PLANT ADAPTATION TO ANTHROPOGENIC FACTORS - 2017

3. ENVIRONMENTAL POLLUTION BY INDUSTRIAL CHEMICAL WASTE

3.5. Sources and Characteristics of Soil Pollution

All soils are characterized by fertility and The ability to provide plants with Water and mineral nutrients. Natural soil fertility depends on numerous factors, including climate, air, water, microorganisms, and topography, and in the conditions of Ukraine, it is subject to a complex of technogenic factors. Depending on The Nature and presence of the primary surface Structure of a territory, M. L. Reva and H. I. Kharkhota recommend distinguishing several forms of technogenic soils in the steppe zone.

They classified the first category of technogenic lands as territories where only the soil layer and partially the soil-forming parent rocks or the illuvial horizon have been disturbed. These soils represent a mixture of humified horizons with the upper layers of parent material and the illuvial horizon. Mixed soils are most characteristic of reclaimed areas following the extraction of non-metallic minerals, the creation of various water reservoirs, and urban or industrial construction. The second category comprises industrial lands created As a result of surface mining for various mineral resources.

The third category includes lands damaged as a result of soil erosion caused by anthropogenic factors. The extent of such lands has increased due to unsystematic plowing, improper and uncontrolled grazing, recreational degradation, and deforestation.

Sources of pollutants entering the soil include metallurgical, chemical, and machine-building enterprises, road transport, and agriculture. For instance, metallurgical plants emit large amounts of metal oxides (oxides of iron, manganese, copper, zinc, lead, etc.) into the atmosphere. Chemical industry enterprises are characterized by emissions of solid particulates in the form of salts (ammonium chloride, fluorine salts, etc.). Some of these form directly during technological processes, while others result from the interaction of gaseous emissions in the atmosphere. In agricultural production, soil pollution arises from the unreasonable application and careless storage of chemical fertilizers, herbicides, insecticides, fungicides, and other toxic substances. For example, studying the content of Fe, Cu, Mn, and Zn across genetic horizons in the Donbas conditions showed that their elevated levels are observed in the humus horizon. The content of total and mobile forms decreases markedly down the profiles. Observations indicate that the migration of heavy metals in the soil is also facilitated by soil contamination with acidic and alkaline gases from industrial emissions. Thus, soil acidification by sulfur and chlorine compounds contributes to a decrease in soil extract pH and an increase in the mobility and availability of heavy Metal Ions, particularly cadmium, lead, and chromium, to plants. A specific feature of heavy metal soil contamination is the extremely low rate of natural soil self-purification.

Acid gases and toxic dust are accumulated by the soil, interact with humus, promote its mineralization, reduce fertility, and disrupt the biological and biochemical STRUCTURE OF THE soil. Under conditions of pollution, changes occur in the physical and Chemical properties of the soil. The ultimate outcome of these processes is The Emergence of soil erosion and the death of natural vegetation, which together lead to The formation of a so-called "industrial desert," devoid of Prospects for phytocoenosis restoration and featuring a severely degraded phytoclimate. Under these conditions, natural vegetation within phytocoenoses is replaced by ruderal flora.

The vegetation consists of typical steppe representatives: perennial mesothermic xerophytic species, predominantly sod-forming grasses andforbs. Depending on the type of vegetation, three subzones are distinguished in the steppe territory from north to south. The northern strip, bordering the Forest-Steppe, is occupied by the forb-fescue-feather grass steppe subzone; further south lie the fescue-feather grass and wormwood-grass steppe subzones, respectively. Thus, Dnipropetrovsk Oblast belongs to the first subzone, a characteristic feature of which is a dense plant cover, with grasses (feather grasses, fescue) forming the core. A significant portion of the plants in the herb layer consists of legumes and forbs. The proportion of ephemerals in the herb layer is quite insignificant. The most widespread formations in this subzone are Representatives of the genera Stipa, Festuca, Poa, and Bromopsis.

Synecological studies of the herb layer in technogenic areas (Lykholat, 1999) make it possible to summarize the inventory stage and conduct a structural Analysis of the flora in the industrial zone of the region's cities. In total, 126 vascular plant species belonging to 97 genera and 28 families were identified in the studied territories. This list also includes lawn grasses that have naturalized and constitute a significant part of the grass cover. The family Asteraceae is the most widespread in the herb layer (27% of species, the majority of which are ruderals, i.e., forming herbaceous coenoses). Representatives of the Asteraceae family form the following series of decreasing Abundance in these coenoses: Ambrosia artemisiifolia, Erigeron canadensis, Cichorium intybus, Taraxacum officinale, Picris hieracioides, Crepis tectorum.

The second place is held by the family Poaceae (20.6%). Its various taxa participate in the formation of steppe and meadow-type communities. Among them, Elytrigia repens, Poa angustifolia, P. compressa, and Agropyron cristatum are the most widespread, frequently acting as coenosis edifiers. A significant portion of this family consists of ruderals — Setaria viridis, S. glauca, Echinochloa crus-galli, etc.

An interesting finding of ours in the surveyed territories is Cynodon dactylon (L.) Pers., the northern distribution limit of which runs halfway between the cities of Dnipro and Zaporizhzhia.

The third place is occupied by the Fabaceae family (7.9%), the fourth by Caryophyllaceae (6.3%), the fifth by Brassicaceae (5.5%), and the sixth by Chenopodiaceae (4%). The Fabaceae family includes species of the genera Coronilla, Desmodium, Lathyrus, Lotus, Medicago, Melilotus, Trifolium, Vicia; Caryophyllaceae includes Arenaria, Gypsophila, Saponaria, Silene, Stellaria; among Chenopodiaceae, Atriplex and Chenopodium are encountered more often than others, with Kochia being slightly less frequent. In seventh place is Polygonaceae (3.1%), combining only the genera Polygonum and Rumex. The eighth place is shared by the families Amaranthaceae, Apiaceae, Plantaginaceae, and Rosaceae (2.4% each). Following in terms of species number are Boraginaceae, Euphorbiaceae, and Scrophulariaceae (1.6% each). The remaining families (Balsaminaceae, Convolvulaceae, Cucurbitaceae, Cuscutaceae, Cyperaceae, Dipsacaceae, Hypericaceae, Lamiaceae, Onagraceae, Resedaceae, Rubiaceae, Santalaceae, Solanaceae, Violaceae) are represented by a single species. The type of industrial pollution of the territory did not affect the number of families.

It turned out that herbaceous polycarpics predominate in the territories of industrial enterprises, among which plants with a short life cycle play a significant role in the herb layer. Thus, spring annuals make up a third of the species. Among perennials, taprooted plants are the most common. The presence of the latter species is explained by their ability to extract moisture from deep horizons, even during summer droughts, which places them beyond competition with other plants.

The Features of the ROOT system largely reflect the species' relationship to the substrate and its hydrological properties. According to another trait in the ecomorphic spectrum of the flora, xeromesophytes predominate (40%). Mesophytes and xerophytes are less abundant in the herb layer, accounting for 22% and 7% of species, respectively. Heliophytes prevail among geomorphs (67%). Almost all plants registered by us are autotrophic (99%), while the number of parasites is negligible (1%). The flora of technogenic territories includes both natives (76%) and adventive plants (24%). Most of the latter are found in areas prepared for planting ornamental species and along railroad tracks.

Coenomorphic analysis showed that ruderals dominate in the surveyed areas. The proportion of other groups (stepants, protants, paludants, sylvants) is significantly smaller. In the trophomorph spectrum, mesotrophs dominate, with megatrophs being considerably fewer. Despite significant pressure from technogenic factors, dicotyledonous species (almost half), which are insect-pollinated (entomophiles), predominate in the studied vegetation: among them, proterandrous entomophiles are the most widespread (17%), anemophiles account for 35%, and autogamous species make up 2%. Regarding the method of diaspora dispersal, balistochores predominate in the flora of technogenic territories (65%), anemochores are somewhat fewer (16%), while barochores (8%) and automechanochores (7%) are relatively scarce. Species with Other types of dissemination are even less widespread.

Modern observations of the floristic composition have revealed changes compared to the indigenous vegetation of the late last century. Feather grass has completely disappeared. Among grasses, Poa angustifolia dominates in the first half of summer. In the second half of summer, communities dominated by Polygonum aviculare, P. convolvulus, Artemisia absinthium, and A. vulgaris are formed, characterized by intensive GROWTH AND DEVELOPMENT. Remnants of fescue (Festuca valesiaca) are also encountered in the herb layer. It is this species, along with feather grass, that serves as a dominant of the natural steppe vegetation. Most likely, the transformation of fescue communities at industrial sites will continue toward the intensification and predominance of weed species. In the future, a further reduction in the abundance of other remaining typical steppe plants is also possible. Among the features of phytocoenoses in technogenic territories, one should note the co-dominant role of steppe dense-sod grasses and weed rhizomatous grasses, some of which, along with the majority of forbs, are obligate under these conditions. Thus, project cover and productivity of herb layers are largely determined by Elytrigia repens, which is more resistant to anthropogenic load than other species.

Spontaneous vegetation in industrial enterprise territories exhibits all forms of anthropogenic dynamics highlighted in the works of Lyholat (1999) and Hryhoryuk et al. (2014). A feature of restorative successions is the gradual replacement of ruderal vegetation by natural vegetation. During this process, certain species and their biological groups are replaced by others, for example, annual species give way to perennials. Taking into account the fact that the operation of enterprises does not cease, plant communities can remain at one of the development stages for a long time. This process is accompanied by the appearance and expansion of new communities alongside the reduction or even disappearance of others. The appearance of species such as Ambrosia artemisiifolia on industrial sites, combined with local flora species, promotes the formation of aggressive associations, an example of which is Ambrosietum artemisiifolia + Elytrigiosum repens, which dominate the vegetation even in dry years for the steppe Dnieper region (1992, 1998, 2016). Particularly significant changes occurred in years with varying levels of atmospheric precipitation. Confirmation is provided by associations identified via dominant vegetation Classification, taking into account herb sub-layers. Thus, in dry years, the industrial sites of the studied enterprises were dominated by Ambrosietum artemisiifolia + Elytrigiosum repens, Setarietum viridis + Convolvulosum arvensis, Elytrigietum repens - Taraxacosum officinale, and Artemisietum absinthium - Poaosum angustifolia associations, in which grasses act as edifiers (Setaria viridis) or sub-edifiers (Poa angustifolia, Elytrigia repens). Other associations (Erigeronetum canadensis + Lactucosum tatarica; Sonchusetum arvensis — Elytrigiosum repens; Chenopodietum album — Setarioso viridis — Polygonosum aviculare) persisted in dry years, but their vitality was lower compared to previous ones. In years with sufficient moisture (1990, 2015), the dominant associations were Ambrosietum artemisiifolia + Elytrigiosum repens, Sonchusetum arvensis — Elytrigiosum repens, Elytrigietum repens — Taraxacosum officinale, and Artemisietum absinthium — Poaosum angustifolia, one of the components of which were sod-forming grasses. Under excessive moisture (1999), associations including sod-forming grasses also retained their prevailing position.

Typical environmental pollutants are heavy metals, the content of which varies significantly in time and space. The biological cycle of heavy metals within the same soil-climatic zone (steppe) in plants changes even under identical environmental conditions. Investigations into the IMPACT OF ENVIRONMENTAL heavy metal pollution on plant development by many researchers have established an ambiguous response of various plant species to excess heavy metal content. For instance, the yield of wheat, cotton, potatoes, and beets in contaminated soil decreased, whereas the biomass of alfalfa increased. Heavy metals cause the destruction of the pigment complex and a significant reduction in leaf water content. Vanadium in coniferous and deciduous species causes oxidative destruction of Cell membranes, increased accumulation of harmful gases, water loss, changes in pigment content, and the suppression of Photosynthesis, leading to enhanced necrosis and reduced plant resistance. The main reason for this phenomenon is that plants poorly absorb many heavy metals (such as lead) even when their content in the soil is high, because they exist in the form of poorly soluble compounds. Therefore, the lead concentration in plants usually does not exceed 50 mg/kg, and even Indian mustard, which is genetically predisposed to heavy metal uptake, accumulates lead at a concentration of only 200 mg/kg, despite growing on soil heavily contaminated with this element. Moreover, the uptake of heavy metals by plants is stimulated by certain substances (such as ethylenediaminetetraacetic acid) that form stable yet soluble complex compounds with metals in the soil solution. Thus, as soon as such a substance was introduced into soil containing lead at a concentration of 1,200 mg/kg, the concentration of the heavy metal in the shoots of Indian mustard increased to 1,600 mg/kg.

Furthermore, an increase in atomic mass leads to increased toxicity, although there are certain exceptions, such as beryllium and copper. Copper is much more toxic to many Cells than metals such as barium, strontium, and others, despite their smaller atomic mass. The strength of iron's effect differs in its divalent and trivalent states, regardless of the element's identical atomic mass in both cases. Such deviations argue against the overriding significance of atomic mass for metal toxicity. It is believed that The connection between the action of metals and their atomic mass lies in the fact that as the latter increases within this group of elements, their content in organisms decreases while their toxicity increases. Indeed, the toxicity of heavy metals with a high atomic mass, such as lead, mercury, gold, and silver, is high, and their normal content in organisms is either denied or very low. At the same time, the physiological activity of a metal is determined by the ease with which it yields its electrons and the degree of affinity of the latter for the element's charge. A stronger bond results in lower electron activity.

Along with this, the oxidation state of the anion's main element can affect salt toxicity. Thus, the toxicity of halogen-containing anions increases with an increase in the halogen's oxidation state, whereas the toxicity of anions comprising elements of groups V-VI of the periodic table (nitrogen, sulfur) decreases, conversely, with an increase in valence. For halogen compounds of metals, the degree of dissociation and, primarily, Hydrolysis resulting in the formation of acids is of great importance. Such hydrolysis is known for the halides of many metals: tin, titanium, tantalum, niobium, germanium, and others. The biological and Toxic Effect of salts can thus vary due to the Specificity of anion action, for example, halogens, as well as through hydrolysis accompanied by the formation of free acids or alkalis. The leading role in these processes belongs to metal cations.

The toxicity of heavy metals (copper, lead, mercury) depending on their concentration is well known. Regardless of dose, metals promoted the induction of peroxidase, with enzyme activity in roots increasing on average by 1.5–2.5 times; in leaves, moderate doses of copper suppressed, while high doses of lead enhanced peroxidase activity. Lead caused a decrease in the fresh and dry biomass of whole plant Organs. The concentration of lead in roots is greater than its content in aboveground organs. Under excess lead in the environment, roots accumulated over 99% of the lead, protecting the aerial part from its action.

The toxicity of heavy metals is related, in particular, to the fact that they block the active centers of Enzymes and exclude them from Metabolic Regulation. The general toxic effect of metals can be associated with the nonspecific inhibition of a series of enzymes due to Protein Denaturation in general. However, A number of metals are at the same time characterized by the specific inhibition of certain enzymes already at very low concentrations. Therefore, the Specific features of poisoning by individual metals become apparent mainly upon prolonged contact with them.

A number of metals, particularly copper and zinc to a greater extent than barium, reduce the photosynthetic and respiratory Functions of plants.

Studies of the content of strontium, cobalt, and chromium in various organs of plants grown in media with different concentrations of salts of these metals showed that an increase in heavy metal concentration leads to an increase in their content in plant Tissues. This relationship is non-linear: at high concentrations, metal accumulation is intensified, with chromium predominantly accumulating in the roots, and strontium in the aboveground part.

Protein compounds play a crucial role in the detoxification of heavy metal ions within plant organisms. Analysis of the obtained data indicates that under METABOLISM/18.html">The Influence of toxic concentrations of hexavalent chromium, the above-ground parts of plants may exhibit either an increase or a decrease in total protein content. In the roots, however, the protein content increases across all studied plants, which corresponds to the primary site of metal localization. The accumulation of total protein under conditions of hexavalent chromium intoxication serves a protective function.

Plants growing in zones affected by industrial environmental emissions exhibit elevated metal concentrations in the tissues of various organs, along with diverse physiological alterations that sometimes serve a protective role.

The most widespread salts in saline soils of Ukraine are those of hydrochloric, sulfuric, and carbonic acids—chlorides, sulfates, and carbonates of calcium, magnesium, and sodium—which, at specific concentrations, cause growth inhibition, developmental stunting, or even plant death. A significant proportion of soil pollution near chemical industry enterprises is attributed to sulfur, chlorine, and fluorine compounds. The effects of these compounds, with the exception of fluorine, are practically identical to The impact of soil salinization by the corresponding anions. For instance, sulfur is an essential nutrient for plants. It is a constituent of many biologically active compounds: Methionine, Cysteine, glutamine, coenzyme A, thiamine, and others. Plants absorb sulfur as sulfate through their roots and as sulfur dioxide through their leaves. Sulfur accumulates in the plant in the form of sulfate because, due to its higher mobility within the plant, it is a more efficient nutrient than sulfur dioxide. The accumulation of sulfates can be viewed as a protective response that enables the plant, under adverse environmental conditions, to maintain concentrations of intermediate oxidized sulfur compounds that inhibit Cell Division processes. Experimental studies have established that under conditions of sulfate salinization, The oxidation of SH-Amino Acids to inorganic sulfate increases sharply in plants. Plant resistance to a range of environmental stressors, including sulfur compounds, is closely linked to cellular sulfur metabolism and, above all, to the reductive assimilation of sulfate, which culminates in the synthesis of two Proteinogenic Amino Acids: Methionine and cysteine. When sulfate is present in excess in the medium, the concentration of numerous low-molecular-weight S-compounds, including amino acids, increases in plant cells. Among various by-products of sulfur metabolism, some may prove toxic to plants—specifically, sulfoxides. Under these conditions, the activation of oxidative degradation leading to the de novo formation of sulfate is the primary mechanism for controlling intracellular S-metabolite concentrations and detoxifying certain compounds. The content of organic sulfur compounds in the leaves of various plants is a relatively constant value. The dry residue of conifer needles typically contains about 0.1% sulfur, while that of deciduous plants contains 0.15–0.3%. While organic sulfur levels remain relatively stable, The amount of sulfates in the leaves of different plants can vary across a wide range. Woody plants demonstrate a selective capacity to accumulate sulfur compounds. Calculated as SO₂, the highest accumulation capacity (up to 33 g/kg of absolute dry matter) is characteristic of tamarisk (*Tamarix ramosissima*), Canadian poplar, green ash, Bolle's poplar, littleleaf linden, black locust, and English oak. The lowest capacity (about 4 g/kg) is typical for the leaves of feathered elm, late bird cherry, white mulberry, and silver maple. Under conditions of fumigation by sulfur compounds, plants growing on sulfate-fertilized soils may experience an excess of the latter, which inhibits Plant Growth and increases their susceptibility to damage.

Unlike sulfur and chlorine, modern understanding holds that fluorides are not essential compounds for plant development. However, as revealed in hydroponic culture studies, fluorides can induce a stimulatory effect. As with the other two elements, fluorides can be absorbed from both soil and air, with the highest concentrations observed in the leaves. In certain plants, such as *Dichapetalum* spp. in South Africa and *Acacia georginae* in Australia, the synthesis of fluoroacetic acid (FCH₂COOH) occurs, which can lead to livestock poisoning. Relatively non-toxic fluoroacetic acid is converted by animal metabolic enzymes into fluorocitrate, which inhibits citric acid oxidation reactions in the Krebs cycle.

Since fluorides do not participate in the metabolism of most plants, their detoxification within The plant cell does not occur. Another reason for the high toxicity of fluorides may be their extensive accumulation in Chloroplasts. The Amplification of fluoride toxicity depends on secondary translocation within the leaf.

It is known that mobile water-soluble forms (alkali metal fluorides) pose a particular hazard to plants because they are passively and easily transferred from the soil into plant tissues. Plant contamination by fluorides leads to:

1) disruption of respiratory activity;

2) decreased oxygen uptake;

3) reduction in chlorophyll content;

4) decreased assimilation of nutrients (including starch);

5) inhibition of certain enzyme functions (pyrophosphatase);

6) inhibition of certain catalyst functions;

7) damage to cell membranes;

8) alterations in cellular organelle metabolism;

9) Degradation of Nucleic acids (DNA and RNA);

10) synthesis of toxic fluoroorganic compounds (in South African plants, soybeans).

The aforementioned processes result in overall plant growth retardation and reduced crop yields. However, the greatest danger of fluorine contamination in plants is that they become a pathway for fluorides to enter the bodies of animals and humans.

The Effect of fluorides on plants is associated with the Direct impact of gaseous fluorine compounds on the above-ground plant parts. Indirect effects caused by the accumulation of fluorides in soils have been noted only near major emission sources. Only a small fraction of soil fluoride is available to plants. This explains the low natural concentrations of fluorides in plants, even though their content in the Earth's crust is 0.07%, meaning fluorine is as abundant as phosphorus and sulfur. Similar to zinc and lead, high quantities of fluorides in soils can exert long-term effects on vegetation that surpass the Damage caused by atmospheric fluoride. Lysimetry studies have demonstrated that, unlike sulfur and especially chlorides, fluorides are leached from soils rather poorly.

Similarly to sulfur and fluorides, chlorine in the form of chlorides can be absorbed by plant roots and leaves. Chlorides—salts of Hydrochloric acid—frequently accumulate in the soils of southern latitudes. Alongside sulfates, they are among the most prevalent salts constituting saline soils and salt lakes. They are characterized by high solubility (342–745 g/dm³) and toxicity. Chlorides are most commonly found in the coastal Regions of the Sivash, Black Sea, and Sea of Azov. In soil, chlorides exist almost exclusively in a dissolved state and are therefore easily leached. Lysimetric studies have demonstrated the stability of chloride content in European soils. Chloride influx and demand are balanced through uptake by plants from soil and air, as well as through leaching, replacement via Fertilization, and precipitation. Indirect plant damage via soil during chlorine accumulation from polluted air is unlikely. Changes in soil structure and pH shifts—for example, due to the formation of readily soluble calcium compounds—likely occur only in the immediate vicinity of major emission sources.

According to the general Conclusions of researchers, chloride uptake is directly proportional to their concentration in the nutrient substrate. The preferential uptake of chloride ions compared to other anions can be explained by THE POSITION OF Cl^- in the lyotropic series after NO₃^- and before SO₄^2- and PO₄^3-. Chlorine participates in osmotic processes, neutralizes membrane charges, and takes part in the oxygen-evolving reaction of photosynthesis and in cell division. This element is widely distributed in nature and readily available to plants. The essentiality of chlorine for plants was proven relatively recently, only after all Reagents and air were purified of chlorine traces during water-culture experiments. Ordinarily, the trace amounts of chlorine present as impurities in reagents and air were sufficient for normal plant growth.

Chloride ions, due to their small volume and high absorption rate, inhibit the uptake of other anions. In combination with chloride ions, cations are absorbed more effectively than, for example, when bound to sulfate ions. The balance between inorganic cations and anions in the plant shifts markedly toward the latter under the influence of chlorides.

As is well-known, chlorides accelerate the growth of various plants, particularly members of the Chenopodiaceae family. However, this effect, much like other chloride-induced effects, is entirely non-specific. The results of certain studies suggest that chlorides qualify as plant nutrients according to the definition proposed by Kick. Despite their participation in various vital metabolic reactions, chloride requirements fall within the range of micronutrient needs and are fully met by the natural chloride content in the air and precipitation. Unlike sulfur deficiency, instances of chloride deficiency have never been reported. Of practical significance is only the excess of chlorides, which manifests as the aforementioned chlorosis, necrosis, growth inhibition, as well as succulence and xeromorphism. In this case, the route of chloride entry—whether via roots from the nutrient substrate or via leaves from the air—appears to be immaterial.

The concentration of chlorides in plants is determined primarily by the influx of chloride ions. On average, the presence of chlorides accounts for about 20% of the total osmotic pressure in cultivated, weed, and other wild-growing plants, with natural variations ranging from 0.5% to 60% depending on the habitat. In halophytes, this value averages 65% and can reach up to 95% in extreme cases. Halophytic plants growing on saline soils accumulate particularly large amounts of chlorides.

The functions of chlorine in plants still require further study and clarification. Chloride is a highly mobile ion. It is known to be a key player in osmotic processes within vacuoles. Chlorine participates in the oxygen-evolving reaction of photosynthesis and in neutralizing membrane charges. In onions, the chloride ion is involved in regulating the opening and closing of leaf Stomata. In these reactions, chloride acts as a counter-ion to potassium. The chloride ion is essential for The Cell division of leaves and stems.

Chlorine deficiency is virtually non-existent in nature because Cl^- is present in the atmosphere, rainfall, and irrigation water in more than sufficient quantities. Plants readily absorb chlorides and can accumulate them in excess. Among crops, species such as spinach, sugar beet, buckwheat, coconut palm, and others grow better in the presence of chloride than in its absence. An excess of chlorides rapidly inhibits potatoes, tomatoes, cucumbers, beans, grapes, certain legumes, tobacco, and fruit trees. Under chloride toxicity, plant growth slows down, general chlorosis is observed, and leaf tips develop a bronze coloration and curl downward.