Roystonea
| Roystonea | ||||||||||||
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Royal Palm ( Roystonea regia ) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Roystonea | ||||||||||||
| OFCook |
Roystonea is a genus of palm trees . It occurs in tropical America in and around the Caribbean and comprises ten species . The best known is the royal palm ( Roystonea regia ), which is often planted as an ornamental plant. They are single-stemmed palms with large, pinnate leaves and a conspicuous crown shaft formed from the leaf sheaths. Roystonea is the only genus of the Roystoneeae tribe .
features
root
The roots are adventitious roots that arise on the trunk. Often they arise just above the soil surface and are therefore visible. As with most palm trees, the roots are thick and branchy. Young roots have root hairs . Small nodules that have been identified as sites of mycorrhizal infection sit on the roots . These are vesicular-arbuscular mycorrhiza .
tribe
The trunk of most species is gray-white and rather strong. It is often compared to marble columns. Exceptions are Roystonea violacea with a purple-brown trunk, as well as Roystonea borinquena and Roystonea altissima with a gray-brown or cinnamon-brown trunk. The leaf scars are usually clearly visible. The trunk of most species is rather thick with a diameter of about 47 cm at chest height . Exceptions to this are the slender trunks of Roystonea altissima and Roystonea maisiana . The stems of Roystonea regia and Roystonea lenis in particular are often swollen. Stressful conditions lead to slender trunks, good growth conditions lead to thick ones, which is why irregular thickenings and thinning can be found along a trunk. The information about the maximum height of the trunk are quite different. The greatest value (without crown shaft) from the 20th century is 38.7 m for a specimen of Roystonea oleracea . In 1838 a 57 m high palm was reported. Even earlier reports from the 17th century of 95 m and more are now regarded as exaggerations. Young plants do not begin to form an above-ground stem until two years after germination.
leaves
The leaf sheaths form a crown shaft, which is very conspicuous and green in all species. The leaves are pinnately divided and arranged alternately or spirally. The individual leaf leaflets are folded twice. The ends of the feathers are pointed. The outward-facing (abaxial) side of the sheaths, the petiole , the rachis and the central ribs of the pinna are covered with chaff-like, multicellular scales. The petiole is up to 50 cm long. Along the lower two thirds of the rachis runs a tissue bar on its upper side, which resembles the hastula of palm-shaped pinnate palms (like sabal ). The feathers are almost opposite along the rhachis. They do not form a uniform plane, which gives the leaves a feathery appearance. The leaflets have a distinct midrib. Furthermore, six second-order veins and two marginal veins can usually be seen. Multicellular hairs with multi-row stems sit on the leaf surfaces. They are particularly close along the central ribs of the feathers. Raphids and silicate bodies occur on cell inclusions in the leaves . Stomata are limited to the underside of the leaves.
inflorescence
The inflorescence appears between the leaves and has a short cover sheet and a single, leathery spathe that envelops the distal part of the inflorescence stalk and all side branches of the inflorescence. A single inflorescence is formed in each leaf axil of the crown. The cover sheet is usually double-keeled and tears open by the growth of the spathe. The bud of the inflorescence is ellipsoidal or obovate to spindle-shaped, the end is pointed. The spathe is around three times as long as the cover sheet. Before the anthesis , the spathe tears open lengthways, curls up and finally falls off. The inflorescence axes are whitish before and during anthesis and turn green as the fruit ripens. The inflorescence is three to four times branched. Branched, colorless hairs are formed on the axes , which peel off before the anthesis.
blossoms
The flowers of all kinds are unisexual and are on the inflorescence axes in groups of three of a female flower and two lateral male. There are only male flowers at the ends of the axes. The flowers are sessile.
The male flowers of most species are white. In Roystonea borinquena they are yellowish ivory with purple anthers , in Roystonea violacea and Roystonea altissima violet-purple. The female flowers are mostly whitish with green pistils , in Roystonea violacea and Roystonea altissima also purple. Both male and female flowers have three sepals . These overlap in such a way that the edges of one sepal are completely covered by the other two, the edges of another are both visible, with the third one edge is visible, the other is covered. The sepals of the female flowers are uniformly kidney-shaped, while the shape of the male flowers differs from species to species. The petals of the male flowers are oval and fused at the lower end, but appear free. In the female flowers, they are fused about half their length, thick, leathery and have a very high tannin content .
The stamens usually appear in numbers of six, with numbers between five and ten occurring. At their base they are fused with the petals as well as with each other. The abaxial (outward-facing) side of the anthers and the connective are colored in all species. The anthers are more or less straight, only curved in Roystonea oleracea . The female flowers have a staminodial ring that is fused with the petals about half of its height. This feature occurs only in this genus. The pollen is monosulcate (has an elongated germinal furrow), its exine is not perforated and forms a tectum . The surface is warty to wrinkled. The size of the pollen grains is 45 to 49 µm .
The gynoeceum is pseudomonomer: only one of the three ovules matures. In rare cases, fruits with two seeds appear. The scar moves to the base of the fruit as the fruit grows, and is therefore called eccentric.
Fruits and seeds
The fruits are stone fruits . Their shape ranges from spherical to ellipsoidal to humped. The sepals are preserved, as are remains of the staminodes and crown. During ripening, the color usually changes from green to dull red to dark purple. In Roystonea borinquena they ripen from green to yellow-brown to purple. The exocarp is smooth and includes the oily, fleshy mesocarp . The endocarp is brittle to hard. At the endocarp there is a paper layer made of numerous fibers, which is probably part of the mesocarp. The endocarp encloses a single seed . The seed is ovate to ellipsoidal. The raphe is circular and clearly visible. The small embryo sits basally on the dorsal side of the seed. The endosperm is bony, white and uniform.
Seedlings
The first two leaves of the seedling are scale-shaped. They are followed by an undivided, finely sawn primary leaf . It is usually linear-lanceolate, short or not stalked and weakly ribbed.
Flower and diaspore ecology
Roystonea is proterandric : the male flowers bloom first at the ends of the inflorescence axes, then towards the base of the inflorescence. The female flowers bloom shortly after the male, the flowering period can also briefly overlap. The male flowers are open for a day and then fall off. The opening time of the female flowers is not known. Nothing is known about the reproductive system of the individual species, but at least some are likely to be self-compatible.
The pollination is expected by insects done, especially by Hymenoptera , especially bees . Adaptations of the genus to this form of pollination are open, panicle inflorescences that are not covered by the spathe, flowering during the day, abundant nectar and pollen production, and thin flower parts. Roystonea regia pollen was found in the stomach of bats , but the proportion of bats in pollination is estimated to be rather low. Several species of birds collect nectar from the flowers of Roystonea borinquena , but they are also considered to be insignificant pollinators.
Various species of birds and bats have been observed eating the fruits that represent the diaspores . The colored, oily stone fruits are produced in large quantities and are likely to form an important food source for many animals.
Distribution and locations
The genus Roystonea occurs on the islands of the Caribbean as well as the surrounding areas on the mainland: Northern Venezuela , Northern Colombia , Central America , Southern Mexico and Florida .
All species need a tropical or subtropical climate, they are sensitive to the cold. In culture, however, they can survive frosts. Locations are the edges of the rainforests , seasonally flooded savannas , open savannas, swamps, mangrove swamps, and river banks. They do not thrive in dry locations. Roystonea oleracea rises up to 1600 m above sea level, the other species up to a maximum of 800 m. Most species grow in calcareous soil. They also need full sunlight after the teenage stage.
Systematics
The genus Roystonea O.F. Cook is placed within the palm family (Arecaceae) in the subfamily Arecoideae and here alone in the tribe Roystoneeae.
Scott Zona accepted 10 species in his generic monograph in 1996. These were adopted in 2005 by Rafael Govaerts and John Dransfield in their World Checklist of Palms .
- Roystonea altissima (Mill.) HEMoore : Home is Jamaica.
- Roystonea borinquena O.F. Cook : The homeland stretches from Hispaniola to the Virgin Islands .
- Roystonea dunlapiana P.H. Allen : It is native to southeastern Mexico, Honduras and Nicaragua.
- Roystonea lenis León : The home is eastern Cuba.
- Roystonea maisiana (LHBailey) Zona : The home is eastern Cuba.
- Roystonea oleracea (Jacq.) OFCook : The range extends from the Lesser Antilles to Venezuela and Colombia.
- Roystonea princeps (Becc.) Burret : The home is southwestern Jamaica.
- Royal palm ( Roystonea regia (Kunth) OFCook ): The range extends from southern Florida to Mexico, the Caribbean to Belize and Honduras.
- Roystonea stellata León : The home was eastern Cuba. The species was last collected in 1941.
- Roystonea violacea León : The home is eastern Cuba.
The genus Roystonea was established in 1900 by OF Cook for the royal palm ( Roystonea regia ) endemic to Cuba , which until then had been listed as Oreodoxa regia . The generic name honors the American pioneer general Roy Stone , who was stationed in Puerto Rico at the time. The fact that Cook named a genus that only occurs in Cuba after an officer stationed in Puerto Rico is probably due to the fact that he was already planning to transfer the species Oreodoxa oleracea, which occurs in Puerto Rico, to the new genus. This took place in 1901. A first revision of the genus by Bailey in 1935 resulted in nine species, including three new. In 1943 Hermano León described three new species from Cuba, which thus became the center of diversity of the genus. Bailey recognized 14 species in 1949, and Allen described two new species from Honduras in 1952. In his 1996 monograph for Flora Neotropica , Scott Zona only recognized 10 species. The cladistic analysis by Zona also showed that the various proposed subdivisions of the genus are obsolete.
use
The trunks of many species are used as construction timber and the leaves are used to cover roofs. The fruits are fed to pigs. The royal palm ( Roystonea regia ) is planted as an ornamental plant in the tropics around the world.
supporting documents
- Scott Zona: Roystonea (Arecaceae: Arecoideae) . In: Flora Neotropica. Volume 71, 1996, pp. 1-35. (JSTOR)
Individual evidence
- ^ Robert Lee Riffle, Paul Craft: An Encyclopedia of Cultivated Palms. 4th edition. Timber Press, Portland 2007, ISBN 978-0-88192-558-6 , pp. 441-443.
- ^ John Dransfield, Natalie W. Uhl, Conny B. Asmussen, William J. Baker, Madeline M. Harley, Carl E. Lewis: A New Phylogenetic Classification of the Palm Family, Arecaceae . In: Kew Bulletin. Volume 60, 2005, pp. 559-569. (JSTOR)
- ↑ Rafaël Govaerts (ed.): Roystonea. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved August 21, 2009.
