Morpho-anatomy and histochemistry of European mistletoe (Viscum album L. subsp. album), a semi-parasite growing on Malus domestica

AbstractThis paper provides detailed morpho-anatomical characteristics of the leaves, stems and berries ofViscum albumL. subsp.album(Santalaceae) growing on the branches ofMalus domestica.Additionally, microchemical analyses of all tissues and Energy Dispersive X-Ray Spectroscopy(EDS) analyses of the calcium oxalate crystals are provided for the first time. The plant grows as a semi-parasite on the branches of host trees and shrubs; it develops as dichasium with pseudo-dichotomous branching stems and well-developed green leaves with parallel veins; 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. The analyzed leaves were isobilateral, 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 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 parts of the plant. The microscopic features of the tissues and structures are illustrated with light and scanning electron micrographs.