Dendrosenecio keniensis
Encyclopedia
Dendrosenecio keniensis (syn. Senecio keniensis and S. brassica is one of the giant groundsels endemic the higher altitudes of Mount Kenya
. It is in the family Asteraceae
and the genus
Dendrosenecio
(previously a Senecio
). Dendrosenecio keniodendron occurs the upper alpine zone of Mount Kenya and D. keniensis in the wetter areas of the lower alpine or the moorland
s.
s of soft brittle wood, with trunk to 5 centimetres (2 in) in diameter; which branch repeatedly at or below ground level, forming a large prostrate clone. The branches each support a great cabbage-like, densely packed leaf-rosettes of 30–40 leaves; each branch cloaked with older, dead foliage. Branches produced near ground-level are capable of rooting that supports a "creeping" horizontal growth-form. The leaves are oblong and narrow slightly where they attach to the rosette; they can be up to 56 centimetres (22 in) long and 18 centimetres (7.1 in) wide. The leaves are capable of secreting limited quantities of a mucilaginous
fluid containing polysaccharide
s. The upper leaf surface has a hair cushion which is also often coated with dried mucilage. The lower surface is covered densely with a thick, white felty covering of lantate hairs. Growth rates are very slow.
Flowers: Tall terminal spikes of groundsel flowers arise from each of the great cabbage-like rosette of leaves, each spike or inflorescence narrowly conical up to 110 centimetres (43.3 in) tall and 20 centimetres (7.9 in) in diameter. The flower heads are upright (as opposed to pendulous in D. keniodenron) each consisting of 12 to 16 bright yellow ray florets up to 25 millimetre (0.984251968503937 in) long and 60-80 disc florets. Each leaf rosette dies after flowering, but the plant lives on because its highly branched growth form consists of multiple rosettes.
zone located at altitudes of 2900 metres (9,514.4 ft) to 3800 metres (12,467.2 ft) that can be characterized by high soil moisture, a thick humus layer, similar terrain, and not a lot of different species present. The upper alpine zone, 3800 metres (12,467.2 ft) to 4500 metres (14,763.8 ft), is more topographically diverse, and contains a more varied flora, including the giant rosette plants Lobelia telekii
and L. keniensis
, Senecio keniodendron and Carduus
spp.. S. keniensis can be found in both the lower and upper alpine zone,
although it is less common above 4000 metres (13,123.4 ft) where it can regularly hybridise with S. keniodendron.
which belongs to a different family
. There was a mix-up in the some of the materials that were collected that united the leaf of Lobelia gregoriana
with the inflorescence of S. keniensis. At that time, Senecio keniensis was rejected as a confused name "nomen confusum" based on the muddled samples from which made it impossible to select a single specimen,
but that practice is no longer permitted and the replacement name S. brassica is superfluous and other names that were based on this basionym are similarly illogical and incorrectly deduced. Examples: Fries
and Fries
(1922) cited the confused material for S. brassica; Hedberg
(1957) selected a single specimen from among the syntype
s that associated S. brassica with Fries & Fries.
Mount Kenya
Mount Kenya is the highest mountain in Kenya and the second-highest in Africa, after Kilimanjaro. The highest peaks of the mountain are Batian , Nelion and Point Lenana . Mount Kenya is located in central Kenya, just south of the equator, around north-northeast of the capital Nairobi...
. It is in the family Asteraceae
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
and the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Dendrosenecio
Dendrosenecio
Dendrosenecio is a genus of flowering plants belonging to the family Asteraceae. It is a segregate of Senecio, in which it formed the subgenus Dendrosenecio...
(previously a Senecio
Senecio
Senecio is a genus of the daisy family that includes ragworts and groundsels. The flower heads are normally rayed, completely yellow, and the heads are borne in branched clusters...
). Dendrosenecio keniodendron occurs the upper alpine zone of Mount Kenya and D. keniensis in the wetter areas of the lower alpine or the moorland
Moorland
Moorland or moor is a type of habitat, in the temperate grasslands, savannas, and shrublands biome, found in upland areas, characterised by low-growing vegetation on acidic soils and heavy fog...
s.
Description
Leaves and stems: Prostrate (even subterranean) trunkTrunk (botany)
In botany, trunk refers to the main wooden axis of a tree that supports the branches and is supported by and directly attached to the roots. The trunk is covered by the bark, which is an important diagnostic feature in tree identification, and which often differs markedly from the bottom of the...
s of soft brittle wood, with trunk to 5 centimetres (2 in) in diameter; which branch repeatedly at or below ground level, forming a large prostrate clone. The branches each support a great cabbage-like, densely packed leaf-rosettes of 30–40 leaves; each branch cloaked with older, dead foliage. Branches produced near ground-level are capable of rooting that supports a "creeping" horizontal growth-form. The leaves are oblong and narrow slightly where they attach to the rosette; they can be up to 56 centimetres (22 in) long and 18 centimetres (7.1 in) wide. The leaves are capable of secreting limited quantities of a mucilaginous
Mucilage
Mucilage is a thick, gluey substance produced by most plants and some microorganisms. It is a polar glycoprotein and an exopolysaccharide.It occurs in various parts of nearly all classes of plant, usually in relatively small percentages, and is frequently associated with other substances, such as...
fluid containing polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...
s. The upper leaf surface has a hair cushion which is also often coated with dried mucilage. The lower surface is covered densely with a thick, white felty covering of lantate hairs. Growth rates are very slow.
- S. keniensis is frostFrostFrost is the solid deposition of water vapor from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air as well as below the freezing point of water. Frost crystals' size differ depending on time and water vapour available. Frost is also usually...
resistant to -10 °C This ability to withstand the colder temperatures that occur in the upper altitudes of Mount Kenya is in part due (at least in Lobelias) to the large amounts of mucilage which are contained by the rosettes of leaves which that might assist in preventing the leaf bud from freezing and the reservoir of fluid from evaporating. As well as the nyctinasticNyctinastyNyctinasty is the circadian rhythmic nastic movement of higher plants in response to the onset of darkness. Examples are the closing of the petals of a flower at dusk and the sleep movements of the leaves of many legumes....
behavior of the leaf rosettes which open during the day and close tightly around the leaf bud and meristemMeristemA meristem is the tissue in most plants consisting of undifferentiated cells , found in zones of the plant where growth can take place....
when it becomes cold at night; the outer leaves bend inwards and form around the central leaf bud.
Flowers: Tall terminal spikes of groundsel flowers arise from each of the great cabbage-like rosette of leaves, each spike or inflorescence narrowly conical up to 110 centimetres (43.3 in) tall and 20 centimetres (7.9 in) in diameter. The flower heads are upright (as opposed to pendulous in D. keniodenron) each consisting of 12 to 16 bright yellow ray florets up to 25 millimetre (0.984251968503937 in) long and 60-80 disc florets. Each leaf rosette dies after flowering, but the plant lives on because its highly branched growth form consists of multiple rosettes.
Distribution
Senecio keniensis makes its home mostly in the lower alpine or moorlandMoorland
Moorland or moor is a type of habitat, in the temperate grasslands, savannas, and shrublands biome, found in upland areas, characterised by low-growing vegetation on acidic soils and heavy fog...
zone located at altitudes of 2900 metres (9,514.4 ft) to 3800 metres (12,467.2 ft) that can be characterized by high soil moisture, a thick humus layer, similar terrain, and not a lot of different species present. The upper alpine zone, 3800 metres (12,467.2 ft) to 4500 metres (14,763.8 ft), is more topographically diverse, and contains a more varied flora, including the giant rosette plants Lobelia telekii
Lobelia telekii
Lobelia telekii is a species of flowering plant in the bellflower family, Campanulaceae, that is found only in the alpine zones of Mount Kenya, Mount Elgon, and the Aberdare Mountains of East Africa. It lives at high altitudes on well-drained sloped hillsides...
and L. keniensis
Lobelia telekii
Lobelia telekii is a species of flowering plant in the bellflower family, Campanulaceae, that is found only in the alpine zones of Mount Kenya, Mount Elgon, and the Aberdare Mountains of East Africa. It lives at high altitudes on well-drained sloped hillsides...
, Senecio keniodendron and Carduus
Carduus
Carduus is a genus of about 90 species of thistles in the family Asteraceae, native to Europe, Asia and Africa. Carduus is Latin for a thistle....
spp.. S. keniensis can be found in both the lower and upper alpine zone,
although it is less common above 4000 metres (13,123.4 ft) where it can regularly hybridise with S. keniodendron.
Name confusion
S. keniensis has a history which includes some confusion between it and other species from other genusGenus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
which belongs to a different family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
. There was a mix-up in the some of the materials that were collected that united the leaf of Lobelia gregoriana
Lobelia deckenii
Lobelia deckenii is a species of giant lobelia of the mountains of East Africa. It grows in moist areas, such as valley bottoms and moorland, in contrast to Lobelia telekii which grows in a similar, but drier habitat. These two species produce occasional hybrids...
with the inflorescence of S. keniensis. At that time, Senecio keniensis was rejected as a confused name "nomen confusum" based on the muddled samples from which made it impossible to select a single specimen,
but that practice is no longer permitted and the replacement name S. brassica is superfluous and other names that were based on this basionym are similarly illogical and incorrectly deduced. Examples: Fries
Robert Elias Fries
Robert Elias Fries , the youngest son of Thore M. Fries and grandson of Elias Magnus Friesand an expert on mushrooms...
and Fries
Thore Christian Elias Fries
Thore Christian Elias Fries was Professor of Systematic Botany at Lund University. He specialized in lichenology and plant geography. This botanist is denoted by the author abbreviation T.C.E.Fr. when citing a botanical name...
(1922) cited the confused material for S. brassica; Hedberg
Karl Olov Hedberg
Prof. Karl Olov Hedberg of Västeråsa botanist, taxonomist, author, professor of systematic botany at Uppsala University from 1970 to 1989 and an Editor of the Flora of Ethiopia; was updating the Umbelliferae manuscript when he died in 2007...
(1957) selected a single specimen from among the syntype
Syntype
In biological nomenclature, a syntype is a term used to indicate a specimen with a special status.In zoological nomenclature, a syntype is defined as "Each specimen of a type series from which neither a holotype nor a lectotype has been designated [Arts. 72.1.2, 73.2, 74]. The syntypes...
s that associated S. brassica with Fries & Fries.
Hybrid
- Senecio keniensis Baker subsp. keniensis x S. keniodendron R.E.Fr. & T.C.E.Fr. ex Hell.