Plant Physiology - Musiyenko, M. M. 2001

Root Nutrition of Plants
The significance of other elements (silicon, aluminum, sodium, chlorine)

Over 60 elements have been found in the ash of various plants, including sodium, silicon, chlorine, and aluminum. Some scientists believe these are also essential for vital activity.

Thus, silicon fortifies Cell walls, rendering them durable and resistant to damage by insects and fungal diseases. A deficiency of this element during the formation stage of reproductive Organs reduces the yield of mature seeds and also stunts the growth of both cereals and dicotyledonous plants. Silicon is not included in any known nutrient solutions; nevertheless, it has proven to be necessary in small amounts for normal growth. This led M.O. Maksymov (1948) to classify silicon as a trace element, despite the fact that it accumulates in significant quantities in certain plants. It is known that SiO₂ has The ability to bind Water, so its compounds help increase the Hydration of plant Tissues.

Aluminum also belongs to the Macronutrients required by certain plants. It is believed to play a role in the METABOLISM of hydrophytes. The Effect of aluminum is described as catalytic.

In plants, sodium accumulates in significant quantities, although it does not play a crucial role in their vital activity, since it can be removed from the nutrient solution without harm. However, for halophytes—plants of saline soils—the presence of sodium promotes growth. Sugar beets also grow somewhat better in the presence of sodium chloride. This is associated with their descent from the wild ancestor Beta maritima, which grows on saline soils.

Chlorine ions are normally present in the soil in considerable amounts. They are not involved in Active Transport, but rather diffuse more or less freely between the xylem, phloem, and surrounding tissues.

There is evidence that chlorine is required to maintain steady-state O₂ evolution in the light during the photo-oxidation of water. The chloride ion can act as an allosteric effector, meaning it stimulates water-splitting by binding to the water-oxidizing complex of PS II at sites distinct from the reaction center itself. It may also participate in processes occurring at the active center as a Ligand forming bridges between manganese atoms, thereby stimulating O₂ evolution by facilitating charge transfer between them. The required concentration of chloride ions is in the range of 7-10^-3 mol per liter; therefore, this element, like iodine and bromine, should be classified among Trace Elements.

To elucidate The Role of chlorine in O₂ evolution, it is necessary to investigate in detail the ability of the oxygen-evolving complex to bind these ions, as well as to identify the functional groups responsible for stimulating O₂ release. Under chlorine deficiency, the water-oxidizing complex becomes more sensitive to hydroxylamine, Tris-buffer, and heating.

Doubling The rate of chloride ions in the soil causes their concentration in plant leaves to increase several fold.

Chlorides significantly reduce Transpiration while increasing the hydration of leaf tissues. They slow down the outflow of assimilates to storage organs, which negatively affects Photosynthesis.

Chlorides, much like sulfates, are the primary cause of soil salinization. An excess of chlorides negatively affects the crop quality of many plants. In potatoes, it reduces tuber starch content; in fiber crops, it diminishes fiber quality; and it increases acidity in grapes, fruits, and vegetables.

Thus, optimizing PLANT Nutrition AND increasing the efficiency of mineral nutrition are closely linked to maintaining an optimal ratio of macro- and microelements in the soil. The rational use of micronutrient fertilizers can be ensured through large-scale cartograms of mobile microelement content in Ukrainian soils, taking into account the specific traits of each crop and even variety. After all, modern high-yielding varieties possess an intensive metabolism that requires a corresponding supply of macro- and microelements.

The application of micronutrient fertilizers is technologically inexpensive. In addition to soil application, they should be widely used for pre-sowing seed Treatment, combining this operation with the application of insecto-fungicidal seed dressings.