| To investigate the fertilizer requirements of the flue-cured tobacco hybrid 'YY021' during the seedling stage and to provide data support for its promotion, the female parent 'MS Yuyan 13' and the male parent 'Heluo 1' were used as controls to assess the effects of different fertilizer application rates on relative chlorophyll content (SPAD value), dry matter accumulation, nutrient uptake, and root growth indices. The results showed that the SPAD value, shoot dry matter accumulation, and nutrient uptake of all three cultivars increased gradually with rising fertilizer levels. In contrast, root dry matter accumulation, root nutrient uptake, root-to-shoot ratio, and root growth indices increased initially and then declined. Under the reduced-fertilization treatment (50 mg/L N), 'YY021' showing the highest total root length, total root surface area, total root volume and root -to-shoot ratio, and outperformed both parents in dry matter accumulation and nitrogen, phosphorus, and potassium uptake. Under the standard-fertilization (100 mg/L N) and excessive-fertilization (200 mg/L N) treatments, aboveground growth was enhanced, with dry matter and nutrient accumulation again exceeding those of the parental lines. In conclusion, reducing nitrogen fertilization during the seedling stage promotes root development, and 'YY021' showes greater responsiveness to nitrogen levels than its parental lines. |
