Rhododendron album

Rhododendron album

Taxobox


status = VU | status_system = IUCN2.3
regnum = Plantae
divisio = Magnoliophyta
classis = Magnoliopsida
ordo = Ericales
familia = Ericaceae
genus = "Rhododendron"
species = "R. album"
binomial = "Rhododendron album"
binomial_authority = Blume
synonyms =

"Rhododendron album" is a species of plant in the Ericaceae family. It is endemic to Indonesia. It is threatened by habitat loss.

__TOC__Generally, the Rhododendron album is known to be white, but it can also appear lilac, depending on the type of hybrid. The stamen is often a different color, such as orange or pink, also depending on the type of hybrid. The flower is generally between four and six inches in height and width, and bloom in the spring, staying green throughout autumn. (Bay Science Foundation, 2008)

In 1998, the Rhododendron album was deemed vulnerable by the World Conservation Monitoring Center (World Conservation Monitoring Centre, 1998), which means it isn’t extinct or endangered, but faces a high risk of extinction in the mid-term future unless proper conservation methods are employed (Whitten et al. 1996).

The Rhododendron album is native to Java (Indonesian Jawa) Indonesia. It is mostly found in the increasingly smaller high elevation forests throughout western and central Java.

Threats

Habitat loss

The Rhododendron album as it grows natively is mainly threatened by habitat loss. The habitat loss of the Rhododendron album is mostly due to agriculture, extraction of trees and other species of plants, and expanding infrastructure throughout Java’s forests. The degradation of Java’s forests is more intense in lower elevations, but the higher elevations where the Rhododendron album grows is also affected and feels the effects of habitat loss (Whitten et al. 1996).

Most of Java’s forests have been cleared, and what is left is generally found in mountain areas. These forests are legally protected, although locals continue to extract trees for timber and firewood, and many depend on the trees for their livelihood. Tree cutting in many places in Java has changed the forest to the point that large parts of former forest are now covered with shrubs, and forest degradation, especially as a result of tree cutting, is widespread throughout Java (Smiet, 1992).

There are many other species who are threatened by the immense degradation of these forests. In order to save the Rhododendron album among other species, more education and a more strict enforcement of the law against tree cutting must be enforced. The Indonesian government must also decide how to reach an agreement with the locals of Java, as their livelihood often depends on the wood from the trees from these thinning forests. It has also been suggested that in order to save two endangered animals, the Javan gibbon and the grizzled leaf monkey, the reserve system in Java should extend into the Dieng Mountains as well (Nijman & van Balen, 1998). In working to save these endangered animals, conditions will improve for multiple other species native to Java.

Uses and Stakeholders

Although the Rhododendron album’s habitat is getting increasingly smaller and it’s getting harder to find in its native habitat, it is still grown fairly widely in nurseries throughout the world, especially America. Much research has been done to find different hybrids with high aesthetic value. One of the earliest hybrids created was the Rhododendron cawtawbiense var. album, known as the Catawba album. It was bred in 1886 by Anthony Waterer, a famous early hybridizer (Paghat, 2008).

Besides maintaining biodiversity, a main reason the Rhododendron album is important is its aesthetic value. The Rhododendron album, along with the many other variations and hybrids, are popular plants in the landscaping industry, and also are used for a variety of other decorations, including wedding and special occasion bouquets, corsages, and other floral arrangements.

Stakeholders in the Rhododendron album include nurseries across the world, and everyone who has ever enjoyed the sight of one of these beautiful plants. Economic value is a factor also, as millions of dollars are spent on flowers for landscaping and aesthetic value each year.

Diseases and research

Although nurseries have contributed to the continued survival of the Rhododendron album, they haven’t been able to save all of them, and there have been some outbreaks of disease. These diseases, caused by various bacteria and fungi, have been severe and widespread, although a lot of research has been done in order to ensure the Rhododendron album’s survival.

Pseudomonas cichorii

The diseases researched include a leaf spot disease caused by Pseudomonas cichorii. In September 1995, the bacteria was discovered on container-grown rhododendrons in a nursery in Georgia. The spots were at first very small, one to five millimeters in diameter, but soon grew into larger, reddish brown. They isolated different bacteria and soon learned that it was caused by the Pseudomonas cichorii (Uddin & McCarter, 1996). The article mentions nothing about finding a cure for the bacteria, but mentions that the disease was "severe and widespread." Phytophthora ramorum

Something else that has been found to cause disease on the Rhododendron album but is not easily cured for lack of information is Phytophthora ramorum. This is also the cause of sudden oak death in trees and ramorum blight on many other ornamental plants (Mcdonalad et al, 2006). In 2002 and 2003, studies were done in many nurseries throughout California and Oregon to test for Phytophthora ramorum. The symptoms of this disease were large necrotic spots with water soaked outside borders and rust colored centers. By collecting symptomatic plants, extracting DNA from the spots, and amplifying it with a PCR assay, GenBank matched the DNA to that of Phytophthora ramorum and P. lateralis. In 2004, Rhododendron leaves with similar symptoms were studied and showed the host range of P. hibernalis as well (Blomquist et al. 2005). In order to prevent these diseases from destroying the Rhododendron album, among many other plants, more must be learned about them. Measurements of fitness parameters of Phytophthora ramorum on different ornamental crops, including R. album would be vital towards understanding how a disease such as this spreads through nurseries, and would lead to better management and prevention of an outbreak of the disease (McDonalad, 2006). In a test of the susceptibility of five different types of Rhododendron to P. ramorum, these types were exposed to the zoospore suspension and left in a moist environment for 10 days. Measurements taken after the incubation period showed much difference in susceptibility between the five types of Rhododendron. Catawbiense album, the only variation of R. album used in the study, was found to be more susceptible than three of the other types of rhododendron (McDonalad et al. 2006).

Tissue Proliferation

Tissue proliferation is another disorder Rhododendron album has encountered in nurseries. It was first found in the mid-1980’s and is characterized by tumor like growths. These growths are usually towards the bottom of the stem, but can be above or below the soil line (Zimmerman, 1997). When it was first discovered, there was some worry among nursery owners and growers, many of whom suffered great losses when choosing to destroy plants that may have been diseased. Much research has been done, and it is believed that the disease is caused by Agrobacterium tumefaciens. Researchers have been working to isolate the bacteria, and also have asked for help from the nurseries and growers themselves in looking for links to possible causes. As of the time of this article, at least 15 states, along with Canada and the U.K. had reported cases of tissue proliferation (Zimmerman, 1997). In 1999, more research was done on tissue proliferation, and its likelihood to spread and create new tumors on normal looking plants. Once again, Rhododendron catawbiense album was one of the plants being tested. The research involved cultivars from TP positive stock plants and TP negative stock plants. They were grown outdoors for two years, then evaluated for symptoms of tissue proliferation. There were many differences between the TP positive and negative plants, and it was found that tumors are more likely to appear when taken from younger plants (three or fewer years) as opposed to older plants. Either way, it was proven that any cuttings from TP positive plants are capable of producing plants that exhibit symptoms of tissue proliferation, including tumor growth (Brand & KIYOMOTO, 1999). Continued research on tissue proliferation is critical, and there were few articles that I found discussing the treatment of TP. All of these diseases threaten Rhododendron album, and it is necessary for nurseries and growers to have education and information available about how to save their plants.

Breeding cycle and repopulation

There have been many steps taken towards saving and repopulating this plant, though. In 1955, researchers attempted to shorten the breeding cycle of the Rhododendron catawbiense album. They knew that if dormant buds of R. catawbiense album were dormant for too long, they were subject to breakage. They found that when keeping the plants at between 15 and 20 degrees Celsius, the number of growth periods was increased, and the speed of growth in many of the plants was twice that of a natural day. When applied to seedlings, this treatment cut the time taken to flower in half also. They developed a method using the treatment in order to cut the time in between generations, thus leading to more plants (Doorenbos, 1955).

Much research has been done on Rhododendrons, but with over 4,800 hybrids of the flower (Salley & Greer, 1992), research for specific types, such as the album, is slim. Hopefully, through awareness of saving the forests in Java and its species as a whole, and by studying the effects of diseases on different types of Rhododendrons, it will be possible to preserve the Rhododendron album in both its natural habitat, and as it is grown commercially for everyone to enjoy.

References

* World Conservation Monitoring Centre 1998. [http://www.iucnredlist.org/search/details.php/31988/all "Rhododendron album"] . [http://www.iucnredlist.org 2006 IUCN Red List of Threatened Species. ] Downloaded on 23August 2007.

Bay Science Foundation. Rhododendron Album. Revised April 27, 2008

World Conservation Monitoring Centre, 1998. Rhododendron album. In: IUCN 2007. 2007 IUCN Red List of Threatened Species. . Downloaded on 27 April 2008.

Whitten, T., Soeriaatmadja, R.E. and Afiff, S.A. 1996. The Ecology of Java and Bali. The Ecology of Indonesia Series. Volume III. Periplus Editions, Republic of Singapore.

Alfred C Smiet. Forest ecology on Java: Human Impact and Vegetation of Montane Forest. Journal of Tropical Ecology May 1992 Vol. 8, No 2 p 129-152.

Vincent Nijman, S. (Bas) van Balen (1998) A faunal survey of the Dieng Mountains, Central Java, Indonesia: distribution and conservation of endemic primate taxa Oryx, Volume 32 Issue 2 Page 145-156, April 1998

[http://www.paghat.com/catawbaalbum.html Paghat, 2008 Paghat’s Garden] Accessed 27 April 2008

W. Uddin & S. M. McCarter. First Report of Rhododendron Leaf Spot Caused by Pseudomonas cichorii . The American Phytopathological Society, May 30 1996

McDonalad, V., Grunwald, N.J., Linderman, R.G. 2006 Evaluation of Infection Potential and Sporulation of Phytophthora ramorum on five Rhododendron Cultivars. Phytopathology. 96:S75. 1 June 2006

Richard H. Zimmerman. A review of tissue proliferation of Rhododendron. International Symposium on Bacterial and Bacteria-Like Contaminants of Plant Tissue Cultures p 355-356. 1997

J. Doorenbos. Shortening the breeding cycle of rhododendron. Euphytica Vol. 4 No. 2 July 1955Brand M. H; Kiyomoto R. Redevelopment of tissue proliferation symptoms in rooted Rhododendron cuttings. HortScience 1999, vol. 34, no 4, pp. 723-726

Homer E. Salley & Harold E. Greer. Rhododendron Hybrids 1992 Timber Press p. viii


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