The seeds of the coffee tree: history and geography and botany...

Article by Vladimir Shamaev
Original Source: magazine "Coffee & Tea in Russia" Number 4 as of 2015

Vladimir Shamaev

The birthplace of the coffee tree is located in one of the geographic centers of origin of species; on the continent, which in the past few million years, as researchers say, experienced  less than others significant global changes.

The great Russian scientist, geneticist, botanist and geographer Nikolai Ivanovich Vavilov identified seven such ancient centers of formation of cultivated plants. Ethiopian, was the place from which about four per cent of all plants, including coffee spread all over the world.

Discovery of "Arabica" was due to the unique properties of this tree seeds, as well as to the geographical location of the homeland of coffee in the immediate closeness to "Fertile Crescent" and "Great Silk Road."Coffee tree turned out, they say, in the right place at the right time.

The birthplace of coffee

On the territory of modern Federal Democratic Republic of Ethiopia, the oldest Christian country and one of the oldest countries in the world, in the most inaccessible part of the Abyssinian plateau until 1897 there  was state Cuff located. Each time touching the cup filled with the most popular hot drink - coffee, millions of people mention the word derived from the name of the country, unaware of its existence. History of Kaffa is interesting for those who work in the coffee business, not only because  coffee was first discovered there and the technology of transformation of the coffee tree seeds in the drink started there, but also due to the special relations existing between Russia and Ethiopia.

Kaffa was located in the southwestern part of Ethiopia among mountain ranges, interspersed with valleys and numerous rivers flowing from the mountains and flowing into the White Nile. Unusual natural conditions ,abundant water, fertile soil, allowing to have up to three crops a year, made such a strong impression on the ancient Semitic tribes who came here from Egypt, that they were ready to consider this area as a paradise on Earth. According to the Ethiopian legend, equally recognized by both local Christians and Jews, the founder of the ruling dynasty in Ethiopia was a king of kings negusMene face of the son of King Solomon and the Queen of Sheba.

Centers of origin of cultivated plants

Until the XII century Kaffa area was sparsely populated part of Ethiopia. Basically Negroid tribes lived there. However, by the end of the XIII century, the region became a state, and the people who settled there started calling themselves kafficho. Kaffa state system and social relations inwere extremely peculiar. Carefully maintained for many centuries, the isolation of the country led to the fact that until now the province of Kaffa is one of the least studied areas of Ethiopia.

Centers of origin of cultivated plants

The dominant stratum led by the king in every way opposed the penetration of the alien influence. Communication with the outside world was done via trade in a special border settlement - the city of Bonga. Arab merchants could stay there only with the permission of the king of Kaffa. Coffe was the strategic goods for them. Most likely, kafficho sold peeled seeds of the coffee tree, which could not be used as a seed, and the inability to penetrate deep into the country for outsiders excluded export seedlings outside Kaffa. Naturally, there were attempts to steal coffee trees. We can assume that coffee first came to Harare, and then to Yemen, but this is unlikely, as the Harare was also closed territory. Most likely, botanical smugglers found wild coffee trees in areas close to Kaffa or Sidamo. Either way, the coffee tree got to the Arabian Peninsula. In that historical period Yemen was a major center of trade between the Arab world and East Africa and was the first to appreciate the new product,  the tradition of the use of khat leaves with a slight narcotic effect also helped. As reported in the chronicles Al -Dzhazira initially "Kahwa" was brewed from  khat leaves. Upon discovering that the coffee beverage is cheaper and saves all the advantages of traditional, they began to prepare the seeds of the coffee tree. Coffee became the most popular product in the entire Arab world. The need for a valuable raw material increased. Thanks to suitable climatic conditions and high demand they began to cultivate coffee in Yemen. The botanical name - "Coffee arabica" came from here. In the XVI century tribes of Oromo invaded the territory of the Abyssinian highlands and separated  Kaffa from Ethiopia.

It seemed that Kaffa would keep their secrets for long, but the terrible events of the XIX century put an end to its isolation. In 1897, three Ethiopian armies entered the Kaffa, and in 8 months the state ceased to exist. Devastated country Negus annexed to Ethiopia. King kafficho Gaki Shirocho was captured, and the commander Wolde Giorgis became the governor of Kaffa.

The first European who managedto visit Kaffa province was the Russian traveler Alexander Bulatovich. The Russian traveler Alexander Bulatovich Alexander Bulatovich was born in Orel. His father Kaverin Vikentievich belonged to the hereditary nobility of Grodno province. The childhood of Alexander passed in rich parents’ estate Lukovka in Kharkov province. Bulatovich graduated from the Alexandrovsky high schools among the best graduates. In 1896, he became a member of the Russian Red Cross mission to Ethiopia, where he became a confidant of the Negus Mene face II. Bulatovich was the first to cross Kaffa from one end to another. Later he compiled the description of the region,  For his work in Ethiopia Aleksandr Ksaverevich received a silver medal from the Russian Geographical Society. Austrian ethnographer Fridrih Bobor in his writings on the study of Kaffa used works by Bulatovich, as well as knowledge of local area and language of kafficha by another traveler and artist from Russia Yevgeny Vsevolodovich Senigov.

Lieutenant of the Russian army E. W. Snegov was in Ethiopia as part of a military mission of N.S. Leontiev in 1899. Falling in love with this place, Snegov decided to stay there. Mene face II gave him a small estate near Addis - Ababa, where he lived, married to an Ethiopian. An excellent connoisseur of the country, Snegov visited Kaffa a few years before F. Bieber came and provided him with substantial help and support. As you can see, the role of our compatriots in the study of the homeland of coffee was very significant.

A coffee tree

The coffee tree belongs to the higher land plants - Embryophytes. Their main feature is the presence of the body, divided into specialized organs - leaves, stem and root, by which they produce organic substances during photosynthesis.

Coffee tree isolated into a separate genus of the family Rubiaceae and has more than 90 species. This is quite a variety of plants. Among them there are deciduous and evergreen, tall and mighty trees, which reach more than 20 meters in height and bushes 1.5 - 2 m high. Most of the species –are small four-meter trees. Not all of these plants are able to bear fruit from the seeds of which at you can prepare a well-known beverage. Only four species present agricultural practical interests: Arabian or Abyssinian (Coffea Arabica), Robusta or Congolese (Coffea Canephora, Coffea Robusta), Liberian (Coffea Liberica) and high coffee (Coffea excelsa, Coffea dewevrei). Since 2006 Coffea dewervrei, Coffea excelsa Coffea dybowskii are not considered as separate species, and qualify as a kind of Liberica coffee (Table 1).

Table 1
Characteristics Type Arabica kind (Coffea) - «C» Type Robusta kind - «C» Other species - «C»
Ploidy Self-compatible. Polyploid with 2n=4x=44 chromosome set. Incompatible. Diploid with 2n=2x=22 set of chromosomes. With vegetative reproduction ploidy is maintained. Other species have the same as Robusta.
Habitat. Ecology Wet Tropics. Highlands. Mountain forests. Shade tolerance. Altitude 1200-1950 m (critical 950m). Temperature- low - moderate 15-24°C. Rainfall is 1200-2200 mm per year. Tropical lowland. Lowland forests. Savannah. Open slopes. Photophilous plant. Altitude 250-1500 m (critical 50m). Temperature - warm 1-36°C. Rainfall is 2200-3000 mm per year.
The extract (soil) Mountain fertile, young volcanic soils. Porous. Humus layer builds up slowly because of the rapid decay caused by bacteria. Red and yellow soils. Soil of washing water regime.
Height of a plant 4-6m. Pruning 2-3m. 8-12m. Pruning 2-3m.-12м. 16-25m high. Dwarf 1.5-2m.
Crown 1,2-2м. 1,2-2м. More than 2m.
Root system 2-3m deep roots. Shallow roots, surface 1.5-2m.
Leaves Elliptic acuminate 10±5cm. Width 4-6cm. Elliptic acuminate 20 ± 2 cm. Width 12-17cm.
Flowers 16-48 flowers in the bundle. Self-pollinating. Pollination occurs within - 1 day. 30-100 flowers in a bundle. 6 days after flowering it persists fertilization ability.
Fruit The length is 12-18 cm. Maturation 7-9 months. The length is 8-16 cm. Maturation 9-11 months. Ratsemoza. Maturation of 2 months.

Coffee tree is bushy with spreading long, thin flexible branches, which are arranged in pairs leaves. Leaves are dark - green, leathery, glossy, persist on the tree from three to five years. They have an oval shape, pointed at the ends, wavy at the edges. Dense average vein and 9 - 12 side add prominence to leaves. Whole leaves on short stalks reach 20 cm in length and 12 cm in width. In the axils of the leaves white flowers with a strong smell, reminiscent of jasmine hide. The inflorescence consists of four flowers, but not all of them can be fastened. The flower buds begin to grow and turn into a flower after 8 - 12 days in the period of highest humidity. Corolla flower has five petals, inside which there are five stamens and pistil, bifurcated at one end. After two days of flowering, the flowers fade, fall off, leaving the ovary. Pollination occurs of Arabica autogamous – self-pollination  and robusta is allogamous, ie cross by wind and insects. Methods of pollination of the two main botanical species of coffee tree can explain a lot. In the process of cross-pollination there is an exchange of genes that support the unity and integrity of the species. This increases the possibility of recombination of genetic material. As a result a more viable offspring appears  that is better adapted to the different conditions of existence. Cross-pollination is stuck in the process of natural selection and has become dominant in the plant world. Self-pollination is caused by adverse environmental conditions, and from the point of view of evolution is a dead-end path of development. Not surprisingly, the progenitor of arabica coffee, with such genetics refers to the endemic, that is, to the plants, common in a small area bounded by the specific climatic and geological barriers, where the ancient Kaffa was located. The fact that the Arabica coffee is preserved after surviving the global changes in the world is most likely an accident. It is unlikely that other types of coffee, discovered later, could be interesting for people as they do not have such a pronounced taste and aromatic properties.

Coffee tree fruit

Anatomy of the coffee tree fruit does not have fundamental differences from the structure of the fruits of other representatives of the higher plants, the fruits of which belong to the group drupe (lat. Drupe). They as coffee have a clear differentiation of the layers of the pericarp and the presence of hard bone with the seed inside.

Longitudinal and transverse section of the fruit of the coffee tree:

Longitudinal and transverse section of the fruit of the coffee tree
  1. 1. The outer layer of cells.
  2. 2. 3. 4. 5. Mesocarp Layers.
  3. 4. Fibrous vascular bundles.
  4. 5. Mucilaginized polisadnye cells.
  5. 6. Cells endocarp.
  6. 7. 8. Spermoderm sclerenchyma and parenchymal cells.
  7. 9. Cells external (solid) endosperm.

The fruit of the coffee tree has a round shape. In its upper part there is a convex disc framed by the edge of sepals residues. In the middle of the disc, you can see the remains of the stamens and pistil. On the opposite side of the fruit, a depression with a trail of the peduncle in the center is noticeable. Peduncle is short and thick is poor ly separated from the pericarp. The fruit of the coffee tree is made up of two parts: the pericarp - a multi-layered shell that forms the appearance and shape of the fruit. A seed is an embryo with additional structures responsible for its development.

The pericarp (lat -. Pericarpium from the Greek peri - «around something or any" and karpos - «the fruit") is the tissue located around the seed.

Coffee fruit pericarp is composed of three well distinguishable layers:

  • Exterior - exocarp  (the same as the epicarp).
  • Middle -  mezocarp.
  • Internal - endocarp.

Exocarp (lat -. Exocarpium from Greek exo - «outside" or epi - «on» and karpos - «fruit") is the outer layer of the coffee fruit in the form of a thin glossy dense dermis (skin), formed by a layer of parenchymal cells, which have the same dimensions and thin walls. Thickness of the layer is several micrometers.

The technical term - skin.

In the early development of the fruit the exocarp cells contain a large number of chloroplasts, which explains its bright green color. During maturation the chloroplast  disappears, coffee becomes  red, rarely yellow. The  color indicates fetal maturity. The degree of ripeness of coffee fruit is considered over the surface area, which remains green: 5% - very ripe, 10-15% - ripe, 20-25% - relatively ripe (figure 4.).

Exocarpium of coffee tree fruit

Mesocardium (lat -. Mesocarpium from the Greek mesos - «average» and karpos - «the fruit") - the middle layers of the pericarp – fleshy and juicy part of the fruit. Technical term - pulp. Mesocarp thickness is in the range of 1.0-1.7 mm. Around the endocarp (6) the layers of adhesive substances are formed,  so-called  mucilage. Slime is difficult to separate from the endocarp because of the presence of long polisad cells (5).

 It is removed during wet processing by controlled fermentation, in which the cells lose their structural properties and mucus is easily washed off with water. During dry processing mesocarp dries naturally, turning into the shell with thickness of 0.5 mm (Figure 5).

Mesocardium of coffee tree fruit

Endocarditis (lat -. Endocarpium from the Greek endo - «attitude to something - the inner" and karpos - «the fruit") - the inner layer of the pericarp, protecting coffee seed. It consists of several tens of rows of fiber cells.

Technical term - parchment - parchment or husk - husks,  stiff shell coffee seed. Average weight of the parchment under 11% moisture of raw (green) coffee is 3.8% of its total weight. The thickness is 110-150 microns (micrometers).

Despite this endocarp of coffee is strong enough to protect the seeds from ferments and animal enzymes and gastric juice, from excessive moisture and other unpleasant effects of the environment. Endocarp is one of the main elements, it supports and regulates viability of seeds of coffee.

Coffee tree seeds (lat -. Semen), as the pericarp, is a multilayer structure, the central part of which is the germ (embryo). The embryo is surrounded by a nourishing tissue - endosperm. The endosperm, in its turn, is covered with a thin membrane - perisperm.

The seed is a complex multicellular biological structure, the main task of which is to resettle and plant propagation. The size and shape of seeds vary widely. The average length is 10-18 mm and the wiвер is 6.5- 9.5 mm. Some species have smaller seeds;  so bony coffee "Ratsimoza" has seeds 5-7 mm long and 3-3.5 mm wide. Liberica in contrast has larger grains. The fruit of the coffee tree has two seeds. Sometimes only one is fertilized. This happens in about 5% of cases. Very rarely three seeds of angular shape can be found in the same nut. A large percentage of individual seeds is a sign of a general infertility plants.

Perisperm or spermoderm (lat -. Perispermium from Greek peri -. «Around", "outside that - either" and sperma - «seed") in ripe fruit with the thin film surrounds the entire surface of the endosperm. It can always be found in the longitudinal groove.

Technical term for spermoderm is (silver skin) Spermoderm’s thickness is about 70 microns.

Endosperm (lat -. Endospermium from the Greek endo - «inside" and sperma - «seed") consists of identical cells (9) differing in wall thickness, containing vegetable fats and interstitial fluid. The latter allows to divide the endosperm tissue in the hard endosperm (hard endosperm), the endosperm and the outer soft endosperm (soft endosperm), internal. Endosperm cells, located in the immediate vicinity of the embryo, are rectangular in shape, whereas the polygonal - polygonal cells are located in the outer endosperm.

One of the characteristics of the endosperm is the width and depth of the grooves, so-called "striae loop configuration".

Coffee fruit has two seeds . The development process in the form of spherical shell (endocarp) seeds provide pressure on each other. This way the flat portions are formed. In the case, when one of the seeds is underdeveloped or does not existt, there is nothing to prevent the growth of endosperm, and it acquires an almost spherical shape. Such seeds are called Peaberry or Caracolillo (technical terms).

The embryo (lat. - Embrio from the Greek embryos - «fertile» ) (Figure 6.1.).

The embryo after 12 hours of soaking  (Fig. 6.2).

The embryo of the coffee tree - is essentially a microplant with the presence of all main organs:

  • Embryonic root (lat. -  radix), from which the main root develops.
  • Embryonic stalk or hypocotyl (lat -. Hypocotyle) - part of the plant between the main root and the main sprig.
  • Embryonic leaves , cotyledons (lat -. Cotyledon) - the first leaves of the plant, different from the further leaf.
  • Embryonic kidney or plyumula (lat -. Plumula) - part of the embryo, from which the main plant sprig develops.

In belobed, including  coffee there aretwo cotyledons, two heart-shaped leaves, fixed to the axis above the hypocotyl. The dimensions of the embryo are small, just 3-4 mm in length. Relatively thick leaves and thin root, which is sometimes called Axis – axis are clearly distinguished. At the end of the spine there is the suspension (embryosuspensor) which is short-genetically active body, a participant of later stages of embryogenesis.

The embryo is located in the soft endosperm layer along the central line of the dorsal part closer to the rear end of the seed. Above the end part of the spine there is the endosperm, called lid endosperm cap or micropylar endosperm. Endosperm around other parts of the embryo is called the lateral endosperm.

Endosperm and perisperm tissues are the main nutrient fibers. However, the embryo also contains several storage reserves, and in exceptional circumstances, it may provide itself with nutrients in the initial period of development, until it moves to autotrophic state.

The seeds of the coffee tree without protective parchment and silver casing are raw materials for the production of coffee. Flavor, aromatic and aesthetic appeal of the final product depend on physical, chemical and biological characteristics of the raw (green) coffee.

The embryo of coffee