Effect of Planting Density on Marigold (Tagetes erecta L.) Biomass and Cadmium and Lead Accumulation

• Jinbo SUN, 
• Dong YAO, 
• Hongyan ZHAO, 
• Xi MEI, 
• Qilin CAI, 
• Fangdong ZHAN, 
• Tianguo LI, 
• Yuan LI