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Click on markers Click off markers BIOLOGICAL CHARACTERISTICS 28 GENERAL SETTINGS The olive tree belongs to the oleaceae. It's got a short, thick and twisted, sometimes tortuous trunk and a wide top with many branches which is 4 or 5 metres high in our country (*). Their leaves are opposed, persistent and coriaceous; they are in one piece with an eliptical shape, very narrow and sharp. The are also green and gloss on the surface although their tonality changes depending on the variety, and they are whitish on the back because of the presence of starry hairs. The flowers are very white and small, appearing in underarm bunches. Its fruit, the olive, is an ovoid “drupa” from 2 to 4 centimetres long, depending on the varieties. Its colour is yellow green becoming purple when mature.It tastes bitterly. SYSTEMATICS The oleaceae family includes trees and bushes with pinned or entire leaves, normally opposed and without stipulae. The flowers have got a bell-shaped, tubular calyx with four or five lobes and corollas with similar characteristics although, in rare occasions, they can have free petals. The “androceo” is made by two stamens and the “gineceo” shows supero and bilocular ovary. They may have a dry and freshy fruit. (*) Their hight and general aspect vary depending on their pruning. If there is no pruning, they could become bushes. When they are trees they have a pyramid shape and about 12 to 15 metres high. 29 Apart from the olive tree, there are other species that belong to the same family such as ash trees, lilac, “agracejos”, “aligustres” and jasmine. The type of Olea can be found all over the world since they can be found in all continents. Among them, one of the most important of them is the Olea Europaea which corresponds to the olive tree. 30 Distribution map of the type of Olea This type includes 30 species among which we can find the olive tree “Olea europaea”, with numerous subespecies, series and varieties. Summary of the main subdivisions from the species Olea europaea. (Cifferi y Breviglieri 1942). 31 Among all of them we'll mention the followings: * Olea europaea euromediterranea var. oleaster, O.oleaster u O.sylvestris Mill (acebuche) * Olea europaea euromediterranea var. Sativa u O.sativa (cultivated olive) According to some authors, the “acebuche” might come from the wild growing of cultivated olives; in that case, they could be considered within the O. sativa group. Almost all researchers agree that the domestic olive growing started in certain zones in Syria, Iran and minor Asia and spreading towards the west along the two mediterranean shores. We' ll finish this section with a list of the main varieties of olive growing as well as their characteristics and application. (Information given by C.O.I.- International oleic conseil. 32 Varieties found in Spain 33 Varieties found in Spain (cont.) 34 Most common varieties: main characteristics. Footnote: The most frequent applications are shown. 35 MORPHOLOGY The trunk and the brunches In the olive tree we can normally distinguish the main trunk and the primary, secondary and fruit-bearing ramifications or branches THE MAIN TRUNK The olive trunk is easily recognizable because of its dark and cracked bark often showing thick cords and cavities that sometimes get to the centre of the tree. This may happen in mature-aged specimen but in young trees, the trunk is much smoother, lighter-coloured and regular shape. The general aspect of the tree depends on the way it is pruned; therefore, it changes depending on the zone as well as their variety. The most characteristic types of olive trees: a) candelabra shaped, b) three feet shape 36 PRIMARY RAMIFICATIONS Starting from the trunk there are thick branches that constitute the general shape of the tree. The number of branches vary depending on their prune and they are very important to regulate the production and the simplicity for the harvest. When the tree gets older, these branches are pruned, or even cut, so that the growing of the young branches keep the vitality of the fruit-bearing ramifications and, therefore, the production of the olive tree. SECONDARY RAMIFICATIONS From the primary ramifications there come other branches that, by new divisions, make the top of the tree and where fruit-bearing branches are hold. FRUIT-BEARING RAMIFICATIONS The flowers and, therefore, the fruit, don´t grow on any branch of the olive tree; they appear in the shoots put out the previous year. These shoots use to be 50 cm long and the harvest depends on their number and position. If the number is too low, the harvest will be poor but if the number is high, there will be a great deal of small fruit and, therefore, less valuable. The leaves The olive tree leaves are complete and lance-shaped. They are laid on the branches through a petiole short. Like all the Oleaceae, they are opposing. Although their general shape is lance-shaped, their proportion may vary from oval to almost lineal depending on the variety. 37 It’s colour may also change. There are some varieties with light green leaves and others with darker tones. At the back side, the colour vary among silver grey and other more brown because of the presence of starred hair in this position. They are persistent leaves with an average duration of 2 or 3 years. Their size vary between 3 and 8 cm long, and 1 to 2.5 cm wide, depending on the variety. They are normally very hard and have a very marked central nerve. In a cross section we can find the elements which are common to all leaves, showing a thick cuticle on the upper epiderm and the starred hair at the back. Its fenceshaped parenchyma is made by two or three cell layers and are frequently the fibres in the lagunar parenchyma. In the section of “applications in class” we will describe the process of preparation of the leaves for their observation as well as the suitable diagram. The roots The olive tree normally shows fasciclated roots. Nevertheless, if we observe the germination of a seed, we can see that there is only one pivotant root from which we can observe secondary small roots. The reason for this is the way of planting them. That way, the roots grow in a fasciclating way from an “estacón” (stick) and when the tree seedling come from seeds, the pivotant roots blunt to let the secondary roots appear. The definite aspect of the radicular system depend on the physical characteristics of the ground and the depth of the freatic layer. Furthermore, we can also find variety differences that justify the graftings on the feet which develope better roots. 38 The flowers The flowers of the olive tree are small and white. They could be unseen if they were not gathered in axilar inflorescencies (picture 2.3). These are long-shaped compound bunches in which there are dozens of flowers. The flower is “tetrámera”, although it is not very difficult to find “pentámera” flowers with welded petals and two stamen, with a very short filament and an ovary with two carpels (picture 2.4) The fruit itself The olive is a “drupa”, whose mesocarpo represents about 2/3 of the fruit. This is very rich in lipids. Its shape is not constant since there are some varieties such as the “manzanilla”, with a small and almost rounded fruit, la “cornicabra” with a longer, slightly bended fruit, etc. Its size may fluctuate between a bit more than a centimetre (“arbequina”) and more than three centimetres (“gordal”). The endocarpio is woody and its morphology depends on its variety. The epicarpio is welded to the mesocarpio, its colour is green but it changes to purple when mature,gloss (because of the presence of wax) and very soft (picture 2.5) 39 DEVELOPMENT AND GROWING UP We all know the olive tree longevity since we can often find millennial trees. Nevertheless, from the agricultural point of view, we must concentrate in the period from its birth to the notorious diminishing of its productivity. Therefore, depending on its productivity we can divide the life of the olive tree into three stages: • Youthful stage, from 1 to 7 years old ( with no production) • Production stage, from 7 to 150 years old. • Senile stage, from 150 years old onwards (little production) Youthful stage When the seed germinates, or when the seedlings start to take root, the plant starts to develop its roots and brunches. Like in all trees, the formation of new tissues implies the use of bio-elements that will be part of the new plant. The carbon is incorporated to the leaves as CO2; the nitrogen travels through the roots as nitrates mainly. That´s why the quotient C/N (proportion between the quantity of carbon in the elaborated sap glucids and the nitrogen in the brute sap) is useful to evaluate the relative importance of the aerial system with respect to the radicle system. There is a close relationship between all this and the development of the plant and this allows us to know the plant growing point. During the initial stage there is an important development in the branches and mainly in the roots and that's why the relationship C/N keeps low. Apart from its size, there are other characteristics that allow us to distinguish a young plant such as the intense ramification, leaves which are wider than those in an 40 adult plant, and other less evident characteristics. Within this stage,some authors can see a youth stage (until the first blooming) and a final stage in which there are already flowers and even fruit although it isn't real production. Production stage This second stage starts with a transition periodthat goes until its full production period. During this transition there is a progressive growing of C/N approaching to the equilibrium. When the tree has reached that equilibrium, about 35 years old, it is the most productive period, which can get to 150 years if the farming conditions are adequate. The pruning, fertilization and parasite elimination are particularly important as we can see in the corresponding chapter. Senile stage From 150 years old onwards the production starts to diminish and at this point the substitution or renewal of the tree is advisable; nevertheless, this period is not always constant depending mainly in the attention they have received in the previous stages. Among the main characteristics at this stage are the diminishing of the production, the increase of the “vecería” (alternation between good and bad harvest) and progressive degeneration of the wood. Annual cicle Like almost all trees, the olive tree starts its cicle in spring, by developing its leaf bud, apicals and axilars. The axilar leaf buds can originate new ramifications o bunches, called “esquimo” in many places. 41 When the temperature rises, approximately in May, the flowers bloom and pollination starts. The starting of that blooming may vary depending on the annual weather peculiarities. During the summer there is a growing of the fruit and a hardening of the stone, reaching its ripening point at the end of summer or in autumn. The harvest takes place between September and October, for the grazing olive (greenish), and between November and January for the mill olive. After this, the tree starts a rest phase until the following spring. During this rest period, the cold action is necessary for the flowering. That's why, in countries in which there are constant warm temperatures, the olive tree can develop properly but the is no flowering. Later on we will see a simplified diagram of the annual cycle. We will also see in pictures 2.6 to 2.9 some details corresponding to different stages of the olive tree. 42 REQUESTS Although the olive tree is a tough, resistant tree that can be grown in almost any kind of ground even in adverse water conditions, its profitability in these conditions is affected negatively. To be profitable, the olive tree needs at least one metre thick ground and it doesn't tolerate grounds with a high level of CINa. As for pH, develops better with a slightly alkaline ground. They resist the limy ground perfectly. All this makes that its geographical distribution is rarely under 30ºN; therefore they are rarely found in the southern hemysphere. The olive tree looks for the light, so they grow better in the southern orientated sides. In elevated zones, they can grow at 800 metres high, in the south sides, and at 600 metres high, in the north sides. Nevertheless, they can grow at higher altitudes in tropical zones. In the olive groves next to the Sahara desert, we can find that they can resist extreme dry conditions thanks to their six metres long roots. If water is not very deep, the radicle systems are poor and therefore, the stability and dry season resistance. To end up with all these requests we must say that the environmental humidity, mainly fog, damages the tree making fungus and parasites appear. In the chapter corresponding to the the growing techniques we will develop the concrete necessities and the adequate fertilizing. 43 PICTURES 44 45 Go back to the main page 46