Exogenous abscisic acid fate during maturation of hybrid larch (Larix x leptoeuropaea) somatic embryos
2000
Label, Philippe | Lelu-Walter, Marie-Anne
The maturation of somatic embryogenesis of hybrid larch is an essential step for plantlet production. ABA controls not only synchronicity of maturation, but has important consequences on eventual viability of the plantlet. To gain understanding of the role of this plant growth regulator during the maturation process of hybrid larch somatic embryos, we studied the incorporation of [ H]‐(±)‐abscisic acid [tritiated (±)‐ABA] over 6 weeks of culture. Results showed a rapid incorporation of label into the tissues directly in contact with the culture medium. Accumulation of tritiated (±)‐ABA occurred mainly in the maturing somatic embryos found at the periphery of the embryogenic mass but not in direct contact with the culture medium. Tritiated (±)‐ABA was mainly conjugated as a glucose ester form. Rates of tritium incorporation indicated a significant build‐up in tritiated (±)‐ABA metabolization at the third week of culture. The weekly measurement of labelling in the culture medium over 6 weeks showed no localized exhaustion of tritiated (±)‐ABA in positions where the embryogenic masses were placed in Petri dishes. The calculated ABA internal content of the maturing somatic embryos was similar to published ELISA measurements of ABA. This result suggests an absence of endogenous ABA synthesis by somatic embryos of hybrid larch during maturation.
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