Root morphology, growth, and physiology in Begonia (Malus × micromalus) grown in copper hydroxide containers

Abstract A major concern with container seedlings is root circling and deformation that will affect post-planting performance and stability. To improve root quality, 3-year-old Begonia (Malus × micromalus) plants were grown in the containers treated on interior surfaces with different concentrations of copper hydroxide (Cu(OH)2) (0, 40, 80, 120, 160, and 200 g L−1) for 1 year. Compared with the standard container control (SC) and carrier asphalt container control (AC), the number of terminal lateral roots and lateral root volume were increased by 21% and 13% at 80 and 120 g L−1 Cu(OH)2 but decreased by 8% and 10% at 200 g L−1 Cu(OH)2. Only 80 g L−1 Cu(OH)2 increased the plant height and root weight, while other concentrations of Cu(OH)2 resulted in the declines. Phosphorus and potassium were improved with lower concentrations of Cu(OH)2 but decreased with 160 and 200 g L−1 Cu(OH)2. No significant difference in the concentrations of soluble protein and sugars in leaves was observed between Cu(OH)2 treatments and the controls. AC decreased nitrogen concentration in leaves by 12% over the SC across the whole growing season and increased taproot diameter by 17%. Our results indicate that 80 g L−1 Cu(OH)2 was the optimum concentration for root pruning and the maintenance of physiological function. Disadvantages in growth and physiology gradually showed up with increased concentrations.