Abstract:

The paper aims to clarify the appropriate leaf pruning times for cultivating strong flue-cured tobacco seedlings. In this study, different pruning frequencies were set based on different leaf ages. The control (J0) was set as no leaf pruning, leaves were pruned once at 4-leaf stage, 5-leaf stage, and 6-leaf stage (named J41, J51, J61), and then pruned twice from 4-leaf stage and 5-leaf stage (named J42, J52), and then pruned three times from 4-leaf stage (J43). The results showed that the stem height and stem diameter of tobacco seedlings was decreased significantly with the increase of leaf pruning frequency in two-year experimental data. Compared to J0, the reduction range in stem height of J41 to J61 treatment was from 14.51% to 62.18%, and that in stem diameter was from 10.49% to 21.68%. Leaf pruning improved the ratio of stem diameter to stem height and the uniformity of tobacco seedlings. Leaf pruning reduced the maximum leaf length, leaf width and leaf area of single plant tobacco seedlings, while the leaf thickness was increased. The chlorophyll content, net photosynthetic rate and dry matter accumulation of tobacco seedlings were reduced by leaf pruning. The chlorophyll content and net photosynthetic rate of tobacco seedlings were reduced significantly by leaf pruning twice or more than those of J0 treatment, and the dry matter accumulation aboveground and the total dry matter accumulation were significantly reduced. The root development of tobacco seedlings was promoted by leaf pruning. The total root length and root tip number of J42 and J43 treatments were significantly higher than those of J0 treatment, and the total root surface area of J41 and J51 treatments was significantly higher than that of J0 treatment in 2024. The total root length, root surface area and root tip number of J51 and J52 treatments were all significantly higher than those of J0 treatment in 2025. The strong seedling index of tobacco seedlings was decreased by the increase in the frequency of leaf pruning. The strong seedling index of J43 treatment was significantly lower than that of J51 treatment in 2024. The strong seedling index of J52 was significantly lower than that of J0 treatment in 2025. In conclusion, under the conditions of this experiment, no pruning leaves and pruning leaves once are beneficial to the improvement of photosynthetic parameters and dry matter accumulation of tobacco seedlings, promoting the increase of strong seedling index. Therefore, when cellar transplanting at the right time, it was recommended not to prune the tobacco seedlings. If transplanting cannot be done at the right time, it was suggested to prune the leaves to control the stem height of the tobacco seedlings, but the frequency of pruning should not exceed two times.

Key words: flue-cured tobacco, seedling cultivation, pruning leaves, agronomic traits, photosynthetic characteristics, root morphology, strong seedling index