Seed maturation, germination physiology, and storage behaviour of the tropical tree Cochlospermum religiosum (L.) Alston (Bixaceae)
TL;DR
Seeds exhibited a rapid triphasic imbibition pattern, indicating substantial water permeability under freshly harvested conditions, although the possibility of partial physical dormancy developing during drying and storage cannot be completely excluded.
Abstract
Effective conservation of Rare, Endangered, and Threatened (RET) tree species requires a robust, species-specific understanding of seed biology. Cochlospermum religiosum, an ecologically and economically important dry-forest tree currently experiencing population decline, lacks comprehensive information on reproductive maturity, germination physiology, and storage behaviour. This study integrated carpological analysis, germination bioassays, and controlled storage experiments to generate evidence-based conservation guidelines. Sequential sampling (30–80 days after anthesis; DAA) revealed coordinated fruit–seed enlargement, biomass accumulation, dehydration, and physiological enhancement during maturation. The physiological maturity window occurred at 60–80 DAA, with 80 DAA representing the optimal harvest stage, characterized by maximum dry mass, minimum moisture content, and highest germination (40.00 ± 2.88%; Tukey HSD, P ≤ 0.05). Seeds exhibited a rapid triphasic imbibition pattern (~ 80% weight gain within 10 h; ~ 97% hydration by 30 h), indicating substantial water permeability under freshly harvested conditions, although the possibility of partial physical dormancy developing during drying and storage cannot be completely excluded. Pre-sowing treatment with gibberellic acid (GA3) at 500 ppm significantly enhanced germination (26.8%) and seed vigour (VI = 285.05; ANOVA, P < 0.001), whereas higher GA3 concentrations and other chemical treatments were ineffective. Storage experiments suggested intermediate to near-orthodox but chilling-sensitive seed behaviour, with germination performance strongly governed by moisture–temperature interactions. Seeds equilibrated to ~ 11% moisture content and stored at 15 °C retained comparatively higher germination performance for six months, whereas excessive drying (4.9% MC) and room-temperature storage resulted in substantial reduction in germination. These findings provide practical guidance for seed harvesting, nursery propagation, and ex situ conservation of C. religiosum and comparable tropical dry-forest tree species.