Hi, I think you can ahve a look on some papers which are dealing with this tpic. However i would suggest to measure growth rate during this time comparable to control plants. freash waite, dry weit, the hight of the plants. How many leaves they produced and level of chlorosis...
Your question was very broad Zeinab, however I suggest you do some indepth but general reading around the subject. This journal article is a great place to start as it looks specifically at heavy metals in remediation: http://www.asian-energy-journal.info/Abstract/A%20review%20on%20phytoremediation%20of%20heavy%20metals%20and%20utilisation%20of%20it%20s%20by%20products.pdf