Senecio keniensis

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Dendrosencio keniensis

Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Asterales
Family: Asteraceae
Tribe: Senecioneae
Genus: Dendrosenecio
Species: D. keniensis
Binomial name
Dendrosenecio keniensis
(Baker f.) Mabb.
Range of S. keniensis in Afrotropic
Range of S. keniensis in Afrotropic
Synonyms

Dendrosenecio brassica B. Nord.
Senecio brassica R.E.Fr. & T.C.E.Fr.
Senecio keniensis Baker f.
Lobelia gregoriana Baker f.
Sources:[1][2]

Dendrosencio keniensis or as it was known before its reclassification Senecio keniensis is one of the giant groundsels which is endemic the higher altitudes of Mount Kenya and from the family Asteraceae of the genus Dendrosenecio (previously a Senecio). Dendrosenecio keniodendron occupies the upper alpine zone of Mount Kenya and D. keniensis in the wetter areas of the lower alpine or the moorlands.[3] These giant plants, sometimes 6 metres (20 ft) tall, grow in even-aged and even-sized stands, dominate the communities they live in and play host to different eco-communities in their understory.[4]

Contents

[edit] Description

Dendrosenecio keniensis has different looks throughout its long life. In youth, a spherical mass of large radical leaves, looking a lot like a cabbage. As they age, they develop into a thick-stemmed, barrel-shaped plant a few feet in height (1.5 metres (4.9 ft) tall when in flower),[5] finally maturing into a tall woody-stemmed, branching tree capped by immense club-shaped heads of dense leaves.[6]

Leaves and stems
Vertically grooved trunks of soft brittle wood,[7] initially upright, with trunk to 5 centimetres (2.0 in) in diameter, pith to 2 centimetres (0.8 in) in diameter;[5] which branch once or twice, and sometimes a third time. The branches each support a great cabbage-like,[7] densely packed leaf-rosettes of 30–40 leaves; each branch cloaked with withered foliage. Branches produced near ground-level are readily capable of accidental or sparingly spontaneous rooting that potentially supports a "creeping" horizontal growth-form.[5] The leaves are oblong and more pointed 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 mucilaginous fluid containing polysaccharides. The upper leaf surface has a hair cushion which is also often coated with dried mucilage. The lower surface is covered densely with fine hairs.[5]
S. keniensis is frost resistant to −10 °C (14.0 °F)[8] This ability to withstand the colder temperatures that can be found in the upper altitudes of Mount Kenya has been called "adaptive insulation"[9] and is in part due 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 reservior of fluid from evaporating.[10] As well as the nyctinastic behavior of the leaf rosettes which open during the day and close when it becomes cold at night;[9] the outer leaves bend inwards and form around the central leaf bud.[11]
Flowers
Long spikes of groundsel flowers arise from each of the great cabbage-like rosette of leaves,[7] each spike or inflorescence narrowly conical up to 110 centimetres (43 in) tall and 20 centimetres (7.9 in) in diameter. The flower heads are pendulous each consisting of 12 to 16 ray florets up to 25 millimetres (0.98 in) long and 60-80 disc florets.[5]

[edit] Distribution

Giant Senecio; Mount Kenya is paradise.
ぼく, 2006[12]

Senecio keniensis makes its home mostly in the lower alpine or moorland zone located at altitudes of 2,900 metres (9,500 ft) to 3,800 metres (12,000 ft)[3] 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, 3,800 metres (12,000 ft) to 4,500 metres (15,000 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,[13] although it is less common above 4,000 metres (13,000 ft) where it can regularly hybridise with S. keniodendron.[4]

[edit] Name confusion

Nomen confusum
Nomen confusum

S. keniensis has a history which includes some confusion between it and other species from other genus 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 and the other way around also. 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[14], 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 syntypes that associated S. brassica with Fries & Fries. [5]

[edit] Subspecies

  • Senecio keniensis Baker subsp. keniensis x S. keniodendron R.E.Fr. & T.C.E.Fr. ex Hell.[15]

[edit] References

Sketch by John Walter Gregory of giant groundsel from The Great Rift Valley
Sketch by John Walter Gregory of giant groundsel from The Great Rift Valley[7]
Rock hyrax making a meal of D. keniensis
Rock hyrax making a meal of D. keniensis
  1. ^ Dendrosenecio keniensis (Baker f.) Mabb. record n° 105268 (HTML). African Flowering Plant Database (1986). Retrieved on 2008-03-27.
  2. ^ Missouri Botanical Garden (1894). Senecio keniensis Baker (HTML). Nomenclatural Data Base. Missouri Botanical Garden. Retrieved on 2008-03-27.
  3. ^ a b MIZUNO, Kazuharu. "VEGETATION SUCCESSION IN RELATION TO GLACIAL FLUCTUATION IN THE HIGH MOUNTAINS OF AFRICA" (PDF). African Study Monographs (Suppl.30): 195–212. 
  4. ^ a b Young, Truman P.; Mary M. Peacock (March 1992). "Giant senecios and alpine vegetation of Mount Kenya". Journal of Ecology 80 (1): 141–148. JSTOR. doi:10.2307/2261071. 
  5. ^ a b c d e f Aluka. Entry for Dendrosenecio keniensis (Baker f.) Mabb. (HTML). African Plants. Ithaka Harbors, Inc. DOI:10.5555/AL.AP.FLORA.FTEA006287. Retrieved on 2008-03-28.
  6. ^ Roosevelt, Theodore; Edmund Heller (1914). "LOGICALLY", Life-histories of African Game Animals (HTML), 1, Charles Scribner's Sons. Retrieved on 2008-03-28. 
  7. ^ a b c d Gregory, John Walter (1896). "The Flora of British East Africa", The Great Rift Valley: Being the Narrative of a Journey to Mount Kenya and Lake Baringo with Some Account of the Geology, Natural History, Anthropology and Future Prospect of British East Africa (HTML), Routledge, 422 pages. ISBN 0714618128. 
  8. ^ Bannister, Peter (2007). "A touch of frost? Cold hardiness of plants in the Southern Hemisphere" (PDF). New Zealand Journal of Botany 45: 1–33. The Royal Society of New Zealand. 0028­825X/07/4501­0001. 
  9. ^ a b Ernst-Detlef Schulze, Erwin Beck, Klaus Müller-Hohenstein (2005). "Temperature", in Translated by G. Lawlor: Plant Ecology (HTML), Springer, 702 pages. ISBN 354020833X. Retrieved on 2008-03-28. 
  10. ^ Truman P. Young, Susan Van Orden Robe (Sep., 1986). "Microenvironmental Role of a Secreted Aqueous Solution in the Afro-Alpine Plant Lobelia keniensis". Biotropica 18 (3): pp. 267–269. doi:10.2307/2388496. 
  11. ^ ERWIN BECK, MARGOT SENSER, RENATE SCHEIBE, HANS-MARTIN STEIGER, PAUL PONGRATZ1 (June 1982). "Frost avoidance and freezing tolerance in Afroalpine ‘giant rosette’ plants". Plant, Cell & Environment 5 (3): Page 215–222. Blackwell Publishing. doi:10.1111/j.1365-3040.1982.tb00913.x. 
  12. ^ I travel in Africa (HTML) (Japanese) (2006-11-23). Retrieved on 2008-03-28.
  13. ^ World Conservation Monitoring Centre (April 1997). UNEP-WCMC Protected Areas Programme -- Mount Kenya (HTML). United Nations Environment Programme. Retrieved on 2008-03-27.
  14. ^ Natural Resources Conservation Service (NRCS). Frequently Asked Questions -- definition for nomen confusum (HTML). The PLANTS Database. United States Department of Agriculture,. Retrieved on 2008-03-28. “nomen confusum (Latin): confused name. Based on heterogenous elements from which it is impossible to select a lectotype.”
  15. ^ Senecio keniensis Baker subsp. keniensis x S. keniodendron R.E.Fr. & T.C.E.Fr. ex Hell. record n° 98700 (HTML). African Flowering Plant Database. Retrieved on 2008-03-27.

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