20033
The concentrations of Zn , Fe , Cu , Cr , Ni , Cd and Pb in roots were higher than in shoots , suggesting that roots are the primary accumulation organs for these metals and there exists an exclusion strategy for metal tolerance .
 Chemical: Zn; Chemical: Fe; Chemical: Cu; Chemical: Cr; Chemical: Ni; Chemical: Cd; Chemical: Pb
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: Zn; Chemical: Fe; Chemical: Cu; Chemical: Cr; Chemical: Ni; Chemical: Cd; Chemical: Pb