Cotyledon tomentosa

Cotyledon tomentosa
	Cotyledon tomentosa in bloom
Conservation status
	; Vulnerable (SANBI Red List)
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Order:	Saxifragales
Family:	Crassulaceae
Genus:	Cotyledon
Species:	C. tomentosa
Binomial name
	Cotyledon tomentosa; Harv., 1862
	Distribution of Cotyledon tomentosa in South Africa subsp. tomentosa subsp. ladismithiensis
Synonyms
	for subsp. tomentosa Cotyledon tomentosa; Harv., 1862; Cotyledon ladysmithiensis; Poelln., misapplied by Boom, 1958; for subsp. ladismithiensis Cotyledon heterophylla; Schonland, 1907 ( nom. illeg. ); Cotyledon ladysmithiensis; Poelln., 1936; Cotyledon tomentosa subsp. ladismithiensis; (Poelln.) Toelken, 1977 (possible nom. illeg. , see § Taxonomy);

Last updated November 28, 2024

Cotyledon tomentosa is a species of flowering plant in the family Crassulaceae, native to South Africa. It is a succulent evergreen shrub with large chunky ovate fuzzy green leaves. Its autonymous subspecies is known as the bear's paw because of the prominent "teeth" at the tips of its leaves. It forms large orange bell-shaped flowers in spring.

Description

Cotyledon tomentosa is a perennial evergreen shrub, which is a member of the Crassulaceae family of succulent flowering plants.^[6]C. tomentosa has red, orange, or yellow bell-shaped flowers between July and September,^[12]^[6] and there are two recognized subspecies, subsp. tomentosa and subsp. ladismithiensis.^[6]

C. tomentosa subsp. tomentosa, the autonymous subspecies, is a small, freely branched shrublet that grows to 70 cm tall. It has chunky green tomentose leaves that are oblanceolate to oblong, with 3-8 reddish teeth at the end.^[12]^[6] The other subspecies, subsp. ladismithiensis, features long cylindrical leaves that generally do not have teeth. Subsp. ladismithiensis also tends to be smaller and less branched than subsp. tomentosa. Finally, subsp. ladismithiensis has brown peeling bark, compared to the green hairy branches of subsp. tomentosa.^[6]

Leaf shape comparison

subsp. ladismithiensis

Taxonomy

Cotyledon tomentosa was described in 1862 by William Henry Harvey, and has no synonyms.^[3]^[4]

Cotyledon tomentosa subsp. ladismithiensis was first described in 1907 by botanist Selmar Schonland, who named it Cotyledon heterophylla. Schonland noted that C. heterophylla seemed "more robust than C. tomentosa, Harv. to which it is probably nearly allied." Schonland also cautioned that the differences he noted between C. heterophylla and C. tomentosa "to be used with great caution" as "relative characters [in the genus Cotyledon] are frequently inconstant."^[8] However, the name C. heterophylla was a nomen illegitimum , because it had already been applied in 1824 by William Roxburgh to what is now called Kalanchoe lanceolata.^[6]^[13]

In 1936, Karl von Poellnitz noted the conflict and gave the taxon a new name, Cotyledon ladysmithiensis,^[9] for its native range near the town of Ladismith, South Africa.^[14] Hellmut R. Toelken reclassified the taxon in 1977 as a subspecies, Cotyledon tomentosa subsp. ladismithiensis, retaining a different spelling of von Poellnitz's name.^[10] This is the current accepted name of the subspecies, as listed on Plants of the World Online.^[3] According to Magrit Bischofberger, von Poellnitz's original spelling should be used according to Article 60.1 of the International Code of Nomenclature , which states a name should not be changed even if it contains a spelling discrepancy (i.e. Ladismith vs. ladysmithiensis).^[11] Another spelling variation used by the Illustrated Handbook of Succulent Plants is "ladismithensis."^[6]

Ecology

Habitat and conservation

Cotyledon tomentosa is native to the semidesert Little Karoo region located in the southern parts of South Africa, from Ladismith to Steytlerville.^[15]C. tomentosa subsp. tomentosa is found near Calitzdorp, Willowmore, and Steytlerville,^[15] in the gravely soil of arid thicket, in slopes of sheltered ravines.^[1] In contrast, subsp. ladismithiensis is found in rocky outcrops in the southern Western Cape,^[2]^[15] between Laingsburg, Ladismith, and Muiskraal.^[15]

As of 2006, both subspecies are listed as vulnerable on the SANBI Red List of South African Plants, because they have only been found in small subpopulations and are threatened by habitat degradation and illegal gathering for the succulent trade.^[1]^[2]C. tomentosa subsp. tomentosa has only been found in five subpopulations,^[1] while subsp. ladismithiensis has only been found in seven subpopulations and has experienced a 10% decline in population over the past 90 years.^[2]

Toxicity

While C. tomentosa may be vulnerable to trampling by livestock,^[1]^[2] it is also known to be poisonous to livestock, dogs, and humans. Cotyledon species are known to contain cardiac glycosides, including bufadienolides,^[16] which are highly toxic to cattle, sheep, goats, and other livestock. The bufadienolides found in Cotyledon cause both acute and chronic poisoning.^[17] On the World Health Organization toxicity scale, cardiac glycosides are considered Class Ia, "extremely hazardous,"^[18] and a dose of only 1.0 g/kg body weight of a related species, Cotyledon orbiculata , was lethal when fed to sheep.^[19]

Bufadienolides are classified as neurotoxins because they are strong inhibitors of sodium potassium pumps which are central to the function of animal nervous systems.^[18] Acute poisoning causes cardiac irregularity and heart failure.^[17] Other acute symptoms include apathy, hypersalivation, and tremors.^[17] Chronic poisoning in sheep and goats causes a paraplegic disease known as krimpsiekte ("shrink disease" in Afrikaans),^[17]^[18] so named because poisoned individuals may arch their backs and bend their necks to one side.^[18] Krimpsiekte may have a mortality rate as high as 90%.^[20] These toxins persist in the flesh of livestock afflicted with krimpsiekte, even after cooking, and dogs who consume this meat can exhibit similar neuromuscular symptoms.^[18]^[21] This secondary poisoning may also affect humans, but has not been thoroughly investigated.^[21]

Cultivation

In cultivation they thrive with bright light and ample airflow. Water thoroughly when soil is dry to the touch. Water with caution in winter, as the plant can lose its roots if the soil stays cold and wet for extended periods. They are dormant in summer. Protect from frost to prevent scarring.^[22]^{[ better source needed ]}

In the UK Cotyledon tomentosa subsp. tomentosa has received the Royal Horticultural Society's Award of Garden Merit.^[12] It does not tolerate temperatures below 5 °C (41 °F), so in temperate zones must be protected with glass throughout the winter months. However, it may be placed in a warm, sunny position outside during summer.

Related Research Articles

The Crassulaceae, also known as the stonecrop family or the orpine family, are a diverse family of dicotyledon flowering plants characterized by succulent leaves and a unique form of photosynthesis, known as Crassulacean acid metabolism (CAM). Flowers generally have five floral parts. Crassulaceae are usually herbaceous but there are some subshrubs, and relatively few treelike or aquatic plants. Crassulaceae are a medium-sized monophyletic family in the core eudicots, among the order Saxifragales, whose diversity has made infrafamilial classification very difficult. The family includes approximately 1,400 species and 34–35 genera, depending on the circumscription of the genus Sedum, and distributed over three subfamilies. Members of the Crassulaceae are found worldwide, but mostly in the Northern Hemisphere and southern Africa, typically in dry and/or cold areas where water may be scarce, although a few are aquatic.

<i>Kalanchoe</i> Genus of flowering plants in the stonecrop family

Kalanchoe, , is a genus of about 125 species of tropical, succulent plants in the stonecrop family Crassulaceae, mainly native to Madagascar and tropical Africa. A Kalanchoe species was one of the first plants to be sent into space, sent on a resupply to the Soviet Salyut 1 space station in 1979. The majority of kalanchoes require around 6–8 hours of sunlight a day; a few cannot tolerate this, and survive with bright, indirect sunlight to bright shade.

Bryophyllum is a group of plant species of the family Crassulaceae native to Madagascar. It is a section or subgenus within the genus Kalanchoe, and was formerly placed at the level of genus. This section is notable for vegetatively growing small plantlets on the fringes of the leaves; these eventually drop off and root. These plantlets arise from mitosis of meristematic-type tissue in notches in the leaves.

Kalanchoe daigremontiana, formerly known as Bryophyllum daigremontianum and commonly called mother of thousands, alligator plant or Mexican hat plant, is a succulent plant native to Madagascar. Like other members of Bryophyllum, it can propagate vegetatively from plantlets that develop on its leaf margins, as well as through upshoots from lateral roots, and seeds. All parts of this species contain a very toxic steroid known as daigremontianin.

Cotyledon is one of some 35 genera of succulent plants in the family Crassulaceae. Mostly from Southern Africa, they also occur throughout the drier parts of Africa as far north as the Arabian Peninsula. Ten of its species are mostly confined to South Africa, where unlike Tylecodon, they occur commonly in both the winter and summer rainfall regions. They may be found on coastal flats and rocky hillsides, or as cremnophytes on cliff faces. Their decussate, evergreen leaves are highly variable in shape, even within some species, but the flowers, apart from colour, are very similar.

Adromischus is a genus of flowering plants. They are easily-propagated, leaf succulents from the family Crassulaceae, which are endemic to southern Africa. The name comes from the ancient Greek adros (=thick) and mischos (=stem).

Daigremontianin is a bufadienolide. Bufadienolides are steroids and cardiac glycoside aglycones that are similar to cardenolides, differing only in the structure of the C-17 substituent on the D ring. This chemical has been found to be toxic in experiments on mice. It is one of five bufadienolides that have been isolated from Kalanchoe daigremontiana.

Cotyledon orbiculata, commonly known as pig's ear or round-leafed navel-wort, is a South African succulent plant belonging to the genus Cotyledon.

Tylecodon is a genus of succulent plants in the family Crassulaceae, native to southern Africa.

Kalanchoe delagoensis, formerly known as Bryophyllum delagoense and commonly called mother of millions or chandelier plant, is a succulent plant native to Madagascar. Like other members of Bryophyllum, it is able to propagate vegetatively from plantlets that develop on its leaf margins.

Kalanchoe pinnata, commonly known as cathedral bells, air plant, life plant, miracle leaf, Goethe plant, and love bush, is a succulent plant native to Madagascar. It is a popular houseplant and has become naturalized in tropical and subtropical areas. The species is distinctive for the profusion of miniature plantlets that form on the margins of its leaves, a trait it has in common with some other members of Bryophyllum.

Crassula brevifolia is a succulent plant in the family Crassulaceae. It is native to the arid western edge of South Africa as well as southern Namibia.

Crassula subaphylla is a succulent plant belonging to the family Crassulaceae. It is widespread in the Karoo regions of South Africa and Namibia.

Crassula pellucida is a creeping, succulent ground-cover, or low-growing, spreading succulent shrub. It is native to eastern and southern Africa, ranging from Kenya and Angola to South Africa.

Tylecodon wallichii is a species of succulent plant in the genus Tylecodon belonging to the family Crassulaceae. The species is named in honour of Nathaniel Wallich, early 19th century Danish plant hunter, botanist and physician.

Tylecodon reticulatus is a species of succulent plant in the genus Tylecodon belonging to the family Crassulaceae.

Tylecodon paniculatus, also known as butter bush, butter tree, butterboom or rooisuikerblom (Afrikaans), is a species of succulent plant in the genus Tylecodon belonging to the family Crassulaceae.

Adromischus filicaulis is a perennial, succulent plant in the family Crassulaceae. It is commonly called brosplakkies in Afrikaans. The species is endemic to South Africa and Namibia.

References

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↑ S. Steyn, Pieter; R. van Heerden, Fanie (1998). "Bufadienolides of plant and animal origin". Natural Product Reports. 15 (4): 397–413. doi:10.1039/a815397y. ISSN 0265-0568. PMID 9736996. S2CID 30031690.
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