The role of different root orders in nutrient uptake

The root system is essential for plant water and nutrient uptake, however, the functions and roles of different root orders are unclear. We investigated the anatomical and physiological differences among different root orders. Tomato plants were grown in either polyethylene bags or a hydroponic system. Mineral uptake, protein profiles, respiration rates, and anatomical profiles of the different root orders were measured. First-order roots absorbed significantly more nutrients than the other root orders. The concentrations of elements surrounding the third-order roots remained constant throughout the experiment. Respiration rates were found to be higher in the first- and second-order roots than in the third-order roots. Analysis of anatomical cross-sections demonstrated different structures in the different root orders. Protein profile analysis presented differences in different root orders, these proteins included element transporters and those related to protein translocation in the cell. Moreover, specific proteins related to mineral absorption were found at higher levels in the first- and second-order roots than in the third-order roots. Our results demonstrate, that different root orders vary in their nutrient uptake and translocation and that distal root orders play a key role in the uptake and translocation of minerals.