Practice question

Organogenesis denotes development of discrete organs, shoots and roots, from callus or explants without forming embryo, contrasting with embryogenesis. It is monopolar, meaning each organ originates separately, producing either shoot or root axis with continuous vascular strand linking to mother callus, unlike bipolar somatic embryo that lacks such connection. Induction follows classic Skoog Miller hormonal balance: moderate auxin plus cytokinin sustains callus, while shifting ratio directs organ fate. Shoot formation activates shoot meristem regulators STM, WUS, KNAT1 and cytokinin signaling via type-B ARRs inducing CYCD3;1 for division in peripheral zone. Root formation employs ARF7/ARF19 mediated activation of LATERAL ORGAN BOUNDARIES LBD16 defining founder cells. Anatomically organogenic centers appear as meristemoids with tunica corpus organization that later protrude as bud or root primordium. This route underpins commercial micropropagation of banana, potato, chrysanthemum, orchids where shoot clusters are multiplied in cytokinin rich medium then rooted separately on auxin medium for mass clonal production maintaining genetic uniformity.