Effetto della disidratazione sui semi recalcitranti di Araucaria Bidwilliii

The changes in several antioxidants as well as in the level of C-centred free radicals and thiobarbituric acid reactive substances (TBARS) were studied in seeds of Araucaria bidwillii Hook desiccated to 37%, 28% and 21% moisture content. The lowest-safe moisture content for the seedling establishment was 37%. The embryo showed higher levels of both enzymatic and non-enzymatic antioxidants than endosperm, besides double amounts of free radicals. Lutein decreased in both organs whereas-tocopherol values were not affected by desiccation. In the embryo at 37% seed moisture content the antioxidant defence system increased giving rise to a decrease in free radicals. Beyond this point, free radicals and TBARS increased in agreement with the umpiring of the ascorbate/glutathione cycle by the decrease in reduced glutathione and glutathione reductase activity. At 21% the decrease in glutathione reductase was related to the disappearance of its lowest band whereas three Cu/Zn superoxide dismutase isoforms were present during the whole desiccation period in both embryo and endosperm. In the endosperm during desiccation, the consumption of ascorbate, total glutathione and lutein prevented the rise in free radicals and TBARS till 28%, at which an increase in oxidised glutathione was also observed.