''Mitrephora glabra'' is a species of

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...

in the family Annonaceae. It is native to

Borneo Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and eas ...

Rudolph Scheffer Rudolph Herman Christiaan Carel Scheffer (born 12 September 1844 in Spaarndam, Netherlands - died 1880 in Singaraja, West Java, Dutch East Indies (now Indonesia) was a Dutch botanist and director of Buitenzorg Botanical Garden. Biography Schefferd ...

, the Dutch botanist who first formally described the species, named it after its hairless ( in Latin) leaves and mature twigs.

Description

It is a tree reaching 15–20 meters in height. Its

twig A twig is a thin, often short, branch of a tree or bush. The buds on the twig are an important diagnostic characteristic, as are the abscission scars where the leaves have fallen away. The color, texture, and patterning of the twig bark are ...

s are hairless when mature. Its papery to leathery, elliptical to lance-shaped leaves are 6.5-25 by 1.5-6.5 centimeters with wedge shaped bases and tips that taper to a point. Both sides of the leaves are hairless except for short hairs on the upper surface of the midrib. The leaves have 5-15 pairs of secondary veins emanating from their midribs that arch to form loops near the leaf margins. Its petioles are 2.5-9 by 1–2.5 millimeters and covered in sparse fine hairs. Its flowers are born opposite the leaves on

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

s in groups of 3 or fewer. The flowers are on fleshy, densely hairy

pedicels In botany, a pedicel is a stem that attaches a single flower to the inflorescence. Such inflorescences are described as ''pedicellate''. Description Pedicel refers to a structure connecting a single flower to its inflorescence. In the absenc ...

that are 5.5-13 by 0.5-3.5 millimeters. The pedicels have an oval, basal bract that is 1 by 1 millimeters, and another bract at their midpoint that is 1-1.5 by 1–2.5 millimeters. Its flowers have 3 triangular to oval

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coined b ...

s that are 1.5-3 by 2–3.5 millimeters. The sepals are covered in dense, brown hairs on their outer surface and sparse hairs on their inner surface. Its 6 petals are arranged in two rows of 3. The yellow, elliptical to oval, outer petals are 1–2.4 by 0.6-1.2 centimeters and come to a point at their tips. The outer petals are covered in light brown hairs on both surfaces, with fewer inside. The inner petals are yellow with pink to purple highlights at their tips. The inner petals are 9-13 by 2.5-5.5 millimeters with a narrow, basal claw and a rhomboidal blade. The inner petals have sparse hairs on their outer surface and dense, brown, woolly hairs on their inner surface. Its flowers have

stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filame ...

that are 0.8-1.1 by 0.3-0.6 millimeters. The carpels have 10-12

ovule In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the fe ...

s. Its flowers have 15-17

carpels Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) ''pistils'' ...

that are 1-1.5 by 0.3-0.5 millimeters. Its fruit occur in clusters of 10–15 on pedicels that are 7-23 by 1.5-4.5 millimeters and covered in sparse hairs. The smooth, oval fruit are 1.8-3.4 by 1.1-2.1 centimeters with flat tips. The fruit are attached to the pedicel by stipes that are 1.5-4 by 1–2.4 millimeters. Each fruit has 6-8 seeds that are 6.5-23.5 by 7-20 millimeters.

Reproductive biology

The pollen of ''M. glabra'' is shed as permanent tetrads. It flowers and sets fruits throughout the year.

Habitat and distribution

It has been observed growing in lowland forests, often near rivers and streams, at elevations of 0 to 450 meters.

Uses

Bioactive compounds isolated from its tissues have been reported to be

cytotoxic Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are an immune cell or some types of venom, e.g. from the puff adder (''Bitis arietans'') or brown recluse spider (''Loxosceles reclusa''). Cell physiology Treating cells ...

in tests with cultured human cancer cells and have antimicrobial activity in tests with both fungi and bacteria.

References

glabra Flora of Borneo Plants described in 1885 Taxa named by Rudolph Scheffer {{annonaceae-stub