Visual-cognitive Skills and Physical Qualities in Elite Soccer: Practical Considerations for Training and Return-to-Play Protocols: Crimson Publishers

Visual-cognitive Skills and Physical Qualities in Elite Soccer: Practical Considerations for Training and Return-to-Play Protocols by Lukasz Bortnik in Research & Investigations in Sports Medicine: Peer Reviewed Research & Investigations in Sports Medicine

 

Abstract

Elite soccer is increasingly demanding, requiring players to cover greater distances at higher speeds while making rapid decisions under high-pressure scenarios. These demands place significant strain on neurophysiological capacities, highlighting the need for integrated training that combines physical, technical-tactical and visual-cognitive development. This is particularly critical for athletes returning from long-term injury, who require both physical rehabilitation and neurocognitive re-adaptation to safely resume competition. Traditional Return-to-Play protocols often overlook compensatory central nervous system adaptations, increasing the risk of movement errors. Contemporary approaches emphasise visual-cognitive skills, supported by divided attention (managing multiple tasks) and selective attention (prioritizing relevant stimuli), while Blood Flow Restriction (BFR) training provides a promising adjunct during rehabilitation, especially when combined with Virtual-Reality (VR) techniques. Integrating these cognitive and physical strategies may enhance performance, reduce movement errors and facilitate safer re-integration into elite soccer.

Keywords: Blood flow restriction; Virtual-cognitive skills; Soccer RTP

Introduction

Elite soccer continues to evolve, with rising physical and technical-tactical demands across many European competitions. As the intensity of the modern game increases, players are expected to cover greater running distances at higher speeds and perform in more dynamic, high-pressure scenarios where decisions made in fractions of a second can determine match outcomes [1]. These evolving demands suggest that players’ neurophysiological capacities are being tested to new limits [2,3]. In practical settings, this underscores the critical need to develop physical and technical-tactical abilities in tandem with visual-cognitive skills. This is especially pertinent for players returning from long-term injury, who must undergo physical rehabilitation and a period of re-adaptation before safely rejoining team training and competitive play [4]. These individuals face an elevated risk of movement errors, often due to compromised motor control under the complex and unpredictable demands of elite competition [4]. For example, evidence indicates that altered brain and spinal cord function (negative neuroplasticity) may persist for years after knee surgery, even following a return to full activity [5]. In addition, persistent biomechanical deficits have been observed long after knee reconstruction, particularly during the penultimate foot contact of the injured limb in change-of-direction tasks [6]. These findings suggest that RTP protocols should place greater emphasis on movement mechanics and sensorimotor control, alongside traditional performance outcomes. Ultimately, a paradigm shift is needed in rehabilitation. The one that integrates elements of “brain training” and cognitive training to more comprehensively address the long-term consequences of injury.

Modern training and preparation must therefore utilize a deep analytical approach and explicitly integrate key visual-cognitive aspects into these processes. Skills such as perception, anticipation and rapid reaction should be considered essential components of contemporary training programs [7]. Both divided and selective attention are vital to stimulate visual-cognitive processes effectively. Divided attention (dual-tasking) refers to the ability to manage multiple tasks simultaneously or switch between them without attentional loss [8]. Selective attention (Table 1) involves identifying relevant and ignoring irrelevant stimuli [9].

Table 1:Definitions, divisions and examples of selective attention in football.

Visual-Cognitive Processes: Practical Applications

Practitioners might ask how visual-cognitive aspects could be applied in practical settings. In real-match scenarios, the concepts of anticipation and reaction can be utilized in various ways to enhance player performance and impose professional development. Table 2 & 3 depict real-world situations that offensive and defensive positions could experience during official matches. In practical settings, embedding visual-cognitive processes in individual and team-based training, including rehabilitation and Return-to-Play (RTP) protocols, is essential for a holistic and safe transition back to full match performance. When injuries limit movement and on-pitch sessions are not possible however, alternative approaches must be considered. A notable example is an Anterior Cruciate Ligament (ACL) injury. It is worth noting that rupture and reconstructive surgery lead to a disruption of sensory input from the knee to the Central Nervous System (CNS), resulting in altered motor behaviours [10]. Consequently, ACL injury should be regarded as a multifaceted musculoskeletal condition, as it encompasses not only mechanical and movement impairments but also cognitive and neurological disruptions. Failing to address these dimensions within rehabilitation, prevention and risk assessment strategies may result in incomplete management and a higher likelihood of recurrent problems [11]. In such cases, a long recovery and multi-staged rehabilitation are required, gradually transitioning from gym-based to pitch-based specific exercises [12] (Figure 1). Rehabilitation, even at early stages, should include tasks that challenge attention, working memory, and visual-spatial processing as shown in Figure 2 & 3. Training plans at more advanced stages must consider the individual’s characteristics and positional demands, where soccer players anticipate, decide and quickly react to constantly changing environments that mimic game-like scenarios [12-15]. For instance, developing the ability to press aggressively, win the ball high and transition instantly into attack has been considered a decisive factor in modern soccer [13]. Figure 1 presents a drill designed to connect defensive pressing behaviors with a quick counter-attack, emphasizing perception, anticipation and reaction in high-tempo game situations. The main aim during this exercise is to condition players for repeated high-intensity efforts in realistic scenarios while enhancing individual and collective awareness in attack and defense [14]. Another practical and progressive approach is the Visual-Cognitive Control-Chaos Continuum (VC-CCC) proposed by Taberner and colleagues [15]. This framework outlines how RTP strategies can progressively integrate various physical and cognitive objectives, which is shown in Table 4. By adopting such structured, cognitively integrated training frameworks, practitioners can maximize the RTP protocols and better prepare athletes for complex, fast-paced scenarios of modern soccer and ultimately enhance their readiness for the match demands.

Table 2:Examples of anticipation scenarios for offensive players in football match-play.

Table 3:Examples of reaction scenarios for defensive players in football match-play.

Figure 1:Specific offensive-defensive drill (3v1 high pressure and counter-attack): a) 3D drill set up; b) 3v1 possession where player nr 6 (blue) applies high pressure to win the ball; c) once possession has been re-gained, counter-attack is initiated; d) 3 blue players counter-attack and 1 red defends (3v1); e) 2 red players are making recovery runs to support defense (3v3); f) blue players quickly enter the box to finish an attack, which must be performed as quickly as possible to use numerical advantage in its early phase. Perform 2 sets of 6-8 actions lasting 20-30 seconds. Use 1:2-3 work-to-rest-ratio. Group activity: 9-15 players. Perception/Anticipation/Reaction. Adopted from Bortnik L [14].

Figure 2:VR goggles used during an ACL rehabilitation.

Figure 3:Virtual reality applications used to improve cognitive skills: A) Inhibition & eye-hand coordination; B) Scanning ability & reaction.

Table 4:Examples of integrated objectives during the Visual-Cognitive Control-Chaos Continuum (VC-CCC).

Blood Flow Restriction and Ischemic Preconditioning

Blood Flow Restriction (BFR), first developed in the 1990s, involves the application of external pressure to partially restrict blood flow during low-load exercise [16]. A growing body of evidence indicates that BFR training promotes muscle hypertrophy, strength, peak power, aerobic capacity, recovery and proprioception [17-21]. In addition to physical outcomes, BFR has been associated with enhanced cognitive performance, such as improved cognitive function in elderly populations [22] and increased cognitive flexibility in young athletes [23]. BFR shorts in particular have been shown to be feasible, practical and safe in applied environments [24] (Figure 4a). Importantly, low-load exercise with BFR elicits adaptations comparable to those achieved with high-intensity training [25]. This makes BFR especially relevant in contexts where high mechanical loads are undesirable, such as Anterior Cruciate Ligament (ACL) rehabilitation or in the days immediately before and after competition in soccer [26]. The primary physiological mechanisms underlying BFR include tissue ischemia, which induces metabolic stress, cellular swelling, anabolic hormone upregulation, and increased expression of neurotrophins such as Brain-Derived Neurotrophic Factor (BDNF) [27]. Together, these mechanisms support both physical and cognitive adaptations while reducing joint stress.

Ischemic Preconditioning (IPC) is a BFR method that involves periods of circulatory ischemia, usually 3 to 4 x 5 minutes, followed by circles of reperfusion of similar or shorter duration in the limbs [28]. This approach elicits high hypoxic stress inducing vasodilation, improving muscle blood flow, enhancing oxygen delivery and ultimately positively affecting various exercise performance [29]. Preconditioning efficacy has been widely reported on strength, power and endurance capabilities [30,31]. From a research perspective however, interests should be directed more towards the IPC effect on sensory-motor patterns and muscular coordination in various athletic populations including soccer players. Evidence suggests that IPC might enhance sensory and proprioceptive feedback during physical activity to correct movements and augment its quality. That might ultimately improve physical performance and reduce potential injury risk, which would be considered of high importance in an athletic population [20,21,26].

Virtual Reality: A Novel Technique in Practical Settings

Virtual Reality (VR) provides a computer-generated threedimensional environment accessed through head-mounted displays and motion controllers, creating an immersive sense of presence in virtual space [32]. VR has been applied in both clinical and sporting contexts to enhance motor and sensory function, cognitive processes and perceptual skills, all of which play a critical role in decision-making in team sports [33]. Research has demonstrated that movement patterns and motor control are largely comparable between physical environments and virtual conditions [34]. Furthermore, VR has proven effective in the evaluation and rehabilitation of gait [35], highlighting its potential as both an assessment and training tool. This technique is particularly valuable when physical loading must be limited, for example during injury rehabilitation or recovery phases in a weekly microcycle in soccer [26]. Although BFR and VR have each demonstrated significant promise, no studies to date have examined their combined use in sport [36]. Conceptually, their integration could provide synergistic benefits, enhancing proprioception, motor and cognitive skills, postural control and physiological adaptations such as muscle size, strength and endurance (Figure 4b). A potential protocol (Figure 5) could involve applying BFR at ~70% limb occlusion pressure (LOP; <200mmHg) bilaterally, as recommended by Neal BS et al. [24], for 3 sets of 5 minutes during VR training, interspersed with 2-minute reperfusion periods [21]. This combined approach may augment both sensorimotor and cognitive outcomes while supporting neuromuscular adaptation. Future research should examine this novel paradigm with particular attention to its relevance for soccer performance, rehabilitation and recovery [37].

Figure 4:New training and RTP methods including: A) Blood Flow Restriction (BFR); B) Combined VR and BFR.

Figure 5:Practical protocol combining blood flow restriction and virtual reality training during rehabilitation and RTP.

Summary and Conclusion

Elite soccer is becoming increasingly demanding, requiring players to produce higher physical outputs while simultaneously making rapid decisions under complex, high-pressure scenarios. These evolving demands place significant strain on neurophysiological capacities, highlighting the need for integrated training approaches that develop physical and technical-tactical skills and visual-cognitive abilities. Such an approach is particularly important for athletes returning from long-term injuries, such as ACL ruptures, where Return-to-Play (RTP) protocols must address both physical rehabilitation and neurocognitive re-adaptation to ensure safe and effective reintegration into competition. Failure to address these cognitive and perceptual components may increase the risk of movement errors and compromise performance.

Emerging technologies provide promising tools to support cognitive development in soccer players. Virtual Reality (VR) offers a low-cost, low-impact method to enhance perception, reaction speed, inhibitory control, eye-hand coordination, scanning ability and visual processing efficiency. VR is particularly advantageous for injured athletes, allowing them to maintain cognitive engagement while minimizing physical stress, thereby facilitating smoother transitions from controlled training environments to on-pitch performance. Additionally, VR-based applications can complement conventional gym- and field-based training routines, providing a powerful adjunct for players at all ages and competitive levels. Furthermore, the integration of VR with Blood Flow Restriction (BFR) training may amplify cognitive and neurophysiological adaptations by combining perceptual-cognitive engagement with physiological stimulation. This synergistic approach may represent potentially a promising tool for rehabilitation and performance enhancement, particularly during periods when high-intensity physical training is not feasible. Systematic research is warranted to explore the efficacy, optimal protocols and long-term benefits of this combined methodology.

From a practical approach, coaches and performance staff could incorporate technology-enhanced cognitive drills alongside traditional physical conditioning, ensuring training scenarios replicate the attacking and defending demands of competition. Exercises should challenge decision-making, attention and perception under realistic constraints, while progression should be tailored to each player’s injury status and readiness. Integrating VR and BFR into structured RTP programs may accelerate cognitivemotor re-integration, enhance tactical awareness and reduce the likelihood of re-injury, ultimately supporting safer and more effective preparation for elite match play.

Key Takeaways

A. Cognitive skills training should focus on perception, anticipation, decision-making and rapid reaction.
B. Divided and selective attention should be trained in practical settings.
C. Virtual Reality (VR) provides low-cost, low-impact cognitive training.
D. VR enhances cognitive skills and could facilitate smoother transition from controlled environments to on-pitch performance.
E. BFR can be combined with VR to potentially enhance neurophysiological and cognitive adaptations in addition to well-established physiological benefits.
F. Athletes could perform VR-based training while applying BFR at ~70% of limb occlusion pressure (<200mmHg), structured as 3 × 5-minute bouts with 2-minute reperfusion periods.
G. BFR can be useful when high-intensity physical training is not feasible (e.g., during injury rehabilitation or when fatigued).

Practical Implications

a) Design drills that replicate attacking and defending scenarios relevant to player positions.
b) Progress training based on injury status, readiness and competitive demands.
c) Integrate VR + BFR to potentially accelerate cognitivemotor re-integration and reduce re-injury risk.

References

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Sustainable Ecotechnological Remediation and Recovery of Chromium from Wastewater Using the Floating Aquatic Plant Azolla pinnata: Crimson Publishers

Sustainable Ecotechnological Remediation and Recovery of Chromium from Wastewater Using the Floating Aquatic Plant Azolla pinnata by K Usharani in Environmental Analysis & Ecology Studies: Peer Reviewed Environmental Analysis & Ecology Studies

 

Abstract

Phytotechnology utilizes aquatic macrophytes and their microbiomes to remediate chromium-contaminated waters. This study evaluates Azolla pinnata, a free-floating fern, for its potential in sustainable remediation and recovery of Cr(VI) from synthetic wastewater. Results show successful removal of hexavalent chromium through rhizofiltration, where Azolla and algae synergistically reduce chromium concentration. Batch tests at varying initial Cr(VI) concentrations (5, 10, 25, 40, and 50ppm) using 8g of fresh Azolla biomass indicated significant chromium absorption, evidenced by a dark brown coloration. The experiment lasted 14 days, with chromium quantified via the Diphenylcarbazide (DPC) assay and measurements taken spectrophotometrically at 540nm. The findings confirm the effectiveness of this phytoremediation process and highlight the potential of aquatic plants in addressing environmental challenges while promoting a cleaner, healthier earth.

Keywords:Phytoremediation; Chromium; Azolla pinnata; Bioremoval

Introduction

Heavy metal pollution-particularly chromium-poses a global threat. Conventional treatments (ion exchange, membranes, reverse osmosis, precipitation) can be effective but cost-intensive, whereas phytoremediation offers a low-cost, nature-based solution. Azolla pinnata, which hosts Nostoc azollae, grows rapidly and is easily harvested, enabling rhizofiltration and biosorption of dissolved metals. However, the development of improved solutions is limited, particularly in developing countries, due to economic constraints and the high costs of acquiring quality equipment. Phytoremediation is a cost-effective green technology that has proven effective in various water systems, such as dams and lakes. This bioremediation process utilizes different plant species to remove, transfer, stabilize, or eliminate heavy metal deposits in water. One such plant, Azolla pinnata, is a small free-floating aquatic macrophyte that effectively absorbs heavy metals from concentrated sources.

Azolla thrives in symbiosis with cyanobacteria, which live within the cavities of its fronds. Its rapid growth rate, capable of doubling its biomass in just 2 to 4 days, along with its ability to float, makes it easy to harvest and facilitates the removal of heavy metals from contaminated water. Phytoremediation leverages these plants to degrade, stabilize, digest, or eliminate toxins and other chemical pollutants. The aquatic plants always have an extensive system of roots that helps them and makes them the primary route for the accumulation of contaminants in their roots and shoots. The aquatic free-floating plants have been revealed to be a principled prototype for ecotoxicological studies, and they have the competence to bioaccumulate or biosorb nutrients and metals [1-3].

The benefits of using plants for this purpose include economic advantages, effective harvest management, and the potential utilization of harvested products. Azolla is particularly promising for the removal of metal ions. Chromium, when present in high concentrations, poses toxic risks to humans, animals, and the environment. Specific tests for chromium have been conducted and stored for laboratory studies on phytoremediation. The aquatic plant Azolla is currently being investigated for its effectiveness in removing chromium from solutions at various concentrations, with the levels of chromium analyzed using UV spectrophotometer readings at 540nm. The nearby electroplating industry produces chromium alloys at high levels, making this study crucial for reducing chromium concentrations to safer levels.

Materials and Methods

Plant acquisition and acclimatization

Azolla pinnata was collected from the Azolla growing bed near the Horticulture Centre for the experiment. The plants were washed with running water to remove any mud particles from the roots. To support adaptation to the experimental conditions and to produce substantial biomass, the plants were grown in a plastic tray filled with tap water for approximately 15 days.

Chromium standards, controls, and analytical method

Chromium was quantified via the Diphenylcarbazide (DPC) colorimetric assay (λ=540nm), with acidification by H₂SO₄ and calibration curves from standards and blanks; measurements taken at 5min after reagent addition. A few drops of concentrated sulfuric acid were added to establish acidic conditions. The mixture was then diluted to a final volume of 50mL using distilled water. After 5 minutes, 1,5-Diphenylcarbazide (DPC) reacts selectively with Cr(VI) to afford a complex with a purplish red color. The intensity of the resulting color was measured at 540nm using a UV spectrophotometer.

Estimation of the concentration of chromium after phytoremediation treatment using Azolla pinnata

Stock solutions of potassium dichromate are prepared in water at known concentrations and quantities. Aquatic plant samples of Azolla are weighed and placed into 12-liter plastic containers filled with a specific volume and concentration of the metallic compound in water. The experimental setup is maintained under partially covered conditions. To account for evaporative losses, distilled water is added every third day to maintain a consistent water level. Water samples from the containers are collected every seventh day for analysis. The condition of the plants is visually assessed during these intervals. After 28 days, the plants are removed, weighed, and then returned to their original water source. To analyze the concentration of metal ions in the water samples collected weekly, and analyzed by a UV spectrophotometer. Based on the absorbance readings of the known solution samples, a standard graph is plotted to illustrate the relationship between absorbance and concentration. This graph is then referenced to determine the concentration of the water samples collected from the containers over time [4].

The samples were allowed to cool, and the absorbance in terms of Optical Density (OD) at 540nm was measured using a UVVisible spectrophotometer. The initial and residual concentration of chromium in terms of Optical Density (OD) value was measured using a UV-Visible spectrophotometer (UV-2600 series SHIMADZU).

From this value, the percentage chromium reduction or removal was calculated.

The percentage Chromium removal efficiency (R) was calculated using the formula,
R = (I − F) / I × 100

Where I and F are the Initial and Final concentrations of Chromium, respectively.

The Chromium Removal Efficiency (%R): This measures the percentage of the contaminant removed from the solution/soil relative to the initial amount. It is calculated using the standard formula:
(%R) = (Ci −Cf ) / Ci × 100

where (Ci) is the initial concentration and (Cf) is the final concentration.

An efficiency value of 100% was obtained when no Chromium appeared in the treated water sample (i.e., Final concentration=0). The fresh and dried biomass of A. pinnata plants was measured. Growth of the plant biomass (A. pinnata) was measured in terms of dry weight by the gravimetric method [2,3,5,6].

Estimation of pH after phytoremediation using Azolla pinnata

The pH change in treated wastewater at different concentrations and with varying time intervals, as affected by free-floating aquatic plants A. pinnata, was estimated using a digital pH meter (Scientific Tech, Advanced pH meter, model ST-2002).

Estimation of biomass after phytoremediation treatment

On the 14^th day of the experiment, the fresh and dried biomass of A. pinnata plants was measured. Each replicate was harvested, and the plants were rinsed with distilled water to eliminate any ions adhering to their surfaces. The plants were then blotted with filter paper to remove excess water. After measuring the fresh biomass, the samples were dried in an oven at 80 °C for 48 hours. The dry weights were subsequently recorded [7].

Estimation of chlorophyll after phytoremediation treatment

Approximately 1 gram of finely chopped plant material was mixed with 20 milliliters of 80% acetone and ground in a clean mortar. The mixture was then centrifuged at 500RPM for 5 minutes, and the supernatant was transferred to a 100-milliliter volumetric flask. This centrifugation process continued until the residue became colorless. The solution was then diluted to a final volume of 100 milliliters with 80% acetone, and the absorbance was measured spectrophotometrically at wavelengths of 664nm and 647nm.

Result and Discussion

Effect of chromium after phytoremediation treatment

The results indicate that phytoremediation is effective at a wavelength of 540nm, as measured using a UV spectrophotometer. When compared to standard chromium levels, Azolla pinnata effectively reduces chromium concentrations after the phytoremediation process. Based on these observations, it can be concluded that Azolla pinnata can thrive in chromium concentrations of less than 5ppm and can tolerate a maximum concentration of 50ppm (Figure 1A&1B). After seven days of treatment with Azolla pinnata, the percentage removal of chromium reached a maximum of 94.8% at a 5ppm chromium concentration and a minimum of 16.5% at a 50ppm concentration (Figure 2A). The effects of chromium through sustainable ecological phytoremediation after seven days are shown in Figure 3. After fourteen days of treatment, the percentage removal of chromium by Azolla pinnata increased, achieving a maximum bioremoval of 97.3% at 5ppm chromium concentration and a minimum of 16.7% at 50ppm (Figure 2B). The effects of chromium via sustainable ecological phytoremediation after fourteen days are illustrated in Figure 2. Compared to the results from day seven, Azolla pinnata significantly reduces chromium concentration after fourteen days of phytoremediation. These observations suggest that the reduction in chromium concentration is greater at 5ppm compared to the measurements taken on the seventh day. Removal efficiency decreased as initial Cr(VI) concentration increased, consistent with sorption site saturation and stress effects; at 40-50ppm, removal was notably reduced (≈16-43%). Additionally, Figure 3A&3B illustrates that on the 7th and 14th day, the leaves of Azolla pinnata remained fresh at a concentration of 5ppm; however, at higher concentrations, the leaves became completely dried out due to the stress caused by chromium toxicity. The highest recorded chromium removal rate was 97.34%. It is evident that as the concentration of chromium increases, the percentage of removal decreases. Figure 4 illustrates the impact of pH on chromium levels following phytoremediation, measured on the 14th day. Initially, the pH was acidic; however, after phytoremediation, it shifted to an alkaline state. According to Lindberg and Wingstrand (1985), plants can alter the pH of the surrounding water through their roots, which may help them cope with stress from heavy metals. Specifically, the roots significantly raised the rhizosphere pH under stress, especially when chromium was present in the solution. This shows the effects of chromium on biomass content after 14 days of phytoremediation.

Figure 1:Spectral observation of Chromium removal at 540nm (A) after the 7^th day and (B) 14^th day.

Figure 2:The percentage removal of chromium by Azolla pinnata (A) after the 7^th day and (B) 14^th day.

Figure 3:Effect of Chromium Phytoremediation by Azolla pinnata treatment after the (A) 7^th day and (B) 14^th day.

Figure 4:Effect of pH of the chromium after phytoremediation by Azolla pinnata treatment on the 14^th day.

The growth rate of Azolla pinnata is negatively impacted by chromium stress. According to the analysis, there is a significant increase in the percentage decrease of fresh weight, as well as a notable reduction in the dry-to-fresh weight ratio at higher chromium concentrations. The maximum percentage decrease in fresh weight was observed with a 50ppm chromium solution after 14 days, suggesting that Azolla pinnata may accumulate chromium. Additionally, a higher dry weight-to-fresh weight ratio was noted at the lower concentration of 5ppm during the same 14-day period.

Figure 5 illustrates the impact of chromium on total chlorophyll content following phytoremediation over a period of 14 days. Chlorophyll content was assessed using acetone extracts, in accordance with the Arnon method (1949). The results indicate a decreasing trend in chlorophyll A content as chromium concentrations increased. In contrast, chlorophyll B and total chlorophyll contents showed an increasing trend; however, these overall values still declined with higher chromium concentrations. Elevated levels of chromium toxicity negatively affect photosynthesis. The reduction in chlorophyll content may be attributed to decreased enzymatic activity of protochlorophyllide reductase. Additionally, the lowered levels of photosynthetic pigments in plants could be linked to lipid peroxidation occurring in the chloroplast membranes.

Figure 5:Effect of chromium after phytoremediation by Azolla pinnata on Total Chlorophyll content after treatment on the 14^th day

Figure 6A&6B illustrates the impact of chromium on carotenoid and protein content after 14 days of phytoremediation. It shows that as chromium concentration increases, carotenoid content decreases. According to Hou et al. (2007), carotenoids are nonenzymatic antioxidant pigments that protect cells from Reactive Oxygen Species (ROS) under chromium stress. The decline in carotenoid content can be attributed to metal toxicity, which may hinder the formation of photosynthetic pigments. This explains the observed reduction in photosynthetic pigments with increasing chromium concentration. Moreover, protein content also diminishes as chromium levels rise. Specifically, Azolla pinnata shows a reduction in protein content at higher chromium concentrations.

Figure 6:Effect of chromium after phytoremediation by Azolla pinnata on (A) Chlorophyll, (B) Carotenoid, and Protein content after treatment on the 14^th day.

Phytotechnology harnesses aquatic macrophytes and their microbiomes to remediate chromium-contaminated waters. This study evaluates Azolla pinnata as a free-floating fern for sustainable remediation and potential recovery of Cr(VI) from synthetic wastewater. This study decisively demonstrates the successful removal of hexavalent chromium from contaminated synthetic wastewater using Azolla pinnata, highlighting a healthy, sustainable ecotechnology approach that capitalizes on the synergistic effects of both Azolla and algae. This innovative method, known as phytotechnology, encompasses processes such as bio-removal, bioreduction, and biodegradation. It prominently features rhizofiltration, where free-floating aquatic plants, such as Azolla pinnata, play a crucial role in pollutant removal. The combined action of the algae and Azolla leads to a significant reduction in chromium concentration through rhizofiltration, as these aquatic plants effectively adsorb pollutants from their environment.

As noted by Mishra et al., this decline can be linked to lower protein levels in aquatic macrophytes, as well as increased protein degradation resulting from metabolic processes. Chromium may disrupt the balance of free nucleotides and RNA, leading to reduced RNA biosynthesis, which could explain the decrease in protein synthesis. Azolla pinnata possesses an exceptional ability to hyperaccumulate heavy metals from contaminated water bodies (Wagnar, 1997). Ex situ research conducted by Salt et al. (1995), Bennicelli et al. (2004), Jangwattana (2010), Sood et al. (2011), Deval et al. (2012), Moradi et al. (2013), Sufian et al. [8], and Thayapara et al. [9] has demonstrated the various capacities of A. pinnata to uptake and retain different heavy metal ions. These findings highlight A. pinnata’s potential for the phytoremediation of heavy metal-polluted water reservoirs. The nearby electroplating industry discharges chromium, a heavy metal, into water bodies. The dried biomass of A. pinnata can be easily transported to recycling sites for heavy metal recovery (Sood, 2011). The study of aquatic free-floating plants, including L. minor, has been revealed to be a noble model for ecotoxicological studies, and it can bioaccumulate, or biosorption of nutrients and metals, was reported earlier [1-3].

This study confirms the efficacy of this phytoremediation treatment in removing heavy metals. Additionally, it is suggested that the 33 artificial systems integrated into the lake, planted with A. pinnata, can effectively function as biological filters to remove heavy metal ions from industrial discharges. Implementing such filter systems would ensure that industrial pollutants are captured and eliminated before contaminating public water bodies [10-15]. The results unequivocally demonstrated a significant reduction in total chromium concentration in the samples compared to the controls, confirming the effectiveness of the phytoremediation process. The aquatic, free-floating plants serve as a principled model for ecotoxicological studies, possessing the ability to bioaccumulate or biosorb nutrients and metals, thereby supporting sustainable development [16-21].

Conclusion

The primary characteristics of macrophytes that exhibit strong phytoremediation abilities include rapid growth rates, high biomass, and significant adaptability to a variety of environmental conditions. A notable example is the endosymbiont Nostoc azollae found in Azolla pinnata, which plays a crucial role in assimilating atmospheric nitrogen, enhancing the plant’s overall growth. This feature contributes to the vigorous reproduction of the water fern in irrigated environments. Additionally, the free-floating nature of A. pinnata and similar macrophytes simplifies the harvesting process. Their high-water content in fresh biomass, ranging from 90% to 94%, significantly reduces volume when dried, mitigating disposal challenges for the harvested material. Furthermore, A. pinnata demonstrates an impressive ability to thrive in highly polluted waters with varying pH levels, temperatures, and salinity, making it particularly suitable for phytoremediation applications. This study concludes by advocating for A. pinnata as a viable phytoremediation agent capable of addressing heavy metal contamination in public dams and waterways. Its delicate structure is especially beneficial for use in industrial ponds and rice paddies, where pollution from waste disposal and agricultural chemicals is a significant concern. Harvesting the heavy metal-rich water ferns can be done mechanically or manually, facilitating the chemical extraction of heavy metals, such as chromium, for multiple recycling uses. Although A. pinnata may not serve as a complete solution to heavy metal pollution, it provides a promising approach to restoring water bodies contaminated with specific heavy metals by capturing them within the plant’s tissues. Azolla-based phytotechnology provides a pragmatic pathway to mitigate chromium pollution and support resource recovery; field deployment should pair with upstream source control and routine monitoring. This sustainable remediation approach not only addresses critical environmental challenges but also showcases the remarkable potential of leveraging natural solutions for a cleaner, healthier earth.

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