Dienstag, 25. September 2012

Plant of the Day (September 25th, 2012) - Aristolochia clematitis L.

Today's “Plant of the Day” is Aristolochia clematitis L. from the Aristolochiaceae family. The common German name of this species is “Gewöhnliche Osterluzei”. In English, it's called “European Birthwort”.

A. clematitis - habitus

It's a herbaceous perennial plant, which can reach heights between 30 and 100 centimetres (12.0 to 39.3 inches). The stalk is unbranched and grows upright from a creeping rhziome. The large leaves are heart-shaped and have a long petiole. They are bald and have a lobed margin. Their colour is a yellowish green.

A. clematitis -  leaf

The flowers are arranged in whorls in the axillary of the upper leaves, what is a very conspicuous kind of inflorescence. They are funnel-shaped, short stalked and their petals have a sulfur-yellow colour. The flowers of A. clematitis are designed to work as a trap for insects like flies. A fly flies into the flower, stick to the hairs and is caught within the flower. After pollination, the hairs wither and the flower dismisses the insect by tilting.
Flowering time is between May and June and the ripe fruit is a black, pear-shaped capsule.

A. clematitis - flowers

A. clematitis is native to the Mediterranean but was brought to the Rest of Europe during the Middle Age. It prefers warm places and nutrient-rich soils. So, A. clematitis is a typical species of vineyards but can also be found on warm river banks or riparian forests (I found this individual at the shores of the River Rhine during my Field Trip in June 2012). During the Middle Age, the species was widespread, but today it is rare. However, some plants were planted in gardens and grew wild later..

A. clematitis - leaf

A. clematitis is also one of the oldest medicinal plant of the World. Its ingredients, the Aristolochic acids, were used already in the antique and by the American Indians to cure snakebites. However, the most common use of this plant was to accelerate and ease the birth, because Aristolochic acids have a travail promoting effect. This is also the reason for the English name “Birthwort” and also for the Latin name (“Aristos” = “the best”; “lockeius” = “to do with birth”).

A. clematitis - flowers

Because of the travail promoting effect, A. clematitis was also used as abortifacient but this could be very dangerous, because Artiolochic acids are also very toxic. They can cause kidney failure, promote the formation of ulcers and even damage the genetic material. Therefore, the plant is no longer used as a medicinal plant in many countries. and the use of Aristolochic acids is forbidden.

Dienstag, 18. September 2012

A geological overview of the Ruhr Carboniferous (Westphalium)

This time, my Blog will become a little bit off-topic. I recently took part in a field trip to the northern shores of the Baldeneysee, a lake in the South of Essen, Western Germany. This wasn't a botanical field trip but a geological one, because the rocky slopes and steep faces of the lake give a good overview about the geological history of North-Rhine Westphalia and the “Ruhrgebiet”. Of course, this includes also the history of coal, which was the main mineral resource of this region for a long time.

1) Historical overview

"Geologische Wand" in Essen, NRW

Our story begins about 300 Million years ago in an age, which is called Silesium; The a sub-part of the Carboniferous, which lasted from 359 Million Years to 299 Million years B.C.. The Silesium was again divided into several sections, which depends on the part of the world which was emerged from it. Important for my Article is the Westphalium, which conforms the Pennsylvanium in North America. The Westphalium lasted from 314 to 304 an is the era in which we find ourselves in this article

old headframe of coal mine "Zeche Carl Funke"

The Silesium was also the age of a major event in Earth's history: the collision of the two continents Gondwanaland and Laurasia. On Laurassia, this collision caused the formation of a large mountain range: the Variscan mountains. In Middle Europe, the Variscan mountains were located in the South of Germany, France and the Caucasian. In the north of the mountain there was the sea, and in between them a large marshland and river Delta (similar to the Mississippi estuary).

Flöz "Angelika" - black area (a)

This marshland was populated with many different plants (most of them prehistoric Horsetails) and was flooded again by the ocean. The plants, the rivers and cycle of flooding were responsible for the formation of strata, which we can see today.

2) Geomorphology 

  As I said it before, the marshlands was under the influence of different factors like flooding. Each factor was responsible for the formation of a different geological layer: a stratum. The main factors were:

  • Rivers: The Rivers in the marshlands carry sand as sediment, which was deposited with time. This sand became the Sandstone of today.
Sandstone
  • Roots: The Roots of the plants crossed the sandy soil of the River. Because of this, the sandstone in this area is more porous than rest. In German, this stratum is called Wurzelboden

    Flöz "Dünnebank" - a coal stratum (black areal)
  • Plants: Dead parts of the Plants fell into the river and become peat, which is a large reservoir for carbon. Over time, the peat has developed into coal and formed a coal stratum, which is called Flöz in German. This process is not uniform, why the proportion of carbon within the coal (and thus its value as energy source) can vary. The different types of coal are:


German name
US name
Carbon (in %)
Braunkohle (lignite)
Braunkohle
Lignite
65 - 75





Steinkohle (bituminous coal)
Flammkohle
Sub-bituminous coal
75 - 81
Gasflammkohle
Medium volatile bituminous coal
81 - 85
Gaskohle
Medium volatile bituminous coal
85 – 87,5
Fettkohle
Medium volatile bituminous coal
87,5 – 89,5
Esskohle
Low volatile bitumiuous coal
89,5 - 90
Anthrazit
(Anthracite)
Magerkohle
Semi-Anthracite
90,5 – 91,5
Anthrazit
Anthracite
> 91,5

  • Ocean: Sea levels fluctuated during the time, which was mainly due to the melting of the Ice Age glaciers in the north. In warm periods, sea levels roses and flooded the prehistoric forest. The main sediment, which brought the sea, was clay. The Clay overlaid the peak, which was pressed to coal by this pressure later. Because of this, there is often a stratum of clay above coal layer

    .a clay Stratum above the Flöz
This sequence of Sand, “Wurzelboden”, coal and clay is typical for the soil in the “Ruhrgebiet”. But it should be said that this is not always the case. Sometimes, some strata are missing completely or are weak, A weak layer of coal for example, was formed during a period, where was not so many peat in the prehistoric forest.

Sandstone dosen't have to be yellowish.
He's more black, the yellow color is due to weathering

Moreover, the sequence of the strata is rarely as uniform as in the diagram. Responsible for this are geological processes, dragging or reorder layers. On the Baldeneysee, we are able to take a closer look at two of this processes: saddles and thrust fault.

3) Saddles

"Nöckersberger Saddle" - right side

Saddles are made where the rock is folded by tectonic processes, similar to folding paper. At one point, the rock rises, while it sinks on a different position (forming a hollow). This happens in different dimensions; some saddles are only small folds, while others are large ridges. It isn't also unusual, that minor saddles are existing in major hollows. In our case for example, the “Nöckersberger Saddle” is a minor saddle within the large “Bochumer hollow”.

"Nöckersberger Saddle" - left side

It's very easy to recognize such a saddle; especially if it is a smaller one. The strata being arranged obliquely. They fall on one side from the top left to bottom right and left from the upper right to bottom left.

4) Thrust fault


On the former area of the coal mine “Zeche Carl Funke” at the north shore of the Baldeney See you can find a Thrust fault. A Thrust fault (German: “Überschiebung”) is a break in Earth's crust; caused by tectonic movements, which have lifted one part of the rock upwards. By the associated forces, the rock finally broke and has been moved slightly upward. The unaffected rock slid under the shifted upwards rock.

Thrust-fault "Sutan" - right (older) stratum (c in my drawing)

The breaking point may be located quite easily. The rock is highly compressed in this area and the different strata cannot be distinguished with the eye.

Thrust-fault "Sutan" - left (younger) stratum (b in my drawing)

For this reason, in a thrust fault are older layers are overlying younger layer, what can be a little bit confusing for geological researches, because one part of a Flöz (coal strata) can be found several meters over the other part.

Thrust-fault "Sutan" - breaking point.

5) other phenomena

Saddles, hollows and Thrusts faults are large phenomenons, but they are no the only one in our areal. There are also some smaller, local features.

  • Fossils: in the different strata you can find many fossils of plants of the prehistoric marshland. This plants had a fluted stem, which leaves an impression in the rock. Most of them were prehistoric horsetails (Equisetum) or trees from the extinct genus Sigillaria and other genera.
petrified driftwood

fossilized tree bark of a Siggillaria
 
fossilized tree bark
  • Limonites: Limonites are solid chunks with a high content of oxidized iron. Thereby, they are much heavier than other rocks. The reason for their high iron content can vary greatly. For example, a dead animal can be surrounded by the peat, which leaded to an iron deposits. For this reason, Limonites can be very interesting for paleontologist, because they can contain some remains of prehistoric organisms. It's similar to a pinata. However, they can be dangerous for miners, because they can burst out during the digging and kill the workers.
Limonite
  • Liesegang Rings: Liesegang rings also consist of oxidized iron, which was leached from higher regions, and then failed in an annular pattern. The exact cause is unknown but it is a typical phenomenon of iron.
Liesegang Rings
  • Tuff: Tuff is a volcanic rock, which was spitted out by volcanoes during their eruption. It has a reddish color and is very porous. In our areal, there was one deposit in a Flöz called “Angelika”. Tuff can be very useful for the historical classification of shifted strata. Its deposit acts as a red guideline. Strata with Tuff must been formed at the same time, because only at this time, a volcano erupted.

     Tuff (a) - the thin line, witch looks like a root

Samstag, 15. September 2012

Flowers and inflorescences of the Asteraceae - an introduction

1) Introduction

In my previous four postings, I've shown you four different species from the Asteraceae. With 1500 different genera and 24000 species, the Asteraceae are one of the largest plant-families in the world. The most of them are herbaceous plants (Bellis perennis, Taraxacum officinale, Tanacetum vulgare) but there are also shrubs and even trees.

 Astericus serecius - a shrub, native to the Canary Islands

Members of the Asteraceae can be found all over the world (except Antarctica). In Europe, they are one of the most variable families. Many plants from this family are used as vegetable, medicinal plant or spice (like Stevia rebaudiana; the “natural” sugar).

The most distinctive characters of the Asteraceae are their inflorescences and their fruits.

2) The inflorescences of the Asteraceae and their flowers

The inflorescences of the Asteraceae, often called “head”, are unique. They consist of many small flowers, which form a large “fake” flower in order to seem more attractive for pollinators. This is similar to the Apiaceae and their umbels, but the floral axis of the Asteraceae is reduced so extremely, that the flowers seem to sit directly together. Their bracts are forming a circle of fake sepals: the Inculucrum.


The flowers of these heads have the basic formula K 5 C (5) A 5 G (2): five free sepals, five fused petals, 5 stamens and 2 hypogenous carpels. However, the flowers haven't a uniform appearance. Some of them are cygomorphic, others are radial. In Botany, the cygomorphic flowers are called “ray flowers” (“Zungenblüten” in German) and the radial flowers “disc flowers” (“Röhrenblüten” in German).


  Depending on the composition and morphology of these two types of flowers, the Asteraceae are subdivided into twelve sub-families today. The most important are

  • Asteroideae: the inflorescences of the Asteroideae consist of disc and ray flowers. In the most cases, the ray flowers are sterile and arranged in the periphery of the inflorescence in order to simulate petals. The fertile disc flowers are located in the centre. Typical species from this sub-family are Helianthus annuus (sunflower), Senecio inaequidens (South African ragwort) or Bellis perennis (Daisy)
Senecio inaequidens from the Asteroideae

Helianthus annus - here, you can see the three "teeth"
of the yellow ray flowers
  • Cichorioideae: the heads of Cichorioideae consists only of fertile ray flowers. All five petals of this flowers show in the same direction; so the ray flowers of this family seem to have five teeth instead of three, what is an important difference towards the Asterioideae sub-family. Another distinctive feature of the Cichorioideae is the milky liquid in their stalks. Typical species are Cichorium intybus (Chicory) or Taraxacum officinale (Dandelion)
Cichorium inytbus - ray flowers with five teeth

Taraxacum officinale

  • Carduoideae: The inflorescences from species of this subfamily have only disc flowers. The most popular Genera of the Carduoideae are Cirsium (Thistles), Centaurea (centaury), Arctium (Burdock) and Cynara, the genus of the artichoke (Cynara cardunculus)

    Arctium lappa from the Carduoideae

    Cirsium vulgaris - a species, which only has disc flowers
However, their different morphology isn't the only special character of the flowers of Asteraceae. Another point of interest is their biology of pollination. As you can see in the formula, the stamens are not grown together but they are arranged close together and form a tubular structure. The stylus grows through this tube and slips off the pollen. The stigma is closed in order to avoid self-pollination. After the pollinators like bees have taken the pollen away, the stigma opens for pollination.



3) The fruits of the Asteraceae

The fruits of the Asteraceae are normal, one-seeded nuts. What makes them so special is their kind of distribution. The pericarp is linked with the testa of the nut and the sepals. The sepals are modified and form a kind of “paraglider”: the Pappus, whose morphology can be an important distinctive feature.
In the most cases the pappus is used as paraglider, which gives the fruit the ability to fly with the wind. However in some cases, the Pappus is used as a kind of “hook”, which hang on clothes or fur for distribution.

  
Together, Pappus, pericarp and nut forms the unique propagule of the Asteraceae: the Achene.

Montag, 10. September 2012

Plant of the Day (September 10th, 2012) - Taraxacum officinale agg.

The short series of articles about the Asteraceae tend to an end. But before the series'll end with a final article about the inflorescences of the Asteraceae, we look today at a second, well-known species of the subfamily Cichorioideae. This species is Taraxcum officinale agg.; known as “Gewöhnlicher Löwenzahn” in German 1) and as “common dandelion” in English. This species is very versatile and has many, genetic varieties. Therefore, I will introduce the species generally.

Taraxacum officinale - habitus

T. officinale is a small to medium seized herbaceous plant, which can reach heights between 5 and 40 centimetres (2.0 to 15.7 inches). The hollow stalk is very short and completely leafless; all leaves are arranged in a rosette. These leaves are arrow-shaped and have sharp lobbed margins. The stalk also contains a milky white liquid.

Taraxacum officinale - rosette

This liquid contains Taraxacin, which is a little toxic. High doses can cause skin irritation, liver problems and urination. However, Taraxacin is also used in Homeopathy as laxative.

The inflorescence is one terminal head at the end of a long petiole, which is often mistakenly referred to as stalk As member of the Cichorioideae, all flowers are cygomorphic, tubular flowers with golden yellow petals. Flowering time is between April and July, what makes T, officinale to a important plant for bees. The fruits are winged nuts (Archenes), which are typical for dandelion. However, the “Pusteblume” is not specific for this species. The Archene a very common fruit type of the Asteraceae, which use wind for distribution.

Taraxacum officinale - inflorescence

T. officinale is native to Asia and Europe, but can be found in the whole northern hemisphere as Neophyte today. However, the species is rare in the southern hemisphere and here only as Neophyte. It prefers fresh, nutrient-rich soils and can be found at roadsides, on pastures, in parks and meadows.

Taraxacum officinale - habitus

As I said it before, the species is very diverse and there are many different sorts and varieties. Some scientist believe, that there are over thousand different sorts of this species. Therefore, the species is often stated as Taraxacum sect. Ruderalia in modern literature.

1)The Genus of Taraxkum isn't the only one of the Asteraceae, which is called “Löwenzahn” (Lion's tooth) in German. The other Genus is Leontodon which is known as “Hawkbits” in English. The reason for the same name is the fact, that the species of the Genus Leotodon looks very similar to Taraxacum. However, the petiole of Leotodon species isn't hollow and their Archenes are not arranged at the end of a long stalk.

Mittwoch, 5. September 2012

Dienstag, 4. September 2012

Plant of the Day (September 4th, 2012) - Senecio inaequidens DC.

The “Week of the Asteraceae” continues with Senecio inaequidens DC. from the Sub-family “Asteroideae”. In German, this plant is known as “Schmallblättriges Greißkraut” and in English as “Small-leafed groundsel” or “South African ragwort”. In Afrikaans, this species is known as “Bezemkruiskruid” (the home of this plant are the former Dutch colonies in South Africa).

S. inaequidens - Habitus

It's a herbaceous plant, which can reach heights between 20 and 60 centimetres (7.9 and 26.6 inches). Despite being a herb, the stalk can be woody at the base. It's well branched from basic. The leaves are very narrow, which is also the reason for the German name (“Schmalblättrig” is German for “narrow-leafed”). They are 6 and 7 centimetres long and only 1 to 3 millimetres broad. There is no petiole but the leaves are embracing the stalk with their leaf-base. Their margin is serrated finely.

S. inaequidens - inflorescences

As member of the Asteroideae, the heads of S. inaequidens consist of cygomorphic ray flowers in the periphery and disc flowers in the center. In both cases, the petals are golden yellow. Flowering time is between August and October. The ripe fruits are the typical, winged nuts of the Asteraceae, which I will explain at the end of the week in an extra article.

S. inaequidens -this is a typical, narrow leaf

As I said it before, S. inaqeuidens is native to the South Africa but the species is a Neophyte and can be found all other the world today. The plant owes this rapid spread to humans, which brought seeds of S. inaquidens to Europe with imported cotton at the end of the 19th century. First, S. inaequidens only grew near to harbours but with the construction of highways and railroads during the 20th century, the species also reached the inland.

S. inaequidens - inflorescence with ray flowers 
and disc flowers; typical for the Asteroideae

The natural habitat of S. inaequidens are rocky or grassy slopes on sand or gravel in a height between 1440 and 2850 metres. Outside of South Africa, this plant can be found at roadsides, railroad tracks, ruderal wastelands and rubble tips. It prefers warm places. In some regions, this species is considered as dangerous, but it's also a characteristic species of plant societies on renaturated, former industrial areas.

S. inaequidens - leaf (here you can see, how the
leaf-base embrace the stalk

S. inaequidens - as you can see, the stalk is well
branchend from the basic; the lower regions of
the stalk are also woody.

 Please note: Unfortunatly I've no good Photos of Senecio inaequidens DC. So, I've decided to post the article without any Photos first. I try to make some Photos during the Next day and will insert them here