Bud Removal Affects Shoot, Root, and Callus Development of Hardwood Populus Cuttings

AbstractThe inadvertent removal and/or damage of buds during processing and planting of hardwood poplar (Populus spp.) cuttings are a concern because of their potential impact on shoot and root development during establishment. The objective of the current study was to test for differences in shoot dry mass, root dry mass, number of roots, length of the longest root, and callus dry mass among ten poplar clones subjected to three pre-planting bud removal intensities (0%, 50%, 100%). The ten clones and their genomic groups were: DM115 (P. deltoides Bartr. ex Marsh× P. maximowiczii A. Henry); DN34, I45-51 (P. deltoides× P. nigra L.); NC13446, NC13563, NC13649, NC13685, NC13747 [(P. trichocarpa Torr. & Gray× P. deltoides)× P. deltoides]; and NM2, NM6 (P. nigra× P. maximowiczii). Cuttings, 20 cm long, were processed from shoots collected January 2005 from stool beds established at Hugo Sauer Nursery in Rhinelander, Wisconsin, U.S.A. (45.6 °N, 89.4°W). We measured the traits from harvested cuttings after 14 d of growth. The treatment× clone interaction governed shoot dry mass (P < 0.0001). In general, the top four clones (DM115, DN34, NM2, NM6) exhibited the best shoot dry mass with 0% and 50% of buds removed, while differences among treatments for the remaining clones were negligible. Clones differed for root dry mass (P < 0.0001), while the treatment and clone main effects governed number of roots (P = 0.0126, P < 0.0001, respectively) and length of the longest root (P = 0.0077, P < 0.0001, respectively). Cuttings subjected to the 0% treatment exhibited the greatest number of roots, while cuttings of the 0% and 50% treatment exhibited the greatest length of the longest root. The treatment× clone interaction governed the presence of callus (P = 0.0161), while clones differed for callus dry mass (P < 0.0001). Bud removal did not affect root biomass but it did impact root initiation. Unlike shoot dry mass, the response to removing buds for all rooting traits was not clone-specific. From a practical standpoint, inadvertently damaging and/or removing ≤ 50% of the buds during processing and planting should not be a concern for establishment.