modern agriculture. Callus is of particular use in micropropagation where it can be used to grow genetically identical copies of plants with desirable characteristics. To increase the yield, efficiency and explant survivability of micropropagation, a thorough care is taken for the optimization of the micropropagation protocol. For example, using explants composed of low totipotency cells may prolong the time necessary to obtain callus of sufficient size, increasing the total length of the experiment. Similarly, various plant species and explant types require specific plant hormones for callus induction and subsequent organogenesis or embryogenesis – for the formation and growth of maize calluses, auxin 2,4-Dichlorophenoxyacetic acid (2,4-D) was superior to 1-Naphthaleneacetic acid (NAA) or Indole-3-acetic acid (IAA), while the development of callus was hindered in prune explants after applying auxin Indole-3-butyric acid (IBA) but not IAA. History Henri-Louis Duhamel du Monceau investigated wound-healing responses in elm trees, and was the first to report formation of callus on live plants. In 1908, E. F. Simon was able to induce callus from poplar stems that also produced roots and buds. The first reports of callus induction in vitro came from three independent researchers in 1939. P. White induced callus derived from tumor-developing procambial tissues of hybrid Nicotiana glauca that did not require hormone supplementation. Gautheret and Nobecourt were able to maintain callus cultures of carrot using auxin hormone additions. See also Embryo rescue Somatic embryogenesis Chimera (genetics) Hyperhydricity References Cell culture Biotechnology Cell biology