Practice question

Somatic embryogenesis produces embryo-like structures from vegetative somatic cells, mimicking zygotic embryogeny yet arising without fertilization. Unlike organogenesis which is monopolar and vascularly connected, somatic embryos are bipolar possessing simultaneous shoot and root apical meristems and remain physiologically isolated enclosed by protoderm. Process begins with induction of embryogenic competence using synthetic auxin 2,4-D which triggers global chromatin decondensation, DNA hypomethylation, and upregulation of master regulators SOMATIC EMBRYOGENESIS RECEPTOR KINASE1 SERK1, LEAFY COTYLEDON1/2, BABY BOOM and WOX2. Removal of auxin permits polar auxin transport establishment via PIN1 localization generating apical basal axis. Embryos progress through globular spherical stage, heart stage with bilateral symmetry and cotyledon initiation, torpedo elongation, and cotyledonary maturation accumulating storage reserves and LEA proteins for desiccation tolerance. Single-cell origin prevents chimerism, ideal for transformation, artificial seeds, and large scale bioreactor propagation, providing uniform embryos capable of converting into plantlets upon germination medium without hormone or low ABA, ensuring high fidelity clonal propagation.