Abstract
Excessive nitrogen (N) application and potassium (K) supplement deficiency is a common problem in Panax notoginseng cultivation. However, synergistic effects of lowering N and increasing K application on yield and quality of P. notoginseng have not been reported. Field experiments in two locations with different N and K combined application were conducted to study the effects on yield and quality. Then, the saponin accumulation mechanisms were explored by pot and hydroponic culture with 2- or 3-year-old seedlings. The investigation showed that 70% of P. notoginseng cultivation fields reached abundant levels of total nitrogen (TN) but had deficient levels of total potassium (TK), which may be detrimental to balance the N/K uptake of P. notoginseng. Moreover, the average biomass was 18.9 g, and P. notoginseng saponin (PNS) content was 6.95%; both were influenced by the N/K values of P. notoginseng. The field experiments indicated that compared to the conventional N and K application (N:K = 2:1), lowering N and increasing K application (N:K = 1:2) decreased root rot rate by 36.4–46.1% and increased survival rate, root biomass, and yield, as well as PNS content by 17.9–18.3, 5.7–32.9, 27.8–57.1, and 5–10%, respectively. The mechanism of lowering N and increasing K application on the PNS content improving was due to the decreasing of N/K value, which promoted photosynthesis, sugar accumulation, and the expression of saponin biosynthesis genes. Therefore, lowering N and increasing K application to the ratio of 1:2 would have great potential to improve the synergistic effect on yield and quality of P. notoginseng cultivation.
Highlights
The N/K value in leaf of P. notoginseng was in the range of 0.57– 1.27, with an average of 0.81; the N/K value in root was in the range of 0.65–1.26, with an average of 0.88 (Figure 1A)
The total nitrogen (TN) of the P. notoginseng cultivation soil was in the range of 1.13–3.62 g.kg−1, with an average of 2.09 g.kg−1; the Available nitrogen (AN) was in the range of 97.29–397.76 mg.kg−1, with an average of 167.77 mg.kg−1; the TK was in the range of 3.20–16.70 g.kg−1, with an average of 8.23 g.kg−1; the AK was in the range of 111.70–627.65 mg.kg−1, with an average of 294.40 mg.kg−1 (Supplementary Table S2)
The soil TN/TK value was in the range of 0.08–0.75, with an average of 0.32; the AN/AK value was in the range of 0.26–1.38, with an average of 0.65 (Figure 1B)
Summary
H. Chen (P. notoginseng), belonging to the Araliaceae family, a famous traditional Chinese medicine for the prevention and treatment of cardiovascular and cerebrovascular diseases (Ng, 2006), has been planted for more than 400 years (Wan et al, 2012). More than 100 kinds of saponins have been identified (Wang et al, 2016), of which notoginsenoside R1 and ginsenoside Rg1, Rb1, Re, and Rd are the five most common kinds. Many well-known traditional Chinese patent medicines used its dry root as the main raw material, such as Yunnan Baiyao, Xuesaitong. The revenue from cultivation, processing, and other related industries of P. notoginseng has become one of the most important economic pillars of Yunnan province in China
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