ABSTRACT
The trace element (TEs) metabolism of plants has been extensively studied and the basic information on many topics is available in monographs on plant physiology or plant nutrition. The metabolic fate and role of each TE in plants can be characterized in relation to some basic processes such as:
Uptake (absorption), and transport within a plant• Enzymatic processes• Concentrations and forms of occurrence• De ciency and toxicity• Ion competition and interaction•
TE concentrations in plants are highly associated with the chemical composition of growth media. Plant responses to TEs in soils depend on several factors, however some general trends, expressed by plant/soil Transfer Factor (TF) can be presented as generalized values:
10: Cd• 1: B, Br, Cs, Rb• 10• −1: Ag, Co, Cu, Ge, Hg, Mo, Pb, Sr, Te, Zn 10• −2: Be, As, Li, F, I, Mn, Ni, Sb 10• −3: Ba, Bi, Ga, Fe, Se, V, Tl, Zr
The reaction of plants to chemical stresses that are caused by both de ciencies and excesses of TE cannot be de ned exactly because plants have developed during their evolution and course of life (ontogeny and phylogeny) several biochemical mechanisms that have resulted in adaptation to and tolerance of new or chemically imbalanced environments. Therefore, this always should be investigated for a particular soil-plant system. Plants reveal various tendencies in the uptake of TEs. Three general uptake characteristics can be distinguished: accumulation, indication, and exclusion. To a large extent, this depends on the speci c ability of plants and huge differences in metal uptake between plant species. Also, between genotypes of a species, great variability has been demonstrated in many studies. Alexander et al. (2006) described general genotypic variations comparing tendency to the TE accumulation by vegetables: (1) legumes-low, (2) root vegetables-moderate, and (3) leafy vegetables-high. Also Peris et al. (2007) reported that signi cantly higher TE content (with an exception of Zn) was in lettuce than in artichoke.
