Zinc effects on cadmium uptake in 3 cereals using chelator-buffered nutrient solutions

• Main Author: Green, Carrie Elizabeth
• Format: Dissertation
• Language: English
• Subjects: agriculture, agronomy; agriculture, plant culture; agriculture, soil science; environmental sciences
• ISBN: 0599071125; 9780599071124

Concern persists over the presence of Cd in food grains due to the potential for human health effects. Cadmium concentration in cereals is influenced by the presence of soil solution Zn. The use of chelator-buffered nutrient solutions allows study of very well controlled Zn$\sp{2+}$ and Cd$\sp{2+}$ activities to characterize the Cd-Zn interaction. The first series of experiments studied Cd uptake and translocation in rice, hard red spring wheat (HRSW), and durum wheat under two sets of conditions: (1) adequate to potentially phytotoxic Zn$\sp{2+}$ activities when pCd$\sp{2+}$ was held constant and (2) normal to high Cd$\sp{2+}$ activities when pZn$\sp{2+}$ is held constant. While rice dry matter accumulation was significantly reduced by high levels of solution Zn$\sp{2+},$ the dry matter accumulation of the two wheats was not significantly effected. The effectiveness of increasing the Zn activity in the nutrient solution in reducing Cd uptake varied among plant species; with the order of Cd accumulation in total shoots being durum wheat $>$ HRSW $>$ rice. The concentration of Cd in plant tissues was always root $>$ shoot $>$ young leaves. Until potentially toxic levels of Cd were introduced into solution, as Cd$\sp{2+}$ activities were increased, the presence of adequate Zn suppressed Cd uptake. At potentially phytotoxic pCd$\sp{2+},$ normal levels of Zn did not suppress Cd uptake. The second series of experiments looked at the effect of deficient to adequate Zn$\sp{2+}$ activities on Cd accumulation in HRSW and durum wheat; and the effect of Cl on the redistribution of Cd in durum wheat. With decreasing pZn$\sp{2+},$ both wheats had reduced dry matter accumulation, an increase in Cd accumulation, and reduced Zn concentrations in plant tissue. Shoot Zn concentration clearly indicated Zn deficiency was achieved in the low pZn$\sp{2+}$ treatments. When grown in Zn deficient conditions, Cd accumulation in total shoots was substantially increased, but added Zn$\sp{2+}$ strongly reduced Cd$\sp{2+}$ uptake. Cadmium uptake is inhibited to a greater extent in HRSW than durum wheat. In durum wheat, after the supply of Cd to the roots was discontinued, added Cl$\sp{-}$ caused little change in the pattern of Cd redistribution within the root and shoot of durum wheat.