Effect of sole and combined pre-treatments on reserve accumulation, survival and germination of encapsulated and dehydrated carrot somatic embryos

In order to obtain dry artificial seeds, carrot somatic embryos were pre-treated before being encapsulated into calcium-alginate-gellan gum, and slowly dehydrated unitil 15% RH (relative humidity of the chamber). ABA (1 to 10 μM), 1 to 5 mM proline, an osmotic pressure of ±520 mOsm, or heat (35°C) enhanced the desiccation tolerance of encapsulated somatic embryos. Some treatments were complementary, like 10 μM ABA and 10% sucrose, 10 μM ABA and heat (35°C), or 10% sucrose and cold (4°C). In such conditions, complete or almost total (95.6–100% germination) desiccation tolerance was then obtained. These treatments may act by the acquisition of sufficient-and well-balanced-protein and starch reserves. osmotic treatments, ABA, and above all proline, promoted protein accumulation, meanwhile starch reserves were slightly depleted by 10–20 μM ABA, proline, and poor sucrose-osmotic treatments (8% trehalose). All the treatments were found to enhance viability during dehydration, as observed by fluorescence. Sucrose may be partly replaced by other osmotica. Alone, it has a negative effect on the depletion of starch reserves. Cold (4°C) with 10% sucrose may favor the glassy state transition. ABA and proline appear to be involved in the same process leading to the acquisition of partial desiccation tolerance. Heat (35°C), or 10% sucrose, have been found to complement ABA action in the acquisition of full desiccation tolerance.