Mistletoe (Viscum album) reduces the growth of the Scots pine by accumulating essential nutrient elements in its structure as a trap

The mistletoe [Viscum album ssp. austriacum (Wiesbaur) Vollm.] is a hemiparasitic plant, and its infestation is known to play an important role on the mortality of Scots pines (Pinus sylvestris L.), but there is little knowledge about its action mechanism. This study, therefore, tried to gain a better understanding of the destructive effect of the mistletoe on the growth and water uptake mechanism of the Scots pine. Identical needles from neighboring plants (healthy and infested) were harvested in the middle of each month (from April to October 2013) and used as research material. Infestation success of the mistletoe was investigated by evaluating the contents of the endogenous nutrient elements such as potassium, phosphorus, calcium, sulfur, magnesium, iron, copper, zinc, manganese, boron, nickel, and sodium in both mistletoe leaves and the needles of healthy and infested Scots pine. Its effects were also evaluated by determining the content of water, chlorophyll, and dry matter, and the length of the newly formed needles of the healthy and infested trees. Mistletoe infestation led to a decrease in the availability of water and mineral nutrients, and caused a powerful inhibition on the growth parameters such as chlorophyll, dry matter, and the length of needles by accumulating the essential nutrient minerals in its structure. The findings of this study indicate that the mistletoe accumulates the nutrient elements in its structure as a trap and causes a severe drought stress in the Scots pine in dry summer seasons, thereby playing a potent role in the increasing mortality rate in the Scots pine.