Flow environment affects nutrient transport in soft plant roots

Abstract

This work estimates Michaelis–Menten kinetics parameters for nutrient transport under varying flow rates in the soft roots of Indian mustard (Brassica juncea) using a plant fluidic device. To find the metallic components within the roots, inductively coupled plasma mass spectrometry (ICP-MS) analysis was performed. The flow rate-dependent metabolic changes were examined using Raman spectral analysis. In addition, three-dimensional numerical simulations were conducted to assess mechanical stresses resulting from the concentration difference that enhances osmotic pressure and flow loading at the root–liquid interface. Convection, the primary mode of nutrient transport in flowing media, was observed to reduce nutrient uptake at higher flow rates. In contrast, diffusion became more prevalent in areas where the complex root structure restricted the flow field. The concentration gradient between the upstream and downstream regions of the root caused nutrient diffusion from downstream to upstream. As seen, an increase in flow rate resulted in a decrease in root length due to the reduction of advantageous metabolites, which led to lower average mechanical stress and osmotic pressure loading. Additionally, osmotic pressure at the root–liquid interface was found to increase over time. Numerical simulations revealed that the average internal mechanical stress was substantially greater when osmotic pressure was considered. This emphasizes the importance of accounting for osmotic pressure when assessing mechanical stress in roots. This study uses a fluidic device that replicates hydroponic conditions for the first time in order to evaluate the convection-dependent Michaelis–Menten kinetics of nutrient uptake in plant roots.