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katiajewelbox · 1 year

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Merry Christmas Eve! This week's post is a guest post from the Copenhagen Plant Science Centre in Denmark, used with their generous permission.

PLANT OF THE WEEK – Viscum album (common name: Mistletoe, mistelten). Mistletoe is particularly eye-catching during wintertime as lush, green globes high in the leafless treetops. Its many small, pearly white berries form a striking contrast to its evergreen foliage. Mistletoe is an evergreen hemiparasite with branches more than 50 cm long. The shoot system is dichotomous with opposite, ligulate leaves. There are female and male plants. The 1-3 mm long yellow-greenish flowers are placed apically in groups of three. In male flowers, the anthers are fused with perianth segments. Female flowers have an inferior ovary with a sessile stigma. They are pollinated in April, mainly by small flies. The fruit is a white berry with a very sticky pulp. All parts of the plant are moderately poisonous. The berries develop in autumn and winter and provide food for migrating birds, mainly Bohemian waxwings and mistle thrushes. The berries quickly pass through the bird, and the defecated seeds can be seen dangling from branches in sticky garlands strung together by undigested remnants of the pulp. The Eurasian blackcap uses its beak to squeeze the seed from the fruit before it is eaten. To remove the sticky seed, the bird rubs its beak against a twig, thus depositing the seed in a place it is likely able to germinate. Mistletoe grows on many species of deciduous trees (some on conifers). It attaches to its host by a haustorium, a modified root, which penetrates the vessels, from where it obtains water and nutrients. The mistletoe has chloroplasts and can perform photosynthesis; hence the term ‘hemiparasite’. Interestingly, the mitochondrial genome of mistletoe is much smaller than that of other plants and lacks many important genes, causing inefficient energy production. The mistletoe can cope on this low energy budget due to its very slow growth and parasitic lifestyle. Today, mistletoe is widely distributed in Europe south of Denmark. Fossil records from 9,000 – 6,000 years ago show that mistletoe has previously been present in Denmark. After being extinct for many years, introduced specimens from gardens are now spreading in Denmark, especially around Copenhagen. Throughout history, mistletoe has played a role in many cultures. It was believed to possess magical powers, e.g. by the Celtic druids. In Denmark, we know the mistletoe from Nordic mythology, where the goddess Frigg forgot to extract an oath from the deceptively innocuous mistletoe, when she made all beings swear to never harm Balder. Today, it is mainly associated with the Christmastime custom that whoever stands beneath a mistletoe may be kissed. Though mistletoe has long been regarded as a fertility symbol, this custom is fairly new as it is first described in England in the mid-18th century. This Plant of the Week is presented by Niels Jacobsen, Kira Tendal, Karen Rysbjerg Jensen and marian ørgaard, employees at the Department of Plant and Environmental Sciences, University of Copenhagen.