Investigations on the morpho-anatomy and histochemistry of the European mistletoe: Viscum album L. subsp. album

Viscum album L. (Santalaceae) is an important medicinal plant traditionally used to treat several diseases, including cancer therapy. This paper provides detailed morpho-anatomical characteristics of the leaves, stems and berries of Viscum album subsp. album growing as hemi-parasite on the branches of Malus domestica (Suckow) Borkh. (Rosaceae) to aid species identification and botanical characterization. Additionally, for the first time, microchemical analyses of all tissues and Energy Dispersive X-Ray Spectroscopy analyses of the calcium oxalate crystals are provided for the first time. The plant features leathery presents green leaves with parallel veins, small yellow unisexual flowers in 3-flowered cymes, and the dioecious inflorescences usually consist of three flowers, with female flowers generating white fleshy berries, in which a seed is embedded in the mucilaginous mesocarp, normally containing two embryos. Anatomically, the analyzed leaves were isobilateral and amphistomatic, and showed straight anticlinal epidermal cell walls, thick cuticles with epicuticular wax crystalloids, and paracytic stomata. The midrib is flat on both sides and has a single vascular bundle, whereas the strongly shortened petiole is concave-convex in shape and contains five bundles. The stems show a primary structure with a ring of nine vascular bundles enclosing the pith. Calcium oxalate druses and cubic and quadrangular prisms were observed in different plant parts. The results of this study provide new microscopy information that can help in the authentication of mistletoe raw materials.

Automated summary

This study provides detailed morpho-anatomical characteristics of Viscum album subsp. album, a type of mistletoe that grows as a hemi-parasite on the branches of Malus domestica. It also presents microchemical analyses and Energy Dispersive X-Ray Spectroscopy analyses of the calcium oxalate crystals for the first time. The results contribute to the authentication of mistletoe raw materials and enhance our understanding of the morphology and anatomy of Viscum album subsp. album.