Neutron-Radiography Technique for Studying Young Roots Growing in Soil

摘要

An indirect technique for taking neutron radiographs using indium collector foils has been used to study seed germination and root growth in soils. This paper describes the work done at Ames Laboratory Research Reactor, Ames, Iowa, in 1977-1978 to develop this technique for in situ studies to replace destructive sampling techniques. A diverging thermal neutron (.04 eV) beam of 10 exp 7 n/cm exp 2 /sec was used to irradiate samples for 8 to 10 min. to a total exposure of 5 x 10 exp 9 /n/cm exp 2 . Plants grown in loamy sand soil wetted to 9% volumetric water content in aluminum boxes of 2.5 and 5 cm thickness were photographed with this technique. An indium collector plate attached to the back of the box produced a transfer screen during exposure in the neutron beam which was subsequently placed in direct contact with photographic film to produce an image of the plant roots. The resulting indirect images were useful in measurements of root elongation, seed germination, compacted soil surface penetration, and rate of growth, with resolution of roots at about 0.3 mm size being obtained in low moisture soil conditions. Serial neutron radiographs of the same plant allowed sequential studies of root systems that had never been possible prior to development of this technique. (ERA citation 07:044679)