Drought tolerance during germination of native and commercial forage grasses: implications for pasture management in semi-arid lands

Abstract

Drought stress limits forage production in semi-arid grasslands, threat-ening the sustainability of grazing systems. This study evaluated whether native perennial grasses from the semi-arid Pampas of Argentina exhibit drought-tolerant germination traits comparable to commercial forages. Germination experiments were conducted using diaspores of eight native and two commercial grass species (cool- and warm-season functional groups) exposed to six water potential levels (0 to −1.5M Pa). Germination responses were analyzed using the hydrotime model to estimate the hydrotime constant (θH) and the base water potential for 50% germination (Ψb(50)). Warm-season spe-cies showed more negative Ψb(50) values (−0.96 to −1.21M Pa) and lower θH (1.90–2.69M Pa.day), indicating greater tolerance to water stress than cool-season species, which exhibited broader variation (Ψb(50): −0.55 to −1.27 MPa; θH: 3.48–9.24 MPa.day). Within the cool-season group, the commercial Thinopyrum ponticum showed the highest tol-erance, being the only species able to germinate at −1.5M Pa. Among native species, Jarava plumosa, Pappophorum vaginatum, and Digitaria californica displayed drought-tolerant germination traits comparable to or exceeding those of commercial species. These results demon-strate that native grasses possess diverse and effective germination strategies under water limitation, supporting their integration into forage systems and restoration efforts aimed at increasing resilience in semi-arid rangelands.