Root growth is particularly affected by

Root growth is particularly affected by the availability of Phosphorus. It helps in encouraging plants to put down a dense collection of new roots and strengthen roots as they develop.
The root is the most important plant part, it serves as the base of any plant, provides anchorage to the plant, along with the absorption of nutrients and water and conduction of these to the stem, also storage of reserve foods. Thus if roots are strong plants can sustain any harsh effects.