Behavior of herbaceous species in soil mixes with different degree of contamination with heavy metal

In a study developed under greenhouse conditions using soil mixes with different degrees of contamination with heavy metal the behavior of herbaceous species in relation to the excess of Cd and Zn in the soil was evaluated. Gradient of soil contamination was established through soil mixes of heavy metal contaminated with uncontaminated soils at different proportions. Seeds of different species and origins were sowed in 250 mL plastic tubes and plants allowed to grow for 90 days when they were harvested and assessed. It was found a similar behavior for most species that exhibited growth depressions due to increasing soil contamination. At soil mix with 15% of contamination soil plants showed high concentration of Cd and Zn. In contrast to those species Pffafia sp. exhibited high tolerance to contamination, growing quite abundantly in soil mix with 90 and 1,450 mg kg(-1) of Cd and Zn, respectively. Moreover, this species showed Cd concentration higher than 100 mg kg(-1), being considered Cd hiperacumulator. Sida glaziovii, Bidens pilosa, Rhynchelytrum repens, Cenchrus echinatus and Nicandra physaloides were severely affected by the contaminants. While the species Trifolium repens, Euchlaena mexicana, Cynodon dactylon, Avena strigosa, Cenchrus ciliares and Cyperus sp. presented adequate growth. These species are promising for further studies on rehabilitation of heavy metal degraded land.