Impact of insect root herbivory on the growth and nitrogen and carbon contents of white clover (Trifolium repens) seedlings

The impact of root herbivory by larvae of the weevil Sitona flavescens (Marsh.) on the growth and carbon and nitrogen economies of seedlings of white clover (Trifolium repens L.) and the nature and extent of nitrogenous compounds found in the root exudates taken from the rhizosphere were investigated. The seedlings were grown in sand culture in a system of microlysimeters that enabled sequential sampling of root exudates. Weevil infestation significantly reduced foliar biomass and total N and C contents and impaired N-fixation. The C:N ratios of the infested plants were significantly increased compared with those of uninfested seedlings. The most abundant amino acids in the exudates were aspartic acid and serine. Keywords: nitrogen fixation, Sitona spp., root exudates, white clover.