The processed sap is an aqueous substance that flows through the interior of plants and whose composition is derived from the raw sap modified through the process of photosynthesis. It should not be confused with other substances produced by plants, such as resins or latex, since its function is completely different.
Sap is the substance that travels inside the small cavities and ducts located inside plants, including trees. When the sap has not undergone the photosynthesis process, it is called raw sap. It flows through capillaries known as xylems.
Once the plant photosynthesizes, the composition of the raw sap is altered, and it is then that it is called "processed sap", and its displacement occurs through different types of tubular conduits, called phloemes.
The elaborated sap, therefore, is known to be the substance that runs through the phloem, and whose main objective is to distribute the sugar, nutrients and water present in it throughout the body of the plant (including the leaves and roots).
The processed sap is mainly composed of high amounts of sugars, minerals, amino acids, organic acids, vitamins, phytoregulators, and inorganic ions.
On the other hand, it is responsible for hydrating the leaves of the plants once the water present in them evaporates. The way in which sap manages to be transported into plants has historically been the subject of debate.
At present, it is believed that this process of vertical and upward displacement of the sap is possible thanks to the variation of the pressure inside the cells and ducts through which it travels.
Composition of the processed sap
The processed sap is rich in nutrients, contains high amounts of sugars, minerals, amino acids, organic acids, vitamins, phytoregulators and inorganic ions.
Thanks to its richness in nutrients and its purity (it does not contain toxins), it is commonly consumed by insects whose diet and nutrition clearly depend on it.
Sometimes, the composition of the elaborated sap can be altered due to the interaction that the insects that consume it have with it, since these insects can carry easily transmissible pathogens at the moment in which they pierce the structure of the plant.
On the other hand, the processed sap is considered a complete mixture of organic to inorganic substances. Some studies have shown that sugars and amino acids are the predominant substances present in processed sap.
Sucrose is the main sugar found in processed sap, however, other sugars such as glucose, fructose, mannitol, and sorbitol may also be present in its composition.
Amino acids are the main form of reduced nitrogens found in processed sap. Its total concentration varies depending on the plant species.
Organic acids such as malic, succinic, ascorbic, and citric acids can also be found in various species of plants.
Transformation
The process of production of the elaborated sap begins when the plant absorbs nutrients from the soil through its root. In this way, it takes salts, water and minerals present in the earth.
This is how the raw sap is initially formed, which is transported by the stem with the help of xylems or woody vessels until it reaches the leaves.
Once in the small cavities located in the leaves, the raw sap is converted into elaborated sap thanks to the photosynthesis process.
Photosynthesis is the process by which all living beings with chlorophyll (plants, algae and some bacteria), are capable of taking energy from sunlight to convert it into chemical energy.
The processed sap takes place when the raw sap is mixed with the substances resulting from the photosynthesis process. Once transformed, the sap travels through the plant through the Liberian phloem or vessels, with the aim of distributing nutrients, sugars, amino acids and water throughout the plant's body. It also has the ability to store substances like starches.
Transport
The elaborated sap is transported to the interior of the plants through the phloem or Liberian vessels. In this way, it manages to reach all parts of the plant's body, more specifically the tissues where it will be consumed (such as meristems) or stored in the seeds, fruits or roots.
There are several theories about the way in which the elaborated sap moves upwards inside the plant, against the force of gravity, however, the most accepted theory is known as the cohesion hypothesis.
Cohesion hypothesis
The cohesion hypothesis, in botany, is the generally accepted explanation of how sap in plants travels up their bodies with the help of intermolecular attractions.
Various calculations and experiments indicate that the cohesion forces between the water molecules and the adhesion forces between the molecules and the walls of the cell vessels are sufficient to give the water sufficient tensile force to displace it inside the plant.
The tensile force that the water present in the sap obtains inside the plant is sufficient to carry it to the highest part of the tree continuously, that is, without there being any rupture in the flow of sap inside the ducts of plant.
These constant streams of sap are known as columns, and are responsible for the vertical and upward movement of water in plants.
The ascent mechanism of the sap is transpiration, since it involves the evaporation of the water from the leaves, which is why it becomes necessary for the elaborated sap to move vertically to rehydrate them.
The cohesion theory is a hypothesis that various researchers have raised to explain the movement of the sap produced inside plants.
References
- Britannica, TE (2017). Encyclopædia Britannica. Obtained from Sap: britannica.com.
- Britannica, TE (2017). Encyclopædia Britannica. Obtained from Cohesion hypothesis: britannica.com.
- (2017). Escuelapedia. Obtained from Elaborated Sap: schoolpedia.com.
- Hijaz, F., & Killiny, N. (July 11, 2014). US National Library of Medicine. Retrieved from Collection and Chemical Composition of Phloem Sap from Citrus sinensis L. Osbeck (Sweet Orange): ncbi.nlm.nih.gov.
- Luengo, L. (sf). The plant nutrition. Obtained from 3.5 Transport of the elaborated sap: recursostic.educacion.es.
- Scientists, AS (2016). Plants in Action. Obtained from Techniques to collect phloem sap: plantsinaction.science.uq.edu.au.
- Shah, R. (2016). Biology Discussion. Obtained from Phloem Sap in Plants: Composition and Movement - Plants: biologydiscussion.com.