Comparative Effects of Four Seedling Cultivation Methods on Root Architecture, Physiological Characteristics, and Post-Transplanting Growth of Flue-Cured Tobacco Based on Two-Year Field Study

Abstract To systematically compare the effects of four representative seedling cultivation methods on root architecture, leaf protective enzyme activities, and post-transplanting growth of flue-cured tobacco, a two-year field experiment was conducted from 2025 to 2026 using paper pots (PB), plastic trays (PT), two-stage seedling cultivation (TS), and floating seedling cultivation (FS). Root architecture was precisely quantified using WinRHIZO, and protective enzyme activities, root activity, dry matter accumulation, and agronomic traits were systematically measured. The results showed that: (1) The four seedling methods differed substantially in root architecture. Paper pots exhibited a pronounced “air-root pruning” effect, with a two-year mean root penetration rate of 63.7%. Penetration rate was highly significantly and positively correlated with root dry weight at 40 days after transplanting (r = 0.8042, P < 0.01) and significantly and positively correlated with root activity at 40 days after transplanting (r = 0.6138, P < 0.05), but highly significantly and negatively correlated with pre-transplanting root dry weight (r = − 0.8904, P < 0.001). (2) Two-stage seedling cultivation had the highest SOD activity (two-year mean 1828 U·g⁻¹), while paper pots had the highest CAT activity (2.844 mg·min⁻¹·g⁻¹) and relatively high SOD activity (1273 U·g⁻¹), indicating method-specific activation of the protective enzyme system. (3) At 40 days after transplanting, total dry weight per plant was higher in tray (15.28 g) and floating (14.91 g) treatments, and lower in two-stage (11.58 g) and paper pot (10.50 g) treatments, although differences among treatments were not significant. Paper pots showed the highest dry matter increase multiple during 20–40 days after transplanting (10.73-fold) and the largest increase in root activity (80.4%), reflecting compensatory growth. In 2026, agronomic traits were superior in floating and tray treatments, relatively lower in paper pots, and intermediate in two-stage. In summary, this systematic comparison demonstrates that two-stage seedling cultivation performs best overall, while paper pot seedling cultivation has considerable potential for labor saving, root protection, and green production.