The Effect of Cadmium on Nodulation and N2(C2H2)-Fixation by Dry Beans (Phaseolus vulgaris L.)1
- G. T. Vigue,
- I. L. Pepper and
- D. F. Bezdicek2
Experiments were conducted to determine the toxicity of Cd on the nodulation, N2(C2H2)-fixation, and growth of dry beans. Plants were grown in the greenhouse with hydroponic solutions to which 0–500 µm Cd/liter had been added. The total N content of shoots, nodule weight, nodule number, and N2(C2H2)-fixation were significantly decreased at 10 µm Cd/liter. Nodulation was completely inhibited at 500 µm Cd/liter. Nodulation and the N2(C2H2)-fixation rate were negatively correlated with solution Cd concentration (r = −0.97).
Cadmium uptake and translocation were slow; therefore, Cd levels were highest in the roots, much lower in the nodules, and lowest in the shoot tissue. For example, at 20 µm Cd/liter, respective tissue Cd levels averaged 431, 80, and 35 µg Cd/g, on a dry weight basis. Cadmium levels in roots or shoots from comparable Cd treatments were essentially the same whether the plants obtained their N by fixation or from nutrient solution NO3.
Root Cd concentrations were exponentially correlated with nodule number, nodule weight, and acetylene reduction, with correlation coefficients of −0.99, −0.99, and −0.97, respectively. Shoot Cd concentrations were logarithmically correlated with nodule number, nodule weight, and acetylene reduction, with correlation coefficients of −0.89, −0.91, and −0.84, respectively.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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