Fragmented cambia in roots of Coleogyne ramosissima

Abstract

Axis splits are common for desert shrub species. Coleogyne ramosissima, a regionally important shrub species, grows along a transect from the cooler high deserts of Utah and Colorado to the warmer Mojave Desert, between 1200 and 1700 m elevation. The purpose of this study is to document tissue anomalies from transition zones to individual roots of C. ramosissima. Plants were obtained from La Verkin and Ivins, Utah. During secondary growth, axis splits, lobes and fragmented cambia occurred in roots larger than 12 mm in diameter. Lobes occurred in all root samples. The presence of lobes indicates that cambia in roots of in C. ramosissima were fragile. Axis splits and lobes are created fragmented cambia that separated from the original vascular cambium. These fragmented cambia produced growth centers that gave rise to new xylem cells, lead to further lobes and the origination independent roots. The current study hypothesizes that the production of the large number of roots derived from fragmented cambia. The large number of roots provided near the transition zone may provide for hydraulic reductancy to guard against plant death due to cavitations to individual roots caused by moisture deprivations. Overall, roots of C. ramosissima have many secondary xylem irregularities. The overall impact of these root irregularities are unknown, despite the fact that individual plants can live for many decades. To our knowledge, this is first study to document the process for the development of fragmented cambia in tandem with axis splitting and eccentric growth of roots in a shrub species.