Hormonal changes during growth of somatic embryogenic masses in hybrid larch

Conifers such as hybrid larch (Larix x leptoeuropaea) are wanted for reforestation programmes. To improve productivity in somatic embryogenesis, we need a better understanding of the physiology of growth of hybrid larch embryogenic masses cultured in vitro, This paper compares the hormonal status of growing embryogenic masses and nonembryogenic callus. Hormonal analyses were done using an HPLC purification and fractionation of the samples coupled to an ELISA method for hormonal quantitation involving several antibodies elicited against each hormonal family. Hormones analysed were abscisic acid, indole-3-acetic acid, zeatin, isopentenyladenine and their main metabolite as well as 2,4-dichlorophenoxyacetic acid (2,4-D) and benzyladenine (BA) used in the culture medium. Growing embryogenic masses of hybrid larch are distinguishable by their high 2,4-D, indole-3-acetylaspartic acid, abscisic acid glucose ester and isopentenyladenosine level, and low BA level. This report constitutes an original description of such hormonal status during somatic embryo proliferation in hybrid larch and generally for gymnosperms.