Rice Root Physiological and Morphological Traits of Diverse Genotypes Grown in Different Media.

Rice (Oryza sativa L.) is currently grown in 200 countries and supports one-half of the human population. It is a staple food and the chief source of nutrition in developing countries of South America, Asia and Africa. Roots influence mineral uptake and may influence rice grain mineral composition and, in turn, roots may be influenced by the growing medium. The objective of this study was to compare differences in root traits of 24 diverse genotypes grown in different media. The 24 genotypes were selected for this study based on their extreme grain mineral composition exhibited in a prior field study.   Six replications of the genotypes were grown in aerated hydroponics and four replications were grown in sand culture medium in a growth chamber to the same developmental stage of Lemont, a standard US variety. At harvest, roots were thoroughly washed and digitally imaged by scanning so that root morphological traits could be quantified using WinRhizo Pro software (Regent Instruments, Canada). Root respiration was spectrophotometrically measured by treating roots with naphthylamine and quantifying naphthylamine oxidation. Genetic effects were larger than media effects upon many of the root traits (fresh/dry weights, length, volume, area/surface area, and root respiration) and shoot traits (plant height, number of leaves, area, photosynthesis, tillers, and fresh/dry weights), thus indicating the value of using multiple growth media as part of a study examining root traits influencing other plant traits such as mineral uptake and grain composition.