Inductively coupled plasma optical emission spectrometry (ICP-OES)
ICP-OES (Perkin Elmer Optima 5300 DV) was conducted to evaluate metal ion content, as described previously (Lahner et al., 2003; Lin et al., 2009; Yang, Perry, Ciani, Pandian, & Schmidt, 2008). Two-week-old seedlings were removed from 1/2 MS medium and incubated with an additional 100 μM MnCl2 for 24 h with agitation. Aerial parts (shoots) and roots tissues were dried at 60°C for 3 d and an amount of 0.1 g sample was analyzed by ICP-OES. Spinach and tomato leaves (SRM-1570a and SRM-1573a; US National Institute of Standards and Technology) were the standard references.