Effect of Propagation Tray Design on Early Stage Root Development of Acer rubrum, Quercus rubra, and Populus tremuloides 1

Abstract

This experiment investigated the effect of different plug-tray cell designs on root development of red maple (Acer rubrum), red oak (Quercus rubra), and quaking aspen (Populus tremuloides) seedlings. In April of 2015, seeds of each species were sown into three plug trays with different substrate volumes and grown for 17 weeks. Two trays had permeable walls for air-pruning, one with vertical ribs and one without. The third tray had impermeable plastic cell walls. Harvested seedlings were analyzed for root dry weight, length, volume, surface area and number of deflected roots. Root length per volume was highest in the impermeable-walled tray for red maple and quaking aspen. The total numbers of deflected root systems were higher for all species in the impermeable-walled tray. Seedlings grown in the air-pruning trays had smaller proportions of deflected root masses. Greater substrate volume did not influence root deflection development. The air-pruning tray without vertical ribs had the lowest total number of root masses with misdirected roots and lower proportions of root masses with misdirected roots for all species. These results indicate that improved root architecture in root-air pruning tray designs is achievable in tree propagation; however, vertical plastic structures in air-pruning trays can still cause root deflections. Index words: Deflected roots, air-pruning, seedling, propagation, plugs, root architecture. Species used in the study: red maple (Acer rubrum L.); red oak (Quercus rubra L.); quaking aspen (Populus tremuloides Michx.).

From Propagation to Field: Influence of Tray Design on Tree Seedling Quality and Performance1

“…This finding is consistent with other studies (Gilman andPaz 2014, McGrath et al 2017). McGrath et al 2017 found that red maple (Acer rubrum L.), red oak (Quercus rubra L.) and trembling aspen (Populus tremuloides Michx.) seedlings grown in Ellepot TM -bound substrate in an earlier pre-commercial version of the same Open tray used in the present study had a lower proportion of deformed roots as compared to a closed-wall tray.…”

“…Black cherry seeds would typically have been sown in early April and eastern cottonwood in June (personal communication, Alex Verbinnen). Reduced time in propagation trays is known to help avoid formation and worsening of root defects (Balisky et al 1995), which may otherwise have been more pronounced in the Closed Wall tray (McGrath et al 2017). After one year in the field, the eastern cottonwood trees grown in the Closed Wall tray, which had the highest percentage of coarse root defects, had the lowest percentage of root weight outside the container imprint.…”

“…Previous research has found that propagation trays with reduced contact between the substrate and plastic structures tend to reduce the percentage of deformed roots (Gilman and Paz 2014, McGrath et al 2017, Ortega et al 2006, Rune 2003). Depending on the tree variety being propagated and its typical root system morphology, different cell designs will have varying results.…”