Somatic embryos differ from zygotic embryos because they:
Somatic embryos differ from zygotic embryos primarily in origin despite morphological resemblance through globular heart torpedo stages. Zygotic embryos arise through double fertilization process within ovule where haploid sperm fuses with egg producing diploid zygote and central cell forms triploid endosperm providing nourishment, involving sexual recombination generating genetic variation. Somatic embryos originate from diploid vegetative cells such as leaf mesophyll root cortex or callus without gamete fusion fertilization or endosperm formation, developing via mitotic divisions induced by auxin stress, hence genetically identical to mother plant except for somaclonal mutations. They lack suspensor attachment to maternal tissue, seed coat protective testa and endosperm dependence, although they establish protoderm procambium and bipolar meristems similarly. Nutritionally autonomous from culture medium, they exhibit differences in storage reserve deposition and desiccation tolerance. Because they arise from single somatic cell, they are invaluable for clonal propagation avoiding segregation, artificial seed technology, and genetic transformation preventing chimerism, while zygotic embryos represent product of sexual reproduction driving diversity in nature.
Ref: von Arnold et al., Plant Cell 2002 somatic vs zygotic embryo; Nature Plants embryo identity.