Methods of breaking physical dormancy in seeds of the invasive weed Mimosa pudica (Fabaceae) and a comparison with 36 other species in the genus

The herbaceous perennial legume Mimosa pudica is an invasive weed in many tropical and subtropical regions and a serious problem for farmers since it is difficult to eliminate from crop field by hand. Moreover, it has water impermeable seeds, i.e., physical dormancy (PY), which could persist in the soil seed bank for a long period of time, thus making it a big challenge to control. The aims of this study were to test the effect of various laboratory methods on breaking PY in seeds of M. pudica, to identify the site(s) of water entry into seeds of M. pudica and compare results of dormancy-breaking methods for seeds of M. pudica with those of 36 other species of Mimosa reported in the literature. Mechanical scarification, wet heat and cycles of wet heat and ice water effectively broke PY in seeds of M. pudica. Following wet heat at 80 °C for 10 min, water uptake was via the hilar region but not the pleurogram; small cracks made in the pleurogram by this treatment were not deep enough for water to enter the seed. Neither tolerance to summer temperatures nor PY is likely to be the cause of invasiveness of this species, since seeds of rare and endemic species of Mimosa also tolerate summer temperatures and have PY.