Abstract
Background
Eragrostis plana , introduced from South Africa, is the most important invasive perennial weed in the grasslands of Southern Brazil (“Pampa biome”), becoming a threat in neighboring countries. How temperature, light, and water potential affect seed germination is poorly understood but essential to understand its invasiveness and dissemination.
Objective
This study characterized the seed germination of E. plana from locations in the Brazilian Bioma Pampa under different conditions.
Methods
Seed germination was evaluated by using a time-to-event model across a wide range of temperatures (15 to 45C), light (total darkness or 12-h light), and water potentials (0, -0.08, -0.2, -0.25, -0.5, -0.75, -1, and -1.5 MPa).
Results
E. plana seeds did not germinate below 15C and at water potential lower than -0.75 MPa. Among populations, the highest germination was at 40C (> 90%). The base temperature for germination ranged from 12.3 to 15.6C across populations. E. plana did not germinate more than 40% at 25C, except for one population (Caçapava do Sul), with a germination capacity of 73%. Light is a requirement for a fraction of the seeds as darkness inhibits the germination of a fraction of the seeds as well.
Conclusions
E. plana could adapt to cooler temperatures, as shown by the ability of the Caçapava do Sul population to germinate at low temperatures. This ability for seed germination help to explain why E. plana has successfully invaded the rangelands of Southern Brazil, spreading around neighboring countries. Management strategies have to be urgently adopted to avoid its dissemination abroad.
Invasiveness; Rangeland; Tough lovegrass; Water potential
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