A critical reappraisal of Phytolacca acinosa Roxb. (Phytolaccaceae) – A manganese-hyperaccumulating plant

Phytolacca acinosa Roxb. (Phytolaccaceae) was reported in 2004 to be a manganese-hyperaccumulating plant. Phytolacca americana L., growing at the same site was then independently reported in 2007 to have the same property. An apparent confusion in the taxonomy of the genus Phytolacca and interest in the Mn hyperaccumulative trait reported in P. acinosa has led to an extended field sampling, glasshouse cultivation and comparison with herbarium materials of P. americana s.l. Our specific aim was to identify and name the Mn hyperaccumulator plant correctly. P. acinosa is closely related to P. americana but it differs from the former in having an erect infructescence with usually eight distinct carpels, while from the latter has a nutant infructescence usually with 10 concrescent carpels. Our study indicated that the Mn hyperaccumulator plant P. acinosa which we first reported from the Xiangtan Mn tailings wasteland must now be reduced to P. americana as a synonym in order to prevent further confusion in identity and nomenclatural redundancy.