EFFECT OF SOLE AND COMBINED PRETREATMENTS ON RESERVE ACCUMULATION, SURVIVAL AND GERMINATION OF ENCAPSULATED AND DEHYDRATED CARROT SOMATIC EMBRYOS

In order to obtain dry artificial seeds, carrot somatic embryos were p re-treated before being encapsulated into calcium-alginate-gellan gum, and slowly dehydrated until 15% RH (relative humidity of the chamber) . ABA (1 to 10 mu M), 1 to 5 mM proline, an osmotic pressure of +/- 52 0 mOsm, or heat (35 degrees C) enhanced the desiccation tolerance of e ncapsulated somatic embryos. Some treatments were complementary, like 10 mu M ABA and 10% sucrose, 10 mu M ABA and heat (35 degrees C), or 1 0% sucrose and cold (4 degrees C). In such conditions, complete or alm ost total (95.6-100% germination) desiccation tolerance was then obtai ned. These treatments may act by the acquisition of sufficient-and wel l-balanced-protein and starch reserves. Osmotic treatments, ABA, and a bove all proline, promoted protein accumulation, meanwhile starch rese rves were slightly depleted by 10-20 mu M ABA, proline, and poor sucro se-osmotic treatments (8% trehalose). All the treatments were found to enhance viability during dehydration, as observed by fluorescence. Su crose may be partly replaced by other osmotica. Alone, it has a negati ve effect on the depletion of starch reserves. Cold (4 degrees C) with 10% sucrose may favor the glassy state transition. ABA and proline ap pear to be involved in the same process leading to the acquisition of partial desiccation tolerance. Heat (35 degrees C), or 10% sucrose, ha ve been found to complement ABA action in the acquisition of full desi ccation tolerance.