Cellular and metabolic damage induced by desiccation in recalcitrant Araucaria angustifolia embryos

Embryos of Araucaria angustifolia seeds showed no dormancy; they germinated easily at temperatures ranging from 10° to 30°C, and the thermal optimum was about 25–30°C; they were recalcitrant. At harvest, their mean moisture content (dry weight basis) was about 120% and they completely lost viability when their moisture content fell to about 30%. The cotyledons were more sensitive to dehydration than the radicle. Dehydration induced deterioration of cell membranes as indicated by a high increase in leakage of solutes. It also resulted in damage in the nuclei, which was not repaired upon rehydration. During desiccation, respiratory activity decreased; however, O 2 uptake was not an indication of germination ability, since it was significantly affected only when embryo moisture content reached the critical value of 30%. The decrease in the capacity to convert 1-aminocyclopropane 1-carboxylic acid to ethylene, which was observed at 30–60 min of dehydration, was a very early indicator of deterioration in embryos. Desiccation resulted also in a rapid decrease in the ability for protein synthesis as measured by [ 35 S]methionine incorporation into total protein; 50% inhibition was observed after 30–60 min of desiccation for both axis and cotyledons.