The objective of the study was to explore the effects of pre-sowing seed treatments on germination behaviour and to assess the possibilities of increasing the germination rate of Jatropha curcas. Seeds of twenty jatropha accessions obtained from seven different sources were subjected to three pre-sowing treatments viz., control (T0): unsoaked seeds directly sown in the polybag and apply water up to saturation; T1: seed placed on filter paper in the petridis and moistened once with the water; and T2: seeds kept under stone sand and moistened once with the water. Seeds in T1 and T2 were kept for 72 h before sown in the polybag. The study was conducted in the Glass House of Plant Biotechnology Laboratory, Universiti Kebangsaan Malaysia. Study revealed that pre-sowing treatments significantly (p<0.01) enhanced seed germination parameters of Jatropha. Seed germination started 5 days after sowing and continued up to 12 days. The highest germination percentage (95.85%) was observed in T2 and 100% germination was observed in the genotypes viz., UKM-JC-011, UKM-JC-012, UKM-JC-014, UKM-JC-016 and UKM-JC-020 in T1 and T2. None of the genotypes showed 100% germination in T0. The highest Germination Index (GI) and Seedling Vigor Index (SVI) was found in T2 and the lowest in T0. T2 was found more effective in respect to faster germination, high germination percentage, germination index, seedling vigor index, speed and energy of germination. Five accessions viz., UKM-JC-012, UKM-JC-014, UKM-JC-016, UKM-JC-017 and UKM-JC-019 were found suitable in all the treatments including control.
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Jatropha curcas is a multipurpose shrub belonging to the family Euphorbeaceae with significant economic importance since its seed oil can be converted to biodiesel. It is emerging as a renewable energy source, alternative to petrodiesel. Due to an increasing demand for energy and declining fossil fuel resources (Becker and Francis, 2003), biofuels are worldwide recognized as an alternative source of energy. Several reports have demonstrated better performance of the Jatropha biodiesel compared with the conventional petrodiesel (Ghosh et al., 2007; Mandpe et al., 2005). Physic nut (Jatropha curcas L.) is a perennial shrub of the tropics and subtropics grow up to five meter, which produces seeds containing approximately 30% of oil (Heller, 1996; Grimm, 1996; Rockefeller Foundation, 1998) and has low requirements to soil quality and can grow under low rainfall conditions. Before being able to conduct research on generation of physic nut oil using different extraction methods and on combustion properties of the oil in the stove, it is necessary to develop high yielding variety, cultivation technology and grow a sufficient amount of physic nut to obtain the desired oil. Seed germination is one of the important factors in the production process of the crop. Genetic and environmental factors determine germination rate, speed of germination and vigor of seed and seedling in the plant (Hartmann et al., 1990).
One of the main problems in jatropha cultivation is the poor germination of their seeds. This comes from their seed water impermeable testas, which exerts a physical exogenous dormancy (Holmes et al., 1987). Jatropha is normally propagated through seeds and very much unreliable in terms of seed germination. Germination of seed varies from 10 to 95%. Jatropha therefore, will not germinate promptly when placed under condition, which are normally regarded as suitable for germination. Such seeds are said to be dormant. To overcome seed dormancy and obtain rapid and synchronous germination artificially before sowing, the seed must be subjected to some physical or chemical treatment. Such pre-germination treatments will quickly destroy the integrity of impermeable cover and so permit the imbibition of the embryo. Hard-seeded species like, Jatropha curcas require external stimuli to promote seed-coat rupture. Seeds that soaked in water over night before planting showed the highest survival and germination rate (Feike et al., 2008). The general purpose of the pre-sowing treatment of seed is to hydrate partially the seed which results higher germination percentage as compared to untreated directly sown seed. The stone sand acts as a buffer between seeds, improves the environment around the seed by absorbing excess moisture and helps to exchange gases between germination medium and embryo. Another advantage of the stone sand is when the seed expand and radicle pushes for emergence, the sand offers resistance to the seed coat.
There is little published information on the effects of seed pre-sowing treatment on germination of Jatropha curcas. It would be useful to increase the germination rate of jatropha seeds, especially for those interested in commercial production of this crop. Therefore, the objective of this study was to assess the possibilities of increasing the germination rate and contribute that knowledge to the cultivation of Jatropha curcas L to address the energy needs for the future.
MATERIALS AND METHODS
The study was conducted in the Glass House, Laboratory of Plant Biotechnology, Faculty of Science and Technology, University Kebangsaan Malaysia during December 2008 to February 2009. Seeds of twenty jatropha accessions obtained from seven different sources (Swaziland, Cape Verde, India, Thailand, Vietnam, Indonesia and Malaysia) were used as experimental materials. To assess the effects of genotype and pre-sowing treatment on germination behaviour of jatropha, the seeds were sown in the polybag (18x10x7 cm3) containing sand : soil : compost in the proportion of 1: 1: 1. There were three treatments in the experiment including the control (T0): unsoaked seeds directly sown in a depth of 3 cm (method after Henning, 2000) in the polybag and apply water up to saturation (control); T1: seed placed on filter paper in the petridis and was moistened with water; and T2: seeds kept under stone sand and moistened with water. Watering was done once before germination (during sowing) and three times per week after germination. Seeds in T1 and T2 were kept for 72 h before sown in the polybag. Pre-treatment of the seeds enhanced rapid and uniform germination of seeds by cracking each seed. Radicle protrusion occurs by cracking outer seed coat in pre-treated seeds and then seeds were sown in the polybag. One seed per polybag was sown in all treatments. The experiments were directed in completely randomized design with threefold replication and 30 seeds were tested for each replication. Data on different germination parameters were recorded in 24 h intervals and continued until no further germination occurred. The seed germination criterion was visible protrusion on the surface of soil at least 0.5 cm of the cotyledon and hypocotyls of the seedlings. The seedlings were evaluated as described in Seedling Evaluation Handbook (AOSA, 1991).
The Germination Index (GI) was calculated as described in the Association of Official Seed Analysts (AOSA, 1983) by following formula:
The vigor index was calculated according to following formula:
The speed of emergence was calculated according to following formula:
Energy of germination was determined as the percentage of germinating seeds five days after planting relative to the total number of seeds tested (Ruan et al., 2002). Number of days taken for first germination was counted from the date of treatment. Numbers of days to first and last germination for each trial were observed. Moreover, measurements of the percentage of germinated seeds were made.
Final germination percentage (%), seedling length, was recorded after 15 days of planting (Dezfuli et al., 2008). For statistical analysis, the data of germination percentage was transformed to arcsin√(100/X); actual percentage are shown. Experimental data were analyzed by a statistical package SAS (2008), version 9.01. Treatments means were compared using Tukeys test at 5% level of probability (Steel and Torrie, 1980).
The present study was conducted to evaluate the effect of genotype and pre-sowing treatment of seed on germination behaviour and early growth of Jatropha. It was revealed from this study that different genotypes and pre-sowing treatments can have various effects on different seed germination parameters of Jatropha curcas. The earliest germination was observed in pre-sowing treatment, T2 and the delayed germination was found in T0 (Table 1). Seed germination started five days after sowing (UKM-JC-006 and UKM-JC-014) and continued up to 12 days (UKM-JC-004). The minimum days required by the genotypes UKM-JC-015, UKM-JC-017, UKM-JC-019 and UKM-JC-021 in pre-sowing treatment T2 for first germination and maximum days taken by the genotype UKM-JC-004 in all the treatments (Fig. 1). Pre-sowing T2 showed the fastest germination for most of the genotypes (except UKM-JC-004) than other two treatments (Table 3). The control (T0) took most delayed germination for all the genotypes. Pre-treatment enhanced early germination of seeds in Jatropha curcas. Similar results have been reported by Shivanna et al. (2007) for Ber seeds.
Effects of pre-sowing treatments on germination parameters of Jatropha curcas
**p<0.01; NDFG: No. of days to first germination, GP: Germination percentage (%), GI : Germination index, SVI: Seedling vigor index, SE: Speed of emergence and SL: Seedling length (cm); Means with the same letter are not significantly different
The highest germination percentage (95.85%) was observed in T2 (seeds kept under stone sand and moistened with water) which was significantly higher than control (T0) and T1. Similar result was obtained previously by Goda (1987), who found soaking the seeds of Acacia nilotica in tap water for 72 h promoted germination percentage. The lowest germination percentage (77.17%) was recorded from the control treatment (Table 2).
Effect of genotype on different germination parameters of Jatropha curcas
|**p<0.01; NDFG : Number of days to first germination, GP : Germination Percentage (%), GI : Germination Index, SVI : Seedling Vigor Index, SE: Speed of Emergence and SL : Seedling Length (cm);Means with the same letter are not significantly different|
Effect of genotype and pre-sowing treatment on number of days taken for first germination of Jatropha curcas L.
Maximum final germination was observed in genotype UKM-JC-016 (100%) followed by UKM-JC-012 (99.92%). More than 90% germination was observed in 10 genotypes. Pre-sowing treatments of the seed led to an increase in germination rate from 35 to 99.99%. Minimum germination (35%) was observed in the genotype UKM-JC-004 (Table 3). All the genotypes showed 100% germination in treatment T2 except UKM-JC-004, UKM-JC-005 and UKM-JC-010 whereas five genotypes (UKM-JC-011, UKM-JC-012, UKM-JC-014, UKM-JC-016 and UKM-JC-020) showed 100% germination in treatment T1 and none of the genotype showed 100% germination in T0 (Fig. 2). So it can be concluded that seed treated at T2 had the highest germination percentage in Jatropha followed by T1.
Interaction effects of genotype and pre-sowing treatment on germination index, seedling vigor index and speed of germination of Jatropha curcas
GI : Germination Index, SVI:Seedling Vigor Index and SE : Speed of Emergence
This result concurs with that of Magnani et al. (1993), who found a positive effect of pre-sowing treatments of seeds of seven Acacia species on their germination percentage. The germination rate of the seeds of Acacia species also improved when soaked in boiling water (Larsen, 1962).
Germination index increased in the pre-sowing treatment compared to control and the highest in T2 (Table 1). The highest germination index (5.29) was observed in the genotype UKM-JC-017 followed by UKM-JC-016 (4.99) and the lowest (0.94) in UKM-JC-004. Higher value of germination index indicated the earlier germination and lower value indicated late germination.
Most of the genotypes showed higher value of germination index in T2 compared to control (Table 3). The highest germination index was found in the genotype UKM-JC-017 in T2 and UKM-JC-016 in T1, the genotype UKM-JC-004 showed least germination index in all the treatments.
In this study, all genotypes of Jatropha responded differently to pre-sowing treatments for seedling vigor. Pre-sowing T2 showed higher average seedling vigor compared to the control (Table 1). The highest (18.22) seedling vigor index was observed in the genotype UKM-JC-012 and the lowest (5.22) in UKM-JC-004. Pre-sowing treatment resulted in reduced seedling vigor index in compared to the control among the genotypes except UKM-JC-003, UKM-JC-006, UKM-JC-009, UKM-JC-011, UKM-JC-013, UKM-JC-019 and UKM-JC-021 (Table 2).
Pre-sowing treatments (T1 and T2) increased the speed of emergence compared with control (Table 1). The genotype UKM-JC-014 followed by UKM-JC-008, UKM-JC-009 and UKM-JC-016 showed the highest speed of emergence whereas the lowest speed of emergence was observed in the genotype UKM-JC-004 followed by UKM-JC-005 (Table 2). The speed of emergence higher in all genotypes in T2 compared to T0 except UKM-JC-016 in T0 (Table 2).
Effect of genotype and pre-sowing treatment on germination (%) of Jatropha curcas L.
Effect of genotype and pre-sowing treatment on germination behaviour of Jatropha curcas
The genotype UKM-JC-004 showed least speed of emergence in all treatments. The genotypexpre-sowing treatment interactions showed that all Jatropha accessions had the greatest speed germination when soaked in water under sand stone but had lower speed of emergence when soaked in petridish or untreated (Table 3).
Out of three pre-sowing treatments T0 produced the longest seedling than T1 and T2 (Table 1). The longest (18.63 cm) seedling was achieved in the genotypes UKM-JC-019 followed by UKM-JC-006, UKM-JC-012 and UKM-JC-014 (Table 2) while the shortest seedling in UKM-JC-005 (14.02 cm). Figure 3 shows the mean seedling length of 20 Jatropha accessions in three different pre-sowing treatments. The genotype UKM-JC-016 produced the longest (21.00 cm) seedling in T0 and UKM-JC-004 produced the shortest (15.60 cm) seedling in T2 (Table 3).
The present study was conducted to evaluate the effect of genotype and pre-sowing treatment of seed on germination behaviour and early growth of Jatropha. It was revealed from this study that different genotypes and pre-sowing treatments can have various effects on different seed germination parameters of Jatropha curcas. The highest Germination Index (GI) and Seedling Vigor Index (SVI) was found in treatment T2 and the lowest in T0 and T1, respectively. Treatment T2 resulted in lower time taken to 50% germination and higher germination index, seedling vigor index and germination percentage in all accessions. On the other hand, for most of the germination parameters T0 behaved poor than that of T1 and T2. Results showed that, T2 was found more effective in respect to faster germination, high germination percentage, germination index, seedling vigor index and speed of germination than T1 and T0. Jatropha curcas have a hard seed coat, therefore, will not germinate promptly when placed under condition, which are normally regarded as suitable for germination, such seeds are said to be dormant. Mwang'Ingo et al. (2004) investigated the effectiveness of various seed pre-sowing treatments in enhancing germination and early seedling growth. They found complete removal of the seed coat and soaking in hot water enhanced seed germination and promoted early seedling growth and are thus recommended for adoption. The highest germination (66.5%) attained in their study was still unsatisfactory which was due to the existence of other types of dormancies such as chemical dormencies. The seed dormancy can be broken by physical or chemical treatments (Sadhu and Kaul, 1989). Jatropha genotypes showed lower germination percentage in control than those were treated before sowing. Seed germination started five days after sowing and continued up to 12 days. Seed pre-treated in the stone sand gave the higher germination than control and other treatment. Germination of seed varies from 10 to 95% and the low germination is due to physical exogenous dormancy (Holmes et al., 1987). Seeds that soaked by tap water in petridis and under sand stone for 72 h before sowing showed the highest germination than directly sown seed, which is due to external stimulation of seed coat rupture (Feike et al., 2008). The highest germination percentage (95.85%) was observed in T2 and the 100% germination was observed in the genotypes viz., UKM-JC-011, UKM-JC-012, UKM-JC-014, UKM-JC-016 and UKM-JC-020 in T1 and T2. None of the genotypes showed 100% germination in T0. Bohra et al. (1994) have also been reported that pre-treatments enhanced the germination percentage and germination energy in Acacia tortolies seeds. One-day seed soaking in water also accelerated and increased the germination (Grzesik and Nowak, 1998; Emmanuel and Roy, 2001). The effects of the chemicals were also similar to water treatment. The present results are also in accordance with observation of Bennett and Waters (1987) who reported that seed germination and vigor significantly enhanced by water soaking. The highest Germination Index (GI) and Seedling Vigor Index (SVI) was found in treatment T2 and the lowest in T0 and T1, respectively. Treatment T2 resulted in lower time taken to 50% germination and higher germination index, seedling vigor index and germination percentage in both genotypes. On the other hand, for most germination parameters T0 behaved poor than that of T1 and T2. T2 was found more effective in respect to faster germination, high germination percentage, germination index, seedling vigor index, speed and energy of germination. Five genotypes viz., UKM-JC-012, UKM-JC-014, UKM-JC-016, UKM-JC-017 and UKM-JC-019 were found suitable in all the treatments including control. In our study all the genotype responded differently to pre-sowing treatment. It may be concluded from present study that T2 was better than T1 and T0 for high percentage of seed germination, speed of emergence, energy of germination, germination index and seedling vigor index. Further research is needed to explore the exact methods for seed germination of Jatropha.
It may be concluded from present study that T2 was better than T1 and T0 for high percentage of seed germination, speed of emergence, energy of germination, germination index and seedling vigor index. This study suggested that Jatropha seeds have the ability to give more germination under pre-sowing treatment than sown directly. Further research is needed to explore the exact methods for seed germination of Jatropha.
The project is financed by the Universiti Kebangsaan Malaysia, under the Grant UKM-GUP-KRIB-15/2008. The authors would like to thank university authority for financial support.
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