Retzia capensis
| Retzia capensis | ||||||||||||
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Retzia capensis |
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| Systematics | ||||||||||||
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| Scientific name of the genus | ||||||||||||
| Retzia | ||||||||||||
| Thunb. | ||||||||||||
| Scientific name of the species | ||||||||||||
| Retzia capensis | ||||||||||||
| Thunb. |
Retzia capensis is the only species in the genus Retzia . The classification of the genus was questionable for a long time, today it is assigned to the family of the Stilbaceae . The species occurs exclusively in the Cape region of South Africa .
description
Vegetative characteristics
Retzia capensis are weakly branched shrubs with a height of 60 to 130 cm. The twigs are firm, coarse and strong and are tomentose or finely tomentose when young, with great variability in the length and density of the hairiness. The stem axis branches monopodially . On young shoots, clear, longitudinal grooves can be seen that end in a leaf base. On older branches, these leaf scars are more or less distinct points.
The leaves are usually in whorls . These usually consist of three leaves on the thin branches and usually four or five leaves on the main stem. The simple leaves are without stipules, perennial, with entire margins and linear. The widest point is near the base, from where they taper to the obtuse or almost acute-angled tip. The leaf base lies close to the branches. The size of the leaves varies from 30 × 3 mm to more than 50 × 6 mm, whereby they are smaller on the side branches and largest in the flower-bearing region. Most of the leaves are almost hairless and, above all, finely hairy at the base, but the larger leaves of the flower-bearing region are often downy hairy up to the tip of the leaf and densely downy with whitish-colored hairs on the edges. However, this hair is also lost as the leaves age. The upper part of the leaves is strongly bent towards the underside, so that a narrow groove is formed on each side of the leaf margin, which runs down the leaf as a notch. In dry periods, the leaves shrink and the gutter becomes a kind of tube.
Inflorescences and flowers
The inflorescences are densely packed on strongly receding short shoots, which are laterally at the end of the shoots, but do not reach all the way to the tip, which continues to grow. Although the flowers are close together, they appear in pairs in the axils of large, cross-opposed, densely hairy leaves. On each of the short shoots, only one or two flowers develop at a time. They stand on only about 1 mm long, whitish hairy flower stalks and are surrounded by two bracts . These are smaller than the leaves, but are very similar to them.
The pale colored calyx is tubular and tapers at the base. The calyx-tube is 10 to 13 mm long, the base is hairless, the middle and upper parts are hairy with light downy hairs. The calyx lobes are 8 to 12 mm long, pointed, linear-lanceolate and lightly downy to silky hairy, on the edge the hair is thicker and longer. The crown is tubular, 6 to 7 mm in diameter and 55 to 65 mm in length. The five triangular-egg-shaped corolla lobes are 8 to 11 mm long. The bud cover is hinged to double folded. The corolla tube is bright red to orange-red in color, but the corolla lobes have a dark, blue-black color. However, this dark color is hidden at the tip by whitish hairs. The outside of the crown is slightly hairy, but becomes almost hairless at the base.
The filaments of the five stamens are in the arches between the corolla lobes and are about 4 to 5 mm long. The back (dorsal) fixed dust bag are inclined 2.5 to 3 mm long inward and not fused together. The two counters have grown together in the upper half, the lower ends are more or less apart. Both ends are blunted.
A circular, corrugated disk is formed around the base of the ovary . The zweifruchtblättrige stamp has a long, slim style , the mm in the early flowering stage 10 and is more about the still almost closed corolla tube out. A complete septum is formed over about a third of the height of the ovary, above which the two ovary compartments are connected to one another, a rib is only formed on the outer edge between the compartments. The placentas are arranged above the middle of the septum , each is assigned one or two hanging ovules and one upwards-pointing ovule , so that four to six ovules are formed per ovary.
Fruits and seeds
The fruits are longitudinally opening capsules , the surface of which is often heavily folded, but still smooth. The capsules are surrounded by a long-lasting chalice. When fully developed, the capsules are 7 to 9 mm long, but often also smaller. The capsule begins to crack open at the tip, initially extending over a third of the length, where the seed compartments often become bilobed and split open along a longitudinal crack along a longitudinal crack.
The seeds are up to 6 mm long, elongated, triangular and slightly comb-like. The surface is structured like a network. The straight, cylindrical embryo is surrounded by a floury endosperm .
Other features
The number of chromosomes is . The secondary plant substances include various iridoids .
ecology
The flowers of Retzia capensis are largely pollinated by birds, including the golden breast nectar bird ( Anthobaphes violacea ) on the flowers. The protogynen flowers of the plant have been in the early flowering stage an extended stylus , the addition is far above the crown, thereby increasing the likelihood that the plant a visit forming bird the fine scars touched. Later, the crown is further opened, so that the inwardly directed dust bag projecting beyond the corolla tube.
Distribution and locations
Retzia capensis has a restricted distribution area in the South African districts of Somerset West , Caledon and Bredasdorp . In the west and northwest the area is bounded by the mountains Helderbergs (formerly Hottentots Hollands), from there it grows along the Klein River , the Houw Hoek Pass and the Babylon Towers Mountains , to the east, where they reach the Elandskoof Mountains and from the Bredasdorp Mountain be limited.
It grows on sandstone slopes, on sandy or sandy / stony soils, often near rocks. In some areas, the plant is often affected by regular brush fires. If the intervals between the fires are not too short, the plant can survive them. New shoots then sprout from the perennial root crown.
literature
- Rolf Dahlberg, Bent Juhl Nielsen, Peter Goldblatt and JP Rourke: Further Notes on Retziaceae: Its Chemical Contents and Affinities . In: Annals of the Missouri Botanical Garden. Volume 66, 1979. pp. 545-556. (on-line)
