The use of plant growth-promoting microorganisms is an effective agricultural practice to improve plant growth, especially under abiotic stress. In this study, the combined impact of three plant growth-promoting bacteria (PGPB) namely Brevibacterium halotolerans (Sd-6), Burkholderia cepacia (Art-7), Bacillus subtilis (Ldr-2) were tested with Trichoderma harzianum (Th) (possessing ACC deaminase producing activity) in Ocimum basilicum L. cv. Saumya to reduce drought-induced damages to the plants under different level of drought stress [i.e. wellwatered (100 %), moderate (60 %), severe (40 %)]. These PGPB strains, along with Th, were found to be tolerant against osmotic stress when tested in growth media containing different concentrations of polyethylene glycol (PEG 8000), and all were found to endure -0.99 MPa water potential. Compared to non-inoculated control, Th+Ldr-2 treatment improved fresh herb weight (62.45 %) and oil content (61.54 %) and higher photosynthetic rate under severe drought. Besides, in relation to control, the above treatment enhanced nutrient uptake, reduced ABA, ACC as well as ethylene levels and increased IAA content in addition to an increase in important constituents of essential oil, indicating better performance in terms of plant growth under drought. Higher RWC, decreased MDA, and reduced antioxidant activities in Th+Ldr-2 treated plants compared to non-inoculated control under drought support the mechanism of the microbes providing tolerance against drought. Colony forming unit of microbes and scanning electron microscopy (SEM) study support the effective colonisation behaviour of Th+Ldr-2, which protects plants against drought stress. A consortium of diverse microbes, found to improve plant growth under drought through increased nutrient uptake, reducing the levels of ACC and ABA, improving the content of IAA, antioxidant enzymes probably reducing the effect of drought stress and improving plant biomass could be a useful tool to reduce drought-induced losses in crop plants.

This study aimed to evaluate ozone (O3) phytotoxic potential using AOT40F (accumulated O3 concentration over a threshold of 40 ppb for forest protection), document visible foliar O3 injury across eight forest monitoring plots, analyse MDA (malondialdehyde) content in leaves and needles, and assess the relationship between visible injury and plot conditions. Initial findings are based on data from the 2021 and 2022 vegetation seasons. AOT40F values exceeded the critical level of 5 ppmh-1 at all plots, with higher values in 2022. The correlation between AOT40F and visible injury was inconsistent; in 2021, minimal visible O3 injuries were observed, while these were more frequent in 2022, notably on Fagus sylvatica leaves. The altitude effect on O3 concentration indicates greater vegetation damage at higher altitudes. In contrast, the AOT40F-altitude relation was not significant. The 2021 vegetation season was characterised by lower temperatures and higher relative air humidity and soil moisture in comparison to 2022. Stomatal conductance conditions were similar in both years, except for lower soil moisture in 2022. Soil moisture, air humidity, and temperature together accounted for about 50% of the variance in visible injury in 2022. The findings suggest that the AOT40F capability for predicting damage to vegetation is limited and highlight the importance of future research focusing on stomatal O3 flux-based approaches.

Lead is one of the major environmental pollutants which is highly toxic to plants and living beings. The current investigation thoroughly evaluated the synergistic effects of oxalic acid (OA) and salicylic acid (SA) on Zea mays L. plants subjected to varying durations (15, 30, 30, and 45 days) of lead (Pb) stress. Besides, the effects of oxalic acid (OA) combined with salicylic acid (SA) for different amino acids at various periods of Pb stress were also investigated on Zea mays L. The soil was treated with lead nitrate Pb (NO3)(2) (0.5 mM) to induce Pb stress while the stressed plants were further treated using oxalic acid (25 mg/L), salicylic acid (25 mg/L), and their combination OA + SA (25 mg/L each). Measurements of protein content, malondialdehyde (MDA) levels, guaiacol peroxidase (GPOX) activity, catalase (CAT) activity, GSH content, and Pb concentration in maize leaves were done during this study. MDA levels increased by 71% under Pb stress, while protein content decreased by 56%, GSH content by 35%, and CAT activity by 46%. After treatment with SA, OA, and OA+SA, there was a significant reversal of these damages, with the OA+SA combination showing the highest improvement. Specifically, OA+SA treatment led to a 45% increase in protein content and a 39% reduction in MDA levels compared to Pb treatment alone. Moreover, amino acid concentrations increased by 68% under the Pb+OA+SA treatment, reflecting the most significant recovery (p < 0.0001).

Environmental pollutants act as stressors for plants, inducing different stresses like physiological changes, variation in nutritional value, biochemical stress and photosynthetic blockage, and food loss. Phthalate esters are one of the environmental pollutants most commonly used as plasticizers in packaging materials. They leach out into the soil and accumulate in plants via root take-up. The present research work was carried out to check the phytotoxic effect of dibutyl phthalate, dimethyl phthalate, diethyl phthalate, and di-n-octyl phthalate, their exposure to Malondialdehyde contents, and the consequent impact on the total phenolic content of edible parts of plants. The edible plants tomato (Solanum lycopersicum), lettuce (Lactuca sativa), radish (Raphanus sativus), turnip (Brassica rapa subsp. rapa), spinach (Spinacia oleracea), coriander (Coriandrum sativum), cabbage (Brassica oleracea), cauliflower (Brassica oleracea var. botrytis), and carrot (Daucus carota subsp. sativus) were exposed to 0, 10, and 20pbb of all four phthalate esters. After 10 days of exposure, TPC and MDA contents were analyzed spectrophotometrically. The exposure of phthalate esters significantly increased TPC in leaves, and MDA in the root and leaves of plants, except that of DnOP which decreased MDA content in radish leaves.

Chromium (Cr) contamination in soils reduces crop yields and poses a remarkable risk to human and plant system. The main objective of this study was to observe the protective mechanisms of exogenously applied melatonin (Mel- 0.05, 0.1, and 0.15 mu M) in seedlings of Brassica juncea L. under Cr (0.2 mM) stress. This was accomplished by analysing the plant ' s morpho-physiological, biochemical, nuclear, membrane, and cellular characteristics, as well as electrolyte leakage. Superoxide, malondialdehyde, and hydrogen peroxide increased with Cr toxicity. Cr also increased electrolyte leakage. Seedlings under Cr stress had 86.4% more superoxide anion and 27.4% more hydrogen peroxide. Electrolyte leakage increased 35.7% owing to Cr toxicity. B. juncea L. cells with high radical levels had membrane and nuclear damage and decreased viability. Besides this, the activities of the antioxidative enzymes, as POD, APOX, SOD, GST, DHAR, GPOX and GR also elevated in the samples subjected to Cr toxicity. Conversely, the activity of catalase was downregulated due to Cr toxicity. In contrast, Mel reduced oxidative damage and conserved membrane integrity in B. juncea seedlings under Cr stress by suppressing ROS generation. Moreover, the activity of antioxidative enzymes that scavenge reactive oxygen species was substantially upregulated by the exogenous application of Mel. The highest concentration of Mel (Mel c- 0.15 mu M) applied showed maximum ameliorative effect on the toxicity caused by Cr. It causes alleviation in the activity of SOD, CAT, POD, GPOX, APOX, DHAR, GST and GR by 51.32%, 114%, 26.44%, 48.91%, 87.51%, 149%, 42.30% and 40.24% respectively. Histochemical investigations showed that Mel increased cell survival and reduced ROS-induced membrane and nuclear damage. The findings showed that Mel treatment upregulated several genes, promoting plant development. Its supplementation decreased RBOH1 gene expression in seedling sunder stress. The results supported the hypothesis that Mel concentrations reduce Cr-induced oxidative burst in B. juncea.

Background: Arsenic (As) is a highly toxic and carcinogenic pollutant commonly found in soil and water, posing significant risks to human health and plant growth. Objective: The objectives of this study to evaluate morphological, biochemical, and physiological markers, as well as ion homeostasis, to alleviate the toxic effects of As in sunflowers through the exogenous application of salicylic acid (SA), gamma-aminobutyric acid (GABA), and their combination. Methods: A pot experiment was conducted using two sunflower genotypes, FH-779 and FH-773, subjected to As stress (60 mg kg(-1)) to evaluate the effects of SA at 100 mg L-1, GABA at 200 mg L-1, and their combination on growth and related physiological and biochemical attributes under As stress. Results: The study revealed that As toxicity had a detrimental effect on various growth parameters, chlorophyll pigments, relative water content, total proteins, and nutrient uptake in sunflower plants. It also led to increased oxidative stress, as indicated by higher levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2), along with As accumulation in the roots and leaves. However, the application of SA and GABA protected against As-induced damage by enhancing the enzymatic antioxidant defense system. This was achieved through the activation of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities, as well as an increase in osmolytes. They also improved nutrient acquisition and plant growth under As toxicity. Conclusions: We investigated the regulatory roles of SA and GABA in mitigating arsenic-induced phytotoxic effects on sunflower. Our results revealed a significant interaction between SA and GABA in regulating growth, photosynthesis, metabolites, antioxidant defense systems, and nutrient uptake in sunflower under As stress. These findings provide valuable insights into plant defense mechanisms and strategies to enhance stress tolerance in contaminated environments. In the future, SA and GABA could be valuable tools for managing stress in other important crops facing abiotic stress conditions.

Soil salinization has become a major obstacle to sustainable melon production, and single-measure approaches have failed to improve crop yields and quality outcomes. In this study, we explore the effects and underlying mechanisms of a vermicompost (VC) treatment combined with silicon (Si) or salicylic acid (SA) on salt damage to muskmelon seedlings growing in moderately saline soil collected from a greenhouse. We evaluated the effects of four treatments: a control treatment (CK), 10% vermicompost (VC), 10% vermicompost combined with 0.04% Si (VC+Si), and 10% vermicompost combined with 100 mu mol/L salicylic acid (VC+SA). We found that vermicompost could alleviate salt damage and that the combination of vermicompost with exogenous Si or SA could amplify this effect. Compared to CK, plant height and shoot biomass were both greater when vermicompost was applied in combination with SA or Si. A chlorophyll fluorescence analysis indicated that a VC treatment can reduce damage to the PSII reaction center caused by salt stress, whereas it did not have a significant effect on Fv/Fm, Fv'/Fm' or qP. The PSII activity increased significantly under VC+SA and VC+Si compared to CK. We did not measure significant differences in the stomatal conductance, intercellular CO2, or transpiration rate under VC relative to CK, but the VC+Si and VC+SA treatments increased the net photosynthetic rate and intercellular CO2. Superoxide anion and malondialdehyde (MDA) levels were lower across all treatments relative to CK. Moreover, compared to VC, superoxide anion and MDA contents decreased significantly when VC was combined with Si or SA. Superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities increased significantly under the VC+SA treatment compared to the VC treatment group. Proline, soluble sugar and protein contents were higher in all treatment groups than in CK, with the highest values observed in the VC+SA treatment group. Combined with Si or SA, a VC treatment can profoundly strengthen salt tolerance and improve plant growth compared to the application of VC alone.

Alkaline stress is a major environmental factor that limits the growth and productivity of rose plants. Humic acid (HA) is a natural substance that has been shown to have various beneficial effects on plant growth and stress tolerance. Roses (Rosa hybrida L.) are among the world's most important and popular cut flowers, dominating the cut flower export market. This study investigated the effects of HA application on the physiological and biochemical properties of rose plants grown under alkaline conditions. A randomized complete design with three replicates was used. Each replicate consisted of two pots containing a single rose plant. Humic acid was applied at 0, 500, 1,000, and 2,000 mg L-1 through drenching at 15-day intervals for two months. Plants treated with 1,000 mg L-1 HA exhibited significantly higher levels of total protein, proline, catalase activity, guaiacol peroxidase activity, and antioxidant capacity. Control plants (receiving no HA) showed the highest levels of malondialdehyde and electrolyte leakage, indicating greater cellular damage. Plants treated with 500 mg L-1 HA displayed the highest sugar content and ascorbate peroxidase activity. Overall, the results of this study suggest that HA application can be an effective strategy to improve the tolerance of rose plants to alkaline stress and enhance their growth and productivity in alkaline soils.