ENHANCING CARROT SOMATIC EMBRYOS SURVIVAL DURING SLOW DEHYDRATION, BYENCAPSULATION AND CONTROL OF DEHYDRATION

In order to obtain dry artificial seeds, carrot somatic embryos were e ncapsulated and dehydrated. Encapsulation in some hydrogels delayed th e dehydration and preserved the water content of carrot somatic embryo s. In particular, a matrix made of alginate with gellan gum was found to be the most efficient in maintaining a high water activity (a,) aro und somatic embryos. By delaying dehydration, and also rehydration, en capsulation seemed to protect somatic embryos against desiccation and imbibition damages, giving better germination and emergence of cotyled ons. Matrices made of alginate mixed with kaolin or gellan gum were pa rticularly adapted to protect the embryos during the dehydration. Apar t from the matrix composition, the control of dehydration speed enhanc ed the survival and regeneration of encapsulated-dehydrated somatic em bryos. Using a slow dehydration protocol (95-15% RH-relative humidity into the chamber-in 11.5 days), it was possible to exert different deh ydration speeds. Slowing the dehydration between 70 and 45% RH stabili zed the water activity (a(w)) of the encapsulation matrix, and enhance d the survival and regeneration frequencies of encapsulated-dehydrated embryos. In the absence of any maturing pretreatment, alginate-gellan gum encapsulated carrot somatic embryos, dehydrated to 15% RH, and re hydrated in moistured air (90% RH), germinated up to 72.9%. Therefore, encapsulation in alginate-gellan gum, combined with a slow dehydratio n, leads to enhance the somatic embryos' desiccation tolerance.