ABSTRACT
Jatropha curcas L. (physic nut) is a multipurpose plant which belongs to the family Euphorbiaceae. The non-edible oil produced from the seeds is considered a potential renewable source of biodiesel. This research aims at estimating the optimum sucrose concentration for in vitro plantlet regeneration using mature zygotic embryos as explants in Murashige and Skoog (MS) media. Sucrose was employed as carbon source at concentrations ranging from 0 to 5 %. The study showed that mature zygotic embryos of J. curcas have the ability to sprout precociously in the absence of a carbon source without subsequent development. However, the addition of sucrose as carbon source led to a significant reduction in time of sprouting as well as enhanced seedling growth under all the sucrose concentrations (1 – 5 %). The highest percentage sprouting, sprouting rate, number of roots, length of roots, length of shoots, leaf area and fresh weight of plantlets were achieved in the regeneration medium with 3 % sucrose (i.e. 30 g l-1). Data obtained for sprouting and other growth parameters showed that the higher the concentration of sucrose, the greater the growth of the plantlets with 3 per cent sucrose as the optimum concentration for the parameters determined.
CHAPTER ONE
INTRODUCTION
The depletion of world petroleum reserves, oil price hikes and the increased environmental concerns have stimulated the search for alternative sources to petroleum based fuel, including diesel fuel. Biodiesel extracted from vegetable oil is one such renewable alternative under consideration. The production of biodiesel would be cheap as it could be extracted from non-edible oil sources (Openshaw, 2000; Francis et al., 2005; Chhetri et al., 2008; Dermibas, 2009).
Jatropha curcas L. (physic nut), a non-edible oil bearing and drought hardy shrub with ecological and other advantages belonging to the family Euphorbiacea, was found to be a potential renewable source of biodiesel (Raju and Ezradanam, 2002; Chhetri et al., 2008; Idu et al., 2009). In recent years, the plant has received extensive attention due to its medicinal importance and for its seed oil as a potential commercial source of biodiesel. The oil can be used as a mixed fuel for diesel/gasoline engines after transesterification (Achten et al., 2007; Abdullah et al., 2011; Ram et al., 2012). The seed or oil is not edible due to the presence of a toxic substance known as curcin (Joubert et al., 1984 and Makkar et al., 1998). The oil is conventionally used in making soaps, dyes, candles, paints, lubricants and medicinally as a purgative (Kumar and Sharma, 2000; Misra and Misra, 2010).
Conventionally, the seeds and cuttings are used for its propagation but the constraints to seed germination caused by dormancy induced by hard seed coat, poorly developed endosperm and abortion of hybrid embryos in seeds and the seasonal limitation of cuttings are the major constraints. It has also been reported that vegetative cuttings are not deep rooted and are easily uprooted as they do not form a tap root system (Sujatha and Mukta, 1996; Openshaw, 2000; Idu et al., 2009). To overcome the above mentioned difficulties in conventional methods, in vitro cultivation of the plant is the better option as it offers rapid and continuous supply of better planting materials (Sardana et al., 1998; Sathya, 2007; Ram et al., 2012). The evaluation of micropropagated J. curcas has revealed that they were at par with seed propagated plants in terms of yield and yield related traits (Sujatha and Mukta, 1996; Ahmed et al., 2012).
Plant tissue culture and micropropagation techniques play a great role in genetic conservation programs and management of botanical collection of plants in a very efficient manner (Smith, 2000; Kyesmu et al., 2004; Sathya, 2007). Embryo culture techniques can eliminate the constraints to seed germination caused by seed coat and endosperm and provide a long term storage of germplasm in a disease and insect free form (Okezie et al., 1994).
In vitro grown plants are devoid or insufficient of photosynthesis, due to growth taking place in condition unsuitable for photosynthesis. So, they need a readily available source of carbon which is usually provided in the culture medium at 3 % (Garcia et al., 2002; Sadhu, 2007; Okafor et al., 2012; Ram et al., 2012; Rafique et al., 2013). Murashige and Skoog medium (MS) is the most commonly and widely used culture medium in most plant tissue culture laboratories (Jesus et al., 2003; Kyesmu et al., 2004; Ram et al., 2012). Among the sugars, sucrose is used as a principal carbon source for in vitro plant culture probably because it is the most common carbohydrate in the phloem sap of many plants. The carbon source serves as energy and osmotic agent to satisfy the energy need and support the growth of plant tissue in vitro (Paiva and Otoni, 2003; Misra and Misra, 2010; Ram et al., 2012).
