Abstract
Background and aims
– Understanding germination and seedling emergence responses of pastoral legumes is essential for improving conservation and restoration efforts, particularly in arid and semi-arid ecosystems. This study aimed to characterize the germination ecology of two threatened taxa, Onobrychis conferta subsp. conferta and
Onobrychis caput-galli
, which have potential value for rangeland restoration and forage production, to assess their tolerance to key environmental factors.
Material and methods
– Germination and seedling emergence were investigated under controlled laboratory and greenhouse conditions. Seeds were exposed to a range of temperatures at four alternating day/night temperatures (15/5, 20/10, 25/15, and 30/20°C) and four constant temperatures (17, 21, 25, and 29°C), light conditions were under two light regimes: complete dark (24 h) and alternating light/dark (12/12 h), salinity levels in solutions of 0 (control), 50, 100, 200, 300, and 400 mM NaCl at 20/10°C and total darkness, osmotic stress at six osmotic potentials: 0 (control), -0.3, -0.6, -0.9, -1.2, and -1.5 MPa, pH conditions (4, 5, 6, 7, 8, and 9), and burial depths on the soil surface (0 cm) or buried at 1, 2, 3, 4, 5, and 6 cm of soil. The effect of mechanical scarification on germination was also evaluated.
Key results
– Both species achieved high germination percentages (94–97%) at constant 21°C and alternating 20/10°C, with no significant differences between light and darkness. Germination decreased progressively with increasing salinity, remaining possible up to 300 mM NaCl for
O. caput-galli
and 400 mM for
O. conferta
. Both species tolerated osmotic stress down to -1.5 MPa, with
O. caput-galli
exhibiting greater tolerance. Germination occurred across a wide pH range (4–9), although acidic conditions reduced germination more strongly in
O. caput-galli
. Scarification significantly enhanced germination in
O. conferta
, while
O. caput-galli
germinated readily without treatment. Seedling emergence was observed from burial depths up to 5 cm, with optimal emergence at 1 cm.
Conclusion
– The two species display broad ecological tolerance during germination and early establishment. Their threatened status is therefore more likely linked to in situ environmental pressures than to intrinsic germination constraints.