Germination behaviour of Cenchrus pauciflorus seeds across a range of salinities

Cenchrus pauciflorus (field sandbur) is an annual weed native to South America and Africa that has become an invasive plant in farmland and pastures around the globe. It forms two types of seeds that are different in shape and mass, defined as big seeds (M) and small seeds (P). This study examined effects of salinity and seed type on germination efficiency of C. pauciflorus. Increased concentration of salinity solutions (NaCl, Na2SO4 and Na2CO3) reduced germination rate and final germination percentage (FGP) of both seed types, while prolonging the mean final germination time (TFG). M seeds tolerated salinity levels below 400 mmol (NaCl), 350 mmol (Na2SO4) and 300 mmol (Na2CO3), while P seeds tolerated salinity levels below 350 mmol (NaCl), 250 mmol (Na2SO4) and 150 mmol (Na2CO3). Furthermore, M seeds were less sensitive than P seeds, confirmed via increased germination rate (61%, 42% and 40%), FGP (36%, 29% and 26%), and shorter TFG (37%, 19% and 16%) in NaCl, Na2SO4 and Na2CO3 solutions respectively. Moreover, the germination threshold values of M and P seeds were 426 and 365 mmol for NaCl, 354 and 264 mmol for Na2SO4 and 308 and 149 mmol for Na2CO3 respectively. These results add to our understanding of the germination strategy of different seed types of C. pauciflorus. This information on germination ecology may indicate a potential to invade regions with little or no salt stress.