Thursday, July 22, 2010

Lycophytes are Living Fossils

Krauss's Clubmoss, Selaginella kraussiana

The lycophytes (Lycopodiophyta) are a truly ancient division of plants. They have a long and extensive fossil record that includes some of the earliest known land plants. Lycophytes were a major component of Late Paleozoic flora and were prominent in the coal swamps of the Carboniferous period (Wikstrom and Kenrick, 2001 Molecular Phylogenetics and Evolution 19 pp. 177-186). Here, some species like Sigillaria grew to large tree forms that dominated the wetter environments (Wagner and Diez, 2007 Comptes Rendus Palevol 6 pp. 495-504).

Krauss's Clubmoss, Selaginella kraussiana

Living lycophytes however only count for less than 1% of extant land plants and consist of three families - Isotaceae (quillworts), Selaginellales (spike mosses) and Lycopodiaceae (clubmosses). These are small creeping plants with branching stems and simple leaves that possess a microphyll, a single vascular vein (Stace, 1999 Field Flora of the British Isles p. 6). Therefore, though some species are superficially similar to mosses (hence the suffixes in the common names), they are the oldest living vascular plants. Strikingly, living species are very similar morphologically to the earliest fossils (Heuber, 1992 Annals of the Missouri Botanical Garden 79 pp. 474–499).

Lycophytes show a similar reproductive strategy to the Pteridophytes, producing spores (either homosporous or heterosporous) in leaf axils or on the upper side of leaf near its base. The sporangia bearing leaves are often collected into strobili (cones). As in ferns, the sporophyte generation is dominant while the gametophyte generation is either free-living, subterranean, mycorrhizal and saprophytic (homosporous) or much reduced and retained within the spore (heterosporous) on the ground (Stace, 1999 Field Flora of the British Isles p. 6).

Krauss's Clubmoss, Selaginella kraussiana

An interesting naturalised alien lycophyte in Ireland is Krauss's Clubmoss, Selaginella kraussiana (actually a spike moss). Krauss's Clubmoss is a native of the Azores, Madeira, the Canary Islands and South Africa and was introduced to Ireland as ground cover (O'Mahony, 2009 Wildflowers of Cork City and County pp. 333-334). It has a moss like appearance, with a flattened shape and apically forking fronds. In shaded areas S. kraussiana can become the dominant ground cover and its presence near waterways, combined to its ability to reproduce vegetatively, points to its potential as a problematic weed in Ireland, as is the case currently in New Zealand (Roy, 2008 An Illustrated Guide to Common Weeds of New Zealand).

Krauss's Clubmoss, Selaginella kraussiana

Wednesday, July 21, 2010

Aches and Bleed - Herb Robert You'll Need

Herb Robert (Geranium robertianum)

A guest post by Ken.

"My tooth doth ache and my nose doth bleed",
"Well Herb Robert dear fellow is what you need,
For if your nose doth bleed and your tooth doth ache,
Then Herb Robert's the plant thou'll have to take."


In the house of John Hall, physician and son-in-law of William Shakespeare, I discovered a facsimile of the 1633 copy of John Gerard's book The Herball or Generall Historie of Plantes. John Gerard was famous for his herb garden and often noted for being 'Herbalist to the King's Majesty'. Below the book was the usual note 'Please Do Not Touch'. I quickly turned to the index and looked for Herb Robert.

And there it was... P.939 Chap. 27. Herbe Roberte (Geranium Robertianum).

The Herball or Generall Historie of Plantes by John Gerard

It has slender weak and brittle stalks, hairy and red in colour. Leaves can also be red and are jagged and deeply cut. The flowers are of a most bright purple colour and the root is small and thread-like. It grows upon old walls made of brick, stone or even earth. It can also be found among rubbish, in the bodies of trees cut down and in moist and shadowy ditch banks. It flowers from April to Summer be almost spent: the herbe is green in winter too and is harldy affected by the cold. The vertues: Herbe Roberte is good for wounds and ulcers of the dugs & secret parts and thought to staunch bloood. Reference is made to Dioscorides (who wrote a 5 volume book in the first century, De Materia Medica, relating to herbal medicine also), whom Gerard believes is describing Herb Robert when he mentions his third Sideritis, "the vertue of this, faith he, is applied to heale vp bloudy wounds." (Of the Historie of Plants, 1633 revised edtn. [Thomas Johnson], John Gerard, Chap. 27, p 939).

I had found the plant a few weeks back in my local woods and took a snap of it. Coincidentally, 2 days ago my father gave me a colouring book of Wild Flowers and between the covers of this was Herb Robert. Described as a strong smelling annual, a dainty plant, and widespread in shady places. Now does that sound familiar. Published in 2001, more than four centuries have passed and not much has changed. (Wild Flowers Colouring & Guide Book, Sherkin Island Marine Station, 2001, p.15).

So there you go.

Next time you have a bloody wound let Herb Robert be your cure.



Tuesday, July 20, 2010

A Penny for Your Thoughts

Pennywort, Umbillicus rupestris

With its ghostly, green white, pendulous flowers appearing from May to August, Pennywort (or Navelwort, Umbilicus rupestris) is a common sight on rock crevices and walls throughout Ireland. Prior to the appearance of stalked flowers, the succulent, round leaves of this perennial show depressed centers above the leaf stalk, lending U. rupestris its common names of Pennywort and Navelwort.

Leaves of Umbillicus rupestris

It seems to be unaffected by variances in soil pH, thriving in both acidic and calcareous conditions (O'Mahony, 2009 Wildflowers of Cork City and County p. 118) indicating its nutrient demands are quite low.

Living as it does in areas of little soil availability, U. rupestris leaves itself prone to drought. It tackles this stress with a very nifty little metabolic strategy. Under optimal conditions, U. rupestris is a C3 plant, that is it fixes carbon by converting carbon dioxide and ribulose bisphosphate into the 3 carbon 3-phosphoglycerate. However under drought stress, C3 plants close their stomata to reduce water loss which also stops carbon dioxide entering the plant which in turn leads to photorespiration. This limits growth due to a loss of carbon and nitrogen.

Flowers of Umbillicus rupestris

U. rupestris
overcomes this problem by switching its photosynthesis to an incomplete form of crassulacean acid matabolism (CAM) (Daniel et al., 1984 Biochemical Journal 218 pp. 387-393). CAM photosynthesis fixes carbon dioxide at night to form oxaloacetate, which is in turn converted into malate. In daylight, this malate is decarboxylated and the carbon dioxide is re-fixed via the Calvin cycle. Daniel et al. showed that this switch was accompanied by an increase in the activity of the enzyme phosphoenolpyruvate carboxylate. This enzyme also shows several changes in properties, for example a decrease in sensitivity to acidic pH. This explains its apparent indifference to soil pH.

Monday, July 19, 2010

Knotted Wrack Reduces Porcine Intestinal Flora

Knotted Wrack, Ascophyllum nodosum

The brown marine alga Ascophyllum nodosum (Knotted Wrack) has long been recognised as agriculturally important due to its efficacy as a fertiliser. It has been shown to have a wide range of beneficial effects such as increased yield, increased nutrient uptake, increased frost and stress resistance and reduced incidence of fungal and insect attack (Patier et al., 1993 Journal of Applied Phycology 5 pp. 343-349). A. nodosum is found throughout the North Atlantic in the upper and mid-shore of the intertidal zone. It favours sheltered areas as it has only a small disc like hold fast to anchor itself to its substrate. It has egg shaped bladders along its frond length that act as flotation devices to increase contact with sunlight, which lend it its name Knotted (or Egg) Wrack (Sterry 2004, Collins Complete Guide to Irish Wildlife p. 286).

However the agricultural applications of A. nodosum have recently been increased. Dierick et al. (2010, Livestock Science) replicated pig jejunum and caecum conditions in vitro on a diet of the A. nodosum. It was found that the algal diet had a supressive effect on total numbers of E. coli, Streptococci and Lactobacilli in the simulated small gut conditions. The supression of E. coli was especially pronounced, meaning A. nodosum based pig feed could potentially reduce incidence of scour in herds.

Knotted Wrack, Ascophyllum nodosum

The World of the Hydroid

Hydroids are colonial polyps that form upright branching, stem like structures. They attach themselves to substrates using a stolon. The stolon bears shoots that protrude into the water at regular intervals. The ends of these shoots are either occupied with zooids that have feeding and hunting parts or growing tips that serve to elongate the tubes and shape the new zooids (hydranths). The colony body is covered, except for the hydranths, with a rigid chitinous skeleton called perisarc (Kosevich, 2006 Zoology 109 pp. 244-259).


Attaching themselves to various substrates such as seaweeds (like Fucus, as in the example above), rocks, mollusc shells, cnidarians, sponges and even other hydriods (Genzano et al., 2008 Marine Ecology 30 pp. 33-46), they can be found in intertidal rock pools to the the deep sea (+700 m) (Henry et al., 2008 Deep Sea Research Part I: Oceanographic Research Papers 55 pp. 788-800). Some species have even developed symbiotic relationships with other organisms. Brooks and Mariscal (1985, Journal of Experimental Marine Biology and Ecology 87 pp. 111-118) report on one such relationship in the gulf of Mexico. The hydroids Hydractinia and Podocoryne colonise the shells of the hermit crab Pagurus pollicaris in the Gulf of Mexico. The movement of the crab gives these bottom feeding hydroids access to greater amounts of food, which it obtains by catching zooplankton using its gastrozooids. In turn, the hydroids provide the crab with protection from predators by repelling them with stings from their cnidae, capsules containing a colied tubule and venom used for hunting. The stings of some hydroids such as Lytocarpus phillippinus found in the Southern Pacific can cause itchy painful weals (Rifkin et al., 1993 Journal of Wilderness Medicine 4, pp 252-260).

Morphologically, hydroids bear a superficial resemblance to plants (and are often named as such like the Sea Fir, Dynamena pumila). This shape is achieved when the larva settles and undergoes metamorphosis to form the primary hydranth. During further colony development the shoot organisation of the hydroid transforms slowly, until large shoots emerge which have characteristic species specific features (Kosevich, 2006 Zoology 109 pp. 244-259).

Tuesday, July 13, 2010

"And safe and sound beneath a rock shelf"

from "Arion" by Seamus Heaney

The line above refers above to the legend of the poet Arion and the dolphin. The story goes that on being thrown from the ship he was a passenger on, the Greek poet Arion was rescued by a dolphin, the creature being attracted by his singing. The dolphin carried him ashore, saving him from drowning.

It could also refer to the family of animals which now bear his name, the Arionidae. These are a family of robust slugs with roughly tuberculate skin that are found throughout the Holartic region. One of the most striking members of the family is Arion ater. As can be seen in the picture below, colour is variable with orange, reddish brown, brown and black forms present. A. ater is indistinguishable from the species A. rufus, except by dissection. It shows an interesting defensive reaction if irritated by contracting into a hemispherical shape and swaying from side to side (Pfleger, 1990 Molluscs p. 82). A. ater is omnivorous, feeding on carrion, fungi as well as dead and living plant material which marks it out as an agricultural pest.

Arion ater

Biological control of A. ater with the parasitic nematode Phasmarhabitis hermaphrodita has proved quite successful. Wilson et al. (1999, Biological Control 16 pp. 170-176) showed that A. ater actively avoided soil treated with the nematode. A control strategy employing P. hermaphrodita would therefore have the effect of protecting crops yet not wiping out slug populations.

Differentiation in the Common Field Grasshopper

Common Field Grasshopper, Chorthippus brunneus

The seminal work of Clausen, Keck and Hiesey at Stanford University in the 1930s, 40s and 50s on the relationship between plants and climate (1941, The American Naturalist 75, No. pp. 231-250) showed beautifully the influence of phenotypic plasticity on plants native to California. By studying clinal variation in these plants (especially Achillea spp.) over a transect that ran from the coast up to the mountains of the Serra Nevada, they showed that plant size decreased with increasing altitude. Their extensive research also involved taking clones of plants from their individual habitats and replanting them at three different elevations: sea level, 4600 feet and 10,000 feet. They found that races grew well at altitudes similar from where they originated, but often died off at other altitudes.

With plants, such geographic variations in form are often quite obvious. It is less so for animals. Because of this, and the difficulty associated with transplanting experiments, studies on phenotypic plasticity in animal populations are quite few. However a wonderful example was produced in 1999 by Telfer and Hassall (Oecologia 121 pp 245-254) on ecotypic differentation in the common field grasshopper, Chorthippus brunneus.

C. brunneus
is common throughout most of Europe, and can its short chirping song (resembling time signal pips) can be heard in dry grassy areas throughout Ireland from mid-June to August, although it is rarer in the north. 18 to 24 mm in length it flies readily when disturbed, having noticeably long wings and can be distinguished from similar species by its hairy underbelly (Sterry 2004, Collins Complete Guide to Irish Wildlife p. 124).

In studying 27 populations of C. brunneus throughout Britain and Ireland, Telfer and Hassall found that grasshoppers from cooler sites were heavier at hatching, those from nothern sites grew faster but were smaller at adulthood and adults in warmer, sunnier or more southernly locations were larger. They concluded that the observed ecotypic variation in C. brunneus is an evolutionary response to climatic variation.

Monday, July 12, 2010

What Does a Goat Smell Like?

Hypericum hircinum, Stinking St. John's Wort

Native to the Mediterranean, especially central Italy, where it is distributed in damp and shady places (Robson, 1968 Flora Europea 2 pp. 261–269) Stinking St. John's Wort (also Goat's St. John's Wort, Stinking Tutsan; Hypericum hircinum) is a not a plant to be brought indoors. The leaves emit an unpleasant odour when crushed, similar to that of a goat. It is a deciduous shrub that can grow to 1.5m. A rare naturalised occurrence in Ireland, it has become established around Cork harbour where it is present in many locations (O'Mahony, 2009 Wildflowers of Cork City and County p. 375).

Its close relative Common Saint John's Wort (H. perforatum) contains a complex mixture of bioactive substances (Çirak et al., 2007 Biochemical Systematics and Ecology 35 pp. 403-409). Long used in folk medicine for a variety of purposes, H. perforatum contains hyperforins, hypericins and flavonoids that have been shown to have antiviral, antidepressant and antimicrobial activity (Bombardelli and Morazzoni, 1995 Fitoterapia 66 pp. 43–68; Luo et al., 2004 Journal of Ethnopharmacology 93 pp. 221-225).

With such a pharmacologically rich relative it is therefore no surprise to find that H. hircinum also posses a range of chemical activity. Pistelli et al. (2000, Fitoterapia 71 pp. S138-S140) showed that crude extracts from H. hircinum had antimicrobial effects, inhibiting growth in Bacillus subtilis, Staphlococcus aureus, Listeria monocytogenes, Salmonella enteritidis and Pseudomonas aeruginosa. Interestingly, they found that purified extracts had no effect, indicating a synergistic effect of the constituents. Similarly, Maggi et al. (2010, Chemistry of Natural Compounds 46 pp. 125-129 ) showed antimicrobial activity of hydrodistilled essential oils of H. hircinum against not only bacteria such as a range of Staphylococcus species and Escherichia coli, but also the yeast Candida albicans.

H. hircinum extracts have also been shown to have possible antidepressant activity. Chementi et al. (2006, Journal of Natural Products 69 pp. 946-949) showed that a methanol extraction from H. hircinum leaves inhibited monoamine oxidases in vitro. Monoamine oxidases break down monoamine neurotransmitters. Inhibition of monoamine oxidases leads to an increase in the neurotransmitter availability. Further examination of the extracts showed that the inhibitory activity was due to quercetin.

Flower buds of Hypericum hircinum

Conspicuous Mating

Rhagonycha fulva on Hogweed, Heraculeum sphondylium

At this time of year (mid- to late July), the common red soldier beetle (Rhagonycha fulva) is quite visable in hedgebanks and on uncultivated ground. Its vibrant orange-red colour contrasts easily with the green of the plants it visits to hunt other insects. Of these plants, the Apiaceae (umbellifers) are especially preferred (Meek et al., 2002 Biological Conservation 106 pp. 259-271). Mating pairs are a common, conspicuous sight on such plants. Sexual dimorphism is evident with females being larger than the males (see picture below of mating pair) and also at a chemical level where Jacob (1978, Hoppe-Seyler's Zeitschrift für physiologische Chemie pp. 653-656) showed that the composition of cuticular lipids in R. fulva is sex-dependant.

A mating pair of Rhagonycha fulva