Effect of crude oil on the growth and anatomical features of Chromolaena odorata (L.) K.& R.


L.S. Gill and H.G.K. Nyawuame
Department of Botany
Ondo State University, P.M. B. 5363,
Ado-Ekiti, Ondo State, Nigeria

A.0. Ehikhametalor
Department of Botany
University of Benin
P.M.B. 1154
Benin City, Nigeria

 Materials / Methods
 Table 1
 Table 2


Investigations were carried out on the effect of Forcados Blend crude oil on seed germination, regeneration of stumps and anatomical features of leaves of Chromolaena odorata (L.) K. & R. Three concentration via. 25.0 cm3, 50.O cm3 and 75 cm3 applied to soil were found to suppress seed germination, regeneration and caused cellular and stomatal abnormalities. The present study suggests that this plant can serve as bioindicator of pollution in oil producing areas.


According to Dejong (1980) crude oil spillage on soil makes it unsatisfactory for plant growth. This is due to insufficient aeration of the soil because of displacement of air from the spaces between the soil particles by crude oil (Rowell, 1977). In Nigeria quite substantial amount of crude oil is spilled annually, For example, Nwankwo (1989) reported 2,000 oil spillages in Nigeria between 1976 and 1988. During this period about 2 x 106 barrels of crude oil were discharged in the environment.
Considering this large quantity of crude oil going into the environment, especially farmland, and the fact that the inhabitants of these areas are subsistent farmers, there is an urgent need for the various agencies connected with oil production in Nigeria to pay more attention to the problem of oil leakage in future.
It is known that root stress reduces leaf growth via stomata conductance (Smith et al., 1989). Furthermore, Epstein (1972) states that mineral ions absorbed initially by the roots are finally received by the mesophyll cells of the leaves. According to Udo and Fayemi (1975) growth of plants growing in oil polluted soil was generally retarded and chlorosis of leaves results coupled with dehydration of the plants indicating water deficiency. The present project has been undertaken with three main objectives: (1) to determine the extent of damage caused by crude oil pollution to the foliar parts of Chromolaena odorata (L.) K. & R., (2) to ascertain the effect of crude oil on this taxon at the cellular level, and (3) to determine how far this plant can serve as an indicator of oil pollution in Nigeria.

Materials and Methods

Perforated black Polythene bags filled with soil were used for raising plants. Seeds or stumps of C. odorata were either sown or transplanted in these bags. "Forcados Blend" crude oil at 25.0 cm3, 50.0 cm3 and 75.0 cm3 with a control of water were used for soil treatment and foliar application. A foliar treatment with pure crude oil was also included. This experiment was laid out in a randomized complete block design with four replications.
Growth performances of the plants raised were recorded every other day. Anatomical features of the roots, stem and leaf of the treated and control plants have been carried out. The epidermal peels for cuticular studies were obtained following the method outlined by Gill and Karatela (1983). Terminology of mature stomata used in this paper is that of Metcalfe and Chalk (1950).


Apart from the seeds in the control which germinated after three days of sowing, seeds sown in various concentrations of crude oil failed to germinate. Morphological observations carried out on plants from sprouted stumps have been presented in Table. 1.
Stomal distortions observed have been presented in figs. la-e. Analysis of variance of data collected on growth rate and stomatal frequency, length, breadth and pore size were given in Table 2. Crude oil treatment of C. odorata resulted in distortion of cells of the epidermal and cortical regions of root, stem and petiole. In the case of the leaf lamina the distortion of cells was more pronounced in the spongy mesophyll and abaxial epidermal region. The concentration of 75.O cm3 of crude oil treatment was most effective.


Environmental pollution has been shown to have adverse effects on plant growth and these may range from morphological aberrations, reduction in biomass to stomatal abnormalities (Sharma et al., 1980). Similar reports have been made by Gill and Sandota (1976), Ghouse et al., (1980), Wallace (1951)-and Vostokova et al., (1961). Atuanya (1987) reported that waste oil to cause a breakdown of soil texture followed by soil dispersion. However, during the present study fresh crude oil rather showed a coagulatory effect on the soil, binding the soil particles into a water impregnable soil block which seriously impair water drainage and oxygen diffusion. Atuanya (1987) further states that seeds sown in such soil failed to germinate. The results of the present study where seeds failed to germinate even after 30 days of sowing confirm the report of Atuanya (1987)
Udo and Fayemi (1975) reported that oil has adverse effect on plant growth. the present study gave similar results where there was a significant difference in growth between the untreated and treated plants. A positive relationship has been observed between the extent of retardation in growth and concentration of crude oil applied to the soil. these findings are in accordance with previous reports of Atuanya (1987), Ghouse et al., (1980) and Gill & Sandota (1976).
Results of the present study shows that leaf stomata were grossly affected by crude oil. The effect was manifested either in the distortion or reduction in the number of stomata per unit area of the leaf. A strong relationship between degree of disruption and concentration of crude oil in the soil was noticed. This further confirms earlier report of Sharma et al. (1980).
Since uptake of water and salts (ions) is carried out by the roots, the untreated plants with roots undisturbed grew normally while the treated plants suffered morphological and anatomical aberrations. Cell disruption in roots and other organs were eminent. furthermore, anatomical studies of the treated plants revealed the presence of oil films in the epidermal and cortical regions of the root, stem and leaves. Similar finding s have been reported by Anoliefo (1991). However, the absence of oil films in the vascular region suggest that movement of oil films from root to leaves could be via the apopplastic pathway.
From the foregoing, it is not clear whether the damage done to the cells was by toxic hydrocarbons and natural gases contained in crude oil or by smoldering and osmotic effect of the crude oil liquid. It seems to the present authors that the adverse effect noticed on the treated plants may be due to unfavorable conditions created in the soil resulting in drought conditions as well as nonavailability of nutrients rather than cellular destruction by toxic substances contained in the crude oil. the present authors are of the opinion that enlargement of cells in the various tissues is due to oxygen starvation of those tissues whereby the cells coalesce and thus forming large cells in these tissues.


We are grateful to the kind gesture of Prof. F.I. Opute of the Department of Botany, University of Benin who kindly procured for us the crude oil used in this study from the Shell Petroleum Company, Nigeria (Ltd.).


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Table 1. Morphological changes observed in Chromolaena odorata due to crude oil treatment

 Observable effects
 Percentage survival


 Nil. 12 plants survived


 25.0 cm3

 i) Stunted growth

(ii) Leaf buming with resultant brown coloration

(ii) Death of one plant out of 12


 50.0 cm3

 (i) Drasticafly reduced growth rate

(ii) Leaf buniing leading to brown coloration

(iii) Death of 4 plants out of 12


 75.0 cm3

 (i) Terminated growth

(ii) Leaf burning leading to brown coloration

(iii) Death of 4 plants out of 12


Foliage sprayed with
pure crude oil

 (i) Terrninated growth

(ii) Leaf buming, color of leaves turned black

(iii) Stem turned pale

(iv) All 12 plants died



Table 2. Analysis of variances of effect of crude oil on Chromolaena odorata

 "F" Value

 Growth rate

 20.40 **

 Stomotal frequency

 45.90 **

 Stomotal length

 45.69 **

 Stomatal breadth

 26.50 **

 Stomatal pore size

 106.39 **

** P=0.0L