Physiological and Biochemical Mechanisms Underlying Viability Decline in Recalcitrant Seeds of Eugenia uniflora During Cold Storage

Germination is a complex process involving active metabolism and the mobilization of reserves. Orthodox seeds, which are initially dry, begin to germinate once they absorb sufficient water. In contrast, recalcitrant seeds are intolerant to desiccation, making long-term storage and conservation efforts challenging. Unlike orthodox seeds, recalcitrant seeds are dispersed with a high water content. The mechanisms that allow these seeds to maintain viability during storage, as well as the factors influencing their storage potential, remain unclear. These factors may include active metabolism, seed aging, or a combination of both. Moreover, data on the physiological behavior of recalcitrant seeds without desiccation are scarce. This study aimed to investigate the effects of storage at 8°C ± 2°C for 190 days on Eugenia uniflora L. seeds, focusing on viability, biochemical and ultrastructural characteristics, the tetrazolium test, as well as starch, carbohydrate, phenolic compounds, and flavonoid content. The results indicated a reduction in germination percentage, starch levels, phenolic compounds, and flavonoid content after 135 and 190 days of storage, despite moisture levels remaining constant after 190 days. The presence of multiple vacuoles and organelles suggested high metabolic activity in the early stages of storage. Additionally, signs of cellular deterioration and reduced germination percentages indicated seed aging throughout the storage period. The findings suggest that the loss of viability in non-desiccated E. uniflora seeds is a result of both seed aging and elevated metabolic activity.