EXUDATION OF 14C‐LABELLED COMPOUNDS FROM WHEAT ROOTS: INFLUENCE OF NUTRIENTS, MICRO‐ORGANISMS AND ADDED ORGANIC COMPOUNDS

Abstract

SUMMARYWhen tops of 6‐day wheat seedlings grown in nutrient solution, sterile or inoculated with soil, received 14CO2, it was found that the radioactivity of the solution measured after 24 and 48 hours was reduced by the presence of micro‐organisms. Omission of phosphate from the sterile growth medium reduced the radioactivity of the root solution to 47% of the control. The addition of acetate buffer at pH 5 greatly increased exudation whereas the adjustment to a similar pH with H2SO4 or universal buffer or the addition of sodium acetate at pH 7 significantly reduced exudation.These results demonstrate that exudation of organic compounds from roots can be affected by the addition of substrates and butters used in root enzyme studies. From these results, it appears that some organic compounds in soil could influence the loss of carbon compounds from roots growing under natural conditions.