Biominerals in the leaves of Agave karwinskii Zucc

The leaves of two ethnotaxa of Agave karwinskii Zucc., ‘Cuishe’ and ‘Madrecuishe’, were analyzed using field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) to characterize their occurring biominerals. The sharp and high peak at 2θ 21.4° in the XRD patterns and the prominent bands’ envelopes related to aluminosilicates in the FTIR spectra showed the occurrence of chantalite in the leaves of both ethnotaxa. For the first time, chantalite is reported as a biomineral occurring naturally in Agave plants. The FE-SEM/EDX results revealed needle-shaped calcium oxalate profusely dispersed near the upper epidermis, in addition to uncovering the presence of calcium carbonate and silica in particles of irregular shape. Intriguingly, the occurrence of both minerals in Agave plants has not been reported either, suggesting complex biomineralization patterns in Agave karwinskii. It is proposed that calcium carbonate in the leaves of Agave is formed by the reaction of chantalite with CO₂.