Application of Salicylic Acid Improves the Production of Medicinal Components in Mucuna macrocarpa Wall by Regulating Endogenous Hormone and Nutrient Balance

Abstract

The Mucuna macrocarpa Wall, a traditional Chinese medicinal plant, exhibits significant cultivation-dependent variations in the accumulation and yield of its medicinal components. Salicylic acid (SA) has demonstrated the potential to regulate plant growth, which can be strategically used to enhance medicinal yield, offering a promising approach for high-yield cultivation in medicinal plants. This study aimed to investigate the changes in the medicinal components of Mucuna macrocarpa seedlings (4 months old) at different concentrations of SA (0, 0.1, 0.5, 0.9, and 1.3 mM) in a pot experiment. The results indicate that SA significantly increased the basal diameter (BD) by 2.9% to 20.61% and the total biomass (TB) by 14.28% to 48.57%. Notably, SA treatments resulted in alterations in the endogenous hormone content, including indole-3-acetic acid (IAA), abscisic acid (ABA), gibberellin A₃ (GA₃), and trans-zeatin-riboside (ZR), and the balance in leaves. SA regulated the content and balance of nitrogen (N), phosphorus (P), and potassium (K) in all organs, and K content and K: P in roots, stems, and leaves was significantly higher than that of the control under 0.9 mM SA treatment. Crucially, SA significantly enhanced the content of bioactive compounds. The total phenolic content (TPC) and total flavonoid content (TFC) in stems peaked at 0.9 mM (14.89 mg·g^-1 and 3.73 mg·g^-1, respectively), which were 11.87% and 11.68% higher than those in the control. Moreover, compared to the control, SA treatments increased total phenolic production by 20.00% to 61.45% and total flavonoid production by 3.89% to 90.56%. In addition, 0.9 mM SA was found to be more effective than other treatments for increasing total phenolic and d total flavonoid content. In summary, this study investigated the effect of SA as an eco-friendly elicitor to improve the total phenolic and total flavonoid production of Mucuna macrocarpa.

Keywords: Mucuna macrocarpa wall; endogenous hormone; nutrient balance; salicylic acid; total flavonoids; total phenolics.

Figure 1

Images of M. macrocarpa under different SA concentration (mM) treatments. (A–E) represent 0, 0.1, 0.5, 0.9, and 1.3 mM, respectively.

Figure 2

N (a), P (b), and K (c) nutrient content in in root, stem, and leaf. Data are expressed as mean ± standard deviation of three biological replicates. Different capital letters for the same organ in the figure indicate highly significant differences between treatments (p < 0.01), and different lowercase letters indicate significant differences between treatments (p < 0.05).

Figure 3

Characteristics of the N:P (a), N:K (b), and K:P (c) ratio changes in root, stem, and leaf. Data are expressed as mean ± standard deviation of three biological replicates. Different capital letters for the same organ in the figure indicate highly significant differences between treatments (p < 0.01), and different lowercase letters indicate significant differences between treatments (p < 0.05).

Figure 4

TPC (a) and TFC (b) content in root, stem, and leaf. Data are expressed as mean ± standard deviation of three biological replicates. Different capital letters for the same organ in the figure indicate highly significant differences between treatments (p < 0.01), and different lowercase letters indicate significant differences between treatments (p < 0.05).

Figure 5

Changes in TPP (a) and TFP (b) under different SA concentration treatments. Data are expressed as mean ± standard deviation of three biological replicates. Different capital letters for the same organ in the figure indicate highly significant differences between treatments (p < 0.01), and different lowercase letters indicate significant differences between treatments (p < 0.05).