LIST OF FIGURES
Figure 2.1: Chemical
structure of some polyphenolic compounds present in common beans 23
Figure 2.2: Initiation
step of lipid peroxidation 38
Figure 2.3: Initial
phase of propagation step of lipid peroxidation process indicating the 39
Oxygen uptake
Figure 4.1: Effect of
crude oil-impacted soil on height of beans over a period of nine 63
(9) weeks
Figure 4.2: Effect of
crude oil-impacted soil on stem girth of beans over a period of nine
64
(9) weeks.
Figure 4.3: Effect of
crude oil-impacted soil on the relative water content (RWC) of planted 65
Beans over a period of
nine (9) weeks
LIST
OF TABLE
Table 2.1: Characteristic of plant ascorbate
peroxidase 42
Table 4.1: Effect of crude oil impacted soil on
activities of superoxide dismutase (SOD), 66
Catalase (CAT), peroxidase (POD), ascorbate
perioxidase (APX) and glutathione reductase
(GR) activities of beans leaves.
Table 4.2: Effect of crude oil impacted soil on
activities of superoxide dismutase (SOD), 67
Catalase (CAT), peroxidase (POD), ascorbate
perioxidase (APX) and glutathione reductase
(GR) activities of beans stems.
Table 4.3: Effect of crude oil impacted soil on
soluble protein content (SPC) 68
and malondialdehyde (MDA) of beans leaves.
Table 4.4: Effect of crude oil impacted soil on
soluble protein content (SPC) 69
and malondialdehyde (MDA) of beans stems.
ABSTRACT
The effect of crude oil contaminated soil on physical and biochemical
properties
of beans (phaseolus
vulgaris)
was investigated. Fifteen polythene pots with drainage holes at the bottom,
each containing 10 kg of surface soil, were randomly placed on a table in the
screenhouse in a factorial combination of five treatment levels (0.4%, 0.3%,
0.2%, 0.1% and 0% w/w) of crude oil and were designated P4, P3, P2, P1 and P0
respectively. Three seeds of beans per pot were planted. Growth parameters
(plant height, stem girth, relative water content (RWC), and soluble protein
content (SPC)) and antioxidant indices were determined in the beans over a
period of nine weeks after planting (WAP). Results showed that growth of beans
planted in contaminated soil was significantly lower (p<0.05) than that of
control. Beans planted in the contaminated soil also showed a significant
increase (p<0.05) in superoxide dismutase (SOD), catalase (CAT), peroxidase
(POD), ascorbate peroxidase (APX) and glutathione reductase (GR) activities in
leaves when compared with control plants. The results suggest that crude oil
contaminated soil hindered availability of water, air and
nutrients to beans roots, creating a drought condition which could induce
oxidative stress in the plant and consequently retarding growth and yield of
beans plant.
CHAPTER ONE
1.0
INTRODUCTION
Crude
oil is a complex mixture of thousands of hydrocarbons and non-hydrocarbon
compounds, including heavy metals. Nigeria is an established crude oil
exporting nation producing medium and light crude oil, such as bonny light
(Amund et al., 1993). Crude oil
exportation is the main stay of Nigeria’s economy. Crude oil is a colloidal
mixture of different hydrocarbons (90%) and non-hydrocarbon (10%) components
(Cadwellaer et al., 1993). Various
activities in crude oil exploration, exploitation, storage and transportation
lead to spillage of oil to the environment (Agbogidi et al., 2007). Crude oil causes harmful effects on the environment,
where it poses a serious threat to organisms and farmland that are linked in a
complex food chain that includes humans (Lundstedt et al., 2003). The effects of crude oil on the growth and performance
of plants have been reported in many studies (Njoku et al., 2008). Crude oil in soil makes the soil condition
unsatisfactory for plant growth. It can reduce the level of available plant
nutrient in contaminated soils (Jong et
al., 1980) and can also raise the levels of certain elements such as iron
and zinc to toxic amounts (Udo et al., 1975).
Water and oil are usually considered to be immiscible. However, crude oil
contains a very small soluble portion referred to as the water soluble fraction
(WSF). The soluble constituents are dispersed particulate oil, dissolved
hydrocarbons and soluble contaminants such as metallic ions. The components of
crude oil that go into solution make up the WSF. The lower the molecular weight
of the constituent hydrocarbon of crude oil, the higher is its concentration in
the water-soluble fraction (Edema et al.,
2012).
Exposure
of plants to crude oil and heavy metal poisoning has been reported to produce
reactive oxygen species (ROS) and other free radicals which induce oxidative
stress and cause lipid peroxidation (Blokhina et al., 1999). Even at an early stage, it can cause a reduction in
cell proliferation and growth. Various researchers have reported activation of
lipid peroxidation in plants exposed to different pollutants (Chirkova et al., 1998). Increase in superoxide
dismutase (SOD) activity has also been reported in oat, wheat and Arabidopsis
thaliana in soils contaminated with various pollutants (Alscher et al., 2002). Several plant species
have also been shown to have elevated peroxidase activities in response to
increased pollutant concentrations (Jouili et
al., 2003). Reactive oxygen species is thought to increase cellular damage
through the oxidation of several macromolecules such as lipids and proteins
(Ortega et al., 2005).
The
common dry beans or Phaseolus vulgaris
L., is the most important food legume for direct consumption in the world.
Among major food crop, it has one of the highest levels of variation in growth
habit, seed characteristics (size, shape, colour), maturity, and adaptation. It
also has a tremendous variability (> 40,000 varieties). In Africa, beans are
grown mainly for subsistence, where the Great Lakes region has the highest per
capita consumption in the world. Beans are a nearly “perfect” food.
Nutritionally rich, they are also a good source of protein, folic acid, dietary
fibre and complex carbohydrates. Beans are also one of the best non-meat
sources of iron, providing 23-30% of daily recommended levels (Pachico et al., 1993) from a single serving.
Consumption of beans is high mostly because they are a relatively inexpensive
food. For the poor of the world, they are a means of keeping malnutrition at
bay (WHO. 1992).
This
research work is geared towards outlining the effect of soil contaminated with
crude oil (at various levels) on the biochemical properties and growth rate of
beans (phaseolus vulgaris).