Foliar spray of stress protective chemicals alleviates cobalt toxicity by improving root antioxidant defense in maize (Zea mays).

Cobalt (Co2+) is a beneficial microelement for plants but toxic to metabolism in higher amounts. This study determined the influence of sublethal Co2+ level (0.5 mM) on the growth of maize (Zea mays L.) hybrids; Hycorn 11 plus (Co2+ sensitive) and P-1429 (Co2+ tolerant) and its alleviation with foliar spray of pre-optimized levels of stress protective chemicals (SPCs), i.e., salicylic acid (SA, 0.5 mM), thiourea (TU, 1.0 mM), and ascorbic acid (AsA, 0.5 mM) applied at seedling, vegetative, and late vegetative stages. Plants were harvested at early vegetative, late vegetative, and silking stages. Co2+ stress caused a decrease in shoot and root length, dry weight, leaf area, and culm diameter, reduced the activities of enzymatic antioxidants and concentrations of AsA and soluble phenolics more in root than shoot, but P-1429 was more tolerant of Co2+ than Hycorn 11 plus. SPCs spray alleviated oxidative damage by enhancing the antioxidant activity, AsA and soluble phenolics, sulfate-S and nitrate-N contents, which were significantly increased in roots than in shoots; P-1429 displayed better response than Hycorn 11 plus. Principal component analysis and correlation matrix revealed the profound roles of SPCs spray in improving Co2+ resistance in root leading to robust growth of hybrids. AsA was highly promising in reducing Co2+ toxicity while vegetative and silking stages were more sensitive. Results revealed that after translocation to root, the foliar-applied SPCs had individualistic modes of action in mitigating Co2+ toxicity on roots. In crux, the metabolism and phloem transport of the SPCs from shoot to root are plausible mechanism for Co2+ tolerance in maize hybrids.

Glutathione treatment suppresses the adverse effects of microplastics in rice.

Oryza sativa is grown worldwide and exhibit sensitivity to different stresses. Exponential increase in microplastics in agroecosystems is damaging and demand pragmatic strategies to protect growth and yield losses. We evaluated exogenous application of different doses of glutathione (GSH) for mediation of physiological traits of rice plants experiencing two different MPs i.e. PET and HDPE in root zone. All the rice seedlings exhibited MP-induced significant (P ≤ 0.001) growth inhibition compared to the control plants. GSH application (T3) significantly increased the shoot fresh weight (8.80%), root fresh weight (19.22%), shoot dry weight (13.705%), root dry weight (25.52%), plant height (5.75%) and 100-grain weight (9.36%), compared to control plants. GSH treated plants (T4) showed a recovery mechanism by managing the marginal rate of reduction of all photosynthetic and gas exchange attributes by showing 34.44, 20.98, 34.83, 42.16, 39.70, and 51.38% reduction for Chl-a, Chl-b, total cholophyll, photosynthetic rate (A), transpiration rate (E), and stomatal conductance (Gs), respectively, compared to control plants. Under 5 mg L-1 HDPE and PET, rice seedlings without GSH treatment responded in terms of increase in total soluble sugar, total free amino acid, glutathione, glutathione disulfide contents, while total soluble protein and ascorbic acid contents decreased significantly, compared with control plants. Corrleation matrix revealed positive relationship between GSH and improvement in studied attributes. Moreover, exogenous GSH improved rice growth and productivity to counter the negative role of MPs. This unique study examined the effects of GSH on rice plants growing in MP-contaminated media and revealed how exogenous GSH helps plants survive MP-stress.

Interactive effects of polystyrene microplastics and Pb on growth and phytochemicals in mung bean (Vigna radiata L.).

Interaction of different pollutants can aggravate hazards to biotic components in agroecosystems. Microplastics (MPs) are especially needed to be focused on because of their increasing use in life around the globe. We investigated the interactive impacts of polystyrene microplastics (PS-MP) and lead (Pb) on mung bean (Vigna radiata L.). Toxicity of MPs and Pb directly impeded V. radiata attributes. In combination i.e., M2P2 (40 µM Pb + 4.0 mg L-1 MPs) predominantly reduced the shoot root fresh and dry weights. \ Pb and PS-MP impaired the Rubisco activity and chlorophyll contents. The dose dependent relationship (M2P2) discomposed indole 3-acetic acid by 59.02%. Individual treatments P2 (40 µM Pb) and M2 (4.0 mg L-1 MPs) respectively instigated a decline (44.07% and 27.12%) in IBA, while ABA was elevated. M2 significantly enhanced the contents of Alanine (Ala), Arginine (Arg), Proline (Pro), and glycine (Gly) by 64.11%, 63%, and 54% compared to control. Lysine (Lys) and Valine (Val) presented a converse relationship with other amino acids. Except for control, a gradual decline in yield parameters were observed in individual and combined applications of PS-MP. Proximate composition of carbohydrates, lipids and proteins also reflected a clear decrease in these compounds after combined application of Pb and MPs. Although, individual doses caused a decline in these compounds but effect of combined doses Pb and PS-MP was highly significant. Our results demonstrated the toxicity effect of Pb and MP in V. radiata attributes that is mainly linked with cumulative physiological and metabolic perturbations. These collective negative impacts of different doses of MPs and Pb on V. radiata would certainly pose serious implications for humans.

Ecological health risk assessment of microplastics and heavy metals in sediments, water, hydrophytes (Alternanthera philoxeroides, Typha latifolia, and Ipomoea carnea), and fish (Labeo rohita) in Marala wetlands in Sialkot, Pakistan.

For the ecological risk assessment of heavy metals and microplastics in Marala wetlands in Sialkot, Pakistan, samples of sediments, water, aquatic plants (Alternanthera philoxeroides, Typha latifolia, and Ipomoea carnea), and fish (Labeo rohita) were studied from five different locations. Pb, Cd, and Cr concentrations were above permissible limits devised by WHO in sediments and water at most of sites. High concentrations of Cd were recorded in water samples compared to sediments with maximum values recorded at Site-2 (52.08 ± 9.55 mg kg-1) and Site-5 (62.29 ± 10.12 mg kg-1). The maximum concentrations of Cr (7.23 ± 0.40 mg kg-1) and Pb (22.87 ± 0.83 mg kg-1) were found at Site-4 in water samples. The maximum abundance of microplastics (3047 pieces kg-1 of sediments) was at Site-1 with filaments in the highest proportion among the other types. Zn, Ni, and Cu remained generally low in concentrations in both sediments and waters. Plants showed accumulation of heavy metals, notably the amount of Cd (33.36 ± 0.26 mgkg-1) and Ni (163.3 ± 1.30 mgkg-1) absorbed by T. latifolia and A. philoxeroides, respectively were high. Also, photosynthetic pigments in plants seemed to be affected. However, estimated daily intake (EDI) and provisional tolerable weekly intake (PTWI) calculations for the human population consuming fish from this wetland remained below the FAO/WHO limits. PCA analysis revealed the anthropogenic origin of metals that might be causing adverse effects on the biota which depend on this wetland for their food.

Nerium oleander could be used for sustainable management of traffic-borne elemental-enriched roadside soils.

Metal pollutants released from motor vehicles are deposited in roadside environments. Metals are non-biodegradable and biomagnify in the food chain causing significant health hazards at all levels of the ecosystem. Hence, management of contaminated roadside verges is critically important and should be kept in mind while planning specific management strategies of such areas. Native vegetation could help to decontaminate heavy metal polluted soils in the best sustainable way. Therefore, this study was designed to assess the potential of Nerium oleander to accumulate heavy metals commonly released by automobiles such as Pb, Cd, Ni, and Zn along with various C and N compounds from five different locations along a busy road in Punjab, Pakistan, during summer and winter seasons. N. oleander showed the ability to absorb C, N, and heavy metals Pb and Cd; the maximum concentration of Pb and Cd was 8.991 mg kg-1 and 0.599 mg kg-1, respectively. These pollutants negatively affected photosynthetic pigments, gas exchange attributes, soluble proteins, and free amino acids. But antioxidant activity of N. oleander was found to be increased in both seasons. The metal accumulation in the plant was higher in the summer though. We highly recommend that by growing N. oleander at roadside verges for decontamination of vehicular pollutants could lead to sustainable management of these corridors.

Foliar application of silver nanoparticles mitigated nutritional and biochemical perturbations in chilli pepper fertigated with domestic wastewater.

Due to environmental pollution, crop growth and productivity are threatened at different levels. Recapitulation of changes in plant bodies due to water pollution and mitigating strategies reveal the need for précised actions to save crop losses. The present study was carried out to estimate modulations in growth, mineral homeostasis, and nutrient profile of fruits in Capsicum annum L. grown with three concentrations of wastewater (25, 50, 100%) and two levels of silver nanoparticles (40 and 80 mg/L AgNPs). It has been reported that ion accumulation patterns from wastewater clearly vary among crops. Our findings manifested that the application of AgNPs significantly improved the mineral ions in different plant tissues, that ultimately helped to improve growth. Highest improvements were recorded for root shoot P (316 and 197%) at T9 (80 mg/L AgNPs + normal water), while K (273 and 262%), Mg (638 and 916%), and Ca (148 and 273%), at T11 (80 mg/L AgNPs + 50% Wastewater), in comparison with control. Such reduction in elemental uptake that remain detrimental even at low concentrations positively correlates with growth and nutrition of Capsicum plants. Another facet of our observation is dose-dependent improvement in nutritive attributes of fruits i.e., crude fibers, proteins, and carbohydrates by AgNPs. T8 (40 mg/L AgNPs + 100% Wastewater), improved nutritional attributes such as P (55%), Mn (44%), Zn (38%), Carbohydrates (62%), Crude fat (38%), and Fibers (49%) as compared to control. Application of silver nanoparticles (AgNPs) combined with untreated wastewater (WW) reduced the hazards of contaminants in plants. The finding of the current study suggested that AgNPs are a cost-efficient and environment friendly material having the potential to mitigate harmful impacts of WW on plants.

Effects of microplastics on growth and metabolism of rice (Oryza sativa L.).

Present work studied the impact of different doses of polystyrene (PS) and polyvinyl chloride (PVC) microplastics (MPs) on rice plants (Oryza sativa L.). Seven different treatments of PS and PVC MPs viz. D0 (control), D1-D3 (0, 1.5, and 3.0 mg L-1 PS-MP) and D4-D6 (0, 1.5, and 3.0 mg L-1 PVC-MP) were given. In the experiment, sequential variations in growth, ionic homeostasis, and antioxidant metabolism in rice were monitored. Results show that compared to control, maximum repression in shoot and root and fresh and dry weight were recorded in D6. We demonstrate that D3 and D6 reduced the photosynthetic rate up to 31.49 and 43.81% compared to D0 while the transpiration rate was enhanced only under controlled conditions. Water use efficiency and internal CO2 concentration increased due to incremented doses of MPs. Decline in photosynthetic attributes directly corresponded with reduction in SPAD value (34.96%) at D6. Besides, ionic homeostasis was perturbed and concentration of Ca, N, P, and K in root and shoot was imbalanced due to all levels of MPs and D3 and D6 were found most hazardous for these attributes. The resultant oxidative stress caused increment in MDA (49.26 and 138.44%) and H2O2, (66.72 and 125.18%) at D3 and D6, respectively. The maximum increase in SOD (109.08 and 146.08%), POD (232.59 and 289.23%), and CAT (182.65 and 242.89%) was estimated under D3 and D6, respectively as compared to control. Therefore, we concluded that PVC-MPs accumulation is potentially more devastating for rice growth and metabolism than PS-MPs. We recommend further research experimentats not only for translocation but also for tissue-specific retention of different sized MPs in crop plants to completely understand their influence on food safety.