Early pine root anatomy and primary and lateral root formation are affected by container size: implications in dry-summer climates

Although the presence of root anatomical structures of young Pinus ponderosa seedlings grown in containers of contrasting volume (164 vs. 7000 cm3) was similar, seedlings reared 60 days in the large container had more vascular cambium although the xylem thickness was similar. In addition, seedlings in large containers had nearly twice as many resin ducts within the vascular cambium as their cohorts in small containers. Taproot length closely matched container depth. Though lateral root emission rates were similar between container sizes, large container seedlings had more than 2X the number of lateral roots as those from small containers. These differences in morphophysiological characteristics may be important to seedling establishment on sites that experience dry summer conditions, or for seedlings destined to drier, harsher sites. Further work to elucidate the ramifications of these morphophysiological differences on seedling establishment is warranted.