The Effects of Mechanical Stress on the Growth of Roots

The ability of maize roots to overcome a mechanical resistance was examined using an apparatus which enabled the length of the roots to be measured as they grew. In one experiment the apex of the root was compressed in a way that permitted the cells to elongate and differentiate while subject to stress. Growth in length proceeded without interruption, although at a reduced and con tinuously declining rate. In another experiment lengths of root which had differentiated before the load was applied were compressed. Growth in length stopped for a number of hours and then resumed at a low rate. The results are compared and contrasted with those obtained in the classical experiments of Pfeffer.