Prunus grisea

Prunus grisea, most commonly known as lago, is a species of flowering plant in the family Rosaceae, and is endemically distributed throughout East, South, and Southeast Asia, as well as parts of Melanesia, spanning over many countries.

Description

Prunus grisea is a versatile tree or shrub, reaching heights of up to Template:Cvt, with a crooked or straight cylindrical bole that can remain branchless for up to Template:Cvt and reach diameters of Template:Cvt, occasionally displaying small buttresses. The twigs are initially pubescent to puberulous, quickly becoming glabrous. The leaves vary in shape, predominantly elliptic to oblong but sometimes ovate or lanceolate, ranging from Template:Cvt in length and Template:Cvt in width, with a rounded or acute base and typically an acuminate apex, though it can occasionally be obtuse. They exhibit 5–9 pairs of venation, which is inconspicuous to invisible, and are sparsely pubescent to glabrous on both surfaces. Basal glands, typically two but occasionally absent or numbering up to 4, are flat, with additional glands often present. The petiole measures between Template:Cvt and transitions from pubescent to glabrous. Stipules, linear and deciduous, range from Template:Cvt in length, typically glabrous inside but occasionally glandular-serrate on the margins. The solitary axillary racemes measure between Template:Cvt, with a peduncle up to Template:Cvt and a sparsely pubescent rachis. Pedicels are very short, between Template:Cvt. The hypanthium, Template:Cvt high, is pubescent externally, glabrous inside or occasionally with hairs on the bottom. The perianth consists of 6–13 segments that are either subequal or distinguishable as sepals and petals, measuring between Template:Cvt. Flowers lack true petals, with stamens numbering 15–50, possessing filaments up to Template:Cvt long and anthers between Template:Cvt in length. The ovary is generally glabrous but may exhibit some hairs, rarely being distinctly hairy, with a style up to Template:Cvt long. The fruits are globular to transversely ellipsoid, measuring Template:Cvt by Template:Cvt, occasionally pointed or beaked, with a nearly glabrous exocarp that transitions in color from whitish to red, then purple, and ultimately black. The mesocarp is thin, and the endocarp is either glabrous or sparsely hairy internally, and the seed has a smooth, glabrous testa. The wood of Prunus grisea is diffuse-porous, with a density of 0.57 g/cm³, displaying vessels numbering 5–20/mm² and tangential vessel lumina ranging from Template:Cvt. Vessel-ray pits are coarse throughout the ray cells, and perforation plates are simple. Intervessel pits are small, measuring Template:Cvt or less, with occasional helical thickenings. Axial parenchyma appears in diffuse or aggregated apotracheal formations and in scanty or vasicentric paratracheal arrangements, sometimes forming aliform structures with strands of 5–8 cells. Rays exceed Template:Cvt in height and are 1–3 cells wide, composed of procumbent body ray cells with 2–4 rows of upright or square marginal cells. Fibers are very thin-walled, with simple to minutely bordered pits. The heartwood is reddish brown, while the sapwood is lighter in color. The grain is typically wavy or interlocked, and the texture is fine to medium.

Distribution

Prunus grisea is found across a very wide range, encompassing many regions. In Malesia, it is present throughout its near entirety, where it occurs most notably in Bohol, Borneo, Cebu, Java, the Kangean and Lesser Sunda Islands, Leyte, Luzon, the Maluku Islands, Mindanao, Mindoro, New Guinea, Palawan, Sibuyan, Sulawesi, and Sumatra. The presence of Prunus grisea within Indochina extends to Cambodia, Myanmar, Peninsular Malaysia, Singapore, Thailand, and Vietnam. Other countries in Asia include Afghanistan, China, where it occurs in Guangdong and Yunnan, along with India, Japan, and Taiwan. Outside of Asia, the plant has been introduced to Guinea, the Hawaiian Islands, Queensland, and the United Kingdom.

Prunus grisea was inferred to have dispersed from the Sunda Shelf to the Philippines in the early Miocene, having dispersed from Sahul to the Sunda shelf during the late Oligocene and early Miocene, suggesting historical movement across these biogeographic zones. Collections of Prunus grisea from various localities did not form a distinct clade, indicating unresolved phylogenetic relationships within the section Mesopygeum.

Ecology

Prunus grisea is primarily found in the wet tropical biome, thriving across a broad elevational range from Template:Cvt. In its native habitat, it occupies primary and secondary lowland to montane forests, with distinct elevational preferences among its varieties, being a plant that engages in zoochory. In Hawaii, the plant has been naturalized, having been observed forming dense seedling carpets and thickets of scattered saplings around planted trees, the seedlings exceeding 100/m², predominantly within a concentrated 400 m² (1,300 ft²) area surrounding the original plantings.

Taxonomy

Prunus grisea was first described by Carl Ludwig Blume in 1858 as Pygeum griseum, and was later reassigned to its current name by Cornelis Kalkman in 1965. Due to Prunus having a long and complicated taxonomic history, the taxon has changed many times, resulting in a long list of synonyms, totaling approximately 55 across its varieties.

Onomastics

The common names of Prunus grisea vary by region, displaying a variety of terms due to its large extent. In the Philippines, the plant goes by amongyang, amatogan, and lago, which is also its trade name. In China, it goes by 蘭嶼野櫻花, and in Thailand, it goes by nut ton (Template:Langx).

The genus name Prunus is derived from the Latin "prūnus," which is borrowed from Ancient Greek. The species epithet of Prunus grisea is the nominative form of its neuter counterpart, meaning "gray."

Varieties

Prunus arborea is a widespread and variable species, exhibiting morphological variation across its 3 varieties.

Prunus grisea var. grisea

Prunus grisea var. grisea, a variety of unknown taxonomic origin, is a tropical tree reaching up to Template:Cvt found across Asia, inhabiting the primary and secondary forests of the wet tropical biome, at elevations of Template:Cvt. The bark is smooth or lenticellate, varying from gray-brown to dark brown, with an inner bark that is yellowish and has a strong odor. The leaves are elliptic to oblong or ovate to lanceolate, ranging from Template:Cvt by Template:Cvt. Inflorescences appear as racemes Template:Cvt long, with pedicels numbering Template:Cvt. The hypanthium is Template:Cvt high, and perianth segments are subequal, sometimes divided into sepals and petals. Fruits are globular to transversely ellipsoid, and are Template:Cvt by Template:Cvt, changing colors as they age. Morphological variations across its range are gradual, but geographical and altitudinal factors primarily account for distinguishing features rather than strict taxonomic divisions. Terms that distinguish the variety from its parent taxon include huru, kawojang, lego, tanga, tanga-tanga, and tunga. While sometimes reported as a timber tree, it is rarely exploited commercially.

Prunus grisea var. microphylla

Prunus grisea var. microphylla, first described by Cornelis Kalkman in 1965, is a shrub or small tree, rarely exceeding Template:Cvt, where it grows in montane and subalpine forests in the wet tropical biome of New Guinea, at elevations of Template:Cvt. It has rough, brown to gray bark, noted for use in crafting belts. The stiff-coriaceous leaves that are elliptic to elliptic-oblong, measuring Template:Cvt by Template:Cvt, with an obtuse or retuse apex and 2–4 basal glands. Inflorescences are racemes Template:Cvt long, with pedicels Template:Cvt. The hypanthium measures Template:Cvt high, and perianth segments are subequal, occasionally divided into sepals and petals, which are Template:Cvt long. The ovary is glabrous, and the fruits are transversely ellipsoid to subglobular, Template:Cvt by Template:Cvt, with a hypanthium remnant under the fruit sometimes reaching Template:Cvt. Though it shares habitat and elevation ranges with other varieties, it is distinguished primarily by its smaller, thicker leaves, with transitional specimens being rare.

Prunus grisea var. tomentosa

Prunus grisea var. tomentosa, first described by Sijfert Hendrik Koorders and Theodoric Valeton in 1900 as Pygeum latifolium var. tomentosum and later reassigned to its current name by Cornelis Kalkman in 1965, is a small tree or shrub, typically under Template:Cvt in height, with brown bark and ovate to oblong, papery leaves that measure Template:Cvt by Template:Cvt and often bear 2 basal glands. Its racemes are short, Template:Cvt, densely arranged, and bear 7–10 minute perianth segments, which are sometimes differentiated. The ovary is generally glabrous, though occasionally sparsely hairy, and produces fruits that range from transversely ellipsoid to subglobular, measuring Template:Cvt by Template:Cvt, sometimes with a small apical beak. Its range spans throughout Southeast Asia, inhabiting the primary and secondary forests of the wet tropical biome at elevations of Template:Cvt, exhibiting some regional variation across its range. The species faces threats from habitat loss due to logging and shifting cultivation, leading to its listing of VU by the IUCN Red List, although further research is needed for updated conservation assessments.

Uses

Studies on Prunus grisea indicate that its bark and leaves possess antioxidant and cytotoxic properties, with traditional uses including bark applications for skin irritation and leaves for rheumatism relief. Research evaluating its leaf decoction and various extracts has shown potent antioxidant activity, particularly in the decoction, which exhibited a 92.85% antiradical activity at 500 ppm, along with high total antioxidant capacity and phenolic content. Toxicity assessments using the brine shrimp lethality assay revealed that the chloroform extract had the highest toxicity, with an LC50 value of <10 ppm, while bioassay-guided fractionation of air-dried leaf hexane extracts identified PGH13 as the most bioactive fraction, demonstrating 56.67% mortality against Artemia salina.

The wood of Prunus grisea is legally unrestricted for use. It exhibits moderate durability but is generally perishable, making it susceptible to decay and insect damage. Drying is slow and can be challenging, with risks of distortion during the process. In veneer applications, Prunus grisea performs well, demonstrating good lamination properties in both rotary and sliced veneer cutting. Machining characteristics range from easy to fair. This wood is wild-crafted and is primarily used for indoor construction, cabinetry, general housing applications, furniture, plywood, and packing cases.

Conservation status

Prunus grisea has an estimated EOO of 3,181,649.63 km² (1,976,985.42 mi²), far exceeding the thresholds for a threatened category, and it is not considered to be under major global threat. However, no information is currently available regarding its population size or trends. Notably, the species has previously been classified as threatened in localized assessments within the Philippines and Taiwan. Given its broad distribution and lack of major threats, it is assessed as LC by the IUCN Red List.