Growth Response of Ricinus communis L (Castor Oil) in Spent Lubricating Oil Polluted Soil

Abstract

The growth response of castor oil plant, Ricinus communis, in spent lubricating oil (SLO) was investigated using 1-6% w/w SLO and a control. The result showed that highest percent germination of approximately 92, was obtained in control and the least in 5% w/w. The early germination obtained in this study was significant when considered in the light of reported delay and depression of germination by spent lubricating oil in Capsicum annum, Lycopersicon esculentum, Solanum melongena and S. incanum. For parameters like plant height, stem girth, leaf area, fresh and dry weights, and root length, the mean values obtained were higher for 1% w/w than control. There was stimulation of growth at 1% w/w spent lubricating oil in soil. Plants in higher concentration (2–6% w/w) exhibited depression in growth. Plants grown in 1% w/w spent lubricating oil in soil flowered earlier than those grown in control. A difference of eight (8) days was observed. Journal of Applied Sciences and Environmental Management Vol. 9(2) 2005: 73-79

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*Corresponding author: E-mail: vwioko@yahoo.com
Growth Response of Ricinus communis L (Castor Oil) in Spent Lubricating Oil
Polluted Soil
*VWIOKO, D E; FASHEMI, D S
*Department of Botany, University of Benin, Benin City, Nigeria
ABSTRACT: The growth response of castor oil plant, Ricinus communis, in spent lubricating oil (SLO) was
investigated using 1-6% w/w SLO and a control. The result showed that highest percent germination of
approximately 92, was obtained in control and the least in 5% w/w. The early germination obtained in this study
was significant when considered in the light of reported delay and depression of germination by spent lubricating
oil in Capsicum annum, Lycopersicon esculentum, Solanum melongena and S. incanum. For parameters like plant
height, stem girth, leaf area, fresh and dry weights, and root length, the mean values obtained were higher for 1%
w/w than control. There was stimulation of growth at 1% w/w spent lubricating oil in soil. Plants in higher
concentration (2 – 6% w/w) exhibited depression in growth. Plants grown in 1% w/w spent lubricating oil in soil
flowered earlier than those grown in control. A difference of eight (8) days was observed. @JASEM
The disposal of spent lubricating oil into open
vacant plots and farms, gutters and water drains is
an environmental risk considering the water table
in the South-South Region of Nigeria and shallow
bore-holes dug to get water for domestic use
(Odjeba and Sadiq, 2002). Anoliefo et al. (2001)
studied the phytotoxic effect of soil collected from
an abandoned mechanic village and reported that
the soil depressed and inhibited growth of Arachis
hypogaea. The suspected major soil
contaminant/pollutant was spent lubricating oil
from engines and other machinery. Oil in soil
makes the soil condition become unsatisfactory for
plant growth (De Jong, 1980), due to the reduction
in the level of available plant nutrient or a rise in
toxic levels of certain elements such as iron and
zinc (Udo and Fayemi, 1975). There are relatively
large amounts of hydrocarbons in the spent
lubricating oil including the highly toxic polycyclic
aromatic hydrocarbons (PAH) (Wang et al., 2000).
The concentration of PAHs in lubricating oil
increases with time of usage and those with two
and three rings accumulate rapidly in used
lubricating oil to very high levels (Boehm and
Quinn, 1973). Spills arising from disposal of spent
lubricating oil are becoming a visible problem
especially in developing countries such as Nigeria.
Therefore the usual improper disposal of used
lubricating oil generated by service stations and
other users now demands attention in order to
protect the soil.
The castor oil plant (also known as castor bean)
Ricinus communis L., is a member of the
Euphorbiaceae or spurge family. It is the source of
castor oil which has a wide variety of uses and
ricin, a poison (Oyeleye, 2003). Castor bean is a
native of tropical Africa but has naturalized in
moist tropical and subtropical regions throughout
the world (Anonymous, 2000). In Nigeria, apart
from some parts of the middle belt notably Kogi
State (where it is cultivated), castor oil plant grows
in the wild and is treated as weed (Oyeleye, 2003).
This underpins the use in this study. The ability of
the plant to germinate and grow successfully in
disturbed area was considered also. The objective
of the study was to evaluate its growth in spent
lubricating oil contaminated environment.
MATERIALS AND METHODS
Dried seeds of castor oil plant, Ricinus communis
L., were obtained from a fallow farmland in Benin
City, Nigeria. The spent lubricating oil was
obtained as pooled, used engine oil from motor
mechanics in different location in Benin City. The
viable seeds determined by floatation were soaked
in water (seed priming) for twelve hours before
sowing. Primed seeds were sown in soil
supplemented with water (control) and spent
lubricating oil at different strengths
(concentration). Soil of known weight was treated
with 1, 2, 3, 4, 5 and 6% (weight of oil/weight of
soil) spent lubricating oil or water before placing in
polythene pots. Each treatment including the
control was replicated four times. Twelve seeds
were sown in each pot. The whole set up was
transferred to the field. The treatments were
watered every other day. The design of the
experiment was completely randomised one. One-
way analysis of variance was carried out and the
Least Significant Difference (LSD) test was used to
compare the means. The soil used in the study was
obtained from a composite sample of top soil (0 –
20 cm) collected around a fallow plot in the
University of Benin. Teaching and Research farm
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Growth Response of Ricinus communis L (Castor Oil) in Spent
VWIOKO, D E; FASHEMI, D S
(Lat 6o5’ N, Long. 5o5’ E). The soil had been
previously described by Ogunkunle (1983).
Growth parameters recorded were percent
germination, plant height, leaf area, stem girth,
number and length of stomata per leaf surface area,
fresh and dry weight, root length and number of
days to flowering. Germination was observed as
the emergence of the cotyledons above the soil
surface. Thinning to one plant per pot was done
three weeks after planting (3WAP). Plant height
was measured from the soil level to the terminal
bud using a metre rule. Leaf area was determined
by comparing the weight of a cut-out traced area
with standard paper of known weight to area ratio
(Eze, 1965) using the relationship;
Leaf Area (for specimen) =
weight area Standard area standard eight Specimen w ×
Stem girth was measured by wrapping a thin thread
around the stem of the plant at soil level and its
length determined. Number and length of stomata
per leaf surface area were determined by the
impression method (Rice et al., 1979). Leaves at
the third node from the apex of each plant in a pot
of each treatment (including control) were
harvested in the morning hours (between 8 – 9 am),
abaxial surface coated with nail varnish and left to
dry overnight. The dry varnish coating was peeled
off carefully, placed on a slide, two drops of
glycerine added and a cover slip placed over it. The
preparation was viewed under the light microscope.
The stomata were counted and the length of each
stoma was determined using an eye piece
micrometer under the objective lens x 40. Fresh
and dry weights and root length of the plants were
determined after flowering and seed setting. Dry
weights obtained by oven drying at 80˚C for 5
days. The number of days to flowering was
counted from the date of sowing. The pH of soil
was measured in distilled water (soil to water =
1:3).
RESULTS AND DISCUSSION
Three days after planting (3 DAP) seeds sown in
control and 1 – 3% spent lubricating oil
germinated. The highest percent germination was
observed in control soil (0% SLO). Twenty-one
days after planting (21 DAP) germination was
observed in all concentration of spent lubricating
oil contaminated soil considered in the study. The
control (0%) had the highest percent germination
of 92. This was followed by 1% (w/w) spent
lubricating oil contaminated soil. The least percent
germination was observed in 5% (w/w) spent
lubricating oil contaminated soil (See Fig. 1). The
difference in the treatment was found to be very
significant (p = 0.05) (Fig. 1). Ricinus communis
demonstrated good germinability in the SLO
contaminated soil. The species germinated in all
the concentration of spent lubricating oil (SLO)
considered in this study (1 – 6%). This capability is
significant when compared to other crops like
Abelmoschus esculentus (okra), Lycopersicon
esculentum (tomato), Capsicum annum (pepper),
Solanum melongena (eggplant) and Solanum
incanum (Egg plant) which failed to germinate in
concentration of SLO as high as 6% (Anoliefo and
Vwioko, 1995; Anoliefo and Edegbai, 2000). This
ability is purely genetical. The plant has been
reported as a pioneer species of waste land or
disturbed environment (CIR, 1972). Nine days
after planting (9 DAP), germination was observed
in all treatments of SLO including control (see Fig.
1). Seeds germinated early. Previously, Kandambi
and Dabral (1955) reported that seeds of R.
communis germinate between 10 – 21 days after
planting. Oil contaminated (polluted) soil generally
causes delayed seed emergence and that of spent
lubricating oil contaminated soil is not different
(Anoliefo and Vwioko, 1995). This is due to poor
wettability and aeration of the soil (Isirimah et al.,
1989) and loss of seed viability (Rowell, 1977).
Terge (1984) reported that germination of seeds in
soil polluted soil varied with the different plant
species. This delayed seed emergence was not
noticed in this study following the emergence of
seeds in 0, 1, 2 and 3 % SLO treated soil 3 DAP.
This barrier to early seed emergence in polluted
soil may have been minimized (if not eliminated)
by the soaking of the R. communis seeds in
distilled water 12 hours before planting. Seed
priming advances germination by inducing a wide
range of biochemical changes in the seed (DFID,
2002). The result observed in germination suggests
that delayed seed germination in oil contaminated
soil can be eliminated by soaking in water before
planting. This is significant in an attempt to
revegetate an oil-impacted environment and R.
communis is a good species for such. This has in no
means removed the fact that spent lubricating oil in
soil depressed percent germination obtained 21
DAP as SLO concentration in soil increases. The
reduction in percent seed germination 21 DAP
observed can be attributed to absorption of the
applied oil by the soil which came in contact with
the castor oil seeds and penetrated their embryo.
Udo and Fayemi (1975) and Amadi et al. (1993)
observed that increasing the concentration of oil
74

Growth Response of Ricinus communis L (Castor Oil) in Spent
VWIOKO, D E; FASHEMI, D S
beyond 3% in soil reduced percentage germination
by the coating of oil on seed surface, thereby affecting physiological functions within the seed.
0
10
20
30
40
50
60
70
80
90
100
0123456
Spent lubricating oil concentration in soil (%, w/w)
Percent Germination
3 DAP 6 DAP 9 DAP 12 DAP 15 DAP 18 DAP 21 DAP
Fig. 1. Percent germination of seeds of Ricinus communis (castor oil) sown in different concentration of spent lubricating oil
contaminated soil.
The mean plant height obtained is shown in Fig. 2
below. The highest value was obtained for plants
grown in 1% spent lubricating oil contaminated
soil. The least values were obtained for plants
grown in 4% spent lubricating oil contaminated
soil 91 DAP. The difference in treatment was also
observed to be significant (P = 0.05). The LSD test
showed that the response of the plant in terms of
height with respect to concentration (%) of the
contaminant in soil can be gradated in this order as
1 > 0 > 2 > 3 > 5 > 6 > 4. The spent lubricating oil
in soil at concentration greater than 2% (w/w)
decreased mean leaf area (See Table 1 below).
Mean values of 633.00 cm2 and82.19 cm2 were
obtained for 1% and 0% (control) respectively, 70
DAP. The mean value obtained for 2% (w/w),
83.83 cm2, was higher than that for control (82.19
cm2).
Table 1: Leaf area (cm2) of Ricinus communis (castor oil) plants
grown in spent lubricating oil contaminated soil.
*Days after planting (DAP)
Oil concentration 49 70
0 47.61 ± 28.27 82.19 ± 36.60
1 126.25 ± 62.62 633.00 ± 110.95
2 70.08 ± 32.20 83.83 ± 33.93
3 85.06 ± 36.68 93.20 ± 2.76
4 12.30 ± 0.93 15.71 ± 2.23
5 14.44 ± 2.27 22.83 ± 5.44
6 16.91 ± 2.45 24.12 ± 5.44
* = mean ± S.D.
The least value obtained was for 4% w/w
concentration. Figure 3 shows the stem girth of
Ricinus commnnis plants grown in spent
lubricating oil contaminated soil 83 DAP (Fig. 3).
The highest values were obtained in 1% (w/w)
SLO and 0% (control). Least values were obtained
in 3 and 4% (w/w) SLO. The differences in
treatments and control was found to be significant.
No difference was found between 1% SLO and 0%
(control). The data obtained for plant height, stem
girth and leaf area showed significant differences
between the control, 1% SLO treatment and 2 – 6%
SLO treatment. At 1% SLO treatment, the mean
plant height, stem girth and leaf area obtained were
higher than control about 11, 3 and 670%
respectively. Suggesting a growth stimulating
effect at this concentration of SLO. A similar effect
was observed for Solanum melogena at 1% SLO
concentration in soil by Anoliefo and Edegbai
(2000). This effect was not observed for other plant
species like Capsicum annum, Solanum
lycopersicon, Abelmosclus esculentum and
Solanum incanum. For Ricinus communis plants
grown in 2 – 6% SLO in soil showed depression in
height, stem girth and leaf area. The 2 – 6% SLO in
soil resulted in greater changes in soil condition
which imposed stressful conditions that interfered
with water uptake and gaseous exchange. This may
have created a conditions of physiological drought
McCown et al. (1972) stated that the disruption of
75

Growth Response of Ricinus communis L (Castor Oil) in Spent
VWIOKO, D E; FASHEMI, D S
soil physical properties by crude oil with anaerobic
and hydrophobic condition was found largely
responsible for reduction in plant growth. There
may also be accompanying stomatal closure and a
decrease in leaf, stem and root dry weights in
poorly aerated soils (Smith et al., 1989). Table 2
shows that values obtained for number and length
of stomata of leaves. The 1% SLO treatment gave
the highest number of stomata but their sizes were
less than that observed in control. The distinction
between the stomata of leaves of treated and
control plants were conspicuous. Dark glossy spots
were observed in the stomata inner linings of
leaves obtained from treated plants. These dark
glossy spots were oil droplets taken up by the
treated plants which could not evaporate into the
atmosphere. The SLO treatment affected the length
of stomata.
0
5
10
15
20
25
0123456
Spent lubricating oil concentration in soil (%, w/w)
Height, cm
21DAP 35 DAP 49 DAP 77 DAP 91 DAP
Fig. 2. Mean height (cm) of Ricinus communis (castor oil) plants grown in spent lubricating oil contaminated soil.
0
0.5
1
1.5
2
2.5
0123456
Spe nt lubr icating oil conce ntra tion in s oil (%, w/w)
Sterm gi rth, cm
41 DAP 55 DAP 69 DAP 83 DAP
Fig. 3. Stem girth (cm) of Ricinus communis (castor oil) plants grown in spent lubricating oil contaminated soil
76

Growth Response of Ricinus communis L (Castor Oil) in Spent
VWIOKO, D E; FASHEMI, D S
Table 2: Number and mean length (cm) of stomata per surface area of leaves of Ricinus communis grown in spent lubricating oil
contaminated soil. * = mean ± S.D.
Oil concentration Mean number of stomata * Mean length (PIM) of stomata
(mean ± S.D)
0 26 0.029 ± 0.0054
1 32 0.025 ± 0.0022
2 26 0.025 ± 0.0022
3 28 0.023 ± 0.0031
4 28 0.023 ± 0.0031
5 21 0.016 ± 0.0085
6 19 0.025 ± 0.0022
The values obtained for treated plants were lower
than that of control. Plants are known to close their
stomata in response to water stress, thus limiting
water loss. Stomata play a pivotal role in
controlling the balance between water loss and
biomass production. Measurement of the size of
the stomatal opening (stomatal aperture) or of the
resistance to CO2 and water vapour (H2O) transfer
between the atmosphere and the internal tissues of
the leaf imposed by the stomata (stomatal
resistance) are important in many studies of
biomass production (Rice et al., 1979). In plant
growing under stress conditions, changes in
stomata size are mostly observed in the length and
not width. In this study the distinction between the
stomata of control plants and treated was very
glaring. Larger and very conspicuous outlined
stomata were observed in the control as compared
to treated plants. The number of stomata observed
was higher for 1% SLO than control. In terms of
size, 1% SLO treated plants have smaller stomata
than control (see Table 2). The number of stomata
per leaf surface area should suggest the
photosynthetic rate of that plant. However, the rate
of CO2 movement into the leaf depends, among
others, upon the number of stomata present per unit
area of leaf (Causton and Venus, 1981). Increased
rate of CO2 increases rate of photosynthesis. The
spent lubricating oil treatment reduced the length
of stomata in R. communis. The adverse effects of
environmental pollution on plant growth range
from morphological aberrations, reduction in
biomass to stomatal abnormalities (Sharma et al.,
1980). Gill et al. (1992) reported that stomata in
Chromolaena odorata were grossly affected by
crude oil which manifested as distortion and
reduction in the number of stomata per unit area of
the leaf. In this study 2 – 6% SLO concentration in
soil reduced fresh and dry weights and root length.
The ranges of reduction were: fresh weight 9 –
88%, dry weight 27 – 87% and root length 32 –
60% (see Table 3). This indicates that the SLO
treatment affected dry matter accumulation in R.
communis. Table 3 shows the fresh weight, dry
weight and root length (cm).
Table 3: Fresh weight (g), dry weight (g) and mean root length (cm) of Ricinus communis
grown in spent lubricating oil contaminated soil.
Oil concentration Fresh weight (g) Dry weight (g) Mean root length (cm)
0 155.00 ± 12.73 67.00 ± 2.64 52.70 ± 2.40
1 647.70 ± 28.23 312.50 ± 25.17 106.2 ± 26.53
2 141.05 ± 6.44 49.09 ± 1.29 31.25 ± 0.35
3 77.50 ± 8.44 25.11 ± 4.39 36.00 ± 6.27
4 45.95 ± 6.15 17.37 ± 4.31 20.00 ± 3.54
5 36.50 ± 9.19 8.64 ± 0.95 28.85 ± 7.71
6 18.35 ± 2.33 9.05 ± 1.18 20.65 ± 8.70
Figures are mean ± S.D.
Table 4: Mean number of days to flowering of Ricinus communis (castor oil)
plants grown in spent lubricating oil contaminated soil
Oil concentration (%) Number of days to flowering after planting
0 96
1 88
2 -
3 -
4 -
5 -
6 -
77

*Corresponding author: E-mail: vwioko@yahoo.com
The plants in 1% SLO treated soil produced flowers
earlier than the control (0%). The treated plants
flowered 88 DAP while control flowered 96 DAP, a
difference of 8 days. Table 4 shows the numbers of
days to flowering. The plants in 2% SLO and
higher failed to flower before the termination of the
study. The results of our study showed that the 1%
SLO treated plants flowered earlier than the control
– a difference of about 8 days was recorded. For
concentration higher than 1% SLO, the plants failed
to flower before the termination of the experiment.
The early flowering in 1% SLO in soil is not
unconnected with the growth enhancement and early
maturity observed. We are of the view that spent
lubricating oil at low concentration has proven to be
beneficial to R. communis. This is because oil
pollution up to 1% could easily be degraded by
natural rehabilitation in soils, increase organic
matter in soil and improve the fertility, physical and
chemical properties of the soil (Anoliefo and
Edegbai, 2000). The early flowering observed in this
study following the 1% SLO concentration in soil
may have physiological and genetical dimensions.
The increasing acidic condition of the soil following
increased SLO concentration increases the
availability of heavy metals to plants. This suggests
an explanation for the poor plant growth obtained in
SLO concentration greater than 3%. Table 5 shows
the mean pH values obtained. pH values decreased
as the concentration of SLO increased.
Table 5: Mean pH values of spent lubricating oil
contaminated soil before planting Ricinus communis (castor oil)
seeds
Oil concentration (%) in soil Mean pH values
0 5.28
1 5.09
2 4.96
3 5.04
4 4.90
5 4.83
6 4.82
Measurement was done using distilled water
(soil: water = 1:3)
There is need for further studies on metal
accumulating ability of R. communis. It may be
necessary to evaluate the performance of R.
communis in revegetation of cleaned up oil polluted
soils. More importantly, we need to look at the
production of growth hormones in R. communis
plants grown at 1% SLO.
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