#hemiparasite

[dougdimmadodo]

European Mistletoe (Viscum album)

Family: Santalaceae (Sandalwood Family)

IUCN Conservation Status: Least Concern

Native to western and southwestern Asia as well as almost all of Europe, European Mistletoe is a hemiparasite, meaning that in addition to producing nutrients independently through photosynthesis it also meets part of its nutritional needs parasticially, growing attached to the branches of trees and forcing its roots into the internal vessels of its hosts to steal nutrients and water. After settling and maturing on a host tree, members of this species produce tiny pale-yellow flowers between February and April (with each individual plant producing either pollen-producing "male" flowers or seeds-producing "female" flowers,) and after being pollinated by small insects "female" flowers develop into round, typically white berries (although a small number of individuals instead produce yellow berries.) Unlike many plants within its range, European Mistletoe bears fruit during the winter (possibly as an adaptation to avoid having to compete with fruit-bearing host trees) and as such while the berries of this species are poisonous to most mammals many birds rely heavily on them as a winter food source, carrying the seeds within them away from their "mother" to allow them to spread to new trees. Each berry contains a single seed surrounded by an extremely sticky pulp, and after being swallowed and eventually excreted in a bird's droppings this pulp allows the seeds to adhere to branches, where they will eventually germinate, force their way into the nutrients-filled internal vessels of their host and begin their development into adulthood.

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Image Source: https://www.inaturalist.org/taxa/57512-Viscum-album

[katiajewelbox]

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.

[cedar-glade]

Lithospermum caroliniense

Carolina puccoon, a much denser cluster of flowers are known at the top compared to hoary puccoon, the hairs are bristly with pointed bracts(sepals) with upright stiff hairs, these bracts are at the base of the floral tube, (gamopetalous tube).  It’s a much later bloomer than hoary puccoon blooming late june to mid summer. It usually forms dense colonies however, in this photo it does not seem to follow that characteristic as closely. I really also should mention that the bottom of the L. canescence leaves is densly pubescent where this species is sparsly pubescent. L. canescence has a bit more of a bicolor look due to this, its just dense pubescence(canescent). 

bonus: cute little bold jumper lurking hard. 

[coyote-mints]

Indian paintbrush (Castilleja) is a hemiparasite-a plant that obtains some or most food by parasitism but still photosynthesises. This one seems to be feeding on ceanothus

[birdsy-purplefishes]

First time finding #PedicularisDensiflora/#WarriorsPlume and I almost didn’t! It’s a hemiparasitic plant, as you may have guessed from the color. #orobanchaceae #parasiticplant #hemiparasite #pedicularis #californianativeplants #californianativewildflowers #canativeplants #otaymountain #botany (at Otay Mountain Wilderness Area) https://www.instagram.com/p/CMAINZaDUhL/?igshid=87oswsgh6g4u

[continent-of-wild-endeavor]

Aureolaria virginica - Downy yellow false foxglove or downy oak leach

Hemiparasitic on oaks, which is neat.

[indefenseofplants]

On Parasites and Diversity

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We all too readily demonize parasites. It is kind of understandable though. The thought of something living in or on you at your expense is enough to make our skin crawl. There are a lot of evolutionary pressures that make us look unfavorably about organisms with such lifestyles. However, to completely write parasites off as a bane to life as we know it may be a huge mistake on our part. More and more we are realizing that parasites play an important role in ecosystem functioning and may even serve as indicators of environmental health. 

Plants are no stranger to such parasitic dynamics. Many species have forgone some if not all photosynthetic ability in exchange for a parasitic lifestyle. There is no question that plant parasites can and do have net negative effects on their hosts, however, its never that simple. Research is showing that parasitic plants can have profound effects on the structure and productivity of surrounding plant communities. 

For starters, parasitic plants can increase the competitive ability of non-host species. By knocking back the performance of their host, other plant species can pick up the slack so-to-speak. This can often lead to an increase in overall plant diversity in a given habitat. A common thread throughout studies that have looked at parasitic plants is that proportion of grasses declined when parasitic plants were present. This made room for less competitive forbs to increase in number. In effect, parasitic plants can level the playing field for other, less competitive plant species. 

By altering ecosystem structure, parasitic plants can also alter the way nutrients flow through the system. This can have some seriously profound ramifications. For instance, the presence of the hemiparasitic Rhinanthus minor in grasslands has been shown to  increasing rates of nitrogen cycling. Though the ramifications of this are dynamic, it is nonetheless proof that parasites should not simply be maligned and that, despite our perspective, nature is far more complex than we realize. 

Photo Credit: Sannse (Wikimedia Commons)

Further Reading:

http://www.nature.com/nature/journal/v439/n7079/full/nature04197.html#B10

http://link.springer.com/article/10.1007%2FBF00319016

http://www.sciencedirect.com/science/article/pii/S0006320797000104

http://www.jstor.org/stable/10.1086/303294

[indefenseofplants]

Euphrasia

Meet Euphrasia nemorosa, the eyebright. This lovely little plant is native to the northern regions of North America. A quick glance at the flowers of this species may seem to suggest a member of the mint family but this would be wrong. Once placed in Scrophulariaceae, it is now thought to reside in Orobanchaceae. Like other members of this group, E. nemorosa is a hemiparasite. It uses specialized roots to tap into the roots of plants growing around it. In the wild, research has shown that E. nemorosa seems to prefer to parasitize grasses but laboratory experiments have shown that it will parasitize a variety of plants if given the chance. It can even grow without parasitizing other plants but those that did grew small and weak.  Parasitic plants are an interesting bunch. They push the limits of what is traditionally accepted in the realm of plant physiology. Non-parasitic plants usually have to balance between CO2 uptake and water loss. They do this by controlling their stomata, which are tiny openings on the leaf. Because they are attached to a host, parasitic plants do not have to worry about minimizing water loss and instead want to maximize water loss to gain as much carbon from their host plant as possible.  Another interesting aspect of Euphrasia ecology is their preference for disturbance. Euphrasia are plants of disturbed meadows, fields, and man-made habitats. There is a lot of work being done to examine which kinds of species thrive in and around humans. Research has shown that by selecting for native species like Euphrasia, the species composition on these types of disturbed habitats can take on a more biodiverse character instead of the usual non-native monoculture. Further Reading: https://gobotany.newenglandwild.org/species/euphrasia/nemorosa/ http://www.archive.bsbi.org.uk/Wats6p1.pdf http://jxb.oxfordjournals.org/content/39/8/1009.short http://www.archive.bsbi.org.uk/Wats5p11.pdf