Lavandula genus is a considerable medicinal plant in pharmaceutical and cosmetics industries. Considering increasing threat of drought in the world, it is important to identify genotypes which can tolerate drought. It is also important to characterize quantity and quality of essential oils, and tolerance indicators of these genotypes against drought stress. Therefore, an experiment was conducted in Gorgan University of Agricultural Sciences and Natural Resources, Iran, during 2017 and 2018, to investigate these factors. It was a factorial experiment based on randomized complete block design with two treatments, three genotypes (Lavandula angustifolia cv. Hidcote, Lavandula angustifolia cv. Munstead, and Lavandula stricta), and four levels of drought stress (irrigation regimes) (I₁: 100–90% (control), I₂: 80–70%, I₃: 60–50% and I₄: 30–40% of field capacity) which was done with three repetitions. Drought increased amount of proline in leaves, antioxidant activity, activity of catalase, peroxidase, ascorbate peroxidase, and superoxide enzymes, malondialdehyde content, total flavonoids, total phenol, total sugar and essential oil percentage. The PCA analysis of different irrigation regimes showed that in the first component, the best traits are antioxidant enzymes CAT, SOD, APX, while in the second component, only the trait Catalase is the best trait. The results of PCA analysis in lavender genotypes showed that L. stricta exhibits the most affected physiological changes while trying to adjust to changes in the water status of the environment, under the imposed conditions and shows the highest resistance. But it reduced dry weight of aerial parts, relative water content of leaves, and efficacy of essential oil. Lavandula stricta genotype had the highest amount of essential oil, but the highest dry weight of the aerial parts and essential oil yield were related to L. angustifolia cv. Hidcote and L. angustifolia cv. Munstead genotypes. In all evaluated genotypes, with increasing drought stress, monoterpene compounds were decreased and sesquiterpene compounds were increased. Totally it was shown that drought effect on evaluated traits depends on genotype and nature of traits; this indicates that by choosing drought-tolerant genotypes in breeding programs, high quantity and quality of essential oil, as well as tolerance to drought stress can be achieved.

Environmental issues are a pressing concern for modern societies, and the increasing levels of atmospheric CO₂ have led to global warming. To mitigate climate change, reducing carbon emissions is crucial, and carbon sequestration plays a critical role in this effort. Technologies for utilising CO₂ can be divided into two major categories: direct use and conversion into chemicals and energy, and indirect use as a carbon source for plants. While plants’ ability to absorb and store CO₂ makes them the best CO₂ sink, finding suitable urban areas for significant green spaces is a challenge. Green walls are a promising solution, as they require less land, provide more ecosystem services than horizontal systems do, and can contribute to reducing environmental problems. This study evaluates the conceptual potentials and limitations of urban biomass circulation in terms of energy production, food production, and CO₂ consumption, focusing on growth-promoting bacteria, urban agriculture, and vertical systems. The aim of this research is discovering new methods of carbon sequestration using multi-purpose green walls to achieve sustainable urban development and CO₂ reduction strategies to contribute to a more sustainable future.

Background: Rapid urbanization and population growth exert a substantial impact on the accessibility of drinking water resources, underscoring the imperative for wastewater treatment and the reuse of non-potable water in agriculture. In this context, green walls emerge as a potential solution to augment the purification of unconventional waters, simultaneously contributing to the aesthetic appeal and enjoyment of urban areas. This study aims to optimize water management in green walls by investigating the impact of bacterial strains on the biochemical properties and performance of the ornamental accumulator plant, Aptenia cordifolia, grown with various unconventional water sources. The experiments were designed as split plots based on a completely randomized block design with three replications. The main factor was recycled water with three levels (gray water, wastewater from the Kashfroud region of Mashhad, and urban water (control)). The sub-factor included different bacterial strains at four levels, composed of various bacteria combinations, (B1: Psedoumonas flucrecens + Azosporillum liposferum + Thiobacillus thioparus + Aztobactor chorococcum, B2: Paenibacillus polymyxa + Pseudomonas fildensis + Bacillus subtilis + Achromobacter xylosoxidans + Bacillus licheniform, B3: Pseudomonas putida + Acidithiobacillus ferrooxidans + Bacillus velezensis + Bacillus subtilis + Bacillus methylotrophicus + Mcrobacterium testaceum, and the control level without bacterial application (B0). Result: The findings revealed significant differences at the 5% probability level across all morphophysiological traits, including plant height, the number and length of lateral branches, growth index, and plant coverage. Moreover, superior morphophysiological traits were observed in plants cultivated in substrates inoculated with wastewater irrigation. Substrates inoculated with bacteria exhibited the highest relative water content (RWC) and chlorophyll levels, coupled with the lowest relative saturation deficit (RSD), electrolyte leakage (EL), and carotenoid levels. Furthermore, plant growth-promoting bacteria (PGPB), from a biochemical perspective, were associated with increased carbohydrates, total protein, and anthocyanin. They also contributed to controlling oxidative stress caused by free radicals by enhancing the activity of antioxidant enzymes, such as guaiacol peroxidase (GPX), polyphenol oxidase (PPO), ascorbate peroxidase (APX), and peroxidase (POD), while reducing catalase enzyme (CAT) activity. This led to increased resistance to stress, as evidenced by a decrease in malondialdehyde and proline levels. The study concludes that the MIX B3, being both ecofriendly and economical, represents an effective strategy for mitigating the adverse effects of wastewater on plants. Conclusion: This study showed that plant irrigation using wastewater increases the levels of proline, phenols and oxidative stress. However, the application of plant growth promoting bacteria (PGPB) reduced oxidative damage by increasing antioxidant activity and decreasing proline and phenol levels. These findings show the potential of bacterial treatments to improve plant growth and reduce adverse effects of recycled water irrigation.

Global warming, climate change, and drought are global issues. Thus, drought-tolerant and water-efficient plant species must be chosen. Selection helps maintain crop productivity. Arid-area xerophytic plant Lavandula coronopifolia Poir has little scientific research on its water use and drought tolerance. This study examined the biochemical and phytochemical changes in this plant after ABA treatment and drought stress. Specifically, we analyzed key physiological parameters (relative water content and biomass), biochemical markers (proline content, superoxide dismutase and catalase enzyme activities), and phytochemical components (essential oil composition including monoterpenes and sesquiterpenes). The drought stress treatments were applied at 50–60% and 30–40% of field capacity, while ABA was applied at concentrations of 15 and 30 µM. In low-water conditions, plant biomass and dry weight decreased. However, external ABA application increased RWC, proline, antioxidant response, essential oil percentage, and yield. It reduced drought’s negative effects. Additionally, principal component analysis (PCA) found that measured variables explained 88.42% of trait variance. Changes in essential oil composition, including increased oxygenated monoterpenes and sesquiterpene hydrocarbons, were considerable. Significant changes were noticed in linalool (30.76%), decanal (20.90%), linalyl acetate (21.39%), Kessane (11.50%), and Hexadecane (15.91%). These results are indicative of the excellent drought tolerance of L. coronopifolia and ABA-mediated adaptive strategies, and may provide a basis for future applications in agriculture and essential oil production under water-stress conditions.