Introducing short roots in a desert perennial: anatomy and spatiotemporal foraging responses to increased precipitation.

• The desert flora possesses diverse root architectures that result in fast growth in response to precipitation. We introduce the short root, a previously undescribed second-order root in the aridland chamaephyte Cryptantha flava, and explore fine root production. • We describe the short root anatomy and associated fine roots, correlate standing fine root crop with soil moisture, and explore the architectural level - the short root, third-order lateral roots, or the whole root system - at which fine roots are induced by watering and the amount of water required. • We show that short roots are borne at intervals on lateral roots and produce fine roots at their tips; new fine roots are white and have root hairs, while brown and black fine roots are apparently dead; and fine root production is triggered at the level of lateral roots and with relatively low precipitation (≤ 2 cm). • Short roots are suberized and thus are probably not capable of water uptake themselves, but serve as initiation sites for fine roots that grow rapidly in response to rainfall. Thus, C. flava should be a beneficiary of projected precipitation increases in habitats where rainfall is pulsed.