Introduction
Motor oil or engine oil is used for lubrication of various internal combustion engines. While, the main function is to lubricate moving parts, motor oil also cleans, inhibits corrosion, improves sealing and cools the engine by carrying heat away from moving parts. Motor oil are today mainly blended by using base oil composed of hydrocarbon. Motor oil is a lubricant used in internal combustion engines for car, motor cycles, buses and commercial vehicles. The movement of motor oil through washing of vehicles, rain and drainage contribute to this problem for environment degradation. Crude oil is a naturally occurring hydrocarbon compound used by humans in a variety of ways: fueling of cars, Lorries and trucks; heating of homes, cooking gas and other fractions utilized in the manufacture of synthetic products (Edema et al., 2009) .
Introduction
The ever increase in the use of petroleum products has significantly damaged air, water and soil of the region. The soil profiles are subjected to a continuous exhaustion in several forms, such as: soil erosion, depletion of nutrients and pollution (Odat and Alshammari, 2011) . The addition of petroleum and its products are of specific concern in pollution studies due to their structural complexity, slow biodegradability and bio-magnification potential (Kathi and Khan, 2011) .
Introduction
It has been reported in literature by various researchers that oil spills have significant effects on agricultural lands, crop, trees, forest, and their seedlings (Udo and Fayemi, 1975; Bartha, 1977) . The study of plant behavior in petroleum contaminated soils allows the identification and selection of oil pollution indicating species (Maranho et al., 2009) .
Introduction
The continuous growth of environmental pollution and anthropological disturbances to ecosystems has made the study of abiotic stress responses in plants (Alkio et al., 2005) . The effect of crude oil pollution on soil pH, temperature, number of plant species and vegetation productivity was observed (Debojit, 2006) . Effects of waste engine oil pollution on physical and chemical properties of soil have been observed (Atuanya, 1987; Ekundayo and Obuekwe, 1994; Benka-Coker and Ekundayo, 1995; Vwioko and Fashemi, 2005) . Effects of crude oil pollution on the growth of some plant species viz. Zea mays, Abelmoschus esculentus, Capsicum annum (L.), Lycopersicon esculentum (Miller) reported (Amakitri and Onafeghara, 1983; Anoliefo and Vwioko, 1994) . The effects of crude oil contaminated soils on seedling growth of six agronomic crop species observed and concluded that Zea mays and Glycine max seedlings show the greatest potential to enhance remediation compared to the Lolium perenne, Triticum aestivum and Vicia villosa observed (Issoufi et al., 2006) .
Introduction
Soil pollution due to motor oil contamination is an important problem in many parts of the world. The disposal of motor oil into the immediate environment is an important environmental issue affecting soil characteristics and plant growth. Information about the effects of motor oil pollution on leguminous tree species are scanty. Therefore, the present study was carried out with the aim to study the effects of motor oil on soil properties and on the growth of an important leguminous flowering tree species Parkinsonia aculeata (L.) in the pea family Fabaceae.
Materials and Methods
This study was conducted at the Department of Botany, University of Karachi, Pakistan. Healthy and uniform size seeds of Parkinsonia aculeata L. were collected from Safari Park, University Road, Karachi. Due to hard seed coat, seeds were placed in distilled water for 24 hours and then sown in garden soil. The different concentrations (1.25, 2.5, 3.75 and 5.0 %) of freshly motor oil solution were watered. The fraction of garden soil was one part natural manure and two parts fine sand. Ten seeds were sown in each pot replicate treatment. Seeds were sown at 1 cm depth in plastic pots, having 7.3 cm in diameter and 9.6 cm in depth. There were five replicates of each treatment and the experiment was completely randomized. Pots were reshuffled to avoid light / shade or any other greenhouse effects. Pots were irrigated with the motor oil solutions alternately. Experiment was conducted for fifteen days, percentage germination of seeds was recorded daily.
Materials and Methods
Seedlings of P. aculeata were grown and maintained in large earthen pots each containing 5 kg of soil. One month after germination, two seedlings were transplanted to each plastic pot containing soil. Each pot was irrigated by the freshly prepared motor oil (1.5, 2.5, 3.75 and 5 %) solution alternately and no nutrient solution was provided. Treatments were replicated five times ad pots arranged in a randomized complete block design on a greenhouse bench. Garden soil was used as control. The fraction of soil was one part manure and two parts fine sand. Every week, pots were reshuffled to avoid light / shade effect or any other greenhouse effects and after every week seedling height, plant cover, leaf length and leaf breadth was recorded. Experiment was conducted for six weeks. After six weeks all the seedlings were carefully removed from the pots and washed to measure root, shoot, and seedling length. The height of the plants was measured from the soil level to the terminal bud using a steel scale. The numbers of leaves were counted as the plant grew. This was done by visual counting of the leaves at regular intervals of seven days. The plants were carefully uprooted and the root part rinsed with clean water. The fresh weight of the root, stem and leaves was then determined separately and kept separated part of the plant in marked paper envelope and finally place in an oven at 80 degree centigrade for 24 hours to obtained dry weight. Fresh and oven dried weights for roots, shoot, leaves and total plant weight was recorded. Root/shoot ratio, leaf weight ratio, specific leaf area and leaf area were determined as follows. Root/shoot ratio = Root dry weight / Shoot dry weight Leaf weight ratio = Leaf dry weight / Total plant dry weight Specific leaf area (cm2 g-1) = Leaf area / Leaf dry weight Leaf area ratio (cm2 /g) = Leaf area / Total plant dry weight (Kang and vanIersel (2004) Leaf area = Length X Breadth X 2 / 3
Soil sample collection
The composite garden soil samples were taken from the nursery of Karachi University, campus. The soil samples were brought to the laboratory in polythene bags for chemical analysis and were kept in air for dried. The soil samples were passed through 2 mm sieve after drying in an oven at 105 degree centigrade. There were three replicates for physical and chemical analysis. The soil was treated with 1.25, 2.50, 3.75 and 5.0% of motor oil solution. Two weeks after the soil treatments, the soil pH was determined in 1:5 soil water extract by direct pH reading meter (Model Mettler, Toledo) while the electrical conductivity (EC) was recorded in 1:1 soil water paste. Available Na + and K + was determined by flame photo meter (Moore and Chapman, 1986) . Maximum water holding capacity M.W.H.C. (%) was measured by the method of Keen (1931) . Soil organic carbon was determined according to Jackson (1958) . Bulk density and total porosity was determined by using the core methods described by Birkeland (1984) . Soil texture and particle size were determined by the Bouyocos hydrometric method (Gee and Bauder, 1986) . Total phosphorous was determined by the methods described by Olson and Sommer (1982) . Cat ions (sodium and potassium) exchange capacity was determined by Rhoades and Poleomio (1977) , soluble chlorides was tested by the methods of Richards (1954) .
Physiological tests
The extract for estimation of the phenols and soluble sugars were prepared according to the method described by Nieman and Poulsen (1963) with minor modification. Dry powered leaves were placed in 80% menthol and the extract was centrifuged. After centrifugation the residue was washed three time with 80% menthol. The supernatant was separated into two parts, one for phenols and the other for the soluble sugars. Phenols was quantified using the methods of Singleton and Rossi (1965) and soluble sugars were determined by the methods of Fales (1951) .
Statistical analysis
Statistical comparisons among all treatments were calculated. Data collected were subject to one-way analysis of variance (ANOVA) with Scheffe's post hoc test. Assumption of all tests were tested and statistically verified. All statistical analysis were performed using personal computer software packages S.P.S.S. 13.0 (SPSS Inc., USA) for Windows. Level of significance for these tests was at P <0.05. 
T.) ± = Standard Error

Results
The effects of varying concentration of motor oil solution (0, 1.5, 2.5, 3.75 and 5 %) on soil properties and seedling growth performance of Parkinsonia aculeata L. was observed (Table 1-3) . The oil pollution treatment significantly p<0.05 affected high percentage of seed germination, shoot length, seedling height, number of leaves and average plant cover of P. aculeata. The mean root, shoot, seedling length, number of leaves and leaf area of P. aceuleata was found high in control soil treatment. The root length, number of leaves and plant cover of P. aculeata ohobbs@example.com% motor oil treatment as compared to control. The treatment of 5% oil polluted soil decreased root, shoot and seedling length of P. aculeata as compared to control soil. Number of leaves and leaf area also decreased at similar contamination of motor oil. The mean values obtained for root length (4.94 cm), shoot length (9.90 cm), seedling length (14.84 cm), number of leaves (104) and plant cover (26.0 cm) for P. aculeata seedlings were found highest in control soil. Seedling length (10.94 cm) and number of leaves (45.20) were found significantly low when treated with 5.0 % concentration of motor oil as compared to control soils. The significant (p<0.05) effects of oil polluted soil on root, leaves, stem and total plant dry weight of P. aculeata were also observed. The effects of oil polluted soil on root, stem, leaves and total plant dry weight were also observed. A significant (p<0.05) relationship was found to exist between the inhibitory effects of oil polluted soil on seedling dry weight with the increase in polluted soil treatment concentrations as compared to control. Principally, 5% oil polluted soil exhibited greater reduction in seedling dry weight of P. aculeata as compared to control. Similarly biomass production of P. aculeata in terms of total seedling dry weight (0.216 g), root dry weight (0.036 g), stem dry weight (0.10 g) and leaf dry weight (0.076 g) was recorded high in control soil treatment as compared to polluted soil. Root length, root / shoot ratio and specific leaf area were non-significantly affected with the all level of oil polluted soil than control soil treatment. Principally, increase in concentration of oil polluted soil treatment exhibited higher percentage of reduction in seedling growth and yield parameter and total plant dry weight of P. aculeata than control.
Results
The soil analysis showed that motor oil treatment had no significant effect on the soil texture, electrical conductivity and total organic carbon content of soil ( Table 2 ). The physical and chemical properties of the oil polluted soil were carried out. Overall, the different response of oil polluted soil was observed. There was no significant difference was found in soil texture, electrical conductivity and total organic contents in oil polluted soil as compared to control. A pronounced variation in physical properties of oil polluted soil sample was also noted. The highest maximum water holding capacity of soil (42.63 %) was recorded in control soil. The lowest maximum water holding capacity of soil (30.44 %) was recorded in 1.25% oil polluted soil sample. The 2.5% oil polluted soil significantly increased soil porosity (43.39) percentage as compared to control (41.69 g/cm 3 ). The treatment of 3.75% motor oil solution concentration produced lowest bulk density value (1.495) as compared to control soil sample (1.545).
Results
A significant variation in chemical characteristic of motor oil polluted soil characteristics was observed. The soil pH of was alkaline in nature and ranging from 7.51 to 7.95. There was a significant p<0.05 increase in concentration of soluble potassium, chloride, organic carbon, cation exchange capacity, Extractable (K + ) and Na + due to motor oil polluted soil ohobbs@example.com% was observed. While, a significant decrease in soluble potassium, exchangeable (K + ) and Na + ion concentration chlorides in the motor oil contaminated treated soil at same concentration as compared to control.
Results
The seedlings of P. aculeata were analysed for the determination of motor oil pollution effects on the phenol and sugar contents (Table 3 ). The amount of phenols contents significantly decreased in the seedlings of P. aculeata with the addition of motor oil ohobbs@example.com% as compared to control. The amount of soluble sugar contents significantly increased in the seedlings of P. aculeata with the addition of motor oil ohobbs@example.com% as compared to control. The phenolic contents in P. aculeata seedlings were found lowest (750000) with the motor oil treatment at 5% concentration as compared to control (970000). Similarly, the lowest concentration of soluble sugar contents level (4870000) was recorded with the motor oil soil ohobbs@example.com% as compared to control (5110000) in P. aculeata seedlings.
Discussion
Pollution caused by petroleum and its derivatives is the most important problem in the environment. The results of the present study showed variability in soil characteristics, seed germination percentage, seedling growth performance of P. aculeata due to motor oil pollution treatment as compared to control soil treatment. Seedling length of P. aculeata was variable and appeared to be decreased mostly by the treatment of different level of motor oil polluted soil. The release of crude oil into the environment by oil spills is receiving worldwide attention (Millioli et al., 2009 ). The toxic effects of spent engine oil on germination of perennial rye grass, Amaranthus hybridus and maize growth performance was reported (Isirimah et al., 1989; Odjegba and Sadiq, 2002; Siddique and Adams, 2002) . This study demonstrated that motor oil application at high concentration in soil has significant effect on the seedling growth performance of P. aculeata. These obtained results are in conformity with the findings of other researcher's recorded negative effects of crude oil as a soil contaminant on the growth of different plant species such as Capsicum annus, Lycopersicon esculentum, Ricinus communis (Anoliefo et al., 2003; Vwioko and Fashemi, 2005) . Reduction in number of leaves for P. aculeata also found as compared to control. Similar trend of decline in leaf growth was recorded by Anoliefo and Edegbai (2001) . The negative effects of oil contamination on reduction of the total biomass and the length of the roots in Avena sativa L., Secale cereale L. and Hordeum vulgare L. observed and suggested that these plants could be used as test organisms in analyzing the toxicity of this pollutant in soil and water (Petukhov et al., 2000) . In another investigation, Maranho et al. (2006a) investigated the effect of petroleum pollution on the leaf structure of Podocarpus lambertii Klotzsch ex Endl. (Podocarpaceae), and concluded that leaf anatomy revealed a large variability related to pollution. Our data also showed the negative influence of oil polluted ohobbs@example.com% concentration on leaf area of P. aculeata as compared to control soil treatment. The relatively low plant cover of P. aculeata was observed in motor oil polluted soil at the all concentration of motor oil and can be attributed to the toxic or un-favorable effect of motor oil contamination present in the substrate and make soil unsuitable for the development of plant cover of P. aculeata. Crude oil is phytotoxic because it creates unsatisfactory conditions for plant growth ranging from heavy metal toxicity to inhibited aeration of the soil (Edema et al., 2009) . Motor oil contamination at higher level (3.75-5.0%) affected root growth performance of P. aculeata. Plants are highly sensitive to oil contamination and oil in soil creates unsatisfactory conditions for cereal growth (DeJong, 1980) probably due to insufficient aeration of the soil (Rowell, 1977) . The oil film when covers the roots considered as the main physical effect of source (Xu and Johnson, 1995; Hester and Mendelssohn, 2000; Pezeshki et al. 2000) . According to Bona and Santos (2003) oil diminishes the soil capacity for retaining water, thus interfering with plant growth. The continuous decrease in seedling dry weight of P. aculeata in this study revealed that it is due to low seedling growth resulted due to abiotic stress. Increase in the crude oil contamination which contains a wide variety of elements such as carbon, hydrogen, sulphur, nitrogen and oxygen (Potter and Simmons, 1998; Maranho et al., 2009) can be an important cause of decline in average root, shoot and seedling length of P. aculeata. There was a similar trend of negative effects on the productivity of P. aculeata recorded. The addition of different level of motor oil can leads to some physical and chemical changes in the soil resulting reduction in seedling growth performance of P. aculeata. Furthermore, oil in the soil has toxic effects on bio, chemical and physical properties of soil depending on the dose, type of the soil (Ilangovan and Vivekanandan, 1992; Atuanya, 1987; Agbogidi and Egbuchua, 2012) . The presence of the toxic pollutants from the motor oil in soil can be an important cause of decrease in seedling growth and ultimately resulted in reduction of biomass production performance for P. aculeata. Crude oil contains components that are toxic to plants (Jessup and Leighton, 1996) . Seedlings biomass of P. aculeata was least productive in motor oil contaminated soil and most productive than control soil sample treatment. Phosphorous level also reduced in motor oi polluted soil as compared to control soil and agrees with the findings of Oboghodo et al., (2004) .
Discussion
The present study concludes that the changes in the seedling growth performances of P. aculeata in terms of seedling growth and biomass production was recorded due to treatment of different concentration of motor oil with soil. A clear reduction in the root, shoot, seedling length and productivity was observed at highest concentration (5%) of motor oil polluted soil treatment as compared to control. A variation in seedling tolerance indices was recorded for P. aculeata. The significant changes in seedling growth performance of P. aculeata grown in the motor oil contaminated soil can be served as good pollutant indicator of motor oil pollution monitoring. Similar types of studies are suggested for other plant species to ascertain their possible use of plantation in oil polluted contaminated areas. P. aculeata can be considered a well adaptable legume crop for plantation in such oil polluted soils to some extent. Soils are a heterogeneous composition of substances. The result of the present studies showed that the seedlings of P. aculeata grown in 5% motor oil polluted soil were smaller in height, root, shoot length and leaf area than those treated with unpolluted soil. The above studies suggest that the variation in seedling growth performance of P. aculeata seedlings were due to some changes brought up in physical and chemical nature of soil. The decrease in leaf area, leaf area ratio and relative growth rate of Vigna unguiculata due to gasoline/diesel mixture pollution of soil indicated that the mixture interrupts with the growth of the plant (Njoku et al., 2009) .
Discussion
The response of root growth of P. aculeata seedling to soil treatment is of particular importance because it affects subsequent plant growth and ability to withstand environmental stresses. Soil treatment of motor ohobbs@example.com % significantly p<0.05 produced highest root length as compared with other soil treatment. Bulk density and soil strength are an important soil physical factors for plant growth. The highest bulk density value in treated oil polluted soil sample favored the root, shoot and seedling length of P. aculeata as compared to other soil treatments. High levels of sodium salts does not support for normal seedling growth and contributes to nutrient imbalances in plant. The treatment of different concentration of motor oil significantly p<0.05 affected biomass production of P. aculeata seedlings. The lowest seedling dry weight of P. aculeata was observed in the treatment of 2.50% oil polluted soil and indicating the strong influence of soil characteristics of the studied motor oil treated soil. Low seedling dry weight of P. aculeata might be due to accumulation of certain nutrients. The plants under stress conditions are most likely to be adversely affected by under lying edaphic characters. The concentration of phenolic acids and soluble sugar in the P. aculeata seedlings depends upon the motor oil polluted soil treatment. A comparison of our result showed that the contents of phenolic and soluble sugar in seedling of P. aculeata were high in 3.75% treated soil. Changes in edpahic character usually caused changes in growth performance of plants as found in present findings for P. aculeata seedlings.
Discussion
The seedlings of P. aculeata grown in the same oil polluted soil were analysed for the effects of motor oil pollution on the phenol and sugar contents. The amount of organic C, and exchangeable K, increased in the soil with level of motor oil addition, while extractable K, and exchangeable K were reduced. The poor growth can be due to interference with plant and soil relationships and toxicity from pollutants present in motor oil. The amount of phenols decreased with the increase in concentration of motor oil. Soluble sugars mostly decreased which may suggest that structural form of sugar is not formed in plant under motor oil stress. It is suggested that motor oil accumulation in the soil can permanently damage the soil characteristics and can make it unfavorable for the survival and development of plant. It also can be concluded that motor oil can contaminate soil which may result in low soil fertility. The response of P. aculeata indicates that the plant can be used to monitor polluted sites keeping in view of the toxicity stress to motor oil suspension concentration.

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