Effect of hesperidin on growth, photosynthesis, antioxidant systems and uptake of cadmium, copper, chromium and zinc by Celosia argentea plants.

Rapid industrialization and extensive agricultural practices are the major causes of soil heavy metal contamination, which needs urgent attention to safeguard the soils from contamination. However, the phytotoxic effects of excessive metals in plants are the primary obstacle to efficient phytoextraction. The present study evaluated the effects of hesperidin (HSP) on metals (Cu, Cd, Cr, Zn) phytoextraction by hyperaccumulator (Celosia argentea L.) plants. For this purpose, HSP, a flavonoid compound with strong antioxidant potential to assist metal phytoextraction was used under metal stress in plants. Celosia argentea plants suffered significant (P ≤ 0.001) oxidative damage due to the colossal accumulation of metals (Cu, Cd, Cr, Zn). However, HSP supplementation notably (P ≤ 0.001) abated ROS generation (O2•‒, •OH, H2O2), lipoxygenase activity, methylglyoxal production, and relative membrane permeability that clearly indicated HSP-mediated decline in oxidative injury in plants. Exogenous HSP improved (P ≤ 0.001) the production of non-protein thiol, phytochelatins, osmolytes, and antioxidant compounds. Further, HSP enhanced (P ≤ 0.001) H2S and NO endogenous production, which might have improved the GSH: GSSG ratio. Consequently, HSP-treated C. argentea plants had higher biomass alongside elevated metal accumulation mirrored as profound modifications in translocation factor (TF), bioaccumulation coefficient (BAC), and bioconcentration factor (BCF). In this context, HSP significantly enhanced TF of Cr (P ≤ 0.001), Cd (P ≤ 0.001), and Zn (P ≤ 0.01), while BAC of Cr (P ≤ 0.001), Cd (P ≤ 0.001), and Zn (P ≤ 0.001). Further, BCF was significant (P ≤ 0.05) only in plants grown under Cr-spiked soil. Overall, HSP has the potential for phytoremediation of metals by C. argentea, which might be a suitable strategy for metal-polluted soils.

Effect of exogenous taurine on growth, oxidative defense, and nickel (Ni) uptake in canola (Brassica napus L.) under Ni stress.

Nickel (Ni) contamination and its associated hazardous effects on human health and plant growth are ironclad. However, the potential remedial effects of taurine (TAU) on Ni-induced stress in plants remain obscure. Therefore, the present study was undertaken to examine the effect of TAU seed priming (100 and 150 mg L‒1) as an alleviative strategy to circumvent the phytotoxic effects of Ni (150 mg kg‒1) on two canola cultivars (Ni-tolerant cv. Shiralee and Ni-sensitive cv. Dunkeld). Our results manifested an apparent decline in growth, biomass, photosynthetic pigments, leaf relative water content, DPPH free radical scavenging activity, total soluble proteins, nitrate reductase activity, and nutrient acquisition (N, P, K, Ca) under Ni toxicity. Further, Ni toxicity led to a substantial increase in oxidative stress reflected as higher levels of superoxide radicals (O2•‒) and hydrogen peroxide (H2O2) alongside increased relative membrane permeability, lipoxygenase (LOX) activity, and Ni accumulation in leaves and roots. However, TAU protected canola plants from Ni-induced oxidative damage through the amplification of hydrogen sulfide (H2S) production that intensified the antioxidant system to avert O2•‒, H2O2, and malondialdehyde (MDA) production. Further, TAU-mediated increase in H2S levels maintained membrane integrity that might have improved ionomics and bettered plant growth under Ni toxicity. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01359-9.

Effects of exogenous taurine on growth, photosynthesis, oxidative stress, antioxidant enzymes and nutrient accumulation by Trifolium alexandrinum plants under manganese stress.

Plants essentially require manganese (Mn) for their normal metabolic functioning. However, excess Mn in the cellular environment is detrimental to plant growth, development, and physio-biochemical functions. Taurine (TAU) is an amino acid with potent antioxidant and anti-inflammatory properties in animals and humans. However, no previous study has investigated the potential of TAU in plant metal stress tolerance. The current study provides some novel insights into the effect of TAU in modulating the defense system of Trifolium alexandrinum plants under Mn toxicity. Manganese toxicity resulted in higher oxidative stress and membrane damage through increased superoxide radical, hydrogen peroxide, malondialdehyde, and methylglyoxal generation alongside enhanced lipoxygenase (LOX) activity. Mn toxicity also resulted in limited uptake of potassium (K+), phosphorus (P), calcium (Ca2+), and increased the accumulation of Mn in both leaf and roots. However, TAU circumvented the Mn-induced oxidative stress by upregulating the activities of antioxidant enzymes (ascorbate peroxidase, peroxidase, catalase, glutathione reductase, glutathione-S-transferase, and superoxide dismutase) and levels of ascorbic acid, proline, anthocyanins, phenolics, flavonoids and glutathione (GSH). Taurine conspicuously improved the growth, photosynthetic pigments, hydrogen sulphide (H2S), and nitric oxide (NO) levels of Mn stressed plants. Taurine also improved the uptake of K+, Ca2+, P and reduced the Mn content in stressed plants. Overall, exogenous taurine might be a suitable strategy to combat Mn stress in T. alexandrinum plants but applications at field levels for various crops and metal toxicities and economic suitability need to be addressed before final recommendations.

Effect of different seed priming agents on chromium accumulation, oxidative defense, glyoxalase system and mineral nutrition in canola (Brassica napus L.) cultivars.

The present experiment was conducted to appraise the role of different seed priming agents in circumventing the negative impact of chromium (Cr) toxicity on canola plants. Chromium toxicity resulted in significant decline in photosynthetic pigments and growth attributes of two canola cultivars (Puriga and MS-007). Cr toxicity also resulted in higher oxidative stress mirrored as greater accumulation of hydrogen peroxide (H2O2) superoxide radical (O2•‒), electrolyte leakage (EL) and malondialdehyde (MDA). Further, lipoxygenase enzyme activity that catalyzes the peroxidation of membrane lipids was also enhanced due to Cr toxicity. Canola plants also manifested impaired methylglyoxal (MG) detoxification due to the downregulation of glyoxalase enzymes (GlyI and II) under Cr stress. Seed priming treatments viz. osmo-priming with calcium chloride (CaCl2) and hormonal priming with salicylic acid (SA) remarkably improved growth and chlorophyll content in both canola cultivars under Cr toxicity as compared to other priming treatments such as hydro-priming, redox priming (H2O2) and chemical priming (Se; selenium). Moreover, CaCl2 and SA seed priming also resulted in lower oxidative stress and improved enzymatic (SOD, POD, CAT, APX, GR, GST) and non-enzymatic (GSH, phenolics, flavonoids, proline) antioxidant system of both cultivars under Cr toxicity. Further, hormonal and osmo-priming strengthened glyoxalase and antioxidant systems, thus improving reactive oxygen species (ROS) and MG detoxification. In this background, the cultivar Puriga is considered Cr tolerant as it exhibited better growth and lesser oxidative stress in both seed priming and non-primed conditions under Cr toxicity than cv. MS-007.

Environmental impact and economic sustainability analysis of a novel anaerobic digestion waste-to-energy pilot plant in Pakistan.

A novel medium-large industrial-scale, anaerobic digestion (AD) waste-to-energy pilot plant has been investigated in terms of cost-benefit, environmental impact, and economic sustainability. This pilot plant exclusively features a multi-digester AD system induced by motorized stirring, methane purification, compression, storage and digestate-fertilizer processing systems, and subsequent electricity generation. The operational productivity and success of the pilot plant has been proven on a variety of waste feedstock substrates in the form of cow-buffalo manure and potato waste. The plant has an average energy productivity of 384 kWh/day and an annual rate of return was estimated to be 15.4%. The life cycle environmental impact analysis deliberated the significant impact potentials in terms of climate change (kg CO2 equivalent), and fossil depletion (kg of oil equivalent) for three selected substrates: 100% cow-buffalo manure (CBM), 100% potato waste (PW), and a mixture of 75% CBM and 25% PW. The results show the climate change potential of 70 kg, 71 kg, and 149 kg and fossil depletion potential of - 2.43 kg, - 16.45 kg, and 18 kg per 2000 kg of substrate slurry, respectively. As such, the substrate of 100% CBM posed the least climate change impacts whereas 100% PW has been established most effective under the fossil depletion category.

Phenological application of selenium differentially improves growth, oxidative defense and ion homeostasis in maize under salinity stress.

The underlying mechanism of selenium (Se) mediating plant salt tolerance is not well understood and information on how plant growth and development is regulated by phenological Se application (20 and 40 mg/L) under salinity stress is scarce. In present study, we have appraised the impact of phenological Se application on growth, antioxidant defense system and ionic imbalance in maize under salinity. Salinity (12 dS m-1) reduced growth, concentration of chlorophyll and K+ in root and leaf. Contrarily, salinity increased toxic Na+, malondialdehyde (MDA) and H2O2 concentration that resulted in oxidative damage. Lower level of Se application (20 mg/L) increased growth and chlorophyll by reducing oxidative damage due to high cell concentrations of MDA and H2O2. Se reduced endogenous levels of H2O2 and MDA under salinity. Moreover, Se regulated antioxidant defense system by increasing the activities of antioxidant enzymes (SOD, POD and CAT) and influenced the concentrations of non-enzymatic antioxidants (phenolics and flavonoids). Se-induced better antioxidant system protected plants from oxidative damage. We have also recorded substantial increase in K+ and decrease in Na+ concentration in plants treated with 20 mg/L Se under salinity stress. The impact of Se on plant growth and development is linked with the growth stage of exogenous application. Foliar Se at reproductive and both vegetative and reproductive stages improved salinity tolerance in maize compared with vegetative stage.

Exogenously applied selenium reduces oxidative stress and induces heat tolerance in spring wheat.

Heat stress (HS) is a worldwide threat to productivity of wheat, especially in arid and semiarid regions of the world. Earlier studies suggested the beneficial effects of selenium (Se) on the growth of some crop species grown under stressful environments. In the present study, we assessed whether Se application could increase antioxidative potential, and thus enhance tolerance to heat in wheat at the sensitive stage i.e., heading stage. At the heading stage, after foliar application of sodium selenate solutions (0, 2 and 4 mg Se L(-1)), the plants of wheat cultivars, namely Chakwal-97 (drought tolerant) and Faisalabad-08 (drought sensitive), were subjected to HS (38 ± 2 °C). The HS significantly altered antioxidative potential, affected growth, photosynthetic pigments and grain yield in both cultivars. Exogenous application of low (2 mg L(-1)) Se increased chlorophyll a and total chlorophyll contents and modulated the growth of wheat plants under HS. However, high concentration (4 mg L(-1)) of Se was much more effective in increasing grains per spike and grain yield in heat stressed plants of both wheat cultivars. Exogenous Se increased both enzymatic (catalase and ascorbate peroxidase activities) and non-enzymatic (carotenoids, anthocyanins and ascorbic acid contents) antioxidants while decreased oxidants (hydrogen peroxide and malondialdehyde contents) under HS in both wheat cultivars. In conclusion, foliar application of Se (4 mg L(-1)) was much more effective in mitigating the deleterious effects of HS on grain yield of wheat plants. The results suggested that Se-mediated up-regulation of antioxidative system (both enzymatic and non-enzymatic) helped the wheat plants to increase fertility, and hence avoid reduction of grain yield under HS.