Drosera occidentalis
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Drosera occidentalis subsp. australis |
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| Drosera occidentalis | ||||||||||||
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Drosera occidentalis is a carnivorous plant belonging to the genus sundew ( Drosera ). It belongs to the group of so-called dwarf sundew and is native to southwestern Australia.
description
Drosera occidentalis is a perennial herbaceous plant . This forms a sparse, open, rosette-shaped bud made of horizontal leaves with a diameter of about 1.5 centimeters. The stem axis is short and covered with few or no withered leaves from the preseason. This plant usually reproduces via seeds when a long, hot and dry summer is expected. If conditions are moderate, it will bud from stipules to survive the summer.
The bud of the stipules is ovate, shaggy, 3 millimeters long and 2.5 millimeters in diameter at the base. The stipules themselves are 2.3 millimeters long, 1.5 millimeters wide and three-lobed. The middle lobe is divided into three segments.
The leaf blades are circular, very deeply indented and 1 millimeter in diameter. The leaf stalks are up to 5 mm long, 0.3 millimeters long at the base and taper to 0.2 millimeters at the leaf blade. There are some glandular hairs on the entire surface.
Generative characteristics
The flowering period in Australia extends from November to December. The one to four inflorescence shafts are only about 1 centimeter long and covered with a few glands over the entire surface. The inflorescence usually consists of only one flower, rarely two. The sepals are elliptical with a length of about 1.3 millimeters and a width of about 1 millimeter. The edges and the upper tips are serrated and covered with a few glands. The tops of the petals are white with a reddish tinge or completely light pink. The petals are obovate with a length of about 2 millimeters and a width of about 1 millimeter. The base of the petals forms an approximately 0.3 millimeter long, wedge-shaped finger.
The five stamens are about 1 millimeter long. The stamens are white, the anthers pale yellow and the pollen yellow. The pale green ovary is spherical with a length of 0.4 millimeters and a diameter of 0.5 millimeters. The five greenish-yellow, horizontally elongated styles are very short. The scars are greenish-yellow, club-shaped, 1 millimeter long, 0.1 millimeter wide at the base and expand to 0.15 mm to the tip. The scar section is pimple-like.
The formation of brood scales is typical for dwarf sundews.The lance-shaped, 0.25 millimeter thick brood scales are formed in large numbers from late November to early December and are around 0.6 millimeters long and 0.5 millimeters wide.
ecology
The greatly elongated, glue-free marginal or quick tentacles function as catapults and are able to hurl prey such as springtails (Collembola) into the center of the leaf in a tenth of a second (catapult glue trap). Triggered by the impact, the shorter glue tentacles standing vertically on the lamina then transport the prey for digestion into a central recess (digestive trough) in the center of the leaf. They are hairless on the underside.
Distribution, habitat and status
Drosera occidentalis occurs only on a small area in the extreme southwest of Australia. The plant thrives there on the edges of swamps and damp depressions on peaty soils.
The species is considered critically endangered and rare in Western Australia, but is easy to spot with a knowledge of the life cycle.
Systematics
The specific epithet occidentalis is derived from the Latin word occidens for "west" and refers to the western distribution of this species.
The subspecies is also distinguished from the nominate form :
- Drosera occidentalis subsp. australis : leaf rosette compact with twenty to thirty leaves, inflorescence up to 2.5 centimeters long with up to eight flowers
In 1996 Jan Schlauer also presented Drosera microscapa as a variety to Drosera occidentalis subsp. occidentalis . However, this view is generally not followed.
literature
- Allen Lowrie: Carnivorous Plants of Australia. Volume 2, University of Western Australia Press, Nedlands 1989, ISBN 0-85564-300-5 , p. 114.
proof
- ^ Siegfried RH Hartmeyer, Irmgard Hartmeyer: Several pygmy Sundew species catapult-flypaper traps with repetitive function possess, indicating a possible evolutionary change into aquatic snap traps similar to Aldrovanda . In: Carnivorous Plant Newsletter . tape 44 , no. 4 , December 1, 2015, p. 172-184 .
- ^ S. Poppinga, Siegfried RH Hartmeyer, R. Seidel, T. Masselter, I. Hartmeyer, T. Speck: Catapulting tentacles in a sticky carnivorous plant . In: PLOS ONE. e45735 . tape 7 , no. September 9 , 2012, doi : 10.1371 / journal.pone.0045735 .
- ↑ a b Jan Schlauer: A dichotomous key to the genus Drosera L. (Droseraceae). In: Carnivorous Plant Newsletter. Volume 25, 1996, ISSN 0190-9215 , pp. 67-88, here p. 82, ( digital copy (PDF; 1 MB) ).
