Mistletoe the first plant pathogen

Mistletoe as the first plant pathogen

Mistletoe the first plant pathogen

  • Mistletoes are plants that live as parasites on branches of trees but, for various reasons, they have caught the fancy of people in various cultures and have made a name for themselves way beyond their real properties.
  • Although mistletoe is the first plant pathogen to be recognized as such and the first pathogen for which a cultural control (by pruning affected branches) was recommended, both by Albertus Magnus  around 1200 a.d., a great deal more has been fantasized, said, written, and practiced about it than
    its importance as a pathogen would indicate.
  • Mistletoe, to be sure, both the common or leafy mistletoe (Viscum in Europe and elsewhere, Phoradendron in North America), which infects many deciduous trees and especially the dwarf mistletoes (Arceuthobium), which infects conifers, cause considerable damage to trees they infect.
  • In many cases, the evergreen mistletoe plants can be seen clearly after normal leaf fall in the autumn and make up as much as half of the top of the deciduous tree they infect.
  • They generally damage trees by making their trunks and branches swell where they are infected and then break there during windstorms, thereby reducing the surface of the tree and reducing the quality of timber.
  • Mistletoes, of course, are evergreen parasitic plants that sink their “roots,” usually called sinkers or haustoria, into branches of trees.
  • Through the sinkers they absorb all the water and mineral nutrients and most of the organic substances they need from the plant.
  • True mistletoes, however, have well-developed leaves and chlorophyll and carry on photosynthesis and manufacture at least some of the sugars and other organic substances they need.
  • Mistletoe plants produce separate male and female flowers and berry-like fruits containing a single seed.
  • The seeds are coated with a sticky substance and are either forcibly expelled and stick to branches of nearby trees or are eaten by birds but go through their digestive tract and stick to branches on which birds drop them.
  • The striking visibility of true mistletoes on deciduous trees, and their ability to remain green while their host leaves fall for the winter, excited the imagination of people since the times of the ancient Greeks and inspired many myths and traditions involving the mistletoe plant through the centuries.
  • The plant itself was thought to possess mystical powers and became associated with many folklore customs in many countries.
  • It was thought to bestow life and protect against poison, to act as an aphrodisiac, and to bestow fertility.
  • Mistletoe sprigs placed over house and stable doors or hung from ceilings were believed to ward off witches and evil spirits.
  • The Romans decorated their temples and houses in midwinter with mistletoe to please the gods to whom it was sacred.
  • In Nordic mythology, the mistletoe was sacred to Frigga, the goddess of love, but was used by Loki, the goddess of evil, as an arrow and killed Frigga’s son, the god of the summer sun.
  • Frigga managed to revive her son under the mistletoe tree and, in her joy, she kissed everyone who was under the mistletoe tree.
  • But, for its misdeed to her son, she condemned the mistletoe to, be in the future, a parasite and to have no power to cause misfortune, sorrow, or death.
  • She decreed instead that anyone standing under a mistletoe tree was due not only protection from any harm, but also a kiss, a token of peace and love.
  • So, in Scandinavia, mistletoe was thought of as a plant of peace: under the mistletoe, enemies could agree on a truce or feuding spouses could kiss and make up.
  • In England, a ball of mistletoe was decorated with ribbons and ornaments and was hung up at Christmas.
  • If a young lady was standing under the ball, she could not refuse to be kissed or she could not expect to get married the following year.
  • A couple in love that kiss under the mistletoe is equivalent to promising to marry and a prediction of long life and happiness together.
  • Nowadays, in many parts of Europe and America, a person standing under a ball or even a sprig of
    mistletoe at Christmas time is inviting to be kissed by members of the opposite gender as a sign of friendship and goodwill.
  • There are, actually, more myths and customs associated with mistletoe.
  • Who would think that a minor parasitic higher plant would excite the imagination of so many others and have so many stories about it.

Reference

  • Plant pathology 5th edition George N. Agrios .

Mistletoe the first plant pathogen

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