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Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Principal component analysis of the correlation between soil nutrients and alkaloid contents using PAST 4.03 software. Diagram is plotted with biplot on eigenvalue scale. Black, green, and red dots indicate samples containing MG > 1.5%, 1–1.5%, and <1% w/w, respectively.