FIRST RIMAPS DESCRIPTION OF PATTERNS OF ROOT DEVELOPMENT DISPLAYED IN HYDROPONICS Eduardo A. Favret,* , y Ne ´stor O. Fuentes, y , z Alicia E. Martı ´nez, 1, § and Alberto R. Prina§ *Instituto de Suelos, Centro de Investigacio ´n de Recursos Naturales, Instituto Nacional de Tecnologı ´a Agropecuaria, CC25, B1712WAA Castelar, Buenos Aires, Argentina; y Instituto de Tecnologı ´a ‘‘Prof. J. Sa ´bato,’’ Universidad Nacional de General San Martı ´n–Comisio ´n Nacional de Energı ´a Ato ´mica, Avenida General Paz 1499, B1650KNA San Martı ´n, Buenos Aires, Argentina; zComisio ´n Nacional de Energı ´a Ato ´ mica, Centro Ato ´ mico Constituyentes, Avenida General Paz 1499, B1650KNA San Martı ´n, Buenos Aires, Argentina; and §Instituto de Gene ´tica ‘‘Ewald A. Favret,’’ Centro de Investigacio ´n de Ciencias Veterinarias y Agrono ´ micas, Instituto Nacional de Tecnologı ´a Agropecuaria, CC25, B1712WAA Castelar, Buenos Aires, Argentina Rotated Image with Maximum Average Power Spectrum (RIMAPS) is a new image characterization tech- nique that was recently described as a valuable tool for the analysis and characterization of technical and biological surfaces. The objective of this work was to ascertain whether RIMAPS may be used to obtain a quantitative description of patterns of development displayed by roots in hydroponics. Visual observations on roots of wild-type barley (Hordeum vulgare L.) grown in hydroponics by the sandwich method showed, before their submergence, an erratic growth with windings and turnings, which after several days created a tangle of roots above the water surface. This intricate morphology is difficult to study without disturbing the root development. Hence, RIMAPS is introduced as an original method for the quantitative description of root axes distribution in a nondestructive way. Accordingly, patterns of root development were recorded by a digital camera. The Gaussian fitting of RIMAPS spectra resultant from digital images of roots were used to analyze, quantify, and compare differences in the pattern of root development observed between the wild type and a barley root mutant. Additionally, a parameter G was introduced that is obtained from the Gaussian curve and quantifies differences in angles displayed by root axes during their development with regard to the axial direction. Keywords: barley (Hordeum vulgare), image analysis, patterns of root development, RIMAPS technique, root morphology. Introduction Root systems are typically formed from numerous ramified axes changing morphologically and physiologically in the course of a dynamic interaction with physical, chemical, and biological factors of the soil, which fluctuate as well in time and space. This intricate morphology is very difficult to ob- serve, quantify, and interpret in a nondestructive way. Nu- merous studies on roots have focused on their morphology and topology (Hackett and Rose 1972; Fitter 1982), and sev- eral methods have been used to estimate the total length of roots (Rowse and Phillips 1974; Richards et al. 1979; Zoon and Van Tienderen 1990). Most widely employed methods are based on the principle of line intersect, which was devised by Newman (1966) and later modified (Marsh 1971; Tennant 1975). A number of other authors have proposed a consider- able number of different models for the analysis and descrip- tion of the complex architecture of plant roots (Schiefelbein and Benfey 1991; Lynch 1995; Bauhus and Messier 1999; Costa et al. 2002). Nevertheless, there is still a need for suitable tools that allow the quantification of diverse characteristics of root morphology and the comparison of different root systems. A new image characterization technique was recently de- scribed as a valuable tool for the analysis of technical and bi- ological surfaces. (Fuentes and Favret 2002a, 2002b; Favret and Fuentes 2003a, 2003b, 2004; Favret et al. 2003, 2004, 2006). This technique was identified as Rotated Image with Maximum Average Power Spectrum (RIMAPS). Its applica- tion is independent of the condition in which the surface im- age is captured, provided that it is constant. The objective of this work was to ascertain whether the tech- nique of RIMAPS may be used for obtaining a quantitative de- scription of the patterns of root development. We aimed to introduce an original method for the study of root morphology on the assumption that it will allow a quantitative characteriza- tion of root behavior in diverse conditions of hydroponics, such as after receiving treatment with growth regulators, mutagens, and/or herbicides. Material and Methods RIMAPS Technique The RIMAPS technique consists of rotating the image by using available algorithms of commercial software and of computing for each variable one space-variable integral of the two-dimensional Fourier transform for each value of the 1 Author for correspondence; e-mail: amartinez@cnia.inta.gov.ar. Manuscript received November 2006; revised manuscript received August 2007. 331 Int. J. Plant Sci. 169(3):331–338. 2008. Ó 2008 by The University of Chicago. All rights reserved. 1058-5893/2008/16903-0001$15.00 DOI: 10.1086/526459