Polyamines and antioxidant enzymes are involved in the seed desiccation sensitivity of Eugenia (Myrtaceae) species

Abstract

Eugenia (Myrtaceae) is a Neotropical genus that produces desiccation-sensitive (DS) seeds, for which the metabolism of desiccation damage remains unclear. We analyzed polyamines (PAs), antioxidant enzymes, and malondialdehyde (MDA) in seeds of E. pyriformis, E. involucrata, E. brasiliensis, and E. astringens at four water contents (WC) to investigate their relationship with DS. Species differed in their WC thresholds for viability loss, with E. pyriformis and E. involucrata reaching 50% germination at slightly higher WC than E. brasiliensis and E. astringens. Desiccation induced distinct PAs and antioxidant enzymes across species and WC. Putrescine (PUT) increased during desiccation in E. pyriformis and E. involucrata, whereas spermidine (SPD) increased in E. brasiliensis and E. astringens. Changes in PA ratio were species-specific, with marked reductions in E. pyriformis and E. involucrata. Spermine (SPM) decreased in all species during desiccation. Superoxide dismutase rose in E. involucrata and E. astringens, and catalase rose in E. pyriformis. Ascorbate peroxidase decreased at the WC threshold, except in E. involucrata, and glutathione reductase declined in all species. MDA accumulated in E. pyriformis, E. involucrata, and E. brasiliensis, correlating positively with WC decrease in the first two and correlating positively with PA ratio in E. brasiliensis, whereas E. astringens showed increased MDA only in unviable seeds. Correlation analysis also revealed distinct associations between WC, MDA, PAs, and antioxidant enzymes. Our results reveal species-specific responses of PAs and antioxidant enzymes during desiccation in Eugenia seeds. Correlation analyses provided limited evidence of coordinated responses between these two systems, which may have contributed to metabolic imbalance and viability loss.