Biochemical and structural aspects of storage of recalcitrant seeds of Eugenia uniflora

Germination is characterized by intense metabolic activity and reserve mobilization. Unlike orthodox seeds, which tolerate desiccation, recalcitrant seeds are dispersed with high moisture content and are sensitive to drying, making their storage and conservation challenging. The mechanisms controlling their viability during storage remain poorly understood and may involve active metabolism, seed aging, or both, while information on the physiological behavior of non-desiccated recalcitrant seeds is still limited. This study evaluated the effects of storage at 6 °C ± 2 °C for 190 days on Eugenia uniflora L. seeds, focusing on viability, biochemical and ultrastructural traits, tetrazolium test responses, and starch, carbohydrate, phenolic, and flavonoid contents. Seed moisture content remained stable throughout storage; however, germination and germination rate declined significantly over time (P < 0.005). Germination decreased from 94% to 58% and 41% after 135 and 190 days, respectively, indicating progressive loss of viability, confirmed by the tetrazolium test. Reductions in starch, phenolic compounds, and flavonoids were also observed after prolonged storage. Ultrastructural analyses revealed high metabolic activity during early storage, followed by cellular deterioration at later stages. Overall, the findings suggest that viability loss in non-desiccated E. uniflora seeds arises from the interplay between sustained metabolic activity and aging during storage, with prolonged stable moisture conditions driving metabolic shifts that ultimately reduce viability, likely due to carbon reserve depletion.