Danish and Other Nordic Parasitic Plants

danish and OtHer Nordic ParaSitic planTs Henning S. Heide-JørgenSen KOngenS LYngBY - 2014 Contents What is a parasitic plant? .................................. 3 Basics about haustoria ...................................... 6 The Nordic genera ........................................... 7 Thesium - Toadflax .................................... 7 Viscum - Mistletoe ....................................... 7 Cuscuta - Dodder ..................................... 10 Broomrape family - Orobanchaceae........... 12 Euphrasia - Eyebright ............................... 12 Odontites - Rattle ...................................... 13 The author Melampyrum - Cow-Wheat ...................... 14 Henning S. Heide-Jørgensen was born in 1942. Bartsia - Alpine Bartsia ............................ 16 He received a Candidatum Scientiarum from the Parentucellia - Yellow Bartsia ................... 17 University of Copenhagen in 1970 and PhD in Pedicularis - Lousewort ............................. 17 1974 in ecological plant anatomy, and taught Rhinanthus - Rattle .................................... 21 there as Associate Professor until 1986 when the Lathraea - Toothwort ................................. 22 Institute of Plant Anatomy and Cytology was Orobanche - Broomrape ............................ 24 closed due to budget reductions. He was a Guest Haustoria ....................................................... 27 Researcher at the University of Victoria, Bri- Anatomy and function ................................ 27 tish Columbia in1990-1991, and returned as Re- Establisment of the parasite ........................ 30 search Assistant at the Institute of Biology, Uni- How many hosts? (Host specificity) .............. 32 versity of Copenhagen until retirement in 2007. Further ecological relations .............................. 35 He taught at the Open University for 20 years. Evolution of parasites ..................................... 37 His scientific publications have included studi- Supplementary reading .................................. 40 es af xeromorphic plants, the plant cuticle, carnivorous plants, parasitic plants, and the biological consequences of climate change in Greenland. Acknowledments Copyright Persons mentioned in the figure legends are great- No part of this publication may be reproduced ly acknowledged for contributing illustrations, Dr. without prior written permission from the au- Job Kuijt for comments on the manuscript, Palle thor. One printout for personal use is allowed. Gravesen for information on parasitic plant loca- Links to the paper are allowed. Copyright to lities, and the publisher Brill for permission to use the illustrations belongs to photographers men- figures from H. S. Heide-Jørgensen 2008: Parasitic tioned in the Figure legends. Flowering Plants. Cover The hemiparasitic Toothwort, Lathraea squamaria, mostly parasitizes Hazel, Corylus avellana. Photo: H. S. Heide-Jørgensen. 2 1. European Mistletoe, Viscum album, a rare but well known parasite in southern Scandinavia. Photo: H. S. Heide-Jørgensen. In most people’s minds, the term ‘parasite’ sounds largest single flower Rafflesia, and the smallest as something very unpleasant and it must be ac- and most reduced ones in Balanophoraceae, there knowledged that even among flowering plants is a list of supplementary literature on page 40. some of the most harmful weeds in the world in relation to agriculture and forestry are parasitic What is a parasitic plant? plants. However, in the Nordic countries parasitic Parasitic plants have evolved the ability to obtain plants cause no harm and that is also true for the water and nutrients from their host plants.They majority of the about 4.500 species known world- do so by exploiting the organs of the hosts and wide. From another point of view, many parasitic the most advanced parasites also benefit from the plants exhibit flowers just as beautiful as those of host’s photosynthesis. Usually the exploited hosts orchids, and their nutrient uptake is as specialised will grow a little less and produce fewer and/or as in carnivorous plants. Furthermore, they are smaller fruits but in most cases the hosts does not as important elements in various ecosystems as suffer severely. If the host is drained so hard of any other organism. The present paper focuses on water and nutrients that it dies, the parasite has re- parasitic plants in the five Nordic countries: Den- moved the basis for its own existence. This, how- mark including the Faro Islands and Greenland, ever, is not the case for annual parasites as dis- Norway, Sweden, Finland, and Iceland. Scandi- cussed on page 35. navia refers to Norway, Sweden, and Denmark. More precisely a parasitic plant can be defined The Scandinavian Peninsula to Norway and Swe- as a plant that possesses a so-called physiological den. If the reader wants to know more about bridge used for transportation of water and nu- harmful parasites, explosive flowers in some Lo- trients from the host to the parasite. This bridge ranthaceae (the mistletoe family) and their polli- is called a haustorium, a term derived from the nation and dispersal biology, or about the world’s Latin ‘to drink’. The structure and function of 3 2. Holdfasts of the climbing Japanese Ivy, Par- 3. English Ivy, Hedera helix, has climbing stems thenosissus tricuspidata, attached to brick. adhering to their support by adventitious roots Photo: H. S. Heide-Jørgensen. secreting an adhesive substance. Photo: H. S. Heide-Jørgensen. the haustorium are discussed on page 27. How- phyte) and the visible part outside the host (the ever, the term haustorium for the connection has exophyte). through time been used in very different mean- Yet another problem in relation to the parasitic ings. At first, it was used to describe the physi- plant definition is that some none-parasites are in cal connection between a Dodder (Cuscuta) and tight physical contact with other plants but with- its host. Irrespective of the organism in ques- out absorbing anything from their supporting tion there is the common feature for haustoria plant. This, for example, applies in the rain for- that they are used for the uptake and transport of ests to a great number of orchids, many bromeli- water and nutrients. ads (Bromeliaceae), and to other flowering plants Another problem is the fact that the haustori- besides a great number of lichens, mosses and um is not always visible to the naked eye. After ferns. Such plants which only use other plants for germination and penetration into the host all ex- support are called epiphytes. In climbers such as ternal signs of the presence of the parasites may the Japanese Creeper or Grape Ivy (Parthenosis- have disappeared for a longer period. The entire sus tricuspidata, Fig. 2) and English Ivy (Hedera vegetative body of the parasite may split into cel- helix, Fig. 3) special adhesive organs have de- lular strands which are completely embedded veloped which literally glue the plant to any sup- in host tissue. It may take months or years be- porting surface but lack the capability for water fore flowers or inflorescences are produced and and nutrient uptake. emerge on the surface of the host. This happens There is one more group of plants which may e.g. in Rafflesiaceae, and the most advanced spe- be mistaken for parasitic plants. These plants cies in the mistletoe family (Viscaceae) evolve were earlier known as saprophytes. They have in the same direction. In such cases a haustori- practically no chlorophyll and hence no photo- um cannot be identified and one distinguishes synthesis. This means that the members depend between the parts hidden in the host (the endo- on having all carbon nutrients supplied by other 4 4. Yellow Bird’s nest (Monotropaceae) is a myco- 5. Bird’s Nest Orchid is not a parasitic plant but heterotrophic plant free of chlorophyll. It occurs a myco-heterotrophic orchid. Photo: H. S. Heide- in beech and pine woods. Photo: H. S. Heide-Jør- Jørgensen. gensen. plants. The opinion was that carbon is delivered plants are now called myco-heterotrophic plants. by fungi which decompose dead organic matter There are about 400 species in nine families. in the soil. The fungi have hyphae connections As mentioned there are about 4,500 species of par- (mycorrhizae) to the parasite. Examples of this asitic flowering plants. They are placed in 20 families group of plants from the Nordic flora are Yellow or 28 if a recent splitting up of Santalaceae in 8 fami- Bird’s nest (Monotropa hypopitys, Fig. 4) and the lies is accepted. They occur in all parts of the world orchids Bird’s Nest Orchid (Neottia nidus-avis, except Antarctica and in practically all plant commu- Fig. 5), Northern Coral-Root (Corallorhiza trifi- nities except in water. In the Nordic countries inclu- da), and Spurred Coral-Root (Epipogium aphyl- sive the Faro Islands and Greenland there are about lum). It is possible that some plants are sapro- 50 species in four families. In addition there are some phytes in accordance with the original definition, introduced species and a number of subspecies. i.e. plants that obtain organic carbon through my- Two main types of parasitic plants are recog- corrhizal connections with fungi. However, the nized which each can be divided into two subspecies so far investigated have shown to form types. The main types are either photosynthetic mycorrhizae with different fungi that at the same or non-photosynthetic and they are called hemi- time have mycorrhizae with green photosynthetic parasites and holoparasites

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