Coat-imposed physical dormancy
prevents water-uptake (imbibition) in Ipomoea species (Baskin and
Baskin, 1998; Jayasuria et al., 2008); therefore, an imbibition test
was performed. Any non-germinated fully-intact hard seed (water
impermeable) in the petri-dish was nicked with a razor blade to
remove physical barrier, which resulted in imbibition of the tetrazolium
chloride solution. The germination percentage was calculated
as the number of germinated seeds divided by the total
number of viable seeds, multiplied by 100.