Table_3_Planting Density Affects Panax notoginseng Growth and Ginsenoside Accumulation by Balancing Primary and Secondary Metabolism.DOCX

Adjusting planting density is a common agricultural practice used to achieve maximum yields. However, whether the quality of medicinal herbs can be improved by implementing appropriate planting densities is still uncertain. The medicinal crop Panax notoginseng was used to analyze the effects of planting density on growth and ginsenoside accumulation, and the possible mechanisms of these effects were revealed through metabonomics. The results showed that P. notoginseng achieved high ginsenoside accumulation at high planting densities (8 × 8 and 10 × 10 cm), while simultaneously achieved high biomass and ginsenoside accumulation at moderate planting density of 15 × 15 cm. At the moderate planting density, the primary metabolism (starch and sucrose metabolism) and secondary metabolism (the biosynthesis of phytohormone IAA and ginsenoside) of the plants were significantly enhanced. However, the strong intraspecific competition at the high planting densities resulted in stress as well as the accumulation of phytohormones (SA and JA), antioxidants (gentiobiose, oxalic acid, dehydroascorbic acid) and other stress resistance-related metabolites. Interestingly, the dry biomass and ginsenoside content were significantly lower at low densities (20 × 20 and 30 × 30 cm) with low intraspecific competition, which disturbed normal carbohydrate metabolism by upregulating galactose metabolism. In summary, an appropriate planting density was benefit for the growth and accumulation of ginsenosides in P. notoginseng by balancing primary metabolism and secondary metabolism.

调节种植密度是实现作物最高产量的常规农业栽培措施。然而，通过设置适宜种植密度能否提升药用草本植物的品质，目前尚无定论。本研究以药用作物三七（Panax notoginseng）为试材，解析种植密度对其生长及人参皂苷（ginsenoside）积累的影响，并通过代谢组学（metabonomics）技术揭示该调控效应的潜在机制。结果显示，三七在高种植密度（8×8 cm与10×10 cm）下可实现较高的人参皂苷积累；而在15×15 cm的中等种植密度条件下，其生物量与人参皂苷积累量均处于较高水平。在中等种植密度下，三七的初级代谢（淀粉与蔗糖代谢）及次级代谢（植物激素吲哚-3-乙酸（IAA）与人参皂苷的生物合成）均得到显著增强。但高种植密度下强烈的种内竞争会引发植株胁迫，并促使植物激素水杨酸（SA）、茉莉酸（JA）以及抗氧化物质龙胆二糖、草酸、脱氢抗坏血酸等抗逆相关代谢物的积累。值得注意的是，在种内竞争较弱的低密度种植模式（20×20 cm与30×30 cm）下，三七的干生物量与人参皂苷含量均显著降低，该条件下半乳糖代谢的上调会干扰植株正常的碳水化合物代谢。综上，适宜的种植密度可通过平衡初级代谢与次级代谢，促进三七的生长与人参皂苷积累。