DESICCATION DECREASES ABSCISIC-ACID CONTENT IN HYBRID LARCH (LARIX X LEPTOEUROPAEA) SOMATIC EMBRYOS

Previous studies indicated that the high endogenous abscisic acid (ABA ) content of hybrid larch (Larix x leptoeuropaea) somatic embryos was correlated with low germination frequency. However, when dried, the ge rmination rate of the somatic embryos improved. Therefore, our present objective was to study the effect of desiccation on the levels of ABA and its glucose ester metabolite. Cotyledonary somatic embryos were s ubjected to drying treatments at 4 degrees C under relative humidities of 98 and 59% for one week and the levels of both ABA and abscisic ac id glucose ester (ABAGE) were followed by enzyme-linked immunoassay (E LISA). During desiccation at 98% relative humidity (RH) both ABA and A BAGE levels decreased in an irregular fashion. Regardless of RH, trans ient increases in ABA were observed that were paralleled by marked dec reases in ABAGE. It is concluded that the desiccation of somatic embry os which leads to a decrease in ABA content, could explain the enhance d germination capacity of such embryos.