Abstract
Plant roots function in the critical role of water and nutrient uptake. Although extensive data exist on functioning of seedling roots, little is known of the actual functionality of the fine roots of mature plants. Although this class of root represents 90% or more of the total root length of a given mature plant, their small size has inhibited detailed studies. Commonly, the critical metrics for studies of root function are root length and total weight, expressed as Specific Root Length. The metric that classifies “fine roots,” root diameter, is rarely a focus except as average diameter, even though this is the primary characteristic from which accurate estimates of surface area and volume can be calculated. Using data from several preliminary experiments, this study shows consistent changes in measured fine root diameter with changes in concentration of some nutrients. Twelve different species demonstrated concentration dependent diameter increases, or decreases, in response to increasing concentrations of nitrate, phosphorus, aluminum or tannic acid. On the other hand, Cacao (Theobroma cacao L) fine roots changed diameter in response to changes in nitrate concentration, but not ammonium. Clearly pattern of diameter change in response to nutrient concentration is dependent on nutrient, species and their interaction. It is suggested that the routine assessment of fine root diameter will be essential to understanding nutrient uptake dynamics.
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Acknowledgements
The authors wish to thank Shaun Faulkner and Pamela Brozowski for growing and sampling the roots of Cacao and the legumes and Ms. Billie Sweeney for cultivating the wheat plants and scanning the roots. And, of course, Alain Pierret whose comments have proven very helpful.
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Zobel, R.W., Kinraide, T.B. & Baligar, V.C. Fine root diameters can change in response to changes in nutrient concentrations. Plant Soil 297, 243–254 (2007). https://doi.org/10.1007/s11104-007-9341-2
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DOI: https://doi.org/10.1007/s11104-007-9341-2