Assaí


Related species
Description and phenology
Cytological data
Distribution, abundance and ecology
Uses and economic potential
Research contacts



Marilene L. A. Bovi & Aline de Castro

There are at least two different palm species known as assaí in Brazilian Amazônia: Euterpe oleracea Mart., called açai-do-Pará, an extremely abundant, multistemmed palm, that occurs in the varzeas (annually flooded white water river terraces) and in the Amazon River estuary, where it frequently forms monospecific populations; and Euterpe precatoria Mart., called açaí-da-terra-firma, a single-stemmed palm (solitary), common in Central and Western Amazônia, that occurs along the valley edges on the terra firma (non-flooded, upland plateaus), in areas without permanent flooding. This chapter will deal with both of these species.

Family: Arecaceae (Palmae)

Species: Euterpe oleracea Mart. and Euterpe precatoria Mart. (Glassman 1972).

Common names: E. oleracea - açaí, assaí, açaizeiro, açaí-do-Pará, açaí-da-várzea, açaí-do-baixo-Amazonas (Brazil); uassi, morroke (Venezuela); manicole (Guyana); pina, pinau (French Guiana); palisade pine, prasara, manaka, wasei, wapoe (Suriname); manac (Trinidad).

E. precatoria - açaí, assaí, açaí-do-terra-firma, açaí-do-Amazonas, açaí-do-alto-Amazonas, açai-do-mato, açaí mirim, palmito mole, guassai, jissara (Brazil); huasai, chonta (Peru); palmo, manaco, guasay (Colombia); palma do rosario (Bolivia); rahoo, wahoo, wahoo, weenamori, waboyaka, manicole (Guyana); guassai (Venezuela); monki-monki pine, baboen pine, wapoeiema (Suriname); manac (Trinidad).

Related species


There are numerous other Euterpe species, many of which are of doubtful validity, also known as assaí. Their common names are açaí branco, açaí espada, etc. There are also marked differences between the açaí-do-igapó and the açaí-da-várzea, although they are all classified as E. oleracea. In other parts of Brazil and South America other Euterpe species are used as sources of palm heart: E. edulis was especially important in southern Brazil before its populations were decimated.

Description and phenology


Euterpe oleracea
Euterpe precatoria



Euterpe oleracea


E. oleracea is a slender, multistemmed, monoecious palm that can attain 25+ m. It can have more than 45 stems in different stages of growth and fructification, depending on insolation. In natural stands 4-8 well-developed stems per mature plant are common.

The green to yellowish crown shaft is composed of the leaf sheaths (about 1.2 m long) of the 9-15 pinnate leaves. The mature leaf has a rachis 2.5 m long and 50-62 leaflets, each measuring 39-77 cm. The leaves are well-adapted to high light levels: those exposed to full sunlight are smaller and have a larger number of leaflets hanging vertically, reducing to a minimum the area exposed to direct sunlight.

The slender stems are light gray, measuring 9-16 cm in diameter at breast high (DBH). Rings formed by the scars from old detached leaves appear from the base to the crown shaft. Six to eight leaves, on average, senesce per year. Although flexible, the stem is very resistant.

Adventitious roots are formed continually at the swollen base of the stem. They form a ring of thick (1.5 cm), bright purple aerial roots around the base of the stem that can reach to 80 cm above soil level. The root system is very large and quite superficial, with a radius of 6 m or more. Eighty percent of the total root volume is found in the first 20 cm of soil. The plant is well adapted to periodically waterlogged soils. Special root structures, called pneumatophores, help the root system respire in waterlogged soils. In low lying areas, soil and organic particles trapped on the root system slowly construct a mound around the plant.

Inflorescences are present most of the time in the varzea, singly or multiply, in up to 6 different maturity stages. They develop from the axil of the leaves, and, after the oldest leaf senesces, the inflorescence can be seen, protected by its sheaths. Initially it arises at an erect angle, later dropping to a more horizontal position. When opened, it has a light brown color (beige). The inflorescence is composed of a central stiff rachis about 56 cm long, with an average of 54 rachillae. Bach rachillae bears clusters of two lateral staminate (male) flowers and one central pistilate (female) flower, except on the end portion, where there are only staminate flowers. The flowers are quite small (4.5 × 2.7 mm male; 3.2 × 2.6 mm female). Male flowers are purplish, with purple anthers as well. Pollen viability ranges from 30 to 83%. Female flowers are purple to light brown.

Fruits are globose, 1.1-1.5 cm in diameter, green when young and usually ripening to a darkish purple. There are some assaí populations that have green fruits even when mature and these are locally called açaí branco (white açaí). The fruit is one-seeded. The seed is surrounded by stringy fibrous sheaths and a thin dryish but slightly oily coating. The seeds have a solid and ruminated endosperm and a small, but completely developed, embryo. The seedlings have two or three profile and the first complete leaf is bifid (divided into two leaflets).

E. oleracea is monoecious, with each inflorescence bearing numerous sessile staminate and pistilate flowers. It is protandrous, with the staminate flowers open and shedding pollen before the pistilate flowers are receptive. Thus, the species is predominantly allogamous (outbreeding), but various degrees of autogamy can occur depending on the synchronization of phases between inflorescences in the same or different stems of the same clump (geitonogamy). Pollination is done mainly by small bees and flies. Flowering can start as earlier as 4 years if it is grown in full sunlight. Inside the rainforest, however, flowering starts later as it is directly related to insolation.

E. oleracea flowers throughout the year, with an inflorescence appearing: in the axil of each leaf (Jardim & Anderson 1987). Leaf turnover may be as high as 10 new leaves per year. Nutrient stress during the dry period may cause inflorescence abortion (ibid).

The number of fruit bunches per plant can reach 8, although 3-4 is more common. In any stem, each bunch is at a different stage of development, varying from inflorescences enclosed in the bracts to bunches with ripe fruits. Fruiting occurs throughout the year, with the dry season, July to December, being the period of greatest abundance.

Euterpe precatoria


E. precatoria is a single-stemmed (solitary) palm, growing to a maximum of 20-22 m in height. The crown shaft is composed of 14-19 leaves, each reaching 3.5-4.5 m in length. A large number of pendent leaflets confer a unique, ornamental appearance to this palm. The stem and root system are similar to those of E. oleracea.

The inflorescences are larger than shone of E. oleracea, bearing a larger number of rachillae (70-76) and staminate and pistilate flowers. The flowers are lighter in color, usually a pale yellowish-pink (male) and light brown (female).

The fruits are globose, 1.0-1.8 cm in diameter, dark purple when mature, with a thin (0.5-1.5 mm thick) and juicy mesocarp.

There is also one seed per fruit, with a solid and homogeneous endosperm. The seedlings have initially 2 or 3 profile and a complete leaf divided in 6 leaflets.

E. precatoria has a similar floral biology and reproductive system to that of E. oleracea. In this species, geitonogamy is also possible due to synchronization of male and female phases in different inflorescences on the same stem.

The period of greatest abundance of fruits is December to August, although there is a geographic gradient, earlier (January to June) in Western Amazônia (Coarí to Codajás, Amazonas), intermediate (April to August) in the region of Manaquiri, Amazonas, and later and shorter (middle June to middle September) between Manaus and Itacoatiara, Amazonas.

Cytological data


Chromosome numbers of x=18 (2n=36) were observed in E. Oleracea and in some other Euterpe species. A marked similarity in chromosome size and shape was observed in all the species studied (Maglio, pers. com.). This would be expected, since inter-specific fertility has been demonstrated through crosses between most species (Bovi et al. 1987a, 1988).

Distribution, abundance and ecology


E. oleracea is widely distributed in northern South America but attain their greatest coverage and economic importance in Pará state, Brazil, where it is found in nearly the entire state. The major occurrence is in the Amazon River estuary, an area estimated of 25,000 km2 (Lime 1956). Calzavara (1972) conservatively estimated the coverage of asset in the Amazon estuary to be 10,000 km2. It is especially common on varzeas, slightly less so in the igapós (perennially flooded, black or clear water forest swamps) and less so still on the terra firma.

Plants from these three edaphic conditions look quite different. At times the palms are found in almost pure stands (açaizais), representing, along with buriti (Mauritia flexuosa), the most prominent feature of the vegetation landscape (Peters et al. 1989).

E. precatoria occurs almost exclusively on the terra firma and along the slopes leading to the igapós and varzeas. This species is common in Central and Western Amazônia, including the Peru-Brazil-Colombia borders (Kahn 1988).

Population density of E. oleracea in the Amazon River estuary is high and variable, depending mostly on soil conditions. On average, the plant population is between 230 and 600 clumps/ha, considering only clumps with stems higher than 2 m (Jardim 1991 & pers. com.). Total population ranges from 2,500 to 7,500 plants/ha, most of them (50%) in the first seedling stage (one to two leaves and about 20 to 25 cm tall).

Population density of E. precatoria varies from 50 to 250 plants/ha in the forest ecosystems of Peruvian Amazônia (Kahn 1988). Higher population densities were found in Manaquiri, Amazonas, Brazil (100 km from Manaus). A field survey showed population densities varying from 5,740 to 13,396 plants/ha [2.24-4.88% adult, 1.52-14.00% stemmed juveniles, 22.22-50.00% stemless juveniles and 71.43-91.22% seedlings (one-leaf stage)] (A. Castro, unpublished).

E. oleracea and E. precatoria can both be classified as species of the climax forest by the following characteristics: slow growth, high moisture requirement, low light needed for seedling growth, low plant survival rate and long seedling stage.

The germination process of both species begins soon after the seeds fall, as they are without any mechanisms for long-term dormancy. The fruit epicarp is readily eliminated by natural decomposition, aided by microorganisms, insects or passing through the digestive tract of some birds. Germination lasts 311 months, with the bulk of seeds germinating in the first 30-60 days. Although the germination percentage is high in laboratory conditions, reaching 90% (Bovi et al. 1991), in nature it may reach 50-60%. Microorganisms and predators (some insects and especially rodents), contribute to reduce it in nature. Initial water content of the seeds is 51%, and they lose viability quickly in unfavorable conditions.

Seed dispersal over short distances is done by rats and other rodents. Long distance seed dispersal is done by birds [toucans (Ramphastidae)], jacus (Cracinae), arapongas (Cotingidae), and sabias (Turdus) (Zimmermamm 1991) and by water (floods), mainly along stream banks.

Seedling survival is low, especially from the one-leaf stage until the plants are about 50 cm in height. Competition for light is the main factor limiting survival and seedling growth.

Plant growth rate is slow, especially as compared to some of its forest competitors, and in the first three years. Small seedlings (one-leaf stage) are able to survive without much growth, awaiting more favorable conditions, especially light. Stem growth is usually seen 2-3 years from seedling stage, when the plant is at about 1 m in height. After that, growth in height increases rapidly, which can be easily observed by the distance between leaf scars. Normally it takes 4-6 years for the main stem to reach the minimum size for economically viable palm heart harvest. Once the palm reaches the canopy, stem growth is slower and constant and the leaves show changes in morphology as they adapt to new ecological conditions. Their size is reduced and more leaflets appear, with the interval between leaflets shorter than before.

Suckering starts within one year after germination and the number of suckers is a function of insolation. Under shaded conditions E. oleracea has fewer suckers than in full sunlight (Bovi 1987). Plant height is also function of insolation levels and increment in stem diameter is inversely correlated with it.

Uses and economic potential


Principal uses
Secondary uses
Economic data
Collection methods and yields
Management



Principal uses


E. oleracea produces a wide variety of market and subsistence products (Anderson 1988). This author listed 22 different uses for all plant parts, from the leaves to the roots.

By far, its principal use of both B. oleracea and E. precatoria to local people is for the preparation of a thick, dark purple liquid obtained by maceration of the pulp of the ripe fruits. The liquid, locally called açaí or vinho de açaí (although it is not a fermented or distilled beverage), is not particularly nutritious. The nutrient content reported by Altman (1956), Campos (1951) and Mota (1946) is as follows: 1.25-4.34% (dry weight) protein; 7.6-11.0% fats; 1-25% sugar, 0.050% calcium; 0.033% phosphorous; and 0.0009% iron. It also has some sulphur, traces of vitamin B1 and some vitamin A. Caloric content ranges from 88 to 265 calories per 100 grams, depending upon the dilution and on the complement. Yet the liquid is extremely filling, especially when mixed with manioc (Manihot esculenta) flour. It is usually not drunk, but eaten with a spoon, and forms a major and basic part of the diet of most of the inhabitants of the lower Amazon River. An individual daily consumption of up to 2 liters has been reported. It has a metallic, somewhat nutty flavor, with a texture roughly creamy and appearance slightly oily.

The assaí liquid is so popular that there are special establishments (called açaílandia) in small and large towns which make and sell it in plastic bags. Although a-basic part of the diet of the poor, assaí liquid is popular throughout all socioeconomic levels. Details of assaí liquid making, consumption and marketing are well described by Strudwick & Sobel (1988).

Assaí liquid is extremely perishable and this factor has restricted its consumption to a purely regional level. Attempts have being made to dehydrate the liquid to preserve it (Melo et al. 1988). The dehydrated product is suitable for consumption up to 115 days after packing. With this product, assaí could be made available throughout the year and could be exported to other national and international markets.

The other main product from both E. oleracea and E. precatoria is palm heart. It consists of the tender, whitish, immature leaves of the palm, found just above the growing point oh each stem. Once removed, it is a flexible cylinder about 45 cm long and 2-3 cm wide. It has almost no nutritious value (Ferreira & Yokomizo 1978, Ferreira et al. 1982),- but it is widely appreciated in a variety of dishes. Although regional (Amazonian) consumption of palm heart is minimal, there is a large internal Brazilian market for palm heart, especially in the southeastern states, where a wide variety of dishes can be found in the restaurants.

Commercial extraction of assaí palm heart began in the Amazon River estuary by 1960, as a consequence of the decimation of native stands of E. edulis (a single-stemmed palm very similar to E. precatoria) in southeastern Brazil, caused by heavy exploitation of the natural palm populations (Renesto & Vieira 1977). E. oleracea is currently the world's main source of palm heart, with the Amazon River estuary being the principal producing region. At present there are 120 registered processing industries in the region, most of them situated at the edges of the rivers. Innumerous smaller factories exist based on family labor and associated with or selling their product to the larger ones. The degree of sophistication of those industries varies, but most of them are very precarious and process a low quality product.

Canned heart of palm production per processing plant is variable, ranging from 6 to 30 tons per month. There is already a shortage of the raw material in many locations in the Amazon River estuary, due to over harvesting and lack of management of the native stands, and some processing plants run only 2-3 days per week. This shortage has also spurred the migration of some floating processing plants from the estuary in Pará to varzea areas in Amazonas, where they exploit (again destructively) both local populations of E. oleracea and previously unexploited (for palm heart) populations of E. precatoria, thus denying an important resource to local residences.

Secondary uses


Increased profit from this regional product could also be achieved by extracting its pigment (anthocyanin) in order to provide natural red dyes for the food industry. Iaderoza et al. (1992) showed that E. oleracea, as well as E. edulis, is a potential source of this natural pigment.

Economic data


Anderson (1988) studied the commercial products sold in one year's time by a single family living on the Ilha das Onças, near Belém, Pará, Brazil. He found that some 35,000 hearts of E. oleracea were extracted during this period, representing an income of $US 2,916. At the same time, the family harvested $US 15,532 worth of fruits (78,885 kg of product). Together these two products accounted for 75% of the forest products sold by the family. Anderson (1988) pointed out, the fragility of the system. An increase in demand and in the number of palm heart processing industries can pose a threat to the unstable economic balance of the estuary. A sudden rise in prices for the palm heart could mean the cutting of the stems meant for fruit production and result in general scarcity of fruit for a number of years.

World trade in heart of palm in 1990 exceeded $US 65 million and 85+% of it came from the exploitation of primary forest stands, principally E. oleracea. World consumption is much greater, however. Brazil is both the major world producer (100,000+ MT) and largest consumer. This country is responsible for 70% of the world trade in palm hearts, exporting 10,000+ MT, but consumes nearly 10 times the amount exported. Due to the highly perishable character of the Euterpe species, especially discoloration due to enzyme mediated oxidation, at least 85% of the total internal consumption of heart of palm is in a processed form (cans or jars) and retail prices are almost the same as for export.

Collection methods and yields


Harvesting the fruit bunches is an arduous and frequently dangerous task, done by individuals accustomed to climbing the assaí palms. After scaling a palm, a practiced harvester moves easily from one stem to another, without descending, collecting all the ripe fruit bunches from a clump.

E. oleracea produces 4-8 bunches a year, each one yielding, on average, 4 kg of fruit. Thus, one stem can provide 16-32 kg of fruit, mean 24 kg, per year. E. precatoria is somewhat less productive, producing 2-3 bunches a year, each yielding, on average, 6.5 kg of fruit. Thus, one stem can provide 13-20 kg of fruit per year.

To harvest the palm heart the entire stem must be cut down with an axe, or the harvester may climb the stem with the aid of a device made with palm leaf (called a pecunha) and cut through the base of the crown shaft with a machete in order to bring down the entire crown. A man can harvest as much as 300 palm hearts per day and will be paid about US$ 0.05 for each heart of palm harvested and delivered to the factory. This contrasts with a final consumer price of US$ 5 to US$ 6 per pound in New York.

Uncontrolled extraction of palm hearts has been practiced in the Amazon River estuary since exploitation began and it still continues in many areas, with extremely negative consequences for the regeneration of the natural assaí stands and also for the large segment of the rural population that depends upon the harvest of assaí fruits for subsistence and sale. In the case of palm hearts, independent collectors frequently cut every stem of sufficient size to yield a saleable heart. Currently, a plantation or dense natural stand produces about 3 MT of rough palm hearts per hectare, 20% of which is export quality.

Management


In order to maintain a steady supply of palm hearts from one area, selective cutting of only a certain number of stems per individual is preferable. This system has been used by some Amazon River estuary small holders. Intuitively they developed a management system that allows for the sustainable harvest of palm heart in this region. By practicing a combination of selective harvesting of assaí suckers for each clump, with selective thinning of forest competitors, the small holder can not only make cash from the direct sale of the heart of palm, but also enhances fruit production on the remaining stems.

This alternative management practice, that permits both fruit harvest and palm heart extraction, appears to be increasingly implemented by rural inhabitants in the Amazon River estuary. Although it may reduce estuarian biodiversity in the long run, this practice can sustainably supply income to its practitioners while conserving vital ecosystem service in the area.

There is a need to develop systems for large-scale sustainable exploitation and renewal of populations. In this area, agroforestry systems may be feasible, as well as pure crop plantations, in order to make the product more affordable and support increasing demand. However, as almost all assaí palm heart production comes from natural or managed forest, there is some doubt as to whether the higher yields from a plantation can compensate for the extra cost of management, fertilizing, etc. Nowadays, considering all the costs involved in the processing of heart of palm (raw material, processing, overhead and marketing, amortization and taxes) the raw material represents only 23-25% of the final export value of the product. Nonetheless, if current exploitation practices continue, natural stands will be decimated.

In the Amazon, agroforestry systems, combined with the sustainable management of existing stands, is a major need. On the other hand, heart of palm plantations will probably become a regular feature of the estuarian landscape in the future, as increasing world demand, together with more rigid environmental regulations, limits illogical forest resource exploitation, such as that currently practiced.

Nowadays, assaí and other "new" palms, such as pejibaye (Bactris gasipaes), gariroba (Syagrus oleracea), assaí hybrids, etc., are being cultivated in disturbed areas. With research being carried out in different countries and the introduction of new technologies, the results of plant breeding and cultural management will soon be available for each palm species and for distinct edaphic and climatic conditions. With the new technologies being developed, heart of palm plantations could be more productive and lucrative and the price of the product reduced.

Research contacts


Dr. Marilene Leão Alves Bovi, Tropical Plant Section, Instituto Agronômico de Campinas, P.O. Box 28, 13020-902 Campinas, SP, Brazil.

Dr. Aline de Castro, Dept. Ecology, Instituto Nacional de Pesquisas da Amazônia, Cx. Postal 478, 69011 Manaus, AM, Brazil.

Dr. Anthony B. Anderson, Fundação Ford, Praia do Flamengo, 100 - 12 andar, 22210 Rio de Janeiro, RJ, Brazil.

MSc. Mario A.G. Jardim, Depto. Botânica, Museu Paraense Emilio Goeldi, Cx. Postal 399, 66040 Belém, PA, Brazil.