Short communication: Timing of stinkweed and shepherd's-purse recruitment affects biological characteristics of progeny

Abstract

The effect of recruitment timing (fall versus spring recruitment) on seed characteristics and performance of two common Canadian facultative winter annual weeds; stinkweed (Thlaspi arvense L.) and shepherd's-purse (Capsella bursa-pastoris L.) was investigated. Seed germination proportion was unaffected by maternal emergence timing but germination was faster for spring versus winter cohort seeds of stinkweed. Proportionally more seeds from winter (fall-recruited) cohorts were rendered non-viable by aging treatments, while for shepherd's purse, aging treatments broke dormancy instead of reducing viability and this was especially true for winter cohort seeds. For both weed species, spring cohort seeds produced earlier flowering plants with greater and lesser biomass allocation to reproductive tissues and roots, respectively. These results show the potential importance of germination timing and maternal effects on weed populations and demonstrate additional complexity in the nature of facultative winter annual weeds, in particular.