CHANGES IN THE LEVELS OF ABSCISIC-ACID AND ITS GLUCOSE ESTER CONJUGATE DURING MATURATION OF HYBRID LARCH (LARIX X LEPTOEUROPAEA) SOMATIC EMBRYOS, IN RELATION TO GERMINATION AND PLANTLET RECOVERY

Changes in abscisic acid content during maturation of hybrid larch som atic embryos (Larix x leptoeuropaea), were followed using an enzyme im munoassay (ELISA). In the presence of 60 mu M cis-trans (+/-)-ABA in t he maturation medium, the cis-trans (+/-)-ABA level of the somatic emb ryos in planta increased during the maturation phase to reach a maximu m value at week 5. Concomitantly, an extension of the period of matura tion from 3 to 4 and 5 weeks resulted in a significant decrease in bot h germination and plantlet frequencies. As a consequence, we assume th at it was the level of ABA in planta that was responsible for the inhi bition. ABA acted in both a stimulatory and an inhibitory manner. If A BA promoted the obtention of high qualify somatic embryos in large num bers, it also had a deleterious effect on the subsequent development, i.e. germination and plantlet recovery. The results stressed the impor tance of both the procedure and duration of maturation.