EN
This work is the first characterization at cellular and subcellular level of the main cellular events occurring in the first stages of microspore embryogenesis. Microspore embryogenesis was induced in two varieties of Citrus Clementina (Nules and Monreal). The results showed that one of the most responsive stages for embryogenesis was the vacuolate microspore. Microscopic analysis revealed specific features of the young proembryos still surrounded by the exine: large nuclei, clear areas in the cytoplasm, starch accumulation, and an increase in the thickness of the wall under the exine. Immunogold labelling with JIM 5 antibody showed a high amount of non-esterified pectins in the surrounding cell wall. After exine rupture, different cell types were detected in late proembryos. As embryogenesis proceeded, the normal pattern of development was observed, including heart-shape, torpedo and cotyledonar embryos.