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The importance of the zinc element

 

Zinc deficiency is one of the most common micronutrient deficiencies in most parts of the world, which reduces the performance and quality of nutrition in plants. Plants need a proper balance of all essential nutrients, including zinc, for normal growth and optimal performance.
Zinc is essential for the normal growth and reproduction of plants. If sufficient amount of zinc is not available, plants will suffer physiological stress. In soil, zinc forms a complex with organic acids, humic substances and other types of soluble organic carbon. Total Zn concentration is not used to assess soil Zn availability to plants because only a small amount of total Zn is exchangeable or soluble. The availability of zinc for plants depends on several factors such as the concentration of zinc in the solution, the absorbable ion and the amount of macro and micro elements.
The lack of zinc in crops is revealed when the plant suffers from a relatively severe deficiency of this element. Zinc deficiency may not appear hidden in several consecutive seasons and lead to a decrease in the quality yield of agricultural products. When there is zinc deficiency in plants, many important physiological functions of the plant are disrupted and plant growth is adversely affected. The increase in the use of phosphate fertilizers as well as low availability of zinc in high pH and calcareous and sodium soils aggravates zinc deficiency.

Factors affecting the availability of Zinc element

The term "availability" is commonly used to describe the ability of plants to absorb nutrients from the soil. The availability of zinc to plants can be affected by factors such as total soil zinc content, soil pH, organic matter, soil temperature and moisture, root distribution, and rhizosphere effects. Soils with low zinc concentration are often deficient in zinc for crop production, such as Sandy soils are often deficient in available zinc. For example, Zn deficiency in plants grown in acidic soils is generally associated with low total Zn concentrations. These cases of zinc deficiency are related to absolute zinc deficiency rather than zinc availability.
Total soil Zn concentration in calcareous and non-calcareous soils is often similar. However, zinc deficiency is often reported for calcareous soils. Calcareous soils with moderate to high organic matter content (more than 15 g organic carbon per kg soil) are zinc deficient due to high levels of HCO 3 - in the soil solution. In alkaline soils with low zinc reserves, increasing the application of zinc increases the concentration of zinc in plants and reduces deficiency symptoms.
Soil organic matter content is another factor that contributes to zinc deficiency in plants. Due to increased Zn uptake by ligands and organic components, Zn availability to plants is often low in soils with high organic matter content. A sufficient level of organic matter increases the solubility and diffusion rate of zinc in the soil.
Other factors that play a role in zinc deficiency are low soil moisture and low temperature. Soil moisture affects the supply of nutrients by disrupting diffusion to the root surface. Given that Zn release in soil is highly dependent on soil moisture, plant Zn levels may be compromised in semi-arid and arid regions where soils are typically water-deficient for long periods during the growing season. Based on this, in calcareous soils with zinc deficiency, the reduction of wheat yield is more intense in dry conditions than in wet conditions. Therefore, the decrease in zinc solubility and low absorption of zinc in soils with poor drainage is due to the simultaneous precipitation of zinc with soluble iron and aluminum in the soil. Early in the growing season, Zn deficiency occurs when the soil temperature is still relatively low and subsequently decreases as the temperature increases. Low soil temperature often increases the incidence and severity of zinc deficiency symptoms.
The interaction of zinc with other elements reduces the availability of zinc and affects its absorption, distribution and utilization in plants. These interactions are mainly due to the effect of other cations on the rate of uptake by plant roots rather than their effect on availability or forms. The competition and interaction of zinc with phosphorus and nitrogen are the most important and widespread interactions of zinc in soils with limited reserves of zinc and phosphorus or nitrogen. This element must be in balance with other required elements in the soil, so that high levels of phosphorus in the soil cause zinc deficiency, on the other hand, with a decrease in the amount of nitrogen due to weakness in the plant, zinc absorption also decreases. Copper also competes with zinc due to the same absorption mechanism. On the other hand, the addition of magnesium can also increase the absorption of zinc. High levels of arsenic in old gardens also prevent the absorption of zinc. It has been determined that this element must be in balance with manganese.

Zinc Performance in Plants

Zinc is essential for the normal and healthy growth and reproduction of plants. This element in small amounts is important for the normal, physiological and key function of the plant and cell membrane. Therefore, zinc plays an important role in growth regulation, enzyme activation, gene expression and regulation, plant hormone activity, protein synthesis, photosynthesis, carbohydrate metabolism, fertility, seed production, and defense against disease. Zinc deficiency disrupts these physiological functions and endangers plant health and productivity, leading to severe growth reduction and lower yield.
Zinc is the only metal required in plant enzymes (oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases). The requirement of zinc for the functioning of a wide range of enzymes shows that the metabolism of proteins, carbohydrates and auxin, as well as reproductive processes, are impaired under zinc deficiency.
Zinc plays a role in carbohydrate metabolism through its effects on photosynthesis and sugar conversion. Reduction of photosynthesis under Zn deficiency can be caused by the reduction of carbonic anhydrase (CA) activity, photochemical activity of chloroplasts and chlorophyll content, as well as changes in chloroplast structure. Low CA may inhibit photosynthetic electron transport and consequently limit chlorophyll content

Zinc deficiency in plants

Many plant species in most agricultural regions of the world are affected by zinc deficiency in a wide range of soil types. Crops such as (rice, wheat, barley, corn and sorghum) are all affected by zinc deficiency, and many fruits and vegetables are sensitive to zinc deficiency. The low concentration of available zinc in the soil may not only cause a decrease in yield, but also lead to a decrease in the quality and nutritional poverty of the crop.
Zinc deficiency can disrupt many biochemical pathways in crops, which may manifest as visible symptoms such as small and distorted leaves, interveinal chlorosis in young leaves, and shortened internodes.
Zinc element also has an effect on the speed of seed germination and stem maturity, and also interferes in the formation of chlorophyll and carbohydrates. In addition, the sufficient amount of zinc in the plant can increase the resistance of the plant against cold and low temperature. This element, while interfering in pollination and pollination, causes filling of the grain, increases the percentage of grain protein, reduces the accumulation of cadmium and removes poisoning.
Deficiency of this element appears mostly in sandy and organic soils, calcareous pH, especially in dry and semi-arid areas, high phosphorus and low soil temperature. The western areas of Khorasan, Mazandaran, East Azerbaijan, Gilan and some southern regions of the country lack zinc element.
Zinc is one of the less mobile elements, the first symptoms of its deficiency are found in young leaves, the leaves are gathered at the tip of the branch, and their size is reduced and they change shape. These symptoms are mostly seen in fruit trees, including apple trees. to be The terminal leaves show interveinal chlorosis spots in plants such as corn and the edges of the leaves are wavy. Among the characteristic symptoms are the lack of sweeping of the young leaves at the end of the branch, the stuntedness of the young branches, the small leaves and the weak growth of the buds. It is a side. Also, the growth of the branch is stopped and becomes weak and brittle, and it may cause the branches to dry up in the early season, flowering and fruit formation are also reduced, the fruits are small and their color is reduced, and the fruits lack proper aroma and flavor. to be

Symptoms of Zinc deficiency in plants

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• It usually occurs first in middle-aged leaves and then in old leaves.
• First, the color change from green to dull bronze in the middle part of the leaf (yellowing between the veins) in the form of burnt spots that gradually move to the side of the leaf.
• Then the symptoms are seen on more leaves and the leaves become greasy
• The burns become bigger and green and yellow spots surround them and the leaves become wrinkled
• Later, the young leaves also show symptoms and the leaves become smaller.
• Weak flowering and fruiting

 

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