Generally speaking, the plant organ responsible for nutrient uptake is the plant root. (Are there exceptions?) The nutrients must be dissolved in water to be taken up, whether in soil or soilless systems. For nutrient uptake to occur, nutrients must arrive at the root surface, be taken up into the root, and then transported to the plant organs where they are needed. Therefore, healthy and active roots are a prerequisite for uptake, as are transport processes to the root surface, into the root cortex, and within the plant.