STUDIES ON THE NUTRIENT-UPTAKE BY THE BEET CYST-NEMATODE HETERODERA-SCHACHTII BY IN-SITU MICROINJECTION OF FLUORESCENT-PROBES INTO THE FEEDING STRUCTURES IN ARABIDOPSIS-THALIANA

A method was developed, which enables substances to be injected into t he feeding structure (syncytium) established by Heterodera schachtii i n roots of Arabidopsis thaliana. The technique was used to study the u ptake of nutrients by the feeding nematode. The fluorescent dye lucife r yellow CH (LYCH) and fluorescence-labelled dextrans of different mol ecular weights were injected into the thin and translucent roots of A. thaliana. Such roots are a feature of this plant and they provide opt imal conditions for microinjection. Injected LYCH was taken up by feed ing juveniles and adults, indicated by the staining of the alimentary duct and the digestive system. Fluorescent dextrans of 3, 10 and 20 kD a but not of 40 and 70 kDa were ingested, suggesting that molecules of a maximum Stokes radius of 3.2 to 4.4 nm are taken up. It is likely t hat the feeding tube, forming the interface between the plant cytosol and the nematode's digestive system, is responsible for this size excl usion effect. The injected fluorescent substances were not detected in plant cells adjacent to the syncytium or in the root vascular element s. Injections into parts of roots which were infested by several nemat odes revealed that feeding H. schachtii individuals may share one sync ytium.