Ammannia senegalensis

Ammannia senegalensis, also known as copper leaf ammania, is a flowering plant native to western Senegal. It often grows as a weed in rice paddies. The stem presents opposite leaves that start out green and rather broad and, later, become more narrow and reddish in colour. The leaves especially become red under intense light. There are several varieties, of unknown status, that differ in leaf shape and colour. The flowers are inconspicuous, growing from the leaf axils of emersed plants....read more on Wikipedia.