Chromium VI Induced Structural and Ultrastructural Changes in Bush Bean Plants (Phaseolus vulgaris L.)

The effect of a growth reducing chromium VI concentration (9.6 x 10−5M Cr as Na2CrO4) on the structure and ultrastructure of different organs of bush bean plants (Phaseolus vulgaris L.) grown on perlite was studied using light, transmission electron and scanning electron microscopy. The structural and ultrastructural alterations observed were quite different in the various organs analysed and did not always stay in direct relation to the average Cr content of the whole organ. The primary toxicity effect seemed to be membrane damage, due to the high oxidation power of Cr VI. It is suggested that chromium is retained in vacuoles and cell walls of roots, and that the chromium reaching the leaves may be principally Cr III and present in cell walls. The alterations observed in the upper plant parts seemed principally due to indirect Cr effects on the content of essential mineral nutrients.