FIGURE 2.

RSA is defined as the spatial configuration of root components and determines the soil volume that can be explored by the roots. Dicot roots consist of a main root and several orders of lateral roots. Monocot roots contain in addition seminal roots and shoot-borne roots. Each plant species has genetically defined limits to its RSA. Within these limits, the RSA is plastic and external (abiotic stress) factors modulate the length, number, positioning and angle of root components. The RSA plasticity varies strongly among and within plant species. This figure illustrates the modulations in RSA for a typical dicot root system.