Sulfur nutrition stimulates lead accumulation and alleviates its toxicity in Populus deltoides

Offsetting pb induced oxidative stress in Vicia faba plants by foliar spray of chitosan through adjustment of morpho-biochemical and molecular indices

In the course of their life, plants face a multitude of environmental anomaly that affects their growth and production. In recent decades, lead (Pb) gained an increasing attention as it is among the most significant contaminants in the environment. Therefore, in this study the effects of Pb concentrations (0, 50 and 100 ppm) on Vicia faba plants and attempts to alleviate this stress using chitosan (Chs; 0 and 0.1%) were performed. The results validated that with increasing Pb concentrations, a decline in growth, pigments and protein contents was observed. In the same time, a significant upsurge in the stress markers, both malondialdehyde (MDA) and H2O2, was observed under Pb stress. Nonetheless, foliar spraying with Chs improves the faba bean growth, pigment fractions, protein, carbohydrates, reduces MDA and H2O2 contents and decreases Pb concentrations under Pb stress. Pb mitigation effects by Chs are probably related with the activity of antioxidant enzymes, phenylalanine ammonia lyase (PAL) and proline. The application of Chs enhanced the activities of peroxidase, catalase and PAL by 25.77, 17.71 and 20.07%, respectively at 100 ppm Pb compared to their control. Plant genomic material exhibits significant molecular polymorphism, with an average polymorphism of 91.66% across all primers. To assess the genetic distance created among treatments, the dendrogram was constructed and the results of the similarity index ranged from 0.75 to 0.95, indicating genetic divergence. Our research offers a thorough comprehension of the role of Chs in lessening the oxidative stress, which will encourage the use of Chs in agricultural plant protection.

The Cortisol Levels, Histology, and Fine Structure of Various Tissues of Fish Gambusia affinis (Baird and Girard, 1853) after Exposure to Lead

Background

Aquatic organisms demonstrate a high vulnerability to mortality when exposed to Pb, even at low concentrations. The objective of this investigation is to ascertain the histopathological alterations and cortisol concentrations in diverse tissues of Gambusia affinis, with a specific focus on the eggs and larvae, following exposure to varying concentrations of PbCl2.

Methods

Adult specimens of G. affinis measuring 5-6 cm in length were obtained from a commercial fish breeding facility. A total of 8 fish with a 1 : 1 ratio of 4 pairs of broodstock were placed in an 8-liter aquarium. Following the adaptation phase, the broodstock underwent a spawning process that lasted for a duration of 7 days. Throughout the spawning process, assessments were conducted on the progression of the abdominal growth of the broodstock. Eggs ready to hatch and Gambusia larvae were taken and exposed to 0.1 mg/L PbCl2, 1 mg/L PbCl2, and control (without PbCl2) for 24 hours, with three replications. At the end of the experiment, histopathological analysis was conducted using the hematoxylin Ehrlich-eosin staining method and scanning electron microscopic (SEM) observation. The levels of Pb in gills were determined by employing atomic absorption spectrophotometer. The cortisol concentration in organ samples of fish was determined through the utilization of a cortisol ELISA Kit.

Results

The findings of this investigation demonstrated an important bioaccumulation occurrence of Pb within the gills of Gambusia fish that were specifically subjected to 0.1 and 1 mg/L PbCl2. The histological structures of eggs and larvae that were subjected to PbCl2 exhibited impairment in comparison to the control group. The present study observed a significant elevation in cortisol levels among fish specimens that were subjected to PbCl2 exposure.

Conclusions

The findings of this investigation suggest that the occurrence of Pb is linked to a rise in cortisol concentrations in various organs of G. affinis larvae. Furthermore, the research indicates that the exposure to Pb has a notable impact on the histological alterations in the eggs and larvae of Gambusia fish, implying that they are undergoing stress as a result of the Pb exposure.

Application of exogenous glycinebetaine alleviates lead toxicity in pakchoi (Brassica chinensis L.) by promoting antioxidant enzymes and suppressing Pb accumulation

Lead (Pb) poses an adverse effect on plant growth and development. Glycinebetaine (GB) plays an important role in plants response to stress environment. The study was performed to examine the potential of exogenous GB (0.5, 1, 2, and 5 mM) in alleviating Pb toxicity, the physiological and biochemical responses in pakchoi under 100 μM Pb stress by hydroponic experiment. Pb stress significantly decreased the growth, contents of pigment and mineral nutrient, and activities of antioxidative enzymes (CAT, SOD, and APX) in roots and shoots of pakchoi, while it caused a significant increase in Pb and ROS accumulation both in roots and shoots of pakchoi in comparison to the control. Exogenous application of GB improved leaf and root length, fresh and dry weight, mineral nutrient, and pigment contents of pakchoi under Pb stress. GB also effectively enhanced antioxidative enzyme activities and the accumulation of proline, soluble sugar, and GB and reduced the oxidative stress and Pb contents in shoots and roots of pakchoi. Principle component analysis (PCA) provided useful information on the classification of Pb tolerance according to the response to GB. Overall, the 1 mM GB was more effective to ameliorate the detrimental impacts of Pb stress. These findings suggested that GB application might be considered an effective strategy for alleviating Pb toxicity and enhancing the tolerance of pakchoi plants under Pb stress.

Combined effect of putrescine and mycorrhizal fungi in phytoremediation of Lallemantia iberica in Pb-contaminated soils

As soil contamination with heavy metals is increasing and polyamines have roles in the growth of mycorrhiza and plants, it is important to study phytoremediation, growth, tolerance, and mycorrhization in Lallemantia iberica as a multi-purpose plant, by the application of putrescine along with mycorrhiza in Pb-contaminated soils. For this purpose, the study was performed in a factorial arrangement with Pb (0, 300, 600, and 900 mg Pb/kg soil), mycorrhiza (non-inoculation, Funneliformis mosseae (Fm), and Rhizophagus intraradices (Ri)), and putrescine (0, 0.5, and 1 mM) in a greenhouse. Results showed that antioxidant activities, plant Pb, and mycorrhizal features enhanced, while transfer factor (TF), biomass, and tolerance decreased under Pb levels. Mycorrhiza improved growth, greenness, defense, and tolerance and reduced TF, Pb, and H₂O₂ content under Pb stress. Putrescine (0.5 mM) increased catalase activity, biomass, and colonization and reduced Pb content and TF under Pb levels. Combination of 0.5 mM putrescine with Fm increased shoot biomass (13%), peroxidase (17.2%), root P (7.5%), shoot tolerance (14.4%), colonization (5.1%), and hyphal width (5.5%) and decreased malondialdehyde (20.5%) and shoot Pb content (28.1%). Putrescine (1 mM) had negative effects on all traits in combination with Ri but not with Fm. Combination of putrescine and Fm showed more efficiency in decreasing Pb content in L. iberica and was effective in phytostabilization. It is generally concluded that 0.5 mM putrescine was the beneficial concentration in combination with mycorrhiza, Pb stress, and single use to improve plant performance, and Fm was a useful species for improving the growth and tolerance of L. iberica under Pb levels.

Interaction Between Sulfur and Iron in Plants

It is well known that S interacts with some macronutrients, such as N, P, and K, as well as with some micronutrients, such as Fe, Mo, Cu, Zn, and B. From our current understanding, such interactions could be related to the fact that: (i) S shares similar chemical properties with other elements (e.g., Mo and Se) determining competition for the acquisition/transport process (SULTR transporter family proteins); (ii) S-requiring metabolic processes need the presence of other nutrients or regulate plant responses to other nutritional deficiencies (S-containing metabolites are the precursor for the synthesis of ethylene and phytosiderophores); (iii) S directly interacts with other elements (e.g., Fe) by forming complexes and chemical bonds, such as Fe-S clusters; and (iv) S is a constituent of organic molecules, which play crucial roles in plants (glutathione, transporters, etc.). This review summarizes the current state of knowledge of the interplay between Fe and S in plants. It has been demonstrated that plant capability to take up and accumulate Fe strongly depends on S availability in the growth medium in both monocots and dicot plants. Moreover, providing S above the average nutritional need enhances the Fe content in wheat grains, this beneficial effect being particularly pronounced under severe Fe limitation. On the other hand, Fe shortage induces a significant increase in the demand for S, resulting in enhanced S uptake and assimilation rate, similar to what happens under S deficiency. The critical evaluation of the recent studies on the modulation of Fe/S interaction by integrating old and new insights gained on this topic will help to identify the main knowledge gaps. Indeed, it remains a challenge to determine how the interplay between S and Fe is regulated and how plants are able to sense environmental nutrient fluctuations and then to adapt their uptake, translocation, assimilation, and signaling. A better knowledge of the mechanisms of Fe/S interaction might considerably help in improving crop performance within a context of limited nutrient resources and a more sustainable agriculture.

Differences in stress defence mechanisms in germinating seeds of Pinus sylvestris exposed to various lead chemical forms

Exposure to lead (Pb) can have serious toxic effects on the physiological and biochemical processes of plants. The chemical form of the metal determines the degree of its toxicity. In our research, we examined the effect of lead in the form of lead nitrate [Pb(NO3)2] and lead chloride (PbCl2) in concentrations of 12.5 mM and 25 mM on pine (Pinus sylvestris) seed germination. Nitrogen salt causes more severe changes than chloride salt. Increasing levels of electrolyte leakage, malondialdehyde, and hydrogen peroxide were detected during germination processes. The high levels of ROS lead to redox changes in the cell. We observed a reduction in the level of the reduced form of glutathione (GSH), and at the same time observed increased levels of the oxidised form of glutathione (GSSG) depending on the concentration and also the time of exposure to lead compounds. At the beginning of germination processes, the effective non-enzymatic activity of the antioxidant cycle was dominant, and at the late stage the enzymatic activity was noticed in the presence of Pb compounds. CAT activity significantly increased after Pb compound exposition.

Assessment of phytostabilization potential of two Salix L. clones based on the effects of heavy metals on the root anatomical traits

Willow species (Salix L.) are a useful tool for assessing phytostabilization of the sites polluted by heavy metals. Phytostabilization potential of two willow genotypes (Salix alba L. clone '68/53/1' and Salix nigra Marshall clone '0408') has been evaluated in a 45-day hydroponic experiment, using stem cuttings (diameter 12 to 14 mm, length 20 cm) exposed to two concentrations (10^-4 M and 10^-5 M) of individually applied Cd, Ni, and Pb. Metals were diluted in 25% Hoagland's solution, in forms of CdCl₂·H₂O, NiSO₄·6H₂O, and Pb-EDTA. The control group of cuttings was grown in 25% Hoagland's solution without heavy metals. High Cd concentrations in willow roots, 8637 mg/kg (clone '68/53/1') and 6728 mg/kg of dry weight (clone '0408'), have indicated a high phytostabilization potential. However, detailed analyses of cross-sectional area of the root cortex and the central cylinder revealed that the excess concentration of Cd led to a significant reduction of measured anatomical root's traits of clone '68/53/1' in comparison with the control samples. Excessive concentration of Ni and Pb in nutrient solution increased the values of quantitatively measured root's traits of clone '0408', implying stimulatory effects of the applied concentrations. Concentration of 10^-4 M of each metal had more negative effects on the roots' anatomical traits, notably on parenchymal and exodermal cells and vessels. Deposits of metals were observed in root tissues. Clone '0408' demonstrated an increased tolerance to heavy metals, which could potentially make this clone useful in phytostabilization.

Influence of nitrogen availability on Cd accumulation and acclimation strategy of Populus leaves under Cd exposure

Nitrogen (N) plays crucial roles in chlorophyll concentration, photosynthesis, and stress tolerance of plant leaves. This study conducted a greenhouse experiment combined with Cd and N treatments to elucidate the mechanism underlying the influence of N on Cd accumulation and acclimation strategy in Populus leaves. Chlorophyll concentration and net photosynthetic rates (A) in leaves were unaltered by Cd exposure regardless of N condition. Nitrogen availability alter acclimation strategy of poplar leaves under cadmium exposure. Under sufficient N, Cd accumulation in leaves was elevated with increased intensity and duration of Cd exposure; Cd accumulation reached ca. 28 μg g^-1 dry weight and 260 μg plant^-1 after 60 days of exposure to high level of Cd (20 mg Cd kg^-1 soil), and this finding indicates a large potential for Cd phytoextraction. Poplar leaves exhibited high capacity for antioxidant defense and stress tolerance and avoided oxidative damage under high Cd exposure. The levels of phytohormones and antioxidants in leaves and the relative expressions of critical genes encoding antioxidant enzymes were up-regulated under sufficient N condition. Nitrogen deficiency decreased chlorophyll concentration and net photosynthetic rates (A) and interfered with the production of N metabolites, resulting in a low level of phytohormones and antioxidants that are responsible for stress tolerance. The low levels of Cd accumulation in leaves may be a self-protecting strategy to prevent severe oxidative damage due to the decreased capacities for stress tolerance under N deficiency.

Physiological and molecular mechanisms of heavy metal accumulation in nonmycorrhizal versus mycorrhizal plants

Uptake, translocation, detoxification, and sequestration of heavy metals (HMs) are key processes in plants to deal with excess amounts of HM. Under natural conditions, plant roots often establish ecto- and/or arbuscular-mycorrhizae with their fungal partners, thereby altering HM accumulation in host plants. This review considers the progress in understanding the physiological and molecular mechanisms involved in HM accumulation in nonmycorrhizal versus mycorrhizal plants. In nonmycorrhizal plants, HM ions in the cells can be detoxified with the aid of several chelators. Furthermore, HMs can be sequestered in cell walls, vacuoles, and the Golgi apparatus of plants. The uptake and translocation of HMs are mediated by members of ZIPs, NRAMPs, and HMAs, and HM detoxification and sequestration are mainly modulated by members of ABCs and MTPs in nonmycorrhizal plants. Mycorrhizal-induced changes in HM accumulation in plants are mainly due to HM sequestration by fungal partners and improvements in the nutritional and antioxidative status of host plants. Furthermore, mycorrhizal fungi can trigger the differential expression of genes involved in HM accumulation in both partners. Understanding the molecular mechanisms that underlie HM accumulation in mycorrhizal plants is crucial for the utilization of fungi and their host plants to remediate HM-contaminated soils.