The Study of Crystals in the Fruits of Some Apiaceae Species Using Energy-Dispersive Spectroscopy

Crystals in the fruits of Apiaceae are of great importance for taxonomy. The presence/absence and location of large prismatic crystals, druses, and spherical aggregates characterize genera, tribes, and subfamilies. When the fruits of Apiaceae split into mericarps, cell separation occurs, and probably cell death and the destruction of their walls. In clades Saniculeae and Scandicinae, this process is accompanied by the accumulation of calcium oxalate crystals in the abscission layer. However, reports of smaller crystals are rare, and their taxonomic significance is unknown. To fill this gap, we started research with four species of the clade Apieae: Ammi majus, Modesciadium involucratum, Deverra aphylla, and Rutheopsis tortuosa; in the last two species, crystals were described for the first time. We also studied crystals in Chaerophyllum bulbosum from the clade Scandicinae, and in Sanicula rubriflora from the clade Saniculeae. Conventional optical and polarizing microscopy, scanning electron microscopy, and energy dispersive spectroscopy (EDS) were used. In the clade Apieae, the studied species contained crystals in the exocarp and on the commissure, and often in the mesocarp parenchyma as well; the shapes of the crystals are small druses and crystal sand. The calcium content in the crystals was determined as 10–31%; crystals contain also carbon and oxygen and are most likely composed of calcium oxalate. In the fruits of Apiaceae studied, the silicon content is low (<0.3%).