HORMONAL CHANGES DURING GROWTH OF SOMATIC EMBRYOGENIC MASSES IN HYBRID LARCH

Conifers such as hybrid larch (Larix x leptoeuropaea) are wanted for r eforestation programmes. To improve productivity in somatic embryogene sis, we need a better understanding of the physiology of growth of hyb rid larch embryogenic masses cultured in vitro, This paper compares th e hormonal status of growing embryogenic masses and nonembryogenic cal lus. Hormonal analyses were done using an HPLC purification and fracti onation of the samples coupled to an ELISA method for hormonal quantit ation involving several antibodies elicited against each hormonal fami ly. Hormones analysed were abscisic acid, indole-3-acetic acid, zeatin , isopentenyladenine and their main metabolite as well as 2,4-dichloro phenoxyacetic 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 gluc ose ester and isopentenyladenosine level, and low BA level. This repor t constitutes an original description of such hormonal status during s omatic embryo proliferation in hybrid larch and generally for gymnospe rms.