Although it is known that there is sufficient silicon in the soil of our country, the deficiency of silicon causes serious yield and quality loss due to the fact that the available silicon is not in an easily obtainable form.
Ege University Faculty of Agriculture Department of Plant Protection Lecturer Prof. Dr. We had an interview with Necip Tosun on the role of silicon in plants.
Dear Teacher, you have been working on silicon for years. How much do you think the importance of silicon is known in our country?
Although the importance of silicon in plant development was understood long ago in the world, this situation has only just begun to be understood in our country.
Plants need organic and inorganic elements for their development. In this context, oxygen, hydrogen, carbon, non-mineral elements are essential. Apart from these, macros such as nitrogen (N), potassium (K), calcium (Ca), phosphorus (P), magnesium (Mg), sulfur (S) and boron (B), chlorine (Cl), copper (Cu), iron Micro elements such as (Fe), molybdenum (Mo), Nickel (Ni), Zinc (Zn) are necessary for plant growth. Each element is unique and is important for completing the plant's life cycle.
Apart from all these elements, the role of semi-metal SILICUM (Si), which is not essential for plant development but plays a critical role in plant growth and development, plant physiology, structural and biochemical events, has been ignored for years. Silicon, which is Silicon in English, is a useful element for both humans, animals and plants.
What Role Does Silicon Play in Plant Development?
Silicon in the available form has a catalyst role during the biochemical process of nutrition in plants.
It is known that silicon plays a role in strengthening the cell wall of plants and therefore increases the resistance of the plant against diseases and pests; It is estimated that it contributes to increased tolerance to drought and heavy metals and to crop quality and yield.
Studies have shown that when we look at the biochemical order of nutrition of plants, it is understood that Silicon is in the second place.
As the basis of plant growth ;
1. Boron activates silicon and initiates biochemical processes.
2. Silicon carries all other nutrients, starting with calcium.
3. Calcium binds to nitrogen.
4. It performs nitrogen , amino acids, DNA and cell division. Amino acids, especially chlorophyll and tag trace elements such as magnesium form proteins.
5. Magnesium transfers energy to phosphorus.
6. Phosphorus transports carbon to form sugar.
7. Carbon sends the formed sugars to potassium to transport.
8. Potassium carries them.
Although our soils are known to be rich in silicon, why can't plants benefit from enough silicon?
Silicon is approximately 28% in the Earth's crust, and approximately 0.1-10% according to the dry weight principle in terrestrial plants. However, it is necessary to know which forms of silicon are biologically absorbed by the plant. Polysilicic acid, which is a polymerization of silicic acid, is not in biodegradable form. Monosilicic acid Si(OH) 4 or orthosilicic acid (OSA) forms of silicic acid are the only forms that can be taken by the plant.
When did the studies on plant growth related to silicon start and what results were obtained?
Studies with silicon started with sugar cane in 1840. With the fertilizers developed with silicon, which can form strong bonds with some minerals such as Mo, Zn, Cu, an increase in plant yield was obtained in sugarcane, paddy, tomato, wheat and citrus fruits. With the studies carried out since this date, promising results have been obtained on " metal toxicity, drought, salt stress, resistance to plant diseases" with available silicon (SiO 2 ).
Silicon in the form of stabilized silicic acid is licensed as a plant protection product in our country. Silicic acid, licensed as a plant activator, has been used in 3 different spraying programs for the control of bacterial spot and late blight disease in industrial tomatoes. Silicic acid significantly increased the effectiveness of spraying in all programs compared to farmer conditions.
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How does the working system of silicon in the plant take place?
Silicon plays a role in the plant at the " physical, biochemical and molecular level" .
The diagram in the figure perfectly summarizes the mechanism of silicon in the plant.
Creating a Physical Barrier;
It has been revealed that as a result of the applications of silicon, it is taken directly from the root system or leaves of the plant and suppresses plant diseases and pests by acting as a barrier against biotic stress conditions.
This happens when the plant strengthens mechanically and creates a physical barrier.
Pathogen penetration is prevented by physical structures such as the formation of a thick silica layer under the cuticle, the formation of a double-layered cuticle layer, the thickening of the silicon cellulose membrane, the formation of papillae, the organic compounds in the epidermal cell wall and the block formation.
At the same time, most silicon improves the regeneration and mechanical properties of the plant by providing cross-linking with the hemicellulose in the cell walls. As a result of the studies, pathogen penetration was prevented as a result of the barrier formed against Pyricularia oryzae in rice and Bipolaris sorokiana in wheat, and a decrease in fungal colonization was observed in green parts. Silicon root applications have been shown to be more effective in some plants than leaves.
Biochemical and Molecular Mechanism
Silicon is effective against biotic stress actors, plant diseases and pests by activating defense-related enzymes-chitinase, peroxidase, polyphenoloxidases, β-1,3-glucanase, phenylalanine ammonia-lyase, uperoxide dismutase, ascorbate peroxidase, glutathione reductase, catalase, lipoxygenase and glucanase. is happening.
In this direction, the silicon-based defense mechanism; It is based on the rapid production of defense compounds by primary and secondary metabolite transport pathways.
In studies on the biochemical mechanism of silicon in plants, it activates chitinase and peroxidase in wheat , glucantransase , peroxidase, polyphenol oxidase, Phenylalanine ammonia-lyase, superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, lipoxygenase, polyoxidase , polyoxidase in plant diseases by activating plant diseases. Successful results were obtained with counter silicon applications.
If we summarize
- Plants vary greatly in their ability to accumulate silicon (0.1%-10%)
- Si accumulators are essential for monocot plants (paddy, grass, cereals, maize, sugar beet, orchids etc.)
- Useful for dicot plants that moderately or do not accumulate silicon (strawberry, melon, cucumber, tomato, rose, bean, etc.)
- Silicon has a positive effect on plant health by reducing biotic and abiotic stresses.
- Silicic acid increases calcium uptake, followed by organic nitrogen (from L-Amino acids), magnesium, phosphorus, and potassium. These elements must be available to plants in a bioavailable form.
- Silicon increases the plant immune system against insect attacks and diseases.
- Silicon-modulated phytohormone signaling and enzyme production were analyzed.
- Silicon plays an important role in protecting plants from harmful insects and pathogens.
Do you think the use of silicon in affordable form will increase in our country from now on and to what extent does it contribute to the producers?
I think that the plants grown in the fertile soils of our country still do not reach their yield potential. Silicon deficiency is one of the important factors affecting productivity. I think that the use of silicon in obtainable form will continue to increase in our country. Silicon, which makes a significant contribution to productivity, will reveal the yield potential of plants and producers will gain more profit.
Sources
Mustafa DERE