ABSTRACT
This study was carried out on the nutrient requirements for the in vitro propagation of Ricinus communis employing the basal media of Murashige and Skoog (1962), Gamborg et al. (1968), and Schenk and Hildebrandt (1972) using zygotic embryos as explants. Zygotic embryos were excised from mature seeds and cultured on the three basal media with 3 per cent sucrose and 8 g/l of agar. Plant growth regulators were not added to the media. This study was done to determine the most suitable basal medium for the growth of R. communis zygotic embryo. The results obtained showed that the three basal media employed supported in vitro regeneration of the embryo explants. The highest mean shoot length (4.450±0.231 cm), the highest mean root length (2.190±0.262 cm), highest mean fresh weight (0.365±0.032 g), highest mean leaf area (1.999±0.189 cm2), highest mean per cent sprouting (91.660±0.000), and highest mean number of roots (4.600±0.163) were observed on Murashige and Skoog medium whereas the highest mean sprout rate (0.330±0.000) was obtained on Murashige and Skoog and Gamborg et al. media. The embryo explants were able to develop into normal plantlets even in the absence of growth regulators. This may suggest that endogenous hormones in the zygotic embryo were present at an optimal level to support regeneration. Results from this study indicated that Murashige and Skoog basal medium was the best basal medium for the in vitro propagation of Ricinus communis zygotic embryo. The results are discussed in the light of its potential for mass production of Ricinus communis for its economic values.
CHAPTER ONE
INTRODUCTION
Castor oil plant (Ricinus communis L.) is a non food, drought resistant, energy plant gaining attention for producing biofuel as biodiesel in developing countries (Kamrun, 2013). As an oil bearing biomass feedstock, it can ensure an alternative source of energy and reduce the over dependency on fossil fuel (Kamrun, 2013). Ethiopia is considered to be the most probable site of origin of castor oil plant because of the presence of high diversity (Anjani, 2012). However, according to Sujatha et al. (2008) the plant originated from Abyssinia. It is distributed throughout the tropics and the subtropics, and is well adapted to the temperate region (Sujatha et al., 2008).
Oil extracted from castor seeds is of economic importance especially in the chemical industries (Abayeh et al., 1998). The economic importance of this plant has made it necessary that the plant be properly investigated to develop the most reliable method of propagation. Conventional method of cultivation using the seed is limited by problems of seed viability. Propagation through tissue culture techniques employing embryo is necessary to eliminate the limitations of seed germination.
1.1 Economic importance
Ogiri is a food condiment obtained by traditional fermentation of castor seeds in the eastern part of
Nigeria. This food condiment provides dietary fiber, energy, mineral and vitamins (Kolapo et al.,
2007). At present, the potentials of castor oil have not been fully explored in Nigeria (Oluwole et al., 2012).
Castor seed is an important source of vegetable and medicinal oil and has numerous benefits to humanity. The oil from castor seeds has many industrial applications. Dehydrated oil from castor seeds is used in the paint and varnish industry. The oil is also used in the manufacture of a wide range of sophisticated products like nylon fibers, jet engine lubricants, hydraulic fluids, plastics, artificial leather, and fiber optics (Ogunniyi, 2006).
The seeds contain 40 to 60% oil that is rich in triglycerides mainly ricinolein, a toxic alkaloid ricinine and very toxic albumen called ricin (Zohary, 1987). Oil from castor seed is prescribed for infestation of intestinal worms. In vitro antiviral activity and hypoglycemic activity were also reported from leaf extracts (Khafagi, 2007).
Oil from castor seeds also has great promise in the field of biodiesel production as it is inexpensive and environment friendly (Ogunniyi, 2006). Consequently, there has been a steady increase in the demand of castor oil and its products in the world market due to their renewable nature, biodegradability and eco-friendliness (Ogunniyi, 2006).
Many phytochemicals found in the plant tissue and seeds of castor have potential medicinal uses (Morris, 2004). Castor oil has been used as purgative since ancient times and it is still considered to be a safe and effective laxative (Kalaiselvi et al., 2003). The ricin A-chain has also been linked to antibodies able to target cancer cells while not harming normal cells (Olsnes and Pihl, 1981; Lam et al., 2004). These immunotoxins have been reported to have many potential uses in modern medicine (Scadden et al., 1998; Longo et al., 2000; Sandler et al., 2006). Experimental medicines containing castor oil were also shown to be effective treatments of evaporative dry eye (Khanal et al., 2007).
Historically, castor plant has been used as an ornamental plant (Coopman et al., 2009; Krenzelok,
2009). This species may also provide an option for phytoremediation of soils contaminated with heavy metals since castor plant is tolerant to several heavy metals and a non food plant. Castor plant is a hyperaccumulator of Lead (Pb) (Romeiro et al., 2006; Liu et al., 2008), an effective accumulator of Nickel (Ni) (Sherene, 2009), and moderately tolerant to Cadmium (Niu et al.,
2007; Shi and Cai, 2009). Castor plants also grow well in a soil with high content of Zinc (Shi and
Cai, 2010).
1.2 Problem statement
During the past decades, worldwide petroleum consumption has permanently increased due to the growth of human population and industrialization which has caused depleting fossil fuel reserves (Bankovic-ilic et al., 2012). On the other hand, combustion of fossil fuel contributes to emission of green house gases which lead to atmospheric pollution and global warming (Bankovic-ilic et al., 2012). As a result of these, there is the need for substitute for fossil fuel with a clean and renewable fuel such as biodiesel. According to De Oliveira et al. (2004) oil extracted from castor seeds is a potential feedstock for biodiesel production which will be an alternative for fossil fuel. Kamrun (2013) also reported that castor plant is a sustainable source of second generation biodiesel feedstock species and the overall supply can be increased with different propagation technologies. It is inexpensive and environment friendly (Ogunniyi, 2006). It also has good physico-chemical properties.
The use of castor oil for biodiesel production will also ease the load on edible oil from plants like soy beans that are used for biodiesel production since the oil from castor is inedible (Kamrun,
2013). With these benefits of castor oil, there is need for in vitro propagation of castor seed to make it available all year round
The objectives of the study:
To determine the effect of three different basal media on the growth and development of zygotic embryo of Ricinus communis in vitro.
To determine the most suitable basal medium for in vitro culture of Ricinus communis zygotic embryo.
To work out a propagation protocol for R. communis employing zygotic embryo.
This material content is developed to serve as a GUIDE for students to conduct academic research
NUTRIENT REQUIREMENTS FOR IN VITRO PROPAGATION OF RICINUS COMMUNIS L. ZYGOTIC EMBRYO USING THE BASAL MEDIA OF MURASHIGE AND SKOOG GAMBORG ET AL. AND SCHENK AND HILDEBRANDT
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