Objective To clarify the effect of stem and vine pruning on the growth traits and the accumulation of constituents in the fleshy roots of Morinda officinalis How.

Method This study used rejuvenated virus-free seedlings of the main cultivated variety 'Heisuizai' from the Zhaoqing production area as experimental materials, set up two treatments: stem and vine pruning and unpruning. Field experiments were conducted for three consecutive years to observe plant growth indicators and determine the moisture, water-soluble extract, and nystose contents in fleshy roots.

Result Compared with unpruned plants, stem and vine pruning significantly increased the number of stem branches and the emergence of new leaves. The maximum number of stem branches reached 22.00 (±0.82) in pruned plants, compared with 17.00 (±1.25) in unpruned plants; the stem diameter increased by 28.00% at 1 080 days; and the total number of leaves increased by 89.08% at 720 days. The later-stage chlorophyll content (SPAD value) was also significantly increased (P < 0.05). However, the leaf area of pruned plants was significantly lower than that of unpruned plants at 360~1 080 days(P < 0.05). Stem and vine pruning significantly induced the occurrence and enlargement of secondary and tertiary tillering roots. Compared with unpruned plants, the numbers of secondary and tertiary tillering roots at 1 080 days increased by 56.45% and 49.81%, respectively, and the fresh and dry weights of the underground parts increased by 28.00% and 27.00%. The harvest measurements at 1 080 days showed that the moisture, water-soluble extract, and nystose contents in the dried fleshy roots of pruned plants were 11.00%, 68.40%, and 4.60%, respectively, while those in unpruned plants were 10.40%, 73.30%, and 6.20%, respectively. The moisture, water-soluble extract, and nystose contents in the fleshy roots of both treatments were significantly higher than the pharmacopoeial standards.

Conclusion Therefore, timely stem and vine pruning of virus-free M. officinalis plants can break apical dominance and induce the occurrence and enlargement of tillering roots. This practice effectively promoted root development and fleshy root biomass accumulation, thereby improving the yield and medicinal geoherbal quality of M. officinalis medicinal materials.