The Decline of Allelopathy in the Latter Nineteenth Century

More or less commensurate with the death of Augustin Pyramus de Candolle in 1841, there was a groundswell of overt opposition to the root excretion theory. The reasons for this were manifold. Renewed interest in plant nutrition, led by Justus von Liebig at Giessen in Germany caused a re-examination of many of the precepts of the functioning of the root, at both an anatomical and physiological level. De Candolle had supposed that roots passively absorbed all solutes, and that the root spongioles were the active organs in this function. Since the early parts of the eighteenth century, there had been controversy about the function of the root, particularly in consideration of its structure. Moldenhawer (1820) had uniquely suggested that root exudations were not excretory in function, but occurred to assist in the absorption of food substances. Murray (1822a, 1822b) claimed that the structure of the root was not well suited to the absorption process, but was better suited for excretion.