Temperature-induced inactivation of seeds of the Poaceae family

Abstract

There are still unanswered questions regarding the weed seed hygiene of residues from biogas fermenters. The ability of seeds to survive in humid-warm conditions is species-specific. Predicting the behavior of untested species is difficult. This paper examines whether the origin of the species gives an indication of the temperature tolerance of its seeds. Seeds of six species of the Poaceae family were tested: Alopecurus myosuroides, Cynodon dactylon, Echinochloa crus-galli, Panicum dichotomiflorum, Setaria viridis and Vulpia myuros. Seeds were incubated at 42°C in water baths for up to 12 days. Seeds were taken from the water bath at regular intervals and their germination and viability were tested. 4-parametric time-response curves were modeled. A comparison of species based on mean inactivation time (ET₅₀ values) showed that seeds of C₄ grasses originating from warm floral zones survived longer and germinated better than seeds of C₃ grasses. For species that also occur in tropical regions, the ET₅₀ value exceeded five days. The study shows that the evolutionary conditions that led to their today’s worldwide distribution can be used to estimate the survivability of their seeds. Farmers should be aware of the risk of spreading grass seeds, especially of C₄ grasses, with the fermentation residues.