Sites of Exudation Of¹⁴c‐labelled Compounds From Wheat Roots

S ummary The combination of autoradiography and a filter paper ‘sandwich’technique using wheat plants labelled with 14 C has shown that roots of wheat exude two types of compounds, viz. (a) non‐diffusible material released from the apices of both primary and lateral roots and (b) diffusible material released along the whole length of the roots. The high amount of non‐diffusible material compared with diffusible material suggests that the former may be more significant than previously anticipated in relation to root functions and microorganisms in the rhizosphere.