Boron accumulation in Puccinellia frigida, an extremely tolerant and promising species for boron phytoremediation

Abstract

Excessive concentrations of boron in soils and water are common problems in arid and semiarid regions, reducing both crop yields and the variety of species that can be cultivated. Current boron-removal technologies are either expensive or impractical for arid regions; hence, the use of boron-tolerant plants for phytoremediation of soils and water has gained much attention. Northern Chile is characterized by its arid climate and the Lluta River is an important water resource within the region, but it presents high boron concentrations that limit local agricultural activities. Hydrothermal springs located in the Colpitas River sub-basin are one of the Lluta River’s main sources of boron. A native plant species—Puccinellia frigida—spontaneously colonizes the banks of these hydrothermal springs. To evaluate its phytoremediation potential, we analyzed several plant, soil, and water samples taken along a hydrothermal stream. This article presents and discusses the characteristics of the study site soil and water, molecular identification of P. frigida, and boron distribution within the plant’s tissue. We found that the hydrothermal springs where this species grow are highly toxic to plants (As > 5 mg/L, B > 400 mg/L, EC > 20 mS/cm). We also found that P. frigida is tolerant to extremely high levels of available boron in soil (> 4000 mg/kg) and shoots (> 4900 mg/kg DW). In addition, the boron plant accumulation coefficient (PAC) and translocation factors (TF) were > 1 in most samples (PAC: 0.9 – 2.8 and TF: 1.1 – 3.6); hence, P. frigida acts as a boron accumulator within the study site. Thus, it is established that P. frigida is one of the most boron-tolerant species known and that it has potential for boron phytoextraction purposes or pollution phytomanagement strategies.