Endogenous auxin and its manipulation influence in vitro shoot organogenesis of citrus epicotyl explants

Understanding the effect of hormones on plant growth may lead to strategies for improving the efficacy of propagation via tissue culture or for reproducing plants through shoot regeneration. Regeration of shoots is a prerequesite for genetically engineering . An international team led by Yi Li at the University of Connecticut, Storrs, USA, explored the role of the plant hormone auxin, a crucial regulator of organ develoment, in regenerating citrus shoots. Auxin is produced at the tip of the tiny shoot cuttings used in tissue culture, and transported to the base where it accumulates, blocking shoot growth. The research showed that this effect is prevented by physically washing the auxin out, or by applying an auxin transport inhibitor, NPA. Both washing and NPA may be useful tools for enhancing the shoot regeneration of horticultural species in tissue culture.