Endogenous ethylene in indirect somatic embryogenesis of Medicago sativa L.

Ethylene biosynthesis during different phases of somatic embryogenesis in Medicago sativa L. cv. Rangelander using two regeneration protocols, RPI and RPII, was studied. The highest ethylene production was detected during callus growth on induction medium in both regeneration protocols. Significantly less ethylene was produced by embryogenic suspension than by callus (RPII). Developing embryos synthesized higher amounts of ethylene than mature embryos. Production of ethylene was strongly limited by the availability of 1-aminocyclopropane-1-carboxylic acid and also by ACC-oxidase activity. However, removal of ethylene from culture vessels’ atmosphere using KMnO₄ or HgClO₄ had no significant effect on callus growth, somatic embryo induction and development. Reducing of ethylene biosynthesis by aminoethoxyvinylglycine substantially decreased somatic embryo production and adversely affected their development, indicating ethylene requirement during proliferation and differentiation but not induction.