Thallium Toxicity in Bean

Abstract

AbstractHydroponic, rhizotron, and field studies were conducted to determine the effect of Tl on the biomass and nutrient concentrations in roots and leaves of bean plants. Loamy sand soils in the field and rhizotron cells were treated with Tl, Cd, Cr, Ni, and V. Bush beans (Phaseolus vulgaris L.) were planted in both studies. The hydroponic study consisted of growing soybean [Glycine max (L.) Merr.] in Hoagland's solution treated with Tl. All three studies showed that Tl accumulated in the roots and not in aerial portions of the plant. In the hydroponic study, micromolar concentrations of Tl added to the nutrient solution drastically altered the concentration of certain nutrients in soybean tissues and significantly reduced plant biomass. Thallium‐treated plants had fewer nodes than the normal ones. In addition, Tl caused the roots to become severely stunted with few lateral branches. The lower, more mature leaves of the treated plants exhibited chlorosis in spite of Fe concentrations comparable to the control plants. Based on tissue analyses, there was a concomitant increase in K concentrations in high Tl treatments, whereas Ca and Mg concentrations in leaves decreased below critical levels for normal growth. In addition, diagnosis and recommendation integrated system (DRIS) indicated that Ca was relatively more deficient than Mg; DRIS also identified Mn as being deficient.