Environmental and physiological factors influencing seed longevity of three Brazilian endemic cacti during in situ storage

Seed lifespan is a critical component of biodiversity conservation. Therefore, understanding the environmental and physiological components of seed longevity is crucial for outlining appropriate management strategies in the context of current and future climate. Here, we studied the effects of parental plant environment on cacti seed deterioration during in situ storage and the physiological mechanisms influencing seed viability in populations of Cereus jamacaru, Pilosocereus catingicola ssp. salvadorensis, and Xiquexique gounellei ssp. gounellei from drier and wetter locations of the Caatinga. Seeds were placed in nylon bags at a depth of 5 cm in an area of natural occurrence of the three species. We periodically tested exhumed seeds for germinability, oxidative stress, antioxidant activity, protein, and sugar content. Results showed that all species have potential to form a short-term persistent seed bank. Burial time decreased seed viability, which was accompanied by protein and sugar degradation, increased lipid peroxidation, and decreased antioxidant capacity. Parental environment also affected viability loss in C. jamacaru seeds: after 12 months, 60% more seeds from wetter locations successfully germinated compared to drier ones. These intraspecific variations were linked to differences in sugar metabolism and maintenance of antioxidant capacity. Overall, the findings improve our understanding of cacti seed longevity and potential climate impacts on cacti conservation.