Population-specific germination and physiochemical responses of Aeluropus lagopoides seeds to salinity under controlled conditions

Aeluropus lagopoides is a perennial salt-secreting halophyte grass with broad distribution and multiple economic potentials. While some information exists regarding its seed germination ecology, salt-tolerance mechanisms, adaptations to field conditions, and population genetic diversity, little is known about physiochemical responses of its seeds collected from contrasting habitats. This study examined germination and physiochemical responses of A. lagopoides seeds from two contrasting coastal populations (Hawke's Bay and Manora) under varying thermoperiod, photoperiod, and NaCl treatments in controlled conditions. Fresh seeds from both populations were nondormant, with Hawke's Bay seeds showing 100% germination compared to 75% for Manora seeds under nonsaline conditions. Salinity significantly impacted germination, with Hawke's Bay seeds exhibiting greater salt tolerance, maintaining higher mean final germination and germination rate, while Manora seeds showed a decline in both parameters under increasing salinity. Ungerminated seeds from both populations recovered their germination after transfer from high salinity to water. Hawke's Bay seeds maintained stable mitochondrial respiratory activity and water uptake under salinity, whereas Manora seeds showed reduced mitochondrial activity and slight decline in water uptake. Additionally, H₂O₂ levels increased in Hawke's Bay seeds under salinity, while remaining unchanged in Manora. Antioxidant enzyme activities (catalase and ascorbate peroxidase) decreased in both populations under salt stress, while nonenzymatic antioxidants (ascorbate and glutathione) were higher in Manora seeds under control conditions but decreased with salinity. These findings highlight significant population-specific variations in germination of A. lagopoides seeds, their recovery, and physiological responses to salinity stress, which should be taken into consideration for ecological and conservation efforts in coastal areas.