Lipid composition of somatic and zygotic embryos from Prunus avium. Effectof a cold treatment on somatic embryo quality

In order to evaluate the quality of Prunus avium somatic embryos, a compari son of lipid composition between somatic and zygotic embryos was undertaken , In both zygotic and somatic embryos, neutral glycerolipids (NL) and phosp hatidylcholine (PC) were the 2 major lipid classes. The content of NL incre ased over the course of development in zygotic embryos and reached 490 mu g per embryo, while the PC content reached 100 mu g per embryo. However, the contents of NL and PC in somatic embryos were similar to immature zygotic embryos at stage 3, Fatty acid composition of NL from both zygotic and soma tic embryos revealed more unsaturated than saturated fatty acids, In somati c embryos, the saturated/unsaturated fatty acid ratios of NL and phosphatid ylinositol (PI) were similar to those observed in immature zygotic embryos up to stage 6, Conversely, in phosphatidylethanolamine (PE) the ratio was s imilar to the ratio observed in mature zygotic embryos, at stage 7, Histolo gical studies confirmed the immaturity of somatic embryos: no protein or li pid reserves mere observed in the vacuolated cotyledonary cells, Maturation of somatic embryos was improved by a 2-month cold period. In cold-treated somatic embryos, both NL and PC increased to levels comparable to those obs erved in mature zygotic embryos, and the PE content reached 10 times the le vel of that in mature zygotic embryos, The cold treatment induced a large i ncrease in the saturated/unsaturated fatty acid ratio in phospholipids but only a slight increase in that of neutral glycerolipids, Histological studi es revealed a lipid accumulation at cellular level. Lipid bodies surrounded by protein bodies were observed in cotyledonary cells of cold-treated soma tic embryos, Furthermore, the cold-treated somatic embryos developed into p lantlets with a frequency of 14%, whereas no development,vas obtained with the non-treated somatic embryos.