Nearly 42% of all land in the world experiences temperatures below 20ºC, and in many of these areas temperatures are recorded below 0ºC; the periodic exposure of plants to this condition generates stress due to freezing, which can have harmful consequences in orchards. Ascophyllum Nodosum is presented as an excellent product to combat this environmental stress.
Just as high temperatures in the summer cause stress in plants, low temperatures also do so, causing freezing or frost damage. This condition negatively affects the growth and development of plants, limiting agricultural productivity.
A plant exposed to a frost phenomenon, i.e. temperatures below -0.5 degrees for more than an hour, suffers freezing stress, as intracellular and extracellular ice is formed, which alters the integrity of the cells, causing their death by breaking the cell membranes or walls, and the organelles.
Although a large percentage of crops in temperate zones manage to acquire tolerance to low temperatures, a phenomenon known as cold acclimatization, extreme weather conditions can severely affect them, and even cause the death of the plants.
Added to this is the constant climate change, with episodes of high temperatures and extreme droughts, such as the one Chile has been experiencing for more than 13 years. In this case, heat and lack of water cause dehydration at the cellular level, leading the plant to a point of permanent wilting (cell death), as well as abrupt exchanges of humidity with the environment that can produce collapse in the vascular bundles and also cause physiological disorders in the plant that will affect future performance.
Ascophyllum Nodosum: the algae that mitigates plant stress
Ascophyllum Nodosum is an algae, whose geographical origin is abundantly distributed along the northwest coast of Europe and the northeast of North America; it has an incredible ability to adapt to sudden changes in temperature and humidity.
It was precisely this condition that caught the attention of different scientists. Craigie in 2011 described the unique characteristics of Ascophyllum Nodosum as a prominent source of production and synthesis of biostimulant substances. This algae is a rich source of various bioactive phenolic compounds such as phlorotannins and unique polysaccharides, i.e. alginic acid (28%), fucoidans (11,6%), mannitol (7,5%) and laminarin (4,5%).
Its basic nutritional content presents carbohydrates (44.7 2.1%), ash (18.6 0.9%), proteins (5.2 0.2%), lipids (3.0 0.1%) phenolic (1.4 0.2%) and other compounds (13.6%).
Studies have shown that the bioactive compounds present in various types of Ascophyllum Nodosum extracts can mitigate temperature and drought stress in plants, making this product an excellent alternative when it comes to controlling environmental stress in crops, whether due to low or high temperatures or drought conditions.
When crops are subjected to temperature stress, they tend to accumulate proline, an amino acid found in small amounts in plants when they grow under optimal conditions. In episodes of stress, it has been detected that the proline content increases its levels within the plant to act as an osmotic agent (exchange of water, minerals and organic compounds), when there is a membrane in between, protecting the plant from dehydration.
On the other hand, under conditions of freezing stress, the plant upregulates the concentration of soluble sugars, sugar alcohols, organic acids, and lipophilic components, such as fatty acids, within the cell. The accumulation of sugars helps plants to overcome stress by playing an important role in the stabilization of various components, such as the cell membrane and the membrane of cell organelles, for example the vacuole.
Proline is also attributed a number of roles within stress tolerance in plants:
- Act as a mediator of osmotic adjustment (Delauney & Verma 1993; Kavi Kishor et al. 1995; Yoshiba et al. 1997);
- Stabilizer of proteins and membranes. or Inducer of genes related to osmotic stress (Iyer & Caplan 1998).
- Source of carbon and nitrogen readily available for cellular rehydration (Brugière et al. 1999); source of reducing equivalents (from proline catabolism) to sustain oxidative phosphorylation.
- ATP generator during stress recovery (Hare & Cress 1997; Hare et al.,1998.
- Contribute to the control of cytosol acidosis and can maintain the NADH/NAD+ ratio at values compatible with metabolism (Hare & Cress 1997).
- Helps in the detoxification of excess NH4+.
- It helps cells to overcome oxidative stress (reactive oxygen species harvester). (Ramanjulu & Sudhakar, 2000; Harsh, 2003).
In addition to the relevant help provided by the accumulation of sugars to overcome different types of stress in plants, we must add the relevant work of Ascophyllum nodosum in mineral nutrition. This product, in addition to offering the crop a complete solution to face environmental stress, provides the best nutritional tools to the crops.
In this area, it is relevant to mention the key role in the development of crops represented by two crucial microelements in the metabolic processes of plants: Boron and Zinc.
Boron is mainly associated with fruit set or also known as “binding”; this mineral participates in a series of metabolic and structural processes, such as the metabolism and transport of sugars in the plant, the formation of the cell wall and lignification. In addition, it has an influence on the metabolism of nucleic acids and proteins. Boron promotes the growth of the pollen tube in the stigma and style and is necessary in high concentrations to achieve the physiological deactivation of callose, through the formation of callose borate at the interface of the pollen tube, positively influencing its growth and helping in a better germination of the pollen.
Crops with Boron deficiencies may show symptoms such as death of terminal buds, chlorosis in young leaves, which then become necrotic at the edges and finally curl towards the inside. Corky spots may appear on the wood. Although the symptoms of Boron deficiency in fruits can be confused with those of Calcium deficiencies, the first situation presents signs in early stages of fruit development, and may show symptoms of “corking”, differences in size and irregular shape.
Regarding Zinc, it can be noted that as a micronutrient it has several functions within the metabolic processes of plants:
-Precursor of Auxins (through the synthesis of Tryptophan).
-Correct maturation of the vascular bundles (Xylem).
-Key to the synthesis of Amino Acids.
-Fundamental role in glycolysis.
In the case of a deficiency of this element, “small leaves” and “rosette leaves” can be detected, caused by short internodes. It is also possible to see interveinal chlorosis.
Correct management of environmental stress, as well as the nutritional status of crops, can improve their profitability and development by controlling relevant aspects that achieve the objective of each crop process.
