Feasibility of a radicle of Brassica campestris L. as a bio-indicator of plant growth inhibitors

A computer-aided image analyzing system has enabled sensitive and real time measurement of the growth rate of a plant radicle to a precision of 0.1 mu m min(-1). Among several plant species measured with the present system, Brassica campestris L. was found the most useful one, because the time required for a seed to germinate was very short (within 1 day) and successive growth rate was in a proper range (5-20 mu m min(-1)). The growth rate of a radicle changed in response to physical and chemical factors in microenvironment around the radicle tip. A copper wire placed in front of the growing tip as a physical obstacle caused the increase in the growth rate. In contrast, another radicle caused the growth retardation. On the other hand, the growth was markedly inhibited by the following putative growth inhibitors: three examples of allelochemicals (gallic acid, p-cumaric acid, cinnamic acid) and an example of heavy metal ions (CuSO4). The growth inhibition by these compounds were quantitatively determined. Moreover dynamic response patterns of respective compounds were different, which suggested the difference of action mechanism. These results support the feasibility of a plant radicle as a bio-indicator applicable to the assessment of environment where foods and feeds are produced. (C) 1998 Elsevier Science B.V. All rights reserved.