Physiological behavior trend of Campomanesia xanthocarpa (Myrtaceae) seeds under desiccation and their implication for germplasm conservation

KEY MESSAGE: Seed desiccation sensitivity is not determined only by water content threshold but is a consequence of drying rate, which causes rapid viability loss, and this was associated to mechanical/physical damage Campomanesia xanthocarpa is a tree from Brazilian Atlantic Forest, one of the world’s biodiversity hotspots, that has potential as a model for studies on the physiological behavior of seeds susceptible to desiccation of tropical species. Desiccation sensitivity (DS) seeds are a major concern for ex situ conservation efforts and superficial inferences may generalize their behavior in a wider perspective. Although major physiological responses to stress are shared and relatively well understood, DS seeds responses can be highly variable. In addition, there is a lack of studies concerning DS seeds endogenous polyamines content, antioxidant activity and its relation to desiccation stress and seed viability. Seeds were desiccated and went through germination tests, histological analysis, and estimation of antioxidant enzymatic activity, lipid peroxidation and polyamines content. Due to inherent morphological features, the seeds have a high drying rate and rapidly lose viability within 24 h. During the first 6 h of drying 76% of initial water content is lost, but 96% of the seeds still germinated. Spermidine and H₂O₂-scaveging enzymes activity showed a positive correlation, endorsing polyamines antioxidant role. Although lipid peroxidation increased along seed drying, it was minimal and suggested to be an ongoing process when viability was lost. Due the intensity of tissue water loss it is likely that mechanical/physical damage led to seed viability loss. Assessing the nature of damage and physiological stress response mechanisms contribute to better understand species vulnerability and broad the knowledge of tropical seed behavior.