Pollution's Impact On Seed Germination: A Complex Relationship

Air pollution has a detrimental effect on seed germination and seedling growth. The impact of air pollution on seed germination varies depending on the plant species, the type of air pollution, and the distance from the pollution source.

Some studies have found that air pollution delays seed germination and reduces the germination rate and seedling growth of various plant species, including pine, oak, Indian mustard, and Bengal gram. Heavy metals, such as lead, nickel, and cadmium, are important environmental pollutants that can affect seed germination and seedling development. These heavy metals can cause physiological changes in plants, such as decreased enzyme activity, altered sugar and protein metabolism, and reduced root and shoot elongation.

In addition, air pollution can also affect the biochemical composition of plants, including changes in protein, carbohydrate, and chlorophyll content. The impact of air pollution on seed germination and seedling growth is complex and depends on various factors.

The effect of heavy metals on seed germination

Heavy metals, such as lead, nickel, cadmium, copper, cobalt, chromium, and mercury, are important environmental pollutants that can cause toxic effects on plants, reducing productivity and posing threats to agro-ecosystems. They act as stressors, affecting plant physiology and germination.

Nickel (Ni) is toxic to most plant species, retarding seed germination and growth by affecting amylase, protease, and ribonuclease enzyme activity. It also affects the digestion and mobilization of food reserves, such as proteins and carbohydrates, in germinating seeds.

Lead (Pb) strongly affects seed morphology and physiology, inhibiting germination, root elongation, seedling development, and plant growth. It causes alterations in chloroplasts, obstructs the electron transport chain, inhibits Calvin cycle enzymes, and impairs the uptake of essential elements like magnesium and iron.

Copper (Cu) is toxic to sunflower seedlings, inducing oxidative stress and decreasing catalase (CAT) activity. It reduces the germination rate and inhibits the breakdown of starch and sucrose in reserve tissue by inhibiting the activities of alpha-amylase and invertase isoenzymes.

Cadmium (Cd) delays germination, induces membrane damage, and impairs food reserve mobilization by increasing the cotyledon/embryo ratios of total soluble sugars, glucose, fructose, and amino acids. It also causes mineral leakage, leading to nutrient loss, and accumulates in seeds, resulting in over-accumulation of lipid peroxidation products.

Cobalt (Co) has been reported to induce DNA methylation in Vicia faba seeds.

The effects of heavy metals on seed germination vary depending on the plant species and the specific metal. Some plants have evolved strategies to combat heavy metal stress, such as regulating antioxidant enzymes or altering gene expression.

Salsola vermiculata, a shrub with a wide distribution, was studied for its germination and seedling development under the influence of heavy metals. The results showed that Cu and Zn significantly reduced final germination at high concentrations (4000 μM), while Zn induced radicle growth at lower concentrations. S. vermiculata acted as a good accumulator and tolerant of Mn, Ni, and Cu, with no damage observed.

Overall, heavy metals can have detrimental effects on seed germination and seedling development, and some plant species have evolved strategies to combat this stress.

The effect of air pollution on seed germination

Air pollution can have a detrimental effect on seed germination and seedling growth. The impact of air pollution on seed germination varies depending on the plant species, the type and level of pollution, and the distance from the pollution source.

Air pollution, particularly from industrial activities, can have a significant impact on the germination and growth of wild plant seeds. Studies have shown that heavy metals, such as nickel, copper, cadmium, and lead, which are common pollutants in industrial emissions, can affect seed germination and seedling development.

For example, a study by Lyanguzova (2011) examined the effect of industrial air pollution on the germination and seedling growth of several wild plant species, including bilberry, cowberry, and Scots pine. The results showed that the germination rate and seedling growth were significantly reduced in seeds collected from areas with high levels of nickel and copper pollution.

Another study by Babapour Aliyar et al. (2020) investigated the impact of traffic-induced air pollution on the seed germination of Arizona Cypress and Black Pine. They found that the 1000-seed weight and germination rate of both species decreased significantly with increasing traffic congestion. The study also showed that the contamination rate at the intersection center and up to 40 meters was high enough to affect the seed production process.

In addition to heavy metals, air pollution can also contain particulate matter and other pollutants that can affect seed germination. A study by Maity et al. (2019) examined the effect of water quality on the germination of Cicer arietinum and Brassica juncea seeds. They found that the germination rate and seedling growth were negatively impacted by water contaminated with industrial effluents and domestic waste.

Mitigating the Effects of Air Pollution on Seed Germination

To mitigate the effects of air pollution on seed germination, it is essential to reduce pollution sources and improve air quality. This can be achieved through the implementation of pollution control measures, such as the use of emission control technologies and the development of sustainable practices. Additionally, the selection of plant species that are more tolerant to air pollution can also help reduce the impact on seed germination.

Air pollution can have a significant impact on seed germination and seedling growth, depending on the plant species and the level and type of pollution. Heavy metals, particulate matter, and other pollutants released into the air can affect the germination process and subsequent seedling development. To mitigate the effects of air pollution on seed germination, it is crucial to address pollution sources and improve air quality through sustainable practices and the selection of tolerant plant species.

The effect of water quality on seed germination

Water quality has a significant impact on seed germination and seedling growth. The organic and inorganic contaminants in water can degrade its quality, directly affecting seed germination and plant growth. The effects of water quality vary from species to species.

A study by Pandey et al. (2008) examined the impact of distillery effluent on seed germination and early growth in maize and rice. The effluent had high acidity (pH 5.5), BOD, alkalinity, and TS, which inhibited germination and early seedling growth in maize and rice. The study found a reduction in the germination percentage of seeds, length of the radical and plumule, and fresh and dry weight of seedlings.

Another study by Saravanamoorthy and Ranjitha (2007) investigated the effect of textile wastewater on the morpho-physiology and yield of two peanut varieties. They found that wastewater containing high concentrations of cations and anions induced morphological and physiological disorders, such as reduced growth and inhibition of germination and root growth.

The impact of water quality on seed germination and seedling growth was also studied by Maity, Chatterjee, and Banerjee. They treated seeds of Indian mustard (*Brassica juncea*) and Bengal gram (*Cicer arietinum*) with water from four different water bodies, including one control. The study found that the seed germination and growth of seedlings were highly sensitive to water quality, with polluted water exerting a stress level on their growth. The results showed that different water qualities significantly affected the seed germination and seedling growth of the two plant species assessed.

Water quality can also affect the biochemical parameters of plants. For example, the study by Maity, Chatterjee, and Banerjee found that the total carbohydrate, reducing sugar, total non-reducing sugar, protein content, and total DNA of the two plant species were influenced by the quality of the water used for treatment.

In summary, water quality plays a crucial role in seed germination and seedling growth, and its effects can vary depending on the plant species. Polluted water can exert stress on plants, affecting their growth and biochemical parameters.

The effect of different types of water on seed germination

Water is a critical factor in seed germination. It is required for seed imbibition, enzymatic activation, degradation, translocation, and the utilization of reserve storage material. The germination capacity increased significantly as the water volume increased until it reached the optimal level, and then it decreased slightly as the water level increased.

Water availability plays a significant role in germination, which can be initiated at 0.65 mL, corresponding to 500% of the thousand-kernel weight (TKW). The method of TKW is a more accurate aspect of water application because of the consideration of the seed weight and size. The optimal water range for the accumulation of dry weight, 3.85–5.9 mL (2900–4400% of TKW), was greater than that required for seedling growth, 1.45–3.05 mL (1100–2300% of TKW).

The optimal temperature for oilseed rape germination and seedling growth was 20 °C within a more comprehensive range from 10 °C to 25 °C. Between the optimal and suboptimal ranges, the germination potential decreased.

Heavy metals, including lead, nickel, cadmium, copper, cobalt, chromium, and mercury, are important environmental pollutants that cause toxic effects on plants and, thus, lessen productivity and pose dangerous threats to agro-ecosystems. They act as stress to plants and affect the plant physiology.

The effect of water on seed germination varies with the type of seed. For example, the germination of the oilseed rape was conducted at temperatures ranging from 5 °C to 35 °C across the germination time course, with 5 degrees Celsius intervals. Germination was detected approximately three days after the experiment began, and successful germination occurred on average after four days at temperatures of 15 °C, 20 °C, 25 °C, and 30 °C. The oilseed rapeseed appeared to germinate within a range of temperatures, with 20 °C being the most suitable and optimal temperature for obtaining a high germination percentage.

The effect of water on seed germination also depends on the type of water stress. For example, drought and salinity are environmental factors that impose osmotic stress on seeds, preventing the natural flow of water into the seed from its surrounding environment. Under osmotically stressful conditions, seeds may be unable to achieve the critical moisture levels required for imbibition, and therefore unable to prepare for germination.

The effect of water on seed germination also depends on the type of seed and the type of water stress. For example, the germination of the annual plant Xanthium sibiricum in the water-level-fluctuating-zone of Three Gorges Reservoir was studied. The seeds were collected from seven elevations of the WLFZ of Three Gorges Reservoir (TGR) and exposed at these elevations to submergence. The results showed that the maturity degree of X. sibiricum fruits from different elevations has no influence on the seed production by the plants that are produced from the fruits. Under the present water-level regulation mode, X. sibiricum growing above 155 m are able to generate mature seeds and thus provide seed sources for population maintenance, although the plants growing at an elevation below 165 m failed to produce fruits in 2010 due to unusual flooding.

The effect of industrial effluents on seed germination

Industrial effluents can have a detrimental effect on seed germination and early plant growth. A study by Crowe et al. found that industrial effluents from the Athabasca Oil Sands Deposit in Canada negatively impacted the germination of several plant species, including tomato, clover, wheat, rye, pea, reed canary grass, and loblolly pine. The study also observed reduced fresh weight in the seedlings of some plants.

Another study by Nawaz et al. investigated the effects of industrial effluents on the germination and early growth of Cicer arientum. The researchers collected water samples from three different industries in Rawalpindi, Pakistan: Koh-e-Noor Textile Mill (KNM), Marble Industry (MI), and Attock Refinery Limited (ARL). Two varieties of Cicer arientum, P-91 and P-2000, were grown in different dilutions of the effluents. The results showed that the Koh-e-Noor mill effluent had the most significant impact on plant growth, while the marble and ARL effluents had less of an effect.

The impact of industrial effluents on seed germination can also vary depending on the plant species. A study by Naveed et al. examined the effects of pharmaceutical and domestic industrial wastewater on seed germination and seedling growth. They found that Nigella sativa was highly affected by both types of wastewater, followed by Coriandrum sativum. In contrast, Trigonella foenum-graecum and Hordeum vulgare showed more tolerance, with acceptable performance even under toxic water conditions.

Heavy metals present in industrial effluents can also have toxic effects on plants. A review by Sethy and Ghosh highlights the adverse effects of heavy metals, including nickel, cobalt, cadmium, copper, lead, chromium, and mercury, on seed germination. These metals can cause overall abnormalities, decrease germination rates, reduce root and shoot elongation, and impair seed physiology.

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