Relationship Between Soil Nutrients and Alkaloid Content in Premna integrifolia L.

Premna integrifolia L. is an important medicinal plant containing diverse bioactive compounds, including alkaloids, but the soil‐related factors associated with alkaloid variation remain insufficiently understood. Building on a previous field study that reported higher alkaloid concentrations in plants growing on acid sulfate soils, we extended the field assessment to contrasting soil environments to provide a broader basis for understanding soil–alkaloid relationships relevant to future cultivation of P. integrifolia . The present study characterized soil properties at three sampling locations representing degraded soil (eutri‐plinthic gleysols), acid sulfate soil (endo‐protho‐thionic gleysols), and sandy soil (haplic arenosols), and evaluated their associations with total alkaloid concentrations in young leaves, branches, and roots. Six trees were sampled at each location ( n  = 18), with soil and plant measurements paired at the tree level. Soil pH, organic carbon, total N, total P ₂ O ₅ , available P, total K ₂ O, exchangeable K, and cation exchange capacity (CEC) differed significantly among locations ( p ≤ 0.05). Alkaloid concentrations also differed significantly among soil environments within each tissue ( p < 0.001). After Holm adjustment for 24 tissue‐specific correlation tests, alkaloid concentration was positively associated with CEC, organic carbon, total N, and total K ₂ O across all three tissues. Alkaloid concentration in branches was also negatively associated with soil pH, whereas the unadjusted positive association with available P in branches was no longer statistically significant after Holm adjustment. Because each soil type was represented by a single geographical location and the soil variables were strongly intercorrelated, these findings should be interpreted as observational associations related to the sampled environments rather than independent causal effects of soil type or individual nutrients.