Physiological and Biochemical Effects of Ultra-Dry Storage on Barbados Nut Seeds

In this study, the feasibility of ultra-dry storage of Barbados nut (Jatropha curcas L.) seeds was investigated. The J. curcas seeds were dehydrated to six different moisture contents (1.33-6.98%) and stored at ambient temperature for 3 yr. Then, the indices related to seed vigor were measured. To explore the mechanism of ultra-dry storage, some physiological and biochemical indicators, including electrical conductivity (EC); contents of proline (Pro) and malondialdehyde (MDA); activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR); total soluble sugar content; and fatty acid composition, were determined. Results indicated that moisture content and prehumidification method significantly affected seed germination and vigor. The ultra-dried seeds showed a higher germination percentage than nondehydrated seeds. The germination percentage of ultra-dried seeds was negatively correlated with EC and MDA content and positively correlated with the activities of five antioxidant enzymes. As compared with the nondehydrated seeds, the ultra-dried seeds had lower soluble sugar and higher unsaturated fatty acids contents. The moisture content of 4.06% was found to be the optimal ultra-drying treatment, which is beneficial to enhance the activity of antioxidant enzymes and reduce lipid peroxidation of cell membranes, thereby slowing the decline in viability of J. curcas seeds.