Effect of cadmium on growth, photosynthesis, mineral nutrition and metal accumulation of an energy crop, king grass (Pennisetum americanum × P. purpureum)

An experiment was conducted to evaluate the effect of cadmium (Cd) on growth, photosynthesis, mineral nutrition and Cd accumulation of an energy crop, king grass (Pennisetum purpureum K. Schumach × P. thyphoideum Rich). Leaf shape was more sensitive to Cd than biomass and root length. Leaves had no visual toxic symptoms under 8-100 mg kg−1 Cd. High Cd pollution significantly increased the chlorophyll content of young leaves but showed no effect on mature leaves. Cd enhanced the maximum net photosynthetic rate (Amax), light compensation point (LCP) and light saturation point (LSP). For roots, Cd had a positive relationship with Zn, Mg and Ca. For stems, Cd had a positive relationship with Zn, Cu, Mg and Ca, while had a negative relationship with Mn. For leaves, Cd had a positive relationship with Zn, Mg and K, while had a negative relationship with Mn and Ca. Plant tissues accumulated 98, 21 and 26 mg kg−1 Cd in roots, stems and leaves, respectively, and extracted 477 and 515 μg Cd in roots and shoots for a single plant at 30 mg kg−1 Cd, respectively. King grass would require 23-290 years to remediate contaminated soil with 8-100 mg kg−1 Cd. It could extract 0.94-1.31 kg ha−1 Cd and produce 216-375 t ha−1 of fresh biomass and 28-79 t ha−1 of dry biomass each year. In summary, king grass had high biomass production and phytoremediation potential.