Like other plant organs, roots have a life history in which they pass from birth to death. e size and population structure of the root system is determined by the birth rate and death rate of the individual roots. e study of root population dynamics is of interest to many disciplines, including crop science, physiology, ecology, and soil science. For example, a better understanding of root lifespan could enable agronomists and horticulturalists to increase yields while reducing agrochemical inputs. Severe root losses, such as those caused by drought or pathogens, clearly are not conducive to crop production. Growing too many roots, however, may also be undesirable, since large amounts of carbohydrates and mineral nutrients are needed for root growth and maintenance that otherwise might be allocated to photosynthetic organs or harvested parts. An optimization approach suggests that, other things being equal, total plant growth should be greatest when a root system maximizes water and nutrient acquisition per unit resource supplied from the shoot (e.g., ornley 1998). If roots are produced in the most favorable soil patches and shed when they are no longer ecient in water and nutrient absorption, then production, theoretically, should be maximized.