 The uptake of nutrient and water by the cluster roots peaks through winter and spring , but ceases when the upper layer of soil dries out in summer . The cluster roots are then allowed to die , but the laterals are protected from desiccation by a continuous supply of water from the sinker root . The water supplied to the laterals by the sinker root is continually lost to the soil ; thus this plant facilitates the movement of ground water from the water table into surface soil , a process known as hydraulic redistribution . Cluster roots have been estimated as comprising about 30 % of total root biomass in this species ; the seasonal production of so much biomass , only for it to be lost at the end of the growing season , represents a substantial investment by the plant , but one that is critical in the competition for nutrients . 
