Effects of Physiological Integration and Fertilization on Heavy Metal Remediation in Soil by a Clonal Grass

In this paper, ramets of an annual clonal grass Digitaria sanguinalis were subjected to rhizome severing and heavy metal pollution to determine the effects of physiological integration on growth and heavy metal accumulation traits. The negative effect of pollution on survival of offspring ramets was modified by the presence of a stolon connection. Generally, pollution negatively affected growth of offspring ramets and integrated parents. Offspring ramets in polluted soils and connected parents had higher metal contents than those outside polluted soils. In offspring, pollution and rhizome severing reduced the translocation factor (TF) of copper but pollution increased TF of zinc. The results implied that strengthened resource supply with physiological integration was likely to alleviate heavy metal stress to a greater extent. Therefore, connected clones were induced to three levels of fertilization and four heavy metal pollution treatments, studying to what extent fertilization benefited plants. The application of fertilizer to the parents slightly increased the survival rate of connected offspring. The clones produced more biomass with increasing fertilizer intensity. Fertilization resulted in less biomass allocation to roots, but the specific effect of heavy metal led to more investment to root. Fertilization promoted heavy metal accumulation and positively affected TF through integration. The suggested appropriate utilization of fertilizer in connected clones could compensate for damage induced by heavy metal to the whole system. This method should be of great potential use for remediation of heavy metals in soils by clonal plants.