Abstract
A Cd-tolerant plant species named Boehmeria nivea (L.) Gaudich (ramie) was applied to study its Cd accumulation and translocation mechanisms with the addition of ethylene diamine tetracetic acid (EDTA) or nitrilotriacetic acid (NTA). A pot experiment was designed to systematically investigate the Cd accumulation and subcellular compartmentation in different ramie tissues as well as soil Cd solubility and its physiological response. Results showed that soil EDTA-and NTA-extractable Cd concentrations were remarkably higher than the control, and Cd content in each tissue with Cd translocation factor (TF) after EDTA and NTA addition were significantly increased with elevated chelant concentration. In spite of the decreased cytoderm Cd contents in different tissues, extracellular and intracellular Cd content were increased dramatically under chelant treatment, particularly in ramie leaves with EDTA addition from 2 mmol kg(-1) to 10 mmol kg(-1) (increased by 98% for extracellular Cd and by 29% for intracellular Cd, respectively). Furthermore, the addition of chelant also resulted in an apparent increase of malondialdehyde (MDA) content and decrease of chlorophyll level in ramie leaves. These results revealed that EDTA and NTA could enhance Cd phytoavailability in soil, facilitate apoplastic and symplastic transport of Cd from root to the aboveground tissues and improve leaf Cd accumulation, which may because of the extracellular loading among spongy tissues and intracellular sequestration in mesophyll vacuoles. This study contributes to the control of Cd accumulation by plants.