The Olive Tree: Morphology

 

The embryo sacs emerge in the ovum after meiosis (a process that includes the division of a cell into four sexual cells). These embryonic sacs are then prepared for fertilization when the petals open, i.e., at the time of anthesis.

The development of the sacs can be incomplete in certain ovules, due to an error in meiosis, but this does not usually lead to any reduction in production during normal cultivation seasons.

• Flowering occurs between the months of May and August, at a temperature of approximately 15ºC, with the buds appearing closed.

•  Olive tree flowers will only open when the average ambient temperature is over 18ºC.

• THE LEAVES

The shape of the leaves is heavily influenced by the environment in which the olive tree grows.

The olive is an evergreen tree. The leaves tend to remain on the tree for 2 to 3 years, but this can vary. They have an elliptical or spear-like shape with complete edges.

The face of the leaf tends to have a dark green color, the underside covered with white flakes, having a color ranging between white and silvery. The leaf sheath is from 3 to 8 cm. long, and varies from 1 to 1.8 cm in width.

The central ribbing is quite pronounced, while the secondary veining is hardly visible.


• THE ROOTS

The shape of the roots is influenced as much by the soil conditions as it is by the origin of the tree itself. When the olive tree grows from a seed, it shoots out one main root that dominates the others, such that lateral roots hardly form.

Olive trees that have emerged from vegetative propagation (by means of rooting of cuttings) are a different case. With this method, the young trees form many roots which act as though they were the main root. Trees from nurseries are usually grown this way.

Roots can also be distinguished according to their youth or maturity. The young roots are white, covered by many hairs and have a higher capacity to absorb water and nutrients. Young roots are often more sensitive to infections from fungus or nematodes.

The adult roots, on the other hand, have a brownish color, the result of tissue suberisation, i.e., the permeation of the cellular wall with an organic substance called suberin.

  1. THE FLOWERS

Olive tree flowers are small in size and constantly symmetric. The calyx is greenish-white, with a total of four sepals.


The corolla, on the other hand, has five petals, which are distributed into the shape of a white cross, at times with yellow shades. The corolla also contains two stamens, which in turn have a sizable anther containing the pollen, in addition to a shirt filament.

The pistil holds an ovule which grows over the calyx (superior ovule), along with a papillate and bi-lobed stigma.

The pollen develops throughout the six weeks preceding the flowering stage. From that point, the pollen is released at any time, during a period lasting around five days.

The Exocarp - the outer layer of the olive, comprises the Epidermis and its cuticle.

The olives are usually black when mature, although there are varieties that have a reddish or violet hue.


At times the harvest is done while the olives are still green.

Complete maturity is reached between November and January.

The following varieties are examples of small-sized olives:

-Koroneiki (Greece).

-Arbequina (Spain).


A noteworthy large-sized olive is:

-The Gordal .

• THE FRUIT

The olives are usually small in size (although in some varieties they can weigh up to 10 grams).They have a rounded, spherical or ovoid shape. The olive is drupe - a fleshy fruit with a formation similar to that of the plumb, the peach or the almond.

Its length varies from 1 to 4 cm.

It has a diameter of between 0.6 and 2 cm.

The structure is made up of three tissues:


• The Endocarp (the olive pit)

• The Mesocarp (the pulp)

• The Exocarp (the skin)


All of these tissues form the Pericarp.

The pit begins to grow at the time of fertilization, while the fleshy part (the Mesocarp) - which also begins growth at the same stage - continues to grow until maturity. This does not occur with the Endocarp, the growth of which stops at two months.