Larch ((TOP))
Larches are deciduous conifers in the genus Larix, of the family Pinaceae (subfamily Laricoideae). Growing from 20 to 45 metres (65 to 150 feet) tall,[1] they are native to the cooler regions of the northern hemisphere, where they are found in lowland forests in the high latitudes, and high in mountains further south. Larches are among the dominant plants in the boreal forests of Siberia and Canada. Although they are conifers, larches are deciduous trees that lose their needles in the autumn.
larch
The flames soon kindled the brushwood which lay about that wooden structure and, rising towards heaven, made everybody think that the whole pile had fallen. But when the fire had burned itself out and subsided, and the tower appeared to view entirely uninjured, Caesar in amazement gave orders that they should be surrounded with a palisade, built beyond the range of missiles. So the townspeople were frightened into surrendering, and were then asked where that wood came from which was not harmed by fire. They pointed to trees of the kind under discussion, of which there are very great numbers in that vicinity. And so, as that stronghold was called Larignum, the wood was called larch.
The genus Larix is present in all the temperate-cold zones of the northern hemisphere, from North America to northern Siberia passing through Europe, mountainous China and Japan. The larches are important forest trees of Russia, Central Europe, United States and Canada. They require a cool and fairly humid climate and for this reason they are found in the mountains of the temperate zones, while in the northernmost boreal zones ones they are also found in the plain. At gen. Larix belong to the trees that go further north than all, reaching in the North America and Siberia the tundra and polar ice. The larches are pioneer species not very demanding towards the soil and they are very long-lived trees. They live in pure or mixed forests together with other conifers or more rarely broad-leaved trees.
In the past, the cone bract length was often used to divide the larches into two sections (sect. Larix with short bracts, and sect. Multiserialis with long bracts), but genetic evidence[5] does not support this division, pointing instead to a genetic divide between Old World and New World species, with the cone and bract size being merely adaptations to climatic conditions. More recent genetic studies have proposed three groups within the genus, with a primary division into North American and Eurasian species, and a secondary division of the Eurasian into northern short-bracted species and southern long-bracted species;[6][7][8][9] there is some dispute over the position of Larix sibirica, a short-bracted species which is placed in the short-bracted group by some of the studies and the long-bracted group by others. The genus Larix belongs to the subfamily Laricoideae, which also includes the genera Pseudotsuga and Cathaya.
A well-known hybrid, the Dunkeld larch Larix marschlinsii, arose more or less simultaneously in Switzerland and Scotland when L. decidua and L. kaempferi hybridised when planted together, is still treated as unresolved.[10] Larix stenophylla Sukaczev is another probable hybrid still unresolved.
Larches are associated with a number of mycorrhizal fungal species, including some species which primarily or only associate with larch. One of the most prominent of these species is the larch bolete Suillus grevillei.[11]
Larches are prone to the fungal canker disease Lachnellula ssp. (larch canker); this is particularly a problem on sites prone to late spring frosts, which cause minor injuries to the tree allowing entry to the fungal spores. In Canada, this disease was first detected in 1980 and is particularly harmful to an indigenous species larch, the tamarack, killing both young and mature trees.[12]Larches are also vulnerable to Phytophthora ramorum. In late 2009 the disease was first found in Japanese larch trees in the English counties of Devon, Cornwall and Somerset, and has since spread to the south-west of Scotland.[13][failed verification]In August 2010 the disease was found in Japanese larch trees in counties Waterford and Tipperary in Ireland[14][failed verification] and in 2013 in the Afan Forest Park in south Wales.[15]Laricifomes officinalis is another mushroom found in Europe, North America and northern Asia that causes internal wood rot. It is almost exclusive guest of the gen. Larix. Other diseases are given by mushrooms, fungal rusts, bacteria and insects.
Larch wood is valued for its tough, waterproof and durable qualities. Top quality knot-free timber is in great demand for building yachts and other small boats, for exterior cladding of buildings, and interior paneling. The timber is somewhat resistant to rot when in contact with the ground, and historically was used as posts and in fencing. However, European Standard EN 350-2 lists larch as slightly to moderately durable; this would make it unsuitable for ground contact use without preservative in temperate climates, and would give it a limited life as external cladding without coatings.[16]
From early modern German Larche, Lärche, from Middle High German larche, from Old High German larihha, early borrowing from Latin larix, itself possibly of Gaulish origin. In the first century AD, Vitruvius wrote that the tree was given the Latin name "larigna" when the Romans discovered it at the town of Larignum.
The major commercial sources of arabinogalactan are the North American larch trees, which are genetically different from Eurasian larch tree species [14]. The genus Larix (Larches) is common throughout the world. Table 1 provides an overview of the different Larix species that grow in specific regions [Table 1].
Both the concentration and distribution of arabinogalactan varies between Larix species as well as within a single species, but may constitute up to 35 % by weight of dry heart wood of a larch tree [13, 15, 16]. Unique properties of larch arabinogalactan include its complete solubility and stability over a wide range of concentrations, pHs and temperatures [17].
More specific information on the enhancement of an immune response following a challenge has been obtained using the vaccine challenge method. The impact of a 10-week supplementation period with 4.5 g/d of a proprietary arabinogalactan preparation from larch tree (ResistAid brand) was studied in a vaccine model [31]. The researchers demonstrated that the preparation selectively enhanced the antibody response to vaccination against Streptococcus pneumoniae and observed an increase in pneumococcal IgG antibodies of various pneumococcal antigens [31].
Carbohydrates of plant fibers are known to be digested to varying degrees by the large bowel flora [40] and Isphagula husk (an arabinoxylan of similar structure to arabinogalactan) metabolization by the gut flora reaches 85-100 % in humans [24, 41]. Moreover, Vince et al. have used an in vitro faecal incubation system and suggest complete fermentation of acacia gum arabinogalactan after 48 h [24]. The fermentation by the resident colonic microflora of larch arabinogalactan results in the production of the short chain fatty acids (SCFA) [Fig. 1], butyrate, acetate and propionate [12, 17, 24], with the latter two being predominantly produced [42]. Apart from this pathway, the existence of a transfer of the whole molecule of arabinogalactan to the systemic immune system via the M-cells of the GALT [34] is supported by the study of Yamashita et al. [43] on antitumor peptidomannan KS-2, providing evidence that orally administrated polysaccharides could be absorbed via portal vein and intestinal lymphatics into the general circulation with an intact molecular size.
The common cold is a viral infection with important economic burdens in Western countries. The research and development of nutritional solutions to reduce the incidence and severity of colds today is a major focus of interest, and larch arabinogalactan seems to be a promising supportive agent. Arabinogalactan has been consumed by humans for thousands of years and is found in a variety of common vegetables as well as in medicinal herbs. The major commercial sources of this long, densely branched, high-molecular-weight polysaccharide are North American larch trees. The aim of this article is to review the immunomodulatory effects of larch arabinogalactan derived from Larix laricina and Larix occidentalis (North American Larix species) and more specifically its role in the resistance to common cold infections. In cell and animal models, larch arabinogalactan is capable of enhancing natural killer cells and macrophages as well as the secretion of pro-inflammatory cytokines. In humans a clinical study demonstrated that larch arabinogalactan increased the body's potential to defend against common cold infection. Larch arabinogalactan decreased the incidence of cold episodes by 23 %. Improvements of serum antigen-specific IgG and IgE response to Streptococcus pneumoniae and tetanus vaccination suggesting a B cell dependent mechanism have been reported in vaccination studies with larch arabinogalactan, while the absence of response following influenza vaccination suggests the involvement of a T cell dependent mechanism. These observations suggest a role for larch arabinogalactan in the improvement of cold infections, although the mode of action remains to be further explored. Different hypotheses can be envisaged as larch arabinogalactan can possibly act indirectly through microbiota-dependent mechanisms and/or have a direct effect on the immune system via the gut-associated lymphoid tissue (GALT).
As stated previously, larch trees look like normal coniferous trees during the spring and summer months. Their bright green needles are soft and feathery to the touch. They are also quite small, only growing about an inch to two inches long with each cluster containing 30 to 40 needles at most. During these warmer months, you may find pink flowers in between the needles. These flowers will eventually produce cones that start out red or yellow and then turn brown as they mature. 041b061a72