Prior to starting the experiments, viability of the seeds was
estimated on 3 replicates of 50 seeds per species according to
the 2,3,5-triphenyltetrazolium chloride (TTC) method.28 Seeds
were imbibed in a solution of 1% TTC (Sigma) and incubated
at 37 °C for 3 days to stain the living embryos. After that, the
TTC solution was eliminated and seeds were immersed in a
solution of 50% sodium hypochlorite for 2 min to bleach the
seed testa. Seeds were observed under stereoscopic microscope
at 30× magnification to determine the percentage of living
seeds. Living seeds were considered when embryos were
stained from pale pink to red. Seeds were considered to be dead
when embryos were completely white.