TRANSFER OF NITROGEN FROM DAMAGED ROOTS OF WHITE CLOVER (TRIFOLIUM-REPENS L) TO CLOSELY ASSOCIATED ROOTS OF INTACT PERENNIAL RYEGRASS (LOLIUM-PERENNE L)

An experiment is described in which the magnitude of N transferred from damaged white clover roots to perennial ryegrass was determined, using N-15 labelling of the grass plant. There was no effect on the growth and N-fixation of the clover plants after removing part of the root system. The N-15 data suggested that N had been acquired by all grass plants, even in plants grown alone with no further N supplied after labelling. However, after quantifying the mobile and stored N pools of the grass plants it was evident that significant transfer of N from clover to grass only took place from damaged clover roots. Dilution of the atom% N-15 in the roots of the grass plants grown alone, and in association with undamaged clover roots, was explained by remobilisation of N within the plant.