Effect of harvesting Jatropha curcas L. seeds at different fruit maturity levels on germination, oil content and seed weight

Abstract

The physic nut is a plant species that produce seeds rich in oil that could be transformed into biodiesel; which was native of Central America and Mexico and now naturalized in Ethiopia at farm boundary and hedges. Owing to increasing demand for fossil fuel and its predicted decline, the importance of alternative energy has been increased in Ethiopia. However, research outcomes lack on the effect of fruit maturity levels of physic nut seed on oil content, seed weight and germination parameter. Therefore, this study aims to estimate the maturity level at which physic nut fruits should be harvested for high content of oil, seed weight and germination. Physic nut fruits harvested at different level maturity on mother tree young green fruit, yellow fruit, brown fruit and brown dried fruit dropped on the ground to determine oil content, germination and seed weight. Germination was tested in seed germination chamber in glass house and arranged in CRD with three replicates. In each treatment 100 seeds were sown and germination was recorded starting from 7th day of sowing to 35th day in seven day interval. Randomly 40 g of seed from each treatment were used to obtain oil by using solvent extraction method and 1000 seeds were also counted and weighted with three replicates. Variation in oil content, germination and its parameters and seed weight were analyzed using ANOVA and LSD at P < 0.05. The analysis shows that there is a relation between physic nut fruit maturity level with germination, oil content and seed weight. The germination (%), oil content and seed weight of physic nut increase from young green fruit, yellow fruit and brown fruit. But at late maturity mean that brown dried fruit dropped on the ground became reduced. The highest germination, oil and seed weight has been gotten from brown fruit on mother tree (90%, 34.59% and 592.1 g) and the lowest is from young green fruit (65.67%, 22.88% and 416.16 g), respectively. Weight and oil contents are positive relation: higher seed weight has higher oil content. Therefore, brown fruit on mother tree was ideal for higher germination, oil content and seed weight than yellow fruit and brown dried fruit dropped on the ground. This information will be important for the development of physic nut plantation in Ethiopia.

Keywords: Jatropha curcas L., maturity level, germination, germination parameter, oil content, seed weight.