REVIEW OF LITERATURE
INTRODUCTION
Our focus in this chapter is to critically examine relevant literatures that would assist in explaining the research problem and furthermore recognize the efforts of scholars who had previously contributed immensely to similar research. The chapter intends to deepen the understanding of the study and close the perceived gaps.
Precisely, the chapter will be considered in three sub-headings:
Conceptual Framework
Theoretical Framework
CONCEPTUAL FRAMEWORK
PLANTAIN
Plantain requires about two and a half to four months after shooting before the fruit becomes ready for harvesting or a total of about eight to twelve months after planting (Simmonds, 1948; Swennen, 1990a). At maturity, a constant weight is maintained for two to four days, and then the weight starts to decrease with changes in the peel colour from green to yellow and then to black. The maturity of the fruit may be determined by the weight of the pulp to peel ratio, brittleness of floral ends and disappearance of angularity of the fingers. The chemical composition of plantain varies with the variety, maturity, degree of ripeness and where it is grown (soil type). The water content in the green plant is about 61% and increases on ripening to about 68%. The increase in water is presumably due to the break down of carbohydrates during respiration. Green plantain contains starch which is in the range of 21 to 26%. The starch in the unripe plantain is mainly amylose and amylopectin and this is replaced by sucrose, fructose, and glucose during the ripening stage due to the hydrolysis of the starch (Marriott et al., 1981). The carbohydrate content reduces to between 5 and 10% when ripe. The sugar content is between 0.9 to 2.0% in the green fruit but becomes more prominent in the ripe state. The titrable acidity of plantain is about twice that of sweet potato (Aurand et al., 1987). Plantains therefore have a high carbohydrate content (31 g/100 g) and low fat content (0.4 g/100 g). They are good sources of vitamins and minerals (Adeniji, et al., 2006), particularly iron (24 mg/kg), potassium (9.5 mg/ kg), calcium (715 mg/kg), vitamin A, ascorbic acid, thiamin, riboflavin and niacin. The sodium content (351 mg/kg) is low in dietary terms hence recommended for low sodium diets (Izonfuo and Omuaru, 1988; Stover and Simmonds, 1987; Welford et al., 1988). The amino acid components include -alanine, aminobutyric acid, glutamine, asparagine, histidine, serine, arginine and leucine. The ascorbic acid is high compared to that of banana. As a starchy staple food, plantain supply about 1 g protein/100 g edible portion (USDA, 2009). As a healthy adult requires about 0.75 g protein kg-1 day-1 (Burton and Willis, 1976), plantain alone cannot meet adult protein needs. The fat content of plantains and bananas is very low, less than 0.5%, and so fats do not contribute much to the energy content. Although the total lipid content remains essentially unchanged during ripening, the composition of fatty acids, especially within the phospholipids fraction has been observed to change, with a decrease in their saturation (Ogazi, 1996). The energy value of a food derives from the sum of its carbohydrates, fat and protein content. In the case of plantain, the carbohydrate fraction is by far the most important. The sugars and starches that make up this fraction are present in varying concentrations according to the state of the ripeness of the fruit. The two main components of this starch are amylose and amylopectin, present in a ratio of about 1:5. Sugars comprise only about 1.3% of total dry matter in unripe plantains, but rises to around 17% in the ripe fruit (Ogazi, 1985). Plantains are considered palatable at lower water content than maize, thus boiled and mashed plantain may prove to be a higher energy staple than maize porridge (Chandler, 1995). For example the energy value/100 g plantain is as follows: raw fresh fruit, 112 kcal; boiled fruit, 122 kcal; ripe fried fruit, 267 kcal (Chandler, 1995). Plantains and bananas are a good source of vitamin A (carotene), vitamin B complex (thiamin, niacin riboflavin and B6) and vitamin C (ascorbic acid). Processing and cooking will affect the vitamin content. In comparison with other starchy staples; vitamin C content is similar to those of sweet potato, cassava and potato. Plantains provide a better source of vitamin A than most other staples (Aurand, 1987; Kirk and Sawyer, 1991; USDA, 2009). Although plantains do not provide a particularly good source of several important minerals in human nutrition, such as calcium, iron and iodine, they are notably high in potassium and low in sodium (Marriott et al., 1983; Stover and Simmonds, 1987; USDA, 2009). Non starch polysaccharides (collectively known as fibers) include crude fiber, cellulose, pectic substances, hemicelluloses and other polysaccharides. Unripe plantain pulp has a total of 3.5% dry matter as cellulose and hemicellulose and therefore constitutes a good source of dietary fiber (Kirk and Sawyer, 1991). Plantain is grown in 52 countries with world production of 33 million metric tonnes (FAO, 2005). Locally, plantain constitutes about 13% of the county’s agricultural gross domestic product of Ghana (SRID-MOFA, 2006), and ranks third in volume of production among starchy staples in Ghana. In the agricultural sector, plantain is ranked fourth in Ghana (FAO, 2005). Total annual national production is 2.00 million tonnes (SRID-MOFA, 2006) with per capita consumption of 101.8 kg (SRID- MOFA, 2006; FAO, 2005; Lescot, 2000). Plantain for local consumption undoubtfully, plays a role in food and income security and has the potential to contribute to national food security and reduce rural poverty. This crucial role is still largely ignored by policy makers and therefore special public awareness effort is required to sensitize policy makers in both producing and donor countries. Despite the importance of plantain, major constraints threaten its cultivation in terms of pest and disease infestations, soil fertility, planting materials, post- harvest losses, marketing constraints, particularly poor road system and lack of infrastructure and storage facilities and much of the fruits harvested go waste. In Ghana during the glut season from late August to late April, before the “Easter storms” set in, markets are filled with vehicles laden with loads of the fruits from the remote production areas. The production of food powders is on the increase as a result of gradual urbanization and globalization. For example, in Ghana the production and export of powder from local tuber crops and cereals is gradually gaining market status. Apart from extending the storage life of these staples (due to the low moisture of the dried product), powder products are easy to handle in terms of transport and space. In Ghana a company such as Rosafrik Co. Ltd., produces and exports powdered starchy stables such as “fufu”, “tuozaafi”, “kokonte” (cassava meal), “banku economic sense. An enquiry from a food processing company in Kumasi, Ghana revealed that, plantain processed into “fufu” flour can store for up to a maximum of two years. Although much work or research has been done in the areas of disease and pests (MUSACO research team: Musa network for West and Central Africa) that is, integrated strategies to reverse plantain losses in Ghana (IITA, 1997) through Sigatoka-resistant hybrid production, not much has been done in the area of post harvest losses in terms of long term keeping quality of the matured fruits.
PREPARATION OF PLANTAIN FLOUR
Plantain fingers were plucked from the proximal end of the bunch following the recommendation of Baiyeri and Ortiz (1996). The fingers were washed with portable water, peeled manually with stainless steel kitchen knife and cut into two equal parts. The seeds of one of the portions were removed by cutting the fruits longitudinally and scrapping off the seeds while the second portion was left with the seed. Cooking was carried out on some samples of both parts by dipping in boiling water of 100 oC for 5, 10 and 20 minutes
before slicing. The samples were cut into thin slices of 2 mm thick and were sundried for 3 days. Some samples were dried directly in the sun without treatment, which served as control. The dried samples were milled with the aid of stainless Kenwood Chef Blender, Model KM001 series to obtain the flour. The flours were sieved and stored in an air tight container for further
analysis.
THE PROCESS OF PLANTAIN DEVELOPMENT
Mean annual rainfall
The minimum rainfall requirements for Musa depend on soil type, planting location, sun exposure, and variety or species. For production of commercial cultivars (e.g., ‘Giant Cavendish’), a minimum of 500 mm (20 in) per year
will sustain the plants if the rainfall is evenly distributed throughout the year and the soil is fertile. However, approximately 2000 mm (80 in) per year,
more or less evenly distributed, is considered to be a minimum requirement for a successful commercial banana plantation. There is no upper rainfall limit, given well drained soil.
Rainfall pattern
Seasonal rainy periods and/or drought periods are fairly normal for most banana-growing areas. Bimodal or seasonal rainfall patterns are tolerated well by edible banana growing in forested situations and/or in fertile, deep soils. Uniform rainfall distribution throughout the year is best for commercial production of edible banana; 375,000 l/ha/week (40,000 gallons/ac/week) are required for irrigation of banana plantations in dry areas. Some dwarf Musa species used in ornamental landscapes are relatively drought-tolerant and can tolerate a wider range of rainfall and distribution patterns.
Dry season duration (consecutive months
with <40 mm [1.6 in] rainfall) The ability of Musa spp. to survive for a given length of time in the absence of rainfall is dependent on the following factors: soil type, structure, and drainage shade level; transpiration requirements mono-cropping vs. a diversified/ agroforestry system pest and disease pressure plant nutrition and soil fertility. Because the plants can store a significant amount of water within their pseudostems and rhizomes, they can survive extended periods of drought, although their growth will slow down or cease under such conditions.In Hawai‘i’s rocky volcanic soils, banana suffers significant drought stress and yield reductions after only a few weeks without rain. Since Musa balbisiana is considerably more drought hardy than M. acuminata, increasing proportions of B in a cultivar’s genome are correlated with increased drought tolerance. In other words, cooking varieties such as ‘Saba’ (ABB) and ‘Bluggoe’ (‘Largo’ in Hawai‘i, ABB), can be grown more successfully in dry, windy areas than many other varieties. ‘Sucrier’ (AA), with much A in its genome, is notably difficult to grow and rarely survives with low moisture or humidity
Fire
Banana plants will generally recover from fire by regrowing
from corms.
Frost
Although significant plant damage can occur due to frost, banana plants generally recover from subterranean parts when warm weather returns, especially if provided winter protection in the form of mulch or complete covering.
Waterlogging
Disease-free banana plants can withstand waterlogged soil but will produce poorly. Excessive irrigation or poorly drained sites may cause banana mats to “float”upon loosely rooted corms.
Salt spray
Musa spp. are tolerant of salt spray and may even produce small bunches of fruit if grown in tidal mud flats.
Wind
Winds 40–72 km/hr (25–45 mph) can topple plants when they bear fruit. Height has a dramatic affect on wind tolerance. Tall cultivars are not recommended in areas with a high probability of hurricanes, although strong enough winds will topple any banana variety. Steady winds cause significant leaf shredding, leaf drying, distortion of the crown, or (in extreme winds), complete or partial toppling of the entire plant. Winds cause more damage if the underground corm is weakened by insect pests (banana weevil) or disease (nematodes, fungal pathogens). In windy areas, dwarf varieties are best: ‘Dwarf Chinese’ (AAA, ‘Cavendish’, etc.), ‘Dwarf Cuban Red’, and ‘Dwarf Brazilian’(“apple,”AAB,Pome) varieties such as ‘Santa Catarina’,
‘Rio Nain’, or dwarf native varieties, e.g., ‘Iholena Ha‘aha‘a’ (Hawai‘i). Short cultivars such as ‘Dwarf Pisang Awak’ are characterized by thick, short pseudostems, compact structure, and short, broad leaves; they are excellent choices for homegardeners throughout the Pacific and elsewhere.They also have the dual advantage of being easier to harvest,with
less green waste for disposal.In Kīpahulu, Maui, a popular new short-trunked variety, with an extremely heavy, solid base, is dubbed ‘Hurricane’.
During or before hurricanes, some industrious Pacific islanders may choose to slash off banana pseudostems to about half their height to prevent entire plants from being blown over. In this way, the basal suckers have more
Flowering and fruiting
Flowering and fruiting occur year-round but often fluctuates seasonally, with maximum production during summer and fall.
Potential for invasiveness
Most Musa species are not considered to be invasive. However, due to birds feeding on them, seeded varieties have the potential to spread and become pests.
GROWTH AND DEVELOPMENT
Growth rate
Growth rate is rapid until flowering; after the flower bud shoots, vertical growth of the pseudostem ceases and no additional leaves are added.
Flowering and fruiting
Flowering and fruiting occur year-round but often fluctuates seasonally, with maximum production during summer and fall.
Potential for invasiveness
Most Musa species are not considered to be invasive. However, due to birds feeding on them, seeded varieties have the potential to spread and become pests.
PROPAGATION
Banana and plantain are propagated principally by vegetative division and far more rarely by seeds (usually only for banana breeding, ornamental types, and wild species). In addition, tissue culture has become standard for commercial plantations in recent years, primarily because of the advantage of starting with disease-free planting material.Edible bananas are almost always seedless (however, some,such as ‘Pisang Awak’, produce many seeds when growing near a fertile pollen source).
Propagation by division
Propagule collection Division by rhizomes in banana is referred to as sucker production and collection. This is the most common method used to obtain banana planting material. Sword suckers are preferred to water suckers for planting new fields because of their superior vigor and eventual yield. Sword suckers have narrow, sword-shaped initial leaves and are attached to a healthy,fruiting mother plant.Water suckers are those young plants that no longer have a physical connection with a living mother plant. Water suckers do not have the sword-shaped initial leaves. The sword suckers (with narrow leaves) can be obtained from healthy mother plants that are devoted (either in full or in part) to the production of sword suckers. These sword suckers are not removed during the normal process of thinning out banana clumps,
but are reserved for collection and subsequent planting. Suckers to be used for planting can be given extra light (by trimming overhanging leaves) and fertilizer before removing them from the mother plant to enhance their viability. Suckers are ready for removal from the mother plant when they reach a minimum of 15 cm (6 in) diameter and 50 cm (20 in) height above the soil (Stover and Simmonds 1987). The sucker is removed (cut away and out) from the mother plant using a sharp tool such as a narrow-bladed, straightsided shovel, making sure to obtain an appreciable amount of corm with the sucker. It is not advisable to use “peepers” (suckers less than 30 cm [12 in] tall) for propagation material because they are extremely slow-growing, may not survive, and if they do survive will produce small bunches
the first year. Banana suckers intended for agroforestry should be allowed to develop longer on the mother plant, reaching 2–2.5 m (6.6–8 ft) in height with 6–7 leaves, and given extra nitrogen fertilizer in the weeks before their collection and use as planting material.These plants are better able to
compete in a shaded agroforestry setting.
PESTS AND DISEASES
Susceptibility to pests and diseases in the Pacific
Banana and plantain are susceptible to a wide range of pests and diseases. Some pests and diseases are highly aggressive or very contagious and easily spread, and once established they are persistent and practically impossible to eradicate. In general, the severity and occurrence of pest outbreaks and plant damage depend upon several mitigating factors:
environmental conditions
specific banana variety
specific disease or pest
Environment
Wet, rainy environments favor fungal and bacterial diseases. Relatively dry weather or climate favors many types of insect outbreaks (e.g., mites) and banana virus diseases; however, some pests, such as scab moths, cause damage during normal weather patterns in the Pacific. Disease and pest outbreaks are more common where banana plants are grown together in large numbers (monocultures), rather than where planted in small numbers and spatially separated, as in agroforestry settings.Despite the planting method, the highly contagious nature of some diseases means that many or most plants in a region may become infected by a given pathogen.The severity of the reaction depends upon the environment.
Banana variety
Although most banana varieties are susceptible to certain severe diseases, some varieties are far more sensitive than others. For example, Fusarium wilt was responsible for destroying many commercial plantations of the oncepopular and widely grown variety ‘Gros Michel’, also known as ‘Bluefields’. With regard to banana bunchy top virus—which has now spread throughout SE Asia and much of the Pacific—the most susceptible varieties are in the Cavendish subgroup (‘Chinese’, ‘Williams’, ‘Grand
Naine’,‘Valery’).Members of the Pome subgroup are more tolerant of bunchy top, i.e., ‘Brazilian’ types (Hawaiian “Apple”), French Polynesian ‘Rio’ or ‘Pime’, and ‘Australian Improved Lady Finger’. Some varieties or types of bananas are well suited for local conditions and are tolerant of existing pest and disease populations.These are primarily the “new varieties”such as FHIA-01, FHIA-02, FHIA-03, ‘Giant Kalapua’, which are not quite as well received as the older types but are relatively disease resistant. Researchers worldwide are continually working to develop disease-resistant varieties.
Host to crop pests/pathogens
Several significant pests and pathogens of general agricultural concern are parasites of Musa spp. (e.g., sap-feeding insects and root-knot nematodes). These pests have wide host ranges and may initiate or cause significant damage to some crops (e.g., vegetables). Because Musa spp. Attract ants, some sap-feeding insects (e.g., aphids) may be a concern for certain vegetable intercropping designs with Musa spp.
Insect pests of banana in the Pacific
Insect pests of banana can cause significant damage to fruits (e.g., thrips, moths/caterpillars, scales), leaves (e.g., mites, moths/caterpillars), corms, and pseudostems (e.g., weevils), and can transmit important plant pathogens (e.g., aphids transmit banana bunchy top virus). Damage due to insects can greatly reduce the marketability of banana fruits. Listed and described below are some of the most common and important insect pests of bananas in the Pacific region.
MATERIALAND METHOD FOR MAKING PLANTAIN FLOUR
Source of materials
The plantain fingers of the unripe matured plantain bunch in the processing of the plantain flour were purchased from Ihiagwa Owerri,Imo states.The plantain bunches were identified by a farm officer in school of Agriculture Technology, FUTO as Horn plantain.
Chemical and reagents
The chemical reagents of analytical grades used for the analysis of the work were obtained from FST laboratory and the chemicals include: citric acid and potas- siummetabi sulphite.
Equipments used
The equipments used were obtained from the department of Food Science FUTO.They include:stainless steel kitchen knives, big bowls for washing, oven, measuring cylinder,slicer, blancher, trays. Production of plantain flour About thirty-four (34) good piece of wholesomeunripe horn (green) plantain were selected from the bunch, thoroughly washed to remove sand and dirt, to remove spray (chemical) residues and also to reduce micro bial load.
Peeling
The plantains were peeled to remove the plantain
peels.
Slicing
The unripe plantain was sliced to 2mm, thickness using a slicing machine.
AGROFORESTRY/ENVIRONMENTAL PRACTICES
Mulch/organic matter
Musa species produce profuse amounts of vegetative mass that, upon composting, produces a significant amount of natural mulch and organic matter.The cut leaves and stems are also laid down on the ground around the plants to suppress weed growth. However, it is important to remember
that cut-up trunks used as mulch will stifle the growth of suckers if placed too close to the mother plant (this is a common error, even among backyard gardeners who are anxious to expand their banana mat). Also, if banana corm weevils are present, avoid using cut-up banana pseudostems as mulch, as these will serve as a breeding ground for the weevils.
Soil stabilization
Musa species grow very well on steep, soil-covered banks of stream gulches, provided there is vegetative cover.If the soil is bare and rainfall high, banana plants tend to topple.
Crop shade/overstory
Banana is a source of shade when grown in and around gardens, and in multi-cropping systems. A vigorous monocrop of banana can suppress many weeds with a combination of natural mulch and shade.
Alley cropping
Banana is suitable for alley cropping with a wide range of plants.
Home gardens Banana is ideally suited for home gardens, growing readily
and fruiting reliably and profusely. Dwarf varieties are easy to harvest.Also, dwarf varieties are relatively wind-tolerant and tend to be more disease resistant.
Living fences
Musa coccinea, a brightly colored, crimson-flowered ornamental, has been recommended as a component in a living fence. Musa balbisiana, one of the parents of edible hybrid bananas,was introduced into Hawai‘i for this purpose (as a windbreak). However, because it is seeded and fruit-eating
birds eat the seeds, it has come to be regarded by some as a pest in some areas of Maui.In windy and dry areas, a living fence of banana tends to look ragged and unkempt.
Animal fodder
Banana fruits, stems, and cut-up pseudostems (trunks), are suitable for animal fodder for horses, cattle, and pigs (provided the material is not contaminated by pesticides already recommended in the text)
Wildlife habitat
Birds feed on banana fruits and on the insects that are attracted to the plant.Flying foxes (bats) are banana eaters in the Western Pacific, where they are indigenous.
Ornamentals
Musa species and banana varieties are used ornamentally in many locations and under a wide range of landscapes,from backyards to coastal resorts. Some examples of ornamental Musa species include self-peeling ‘Hot Pink’ or ‘Fuzzy pink’(M. velutina); ‘Ornata’(several varieties of M. ornata);
‘Blood/Rojo/Zebrina’ or ‘Variegated Red’ (M. acuminate subsp. zebrina); and ‘Okinawa torch’(M. coccinea).
USES AND PRODUCTS
Staple food
Bananas, consumed cooked or raw, either as the green, halfripe, or ripe fruit, are one of the most significant sources of calories for the human diet worldwide. Bananas are a particularly good source of potassium. The yellow and orange-fleshed bananas are also rich in provitamin A and other carotenoids. Provitamin A carotenoids (including beta-carotene, the most important one) are important for protecting against vitamin A deficiency and anemia (as vitamin A is involved in iron metabolism). Carotenoid-rich
foods may also protect against diabetes, heart disease, and certain cancers, which are serious emerging problems of epidemic proportion in the Pacific. Recently, attention has been focused on the carotenoid-rich bananas in Pohnpei, in particular the ‘Karat’, a Fe‘i banana with an erect bunch.
It has been shown that levels of beta-carotene may reach as high as 8508 µg/100 g edible portion in some Fe‘i bananas. Other bananas in Pohnpei were also found to be carotenoid-rich, including ‘Kudud’(internationally known as ‘Sucrier’), which contained 315 µg beta-carotene/100 g. This is over 10 times higher than the beta-carotene content in the common Cavendish banana (21 µg/100 g).
Famine food
All banana plants have starchy corms and pseudostem bases that were and still are used in times of famine on Pacific islands (mostly SW islands and New Guinea). This was evidently the original use of banana for human food (de Langhe 1995).
Beverages
Alcohol, beer, vinegar, and wine can be produced from fruit. More of this was done in the past, but even in modern French Polynesia, vinegar is produced in small quantities by small-holding farmers (in this case, using ‘Yangambi km5’ (AAA, Ibota subgroup) bananas, introduced initially
for livestock but found to be perfectly edible and excellent for fermenting into vinegar.
Flowers
The small male flowers (inside the “bud”) of certain varieties, notably ‘Saba’ and ‘Dippig’, are cooked and eaten in the Philippines and within the Filipino community of Hawai‘i. The entire bud can also be cooked as a vegetable; however, it is necessary to use the correct variety and boil it in several changes of water, otherwise it will be very bitter.Thick nectar from the male flowers of the Iholena, Maoli, and Pōpō‘ulu subgroups was traditionally fed to babies in precontact Hawai‘i.In contrast to the flowers,this semi-jelledhoney”is a delightful gift of the banana plant to those with a sweet tooth.
Leaf vegetable
Leaf buds can be eaten as vegetable. Evidently, leaves of the beautiful, red-variegated ornamental M. acuminata subsp. zebrina are particularly tasty.
Medicinal
Flowers, fruits, and roots are still used medicinally in some Pacific cultures, but most of these practices have died out. Stalks were mashed and used as poultice for sprains or broken bones (Hawai‘i). Root sap from certain varieties was used as a medicine for thrush, a child’s mouth irritation (Hawai‘i), and to treat skin warts (French Polynesia). Pounded banana peels—used in many Pacific cultures as a wound “bandage”—have been found recently to contain antibiotic properties.
Flavoring
Ashes produced from burning banana leaves and pseudostems are used in curries and as a salt substitute (India).
Cut flowers
Some Musa species and hybrids with colorful floral bracts and flowers are utilized in ornamental landscapes and tropical flower arrangements.
Fuel wood/cooking
Throughout the Pacific, banana trunks are still used to line underground ovens (to provide steam), together with banana leaves placed over the food to keep it dirt-free.
Fodder and silage
Fruits and stems are made into silage and used as cattle feed. Underground parts are also used for pig and cattle feed (e.g., Marquesas).
Maintenance requirements
Musa species are beautiful landscape plants and add to the tropical feel of a garden. Bananas do require management because the mats tend to expand radially and use up more and more space over time. New suckers along the perimeter of the mat should be cut off to prevent encroachment upon the landscape or nearby buildings. Musa species are heavy feeders and, in the presence of other landscape plants with equally demanding nutritional requirements such as grasses, may develop nutritional deficiencies
rather quickly. However, where esthetically acceptable, banana mats provide a very good place to compost yard waste and mulch; this feeds the plants and helps retain soil moisture during dry periods. Although beautiful ornamental plants, they are not as well suited for high-maintenance, high
visibility landscapes and parks because they tend to create a lot of unsightly leaf and stem debris. For this reason, it is usually better to plant bananas at the edges of landscaped areas, out of full view. In low-maintenance or more natural landscapes, banana debris is not a problem.
THEORETICAL FRAMEWORK
Theory of production
in economics, an effort to explain the principles by which a business firm decides how much of each commodity that it sells (its “outputs” or “products”) it will produce, and how much of each kind of labour, raw material, fixed capital good, etc., that it employs (its “inputs” or “factors of production”) it will use. The theory involves some of the most fundamental principles of economics. These include the relationship between the prices of commodities andthe prices (or wages or rents) of the productive factors used to produce them and also the relationships between the prices of commodities and productive factors, on the one hand, and the quantities of these commodities and productive factors that are produced or used, on the other. The various decisions a business enterprise makes about its productive activities can be classified into three layers of increasing complexity. The first layer includes decisions about methods of producing a given quantity of the output in a plant of given size and equipment. It involves the problem of what is called short-run cost minimization. The second layer, including the determination of the most profitable quantities of products to produce in any given plant, deals with what is called short-run profit maximization. The third layer, concerning the determination of the most profitable size and equipment of plant, relates to what is called long-run profit maximization.