Clonal Variation in Lateral and Basal Rooting of Populus Irrigated with Landfill Leachate

Successful establishment and productivity of Populus depends upon adventitious rooting from: 1) lateral roots that develop from either preformed or induced primordia and 2) basal roots that differentiate from callus at the base of the cutting in response to wounding. Information is needed for phytotechnologies about the degree to which Populus adventitious rooting is controlled by effects of individual genotypes, waste waters used as alternative fertigation sources, and their interactions. Our objective was to irrigate twelve Populus clones with well water (control) or municipal solid waste landfill leachate and to test for differences between initiation of lateral versus basal roots, as well as root growth rate and distributional trends for both root types. We evaluated number and length of lateral roots initiated from upper, middle, and lower thirds of the cutting, as well as basal callus roots. Overall, leachate irrigation affected lateral roots but not basal roots, and there was broad clonal variation between and within root types. On average, there were 129% more lateral than basal roots, which ranged from 3 to 27 (lateral) and 2 to 10 roots (basal). The percent advantage of number of roots from the middle portion of the cutting relative to other sections was 120% (upper), 193% (lower), and 24% (basal). Clones, treatments, and their interaction did not affect root growth rate, which ranged from 1.5 ± 0.6 to 3.4 ± 0.3 cm d⁻¹, with a mean of 2.3 ± 0.2 cm d⁻¹. These results contribute baseline information for clonal selection needed to establish Populus for phytotechnologies, energy, and fiber.