Sonntag, 22. Juni 2014

Portrait: Ornithogalum umbellatum L.

In this article, we want to take a closer look on Ornithogalum umbellatum L. from the Asparagaceae family. In German, this species is known as “Dolden-Milchstern”, while common English names are “Stare-of-Bethlehem”, “grass lilly” or “11'o clock flower”. Please note: in older literature, the plant still belongs to the Lilliace

1) Description

As with many members of the Asparagaceae family, O. umbellatum is a perennial plant and can reach average heights between 10 and 30 centimeters. Each plant has between six or nine leaves, which arise from the base (so the stalk is completely leafless). This leaves are very long and tower over the inflorescences clearly. They are also very fleshy and between five and six millimeters width. Another, distinctive feature of the leaves is the milky-white gutter, which goes until the leaf-tip. 

O. umbellatum - habitus

As I said it before, O. umbellatum is a perennial plant, so it has to outlast harsh times (like winter). For this purpose, the plant uses an underground bulb, which consists of a main bulb and some smaller side-bulbs.

 O. umbellatum - the pictures were made on a cloudy day;
so the flower is nearly closed

The inflorescences are umbel-like racemes, which consist of ten to fifteen flowers. As with all monocotyledons, the flowers of O. umbellatum has two circles of identical tepals with three tepals per circle. Each tepal has a snow-white color and a distinctive green stripe on their dorsal site. Flowering time is between April and May. The ripe fruit is an oval capsule with many seed within. 

 O. umbellatum - another look at the flower

Some of the most interesting features of this species is its phototropism. It reacts on sunlight and open the flowers only at sunshine. During bad weather of at night, the flower is closed.

2) Distribution

O. umbellatum is native to the Mediterranean, but can also been found in Middle Europe, northern Africa and Western Asia. It grows also in some areas in North America, where it was imported as an ornamental plant.

 O. umbellatum - typical habitat

The species prefers a nutrient-rich soil on clay and grows on fresh meadows, vineyards, parks and even roadsides.

Montag, 2. Juni 2014

Portrait: Orobanche caryophyllacea Sm. (and Orobanche caryophyllacea f. citrina A. Dietr.)

This time, we want to take a closer look on a species from the Ororbranchaceae family („broomrape“ in English and „Sommerwurzgewächse“ in German). This species is Orobanche caryophyllacea Sm. (German: „Nelken-Sommerwurz“). We will also take a short look on Orobanche caryophyllacea f. citrina A. Dietr.; a subspecies of O. caryophyllacea

1) Description

The Orobanchaeceae are a family, which is strongly related to the Lamiaceae and Scrophulariaceae families. Actually, the Orobanchaeae were part of the Scrophulariaceae but today, their 12 Genera form an own family. Their leaves have no chlorophyll and as a result, they are not able to make photosynthesis. So, nearly all of them are parasites, which leech on other plants (mostly other Dicotyledones).

1.1) Orobanche caryophyllacea Sm.

O. charyophyllacea (Genus: Orobanche) is probably one of the best-known species from the Orobanchaceae. In Germany, the species is known as “Nelken-Sommerwurz” but other common names are “Gewöhnliche Sommerwurz”. 

O. charyophyllacea- habitus

It's a annual or perennial plant, which can reach a maximum height between 20 and 50 centimeters. Due the lack of any chlorophyll, the stalk has a purple to brownish-purple color and isn't green. The leaves are small an scale like. This morphology is a result of evolution: the plant doesn't need large leaves, because it makes no photosynthesis. So, they were reduced during the time.

O. charyophyllacea- flower (note the glands and the
purple stylus)

The root is a thick bulb. From here, small projections (Hausteria) penetrate into the root of the host plants. This happens right after the germination of the seeds.

The cygomorphic flowers are arranged in a single, loose pannicle. All petals are grown together at their base and form a tubular structure. At the apex of the flower, the two upper petals form a large lip, while the other three petals form three, small tips. Such flowers are mostly pollinated by larger insects or even small bird, which have to crawl into the flower for nectar and as a result, they take many pollen with them.

O. charyophyllacea- habitus


The calyx is small and consists of five, free sepals. The flowers have the same color like the rest of the plant. Another interesting detail: the flowers smells like cloves, what is also the reason for the suffix “caryophyllacea”.

In addition, the whole flowers are covered with glands.

 O. caryophyllacea f. citrina  -
habitus

Flowering time is between Mai and July, which makes O. caryophllacea to one of the earliest blooming members of the Orobanchaceae in Europe. The seeds are very small and only about half a centimeter in diameter. 

O. caryophyllacea f. citrina - flowers
(in contrast to the main species, the stylus is yellow and
not purple)
 
The specific host of O. caryophyllacea are plants from the Genus Galium from the Rubiaceae. By its Hausteria, the parasite robs water from the host and reduces its quality of live. So, O. caryophyllacea is also known as “galium-strangler”.

1.2) Orobanche caryophyllacea f. citrina A. Dietr.

This is a more rare subspecies of O. caryophyllacea, but it's anatomically the same plant. However, the most distinctive difference between the main species and O. caryophyllacea f. citrina A. Dietr. is the color. As you can see on my picture, the flowers and the stalk of the subspecies has a golden yellow color. So, it looks more spectacular than O. caryophyllacea.

O. caryophyllacea f. citrina -
inflorescences 

The exact reason for this contrasting color isn't clear. In my opinion, it's a mutation of the Genes, which are responsible for the pigmentation. This is the most obvious solution for me.

2) Distribution & Ecology

Members of the Orobanchaceae can be found all over the world. However, the most genera are native to the temperate regions of the old world (Europe and Asia). Due the high specification towards their hosts, the distribution also depends a little bit on the distribution of the host.

such a meadow is a typical habitat for
O. caryophyllacea

O. caryophyllacea (and Orobanche caryophyllacea f. citrina A. Dietr.) are native to Europe and Western Asia. It prefers warm places on lime and a nutrient-rich soil. The species can be found on warm, dry meadows (this is a special kind of biotop, which is called “Trockenrasen” in German) and sunny shrubberies along paths.