Methods to Break Seed Dormancy of Rhynchosia capitata, a Summer Annual Weed
Dormancy of weed seeds is a significant feature contributing to their survival rate since it helps the weeds to avoid herbicides and other weeding practices along with unfavorable environmental conditions. We investigated the effects of different dormancy breaking treatments on the germination of Rhynchosia capitata, a common summer annual weed, which is emerging as a weed threat in Pakistan. Seeds were soaked in thiourea, KNO3, HCl, HNO3, and H2SO4, and they were also mechanically scarified (sandpaper). Results indicated that R. capitata seeds show signs of physical dormancy that is mainly due to the impermeability of their coat. Mechanical scarification and acid scarification (soaking of seeds in H2SO4 for 60 and 80 min and in HCl for 12 and 15 h) were very efficient in breaking dormancy and promoting germination. Seed soaking in HNO3 for 1 to 5 d showed little effect whereas various concentrations of thiourea and KNO3 were ineffective in breaking R. capitata seed dormancy.