Serpentine and its vegetation: A preliminary study from Sri Lanka

This study explored the soils and vegetation of four of the five known ultramafic sites in Sri Lanka. Soil chemical and physical features were typical of ultramafic substrates. A preliminary taxonomic survey identified 45 species of angiosperms, none of which is endemic to the island or restricted to ultramafic soils. However, populations of several taxa may represent distinct races or ecotypes specific to the substrate. A thorough taxonomic survey of specimens from on and off this substrate may expose features unique to these ultramafic populations. Plant tissue concentrations of various elements were typical of species,,rowing on ultramafic substrates. Evolvulus alsinoides (Convolvulaceae), Hybanthus enneaspermus (Violaceae), and Crotalaria biflora (Fabaceae) were shown to hyperaccumulate nickel (>1000 mug/g dry tissue). An unusual finding was the discovery of five hyperaccumulators of copper: Geniosporum tenuiflorum (Lamiaceae), Clerodendrum infortunatum (Verbenaceae), Croton bonplandianus (Euphorbiaceae), Waltheria indica (Sterculiaceae), and Tephrosia villosa (Fabaceae). Copper hyperaccumulation (>1000 mug/g dry tissue) in ultramafic substrates is a little known phenomenon and requires further study. Calotropis gigantea (Asclepiadaceae) accumulated sodium to levels often seen in halophytic plants. Sodium accumulation in plants growing on ultramafic substrates is also a rare phenomenon.