteins and
the enzymes involved in metabolism (Kapoor et al., 1996;
Boldt & Jacobsen 1998). It was further emphasized by
Pham et al. (2004) that pesticides were responsible for
genotoxicity. High concentrations of pesticides lead to
reduced functioning and organism survival (Kumar
et al., 2010).

6.3 effects of pesticides
on leguminous plants

Pesticides have an inhibitory effect on the growth of
legumes due to the reduced activity of the microorgan-
isms that promote rhizospheric growth (De Bertoldi
et al., 1978; Siti et al., 1982; Koch et al., 1997). Studies
have found that there is a progressive decline in plant
growth linked with the application of pesticides
(Ahemad, 2014). Lewis et al. (1996) found that pesti-
cides have a fatal effect on the soil microbe population
that is useful for plant growth. However, certain micro-
organisms, such as Rhizobium sp. strain MRL3, have
shown a remarkably high resistance to pesticides of
many chemical families. Physiological changes induce
the formation of novel metabolic pathways to bypass a
biochemical reaction obstructed by a specific pesticide.
This produces temporary resistance or tolerance against
the pesticide (Bellinaso et al., 2003). The effects of var-
ious pesticides on growth, yield and photosynthesis are
summarized below:

6.3.1 effect on growth
Accumulation of insecticides was found to cause a
reduction in the population of nitrifiers as well as
enzymatic activity of soil (Das et al., 2003). High con-
centrations of insecticides led to a loss in agricultural
output and fertility of the soil (Fox et al., 2007). Fipronil
reduced shoot and root growth in legumes. This
reduction occurred as result of its effect on plant organs,
mainly the nodules, which led to disruption of the
symbiotic legume- Rhizobium association and hence of
nitrogen fixation resulting in a growth decline (Evans
et al., 1991). The inhibitory effect of insecticides might
be due to inhibition of the enzymes involved in growth
and development or to the disruption of signalling bet-
ween phytochemicals, such as apigenin, luteolin and
NodD Rhizobium receptor, that are important for nodule
initiation and fixation of nitrogen (Fox et al., 2007).
Reduction in the activity of nitrogenase, nodulation