Germination Requirements of Ottelia cordata (Wall.) Dandy Seeds: Implications for Conservation and Restoration

ABSTRACT Ottelia cordata (Wall.) Dandy, an endangered tropical aquatic macrophyte, exhibits obligate sexual reproduction for population persistence. However, the absence of empirical data on seed storage and germination hinders evidence‐based conservation. This study focuses on the optimal seed storage methods, germination requirements and key factors enhancing germination for O. cordata seeds to advance both ex situ conservation and original habitat vegetation restoration efforts. The results showed that 4°C‐Water storage of O. cordata seeds was optimal for maintaining seed viability (> 90% after 14 months). Germination occurred maximally at 25°C–30°C under photic conditions and exclusively on sediment surfaces. For the first time, we found that both a simple 12‐h desiccation pretreatment and the natural fruit mucilage markedly enhanced seed germination, revealing two previously unrecognised factors promoting germination in aquatic macrophytes. Notably, we observed a positive density‐dependent germination response: high‐density sowing enhanced germination by 40%–75% relative to isolated seeds treatment—contrasting with the commonly reported negative density dependence in many terrestrial species. These findings suggest the following conservation strategies: (1) establish ex situ conservation collections via 4°C‐Water storage, (2) precondition seeds using a 30°C desiccation treatment, (3) sow seeds at the sediment–water interface in photic zones during 25°C–30°C temperature regimes, and (4) apply clustered sowing or mucilage amendments to exploit density‐dependent enhancement. This framework provides a scientific foundation for conserving the endangered aquatic plant O. cordata and restoring its populations in degraded aquatic ecosystems.