Effect of the gaseous environment and water content on seed viability of four Brassicaceae species after 36 years storage

Seeds of four species of Brassicaceae (Brassica oleracea, Diplotaxis virgata, Sinapis alba and Sisymbrium irio) were stored for 36 years in the UPM (Universidad Politécnica de Madrid) seed bank at temperatures between -5°C and -10°C, enclosed in flame sealed vials. For each species, four different storage conditions were tested. Seeds were either desiccated with silica gel (approximately 1-3% water content, fresh weight basis) or held under laboratory conditions (6.7-9.3% water content). In half of the tubes containing seeds of each moisture content, the air was partially substituted by CO₂ before closing the vials. After the storage period seeds were set to germinate. Some persistent (or created during storage) dormancy was observed in all treatments of D. virgata and S. irio, but only in ultra-dried seeds of S. alba. CO₂-enriched atmosphere improved longevity for all four species studied, especially in those seeds that had not been desiccated with silica gel.