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Los días del 3 al 7 de Agosto 2013, fuimos invitados por la ISA, Asociacion Internacional de Arboricultura,  a TECNOVERD como Distribuidor Oficial para España y Portugal del sistema ARBOPROF® y ARBOCAP® asistio en representacion de España, como miembro de la ISA de los Estados unidos, a la Expo Internacional  de Arboricultura  certificaciones ISA y afines en Toronto Ontario, ( Canada ).

Fue espectacular!!!.

 

boton endoterapia boton picudo rojo boton procesionaria del pino boton trunk injection inyeccion en los arboles boton control de plagas
The translocation

TRANSLOCATION AND TRANSPORT OF SUBSTANCES

Transport processes in plants. A plant needs a lot more water than a comparable animal weight. This is because almost all the water entering the roots of a growing plant is released into the air as water vapor and only a small proportion is actually used by plant cells. The loss of water vapor by plants is called transpiration.

As a result of transpiration, plants require large amounts of water.Along with the transpiration stream are essential elements built from the ground mineral inside the cells of the roots.

Besides water and minerals, plant cells also require carbon skeletons, which constitute its source of energy. The movement of organic compounds from the photosynthetic parts of plants is known as translocation. The mineral elements needed by plants are absorbed by the roots of the surrounding solution and are transported from there to shoot in the transpiration stream.

MOVEMENT OF WATER AND MINERAL

The loss of water by plants as steam and is known as transpiration is a consequence of the opening of the stomata. This openness is necessary because through the stomata enter the carbon dioxide used in photosynthesis.

For plants to grow, the rate at which photosynthesis takes place exceed the rate of respiration. At very low concentrations of carbon dioxide or very low light intensities, the amount of energy captured by photosynthesis is equal to or less than that consumed by respiration.

As carbon dioxide is essential for photosynthesis, enters the leaves through stomata water vapor is lost through them. Although this water loss poses serious problems for plants, provides the driving force by which water is absorbed by the roots. Also provides a mechanism which cools the leaves. The temperature of a leaf can be up to 10 or 15 º C lower than the surrounding air. This occurs because the water evaporates, heat brings.

Water enters the plant from the soil by roots. The movement of water into the root cells is possible only when the soil water potential is greater than the water potential in roots.

The processes leading to water entering the root cells themselves are capable under certain conditions to generate a positive pressure that creates a water column. Such pressure, known as root pressure, however, only enough for the water rise a little way up the stem.

The water travels through the body plant in the conducting cells of xylem (vessels and tracheids.) According to the cohesion-tension theory, water moves into the tracheids and vessels under negative pressure (less than atmospheric pressure, also called voltage). Since water molecules are held together (cohesion) is a continuous column of water molecules that is pulled by traction from the solution found in soil within the root, molecule by molecule, due to evaporation of water on top.

The diffusion of gases including water vapor into the interior and exterior of the leaf is regulated by the stomata. The stomata open and close by the action of the guard cells due to changes in turgor. Turgor of these cells increased or decreased by water movement, which follows the movement of potassium ions into or out of the guard cells. Various factors help to regulate the opening and closing of stomata, which include water stress, the concentration of carbon dioxide, temperature and light.

The essential elements are incorporated from mineral soil within the root cells through the activity of specific transporters, and are transported to the stem after being poured into the xylem with the transpiration stream. They perform a variety of functions in plants, some of which are not specific, for example, the effects they have on osmotic potential. Other functions are specific, as the presence of magnesium in the chlorophyll molecule. Some minerals are essential components of enzyme systems.

THE MOVEMENT OF SUGAR: TRANSLOCATION

Photosynthetic cells of a plant, which are typically more abundant in the leaves capture energy from sunlight to produce molecules that for their own use. Furthermore, these organic molecules are the source of energy for every cell of the plant.

The process by which products of photosynthesis are transported to other tissues of the plant is called translocation. This process takes place in the phloem and follows a pattern of "source to destination." According to the hypothesis of the current pressure, sugars enter the sieve tubes of the leaf by active transport in and out to other parts of the body of the plant where they are needed for growth and energy. The water moves inwards and outwards from the sieve tubes by osmosis, according to the sugar molecules.

These processes create a difference in water potential along the sieve tube, which causes water and sugar dissolved in it move by bulk flow along the ribose tube. The sugar molecules enter through an active transport companion cell located at the source, and then move to the sieve tube through the many connections cytoplasmic cell wall common sieve tube and companion of his cell. With the increase in sugar concentration, water potential decreases and water enters the sieve tube.

The sugar molecules leave the sieve tube at the destination and the concentration of sugar in the sieve tube decreases. As a result, the water leaves the sieve tube. Given the active secretion of sugar molecules into the sieve tube in the output source and destination sieve tube, there is a flow of sugar solution along the tube, between the source and destination.

IMPORTANT DEFINITIONS

Apoplast:

It is the free vegetable metabolic activity, is a more or less continuous cell walls, intercellular spaces and xylem cells interconnected. The upward movement of substance absorbed by the roots, is predominantly through this system.

Symplast:

They are the living tissues of the plant cell protoplasts constituted by interconnected by plasmodium’s, phloem being the essential component of the symplast and the substances are transported to photosynthesize tissues or organs where it is used and / or stored.

EVIDENCE ON THE ROLE OF THE PHLOEM.

We obtained convincing evidence about the role of phloem where radioactive tracers were available. If the plants perform photosynthesis in an atmosphere containing carbon dioxide which is radioactive (14CO2), sugar produced shall be marked radioactive. Studies of the trajectory of radioactivity through the plant have shown conclusively that sugars are transported into the sieve tubes.

Aphids, which are small insects that suck sap, have provided valuable information about the movement of substances through the sieve tubes. These insects insert their mouthparts in the form of a stylus in the sieve tubes. If then spreads to their aphid stylet, the latter will phloem fluid. Data collected with the help of aphids indicate that the sap of sieve tubes containing (by weight) of 10 to 25% of solutes, over 90% of which are sugars, especially sucrose.

They also contain low concentrations of amino acids and other nitrogenous substances, in addition to ions. Colors crawlers indicate that the speed of movement of solutes across the sieve tube is remarkably high. It was felt that the sap is moving at a speed of approximately 100 cm. per hour, much faster than would be expected if this movement involving only diffusion. At this speed, each member of a sieve tube empties and refills completely every 2 seconds.

HYPOTHESIS OF THE CURRENT BY PRESSURE

The movement of sugars and other organic solutes in the translocation is what is known as a pattern source to destination. The main sources of these solutes are the leaves that perform photosynthesis, but the storage tissues can also serve as important sources. Moreover, all organs or tissues, unable to meet their own nutritional requirements can act as a destination, or importers of organic solutes. Thus, the storage tissues act as targets when they are importing solutes and as sources when they are exporting them.

The most widely accepted explanation for the movement from source to destination is called translocation hypothesis of the current and pressure. According to this hypothesis, solutes move in the solutions, which in turn move by differences in water potential caused by concentration gradients of active particles in the osmosis (mainly sugars).

The existence of different sucrose concentration gradients along the phloem tissues supported the hypothesis of the current and pressure. This hypothesis could explain the speed of movement in phloem is indicated above. As shown, the sugars in the leaf photosynthetic cells enter the sieve tubes against a concentration gradient. This transfer process appears to involve co-transport of molecules of sucrose and hydrogen ions through a specific transport protein in the sieve tube membrane. Upon reaching a destination, for example, a storage root, the sugar molecules leave the sieve tube. Then, water molecules follow the sugar on his way out, again by osmosis. So water flows in at one end of the sieve tube and outside it at the other end. The rate of transfer depends on the concentration differences between the source and destination.

In the latter, the sugars can be used or stored, but most of the water returns to the xylem and recirculated in the transpiration stream. In plants, water serves multiple functions. Cells must have direct or indirect contact with water, as nearly all cellular chemical reactions, occur in an aqueous medium. For a normally functioning tissue, requires to be saturated with water, keeping cells turgid. All substances that enter the plant cells should be dissolved, because the solutions are making the exchange of nutrients between cells, organs and tissues. Water as a component of living cytoplasm, it participates in metabolism and in all biochemical processes.

A decrease in water content within the plant, accompanied by a loss of turgidity, wilting and decreased cell elongation, thus closing the stomata, reducing photosynthesis, respiration interfering several basic metabolic processes.

 

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