NMR imaging for measuring root system and soil water content.

Abstract

Short communicationEnviron. Control in Biol. 23(4), 99-102, 1985NMR Imaging for Measuring Root Systemand Soil Water ContentKenjl OMASA, Mono ONOE* and Hlroakl YAMADA*Division of Engineering, The National Institute for Environmental Studies,Yatabe, Ibaraki 305, Japan*Institute of Industrial Science , University of Tokyo,Roppongi, Tokyo 106, Japan (Received December 21, 1985)An attempt was made using a nuclear magnetic resonance (NMR) computed tomography (CT) system to measure spatial distributions of soil water and main roots of broad bean and Japanese radish plants growing in the soil without destroying the plants and the soil environment.Computed tomography (CT) is a technique to reconstruct from a set of pro-jection data a cross-sectional distribution of some physical property of a test ob-ject without destroying it. This technique has been widely utilized in medicine and industry since the first development of a commercial X-ray CT scanner by Hounsfield.1) Recently, the X-ray CT scanner was applied to detect rots and an-nual rings in a living tree.2)Nuclear magnetic resonance (NMR) CT is the newest technique in the medi-cal CT family.3-5) It yields not only morphological information but also such physiological information as metabolic process and mass transfer. Especially, the distribution of proton, which is abundant in water, in any section is easily pro-vided by the NMR CT.4, 5)In order to study the growth of seedling and root system it is necessary to measure them without destroying the plant itself and the soil environment. Rhizotrons are the most elaborate installation devised for the direct, sustained observation and measurement of roots growing in soil.6) However, rhizotrons permit observation only through transparent walls or windows abutting on the soil. Gordon et al.7) recently observed a sunflower seedling growing in a rectan-gular cuvette containing 1% agar using a TV camera system. However, this system cannot directly observe seedling and root growing in soil.The growth of seedling and root system is greatly influenced by the soil environment.a' The soil moisture is a major factor affecting the growth. The common methods for measuring soil water content are neutron probes and capaci-tance meters. Electrical resistance blocks and tensiometers can also be used to estimate soil water content as well as matric potential.e' However, these devices affect the growth of root system and cannot measure spatial distribution of water in soil abutting on the spreading roots.We, therefore, examined NMR imaging for measuring water content of soil and root systems growing in a pot. Broad bean (Vicia fava L. cv. Otafuku) and Japanese radish (Raphanus sativus L. cv. Minowase) plants were used. BroadVol.23,No.4(1985)(33) 99