Gnetum acutatum Miq.

Gnetum gnemon is a shade tolerant, slender evergreen tree, up to 15 m tall. Usually branching in whorls from the base and deeply rooted with a strong tap root system. G. gnemon does not develop buttresses, the trunk is most recognisable with regular swollen rings around the girth, marking the position of old branches. Leaves broad (10-20 cm), opposite, dark green, shiny, elliptic with netted veins. Flowers are monosexual; in catkin-like formations; the male flower consists of a stamen and perianth ;female flowers, 5-8 at each node have an ovule with two integuments and a perianth. Fruits ellipsoid usually in clusters,1-3.5 cm long and half as wide, turning yellow to orange-red then purple at maturity. G. gnemon exists in several varieties, such as the tree form (var. gnemon) and the shrub forms (vars. Brunonianum, griffithii and tenerum).

A coupled process of double fertilization and post-fertilization endosperm formation occurs in the genus Gnetum. However the product of the second fertilization event in Gnetum is diploid and expresses the developmental programme of an embryo. In G. gnemon, egg cells are not formed and maternal provisioning of the embryo-nourishing female gametophyte takes place entirely after fertilization. The lack of differentiated egg cells in G. gnemon is unparalleled among land plants, the biological significance of double fertilization that does not form endosperm, in Gnetum, is currently unknown. This process may be biologically neutral. Seeds produced three times yearly in Indonesia, March-April, June-July and September-October. The strobili are visited by nectar-seeking moths of Pyralidae and Geometridae. The sticky pollen of Gnetum attaches on proboscides and antennae of these moths. Lack of showy petals, an apparent disadvantage in entomophily is compensated for by floral fragrancy. Bears one seed per fruit, a maximum yield for 100 year old trees could reach 80-100 Kg of seed/ year. Several varieties have been recognized on the basis of variation in tree habit and fruit /seed size. However two varieties are broadly accepted var. tenerum and var. gnemon.

Melinjo can grow on soils high in clay or sand content, and also on calcerous rocks however moisture must be available during the dry season.

Occasional in lowland ridges and mature fallow forest. Commonly found in secondary humid evergreen dipterocarp forests of S.E. Asia. Commonly cultivated in or near gardens and in home gardens in South East Asia.

The cultivated trees belong to G. gnemon var. gnemon and are larger, with larger fruits.

The popular propagation method is by direct seeding. However, vegetative propagation is possible by air layering, grafting, oculation and cuttings. Addition of humic acids at 400 mg/litre yielded the fastest growth of shoots from nodal segments in tissue culture experiments with G. gnemon.

Daily watering of the sand and seed mixture will hasten germination, possibly to three months. Without a pre-germination treatment, germination may be 1-2% in 6 months and may reach 100% in 12 months. Greater seedling height in inoculated seedlings can be achieved by providing compost and rock phosphate.

Shade or shelter: Provides shade for sciophytic plant species. Reclamation: It is possible to use this tree for dryland rehabilitation and afforestation. It can survive annual rainfall of 750-1000 mm Nitrogen fixing: Has the ability to improve nitrogen levels due to its mycorrhizal associations.with the ectomycorrhizal fungus Scleroderma sinnamariense. In experimental conditions, mycorrhizal inoculation appears to enhance seedling growth under shaded conditions in acidic soils. Soil improver: Has the ability to improve physical soil properties. Intercropping: When intercropped with yams, can act as stakes for climbing yams, pana and other understorey shrubs.

Food: The nutritious seeds are consumed as a snack called emping, and the young leaves, flowers and fruits are used as vegetables; eaten either raw, boiled or roasted. The seed is cooked or preserved as pounded flat cakes from which crispy snacks can be made. An active trade in the seeds exists and small to medium size emping industries exist in Indonesia, specifically in west Java, central Java and northern Sumatra. Fibre: Its bast fibers provide durable cordage for fishing nets, lines, string bags and other durable tools. A potential economic use of this plant is the utilisation of its bark in rope making. Timber: Wood used in Indonesia for pulp and house construction and in Malaysia, and Hong Kong for paper, boxes, and housing. Alcohol: Prospects of making a potable sap from this species should be explored. Poison: Woodsmoke and topical applications reduced biting of human volunteers by the anopheline mosquitoes (Anopheles punctulatus, A. koliensis, A. bancroftii, A. karwari and A. farauti) by 79% and 51%, respectively (Paru et al. 1995). Enzymic inhibition prevents insect predation of foliage. Medicine: Leaf sap used medicinally to cure an eye complication. Other products: The fungus, Scleroderma sinnamariense, usually associated with this tree produces a fruiting body that is edible. Under experimental conditions thermal-shock treatment of seedlings asssociated with S. sinnamariense resulted in early formation of the edible fruiting bodies.