EFFECT OF CADMIUM AND MERCURY ON SEED-GERMINATION AND EARLY SEEDLING GROWTH OF RICE AND ALFALFA

The effects of different concentrations (0.05 to 50 mM) of CdCl2 and HgCl2 and two concentrations of KCI (50 and 200 mM) on percentage seed germination after 2 and 5 days of incubation, and on seedling growth after 5 days of incubation of rice and alfalfa (cultivars, Al-Ahssa) were investigated. Seed germination and seedling growth were inhibited significantly by CdCl2 and HgCl2. Germination inhibition was completely due to heavy metal toxicity, while seedling growth inhibition was mostly due to the toxicity of heavy metals as evident from the effect of KCl. Rice seed germination was more tolerant to heavy metals. In rice, root growth was more sensitive to heavy metals than shoot growth, while the latter was more sensitive to KCl stress.