INHIBITORY EFFECTS OF HEAVY-METALS ON SEED-GERMINATION AND SEEDLING GROWTH OF MISCANTHUS SPECIES

Miscanthus species is a native grass that occurs widely in Taiwan. This experiment was designed to determine the inhibitory effects of heavy metals on seed germination and seedling growth of eight populations Miscanthus spp.; M. floridulus seeds collected from random locations beside the highways in Taiwan, and from mountainous areas (1600-2600 m) were used. The seeds were germinated in petri dishes, moistened with different heavy metal ions in aqueous solutions, i.e., Pb++, Hg++, Cu++ and Cd++ at concentrations of 200, 400, 600, 800 and 1000 ppm. Seed germination percentages and the rate of germination of each species decreased with increased concentrations of heavy metal solutions; the time required to reach 50% of final germination was delayed from 3.8 days in distilled water to 7.0 days in some heavy metal solutions at 1000 ppm. The germination capacity of seeds followed a decreasing order of inhibition: Cd > Cu> Hg> Pb. The inhibitory degree of seed germination after immersing in heavy metal solution at 1000 ppm was as follows: Hg > Cd > Cu > Pb. Potassium ions leached from the seeds after immersing in mercury solutions was the highest. Inhibition of heavy metals to seedling growth of Miscanthus species was as follows: Cd > Cu > Hg > Pb with M. transmorrisonensis to be the most tolerant to heavy metals among the species tested. The germination and development of Miscanthus spp. that are tolerant to heavy metals concentrations indicate that these species may be suitable for planting along the roadsides in Taiwan.