Hasna Ellouzi

Water deficit strongly constrains sesame growth and productivity, highlighting the need for sustainable strategies to maintain plant performance under limited water availability. Although silicon (Si) and seaweed extracts have been reported to improve plant responses to abiotic stress, the effects of their application as seed priming agents, particularly in combination, on subsequent PSI and PSII performance in sesame under water deficit remain insufficiently characterized. This study aimed to evaluate whether seed priming with silicon treatment (Si; nominal 4 mM SiO₂), Sargassum muticum extract (SWE; 10%), or their combination improves sesame tolerance to water deficit, with particular emphasis on growth, water status, gas exchange, photosynthetic pigments, and PSI and PSII performance. The experiments were carried out in greenhouses under well-watered and water-deficit conditions (80% and 40% field capacity (FC), respectively). We assessed plant growth, leaf relative water content (LRWC), photosynthetic pigments, gas exchange, and PSI and PSII activities. Water deficit strongly reduced shoot and root growth and significantly decreased chlorophyll content, photosynthetic efficiency, and biomass. Seed priming considerably reduced these negative impacts. Si priming and SWE priming alone significantly enhanced shoot length (by 62% and 72%, respectively) relative to unprimed water-deficit-stressed plants. Under water deficit, SWE priming produced the strongest chlorophyll response, increasing chlorophyll a, chlorophyll b, and total chlorophyll by 325.2%, 262.6%, and 240.3%, respectively, whereas Si priming increased carotenoid content by 414.6%. Relative to unprimed water-deficit-stressed plants, the combined Si + SWE priming treatment increased whole plant dry biomass by 119% net photosynthetic rate by 533.9%, and transpiration rate by 522.2%, while also improving several PSI and PSII photochemical efficiencies, increasing regulated energy dissipation, and reducing unregulated energy loss under water deficit. In contrast, SWE priming alone produced the highest chlorophyll a, chlorophyll b, and total chlorophyll contents, whereas Si priming enhanced carotenoid accumulation. Furthermore, the combined Si + SWE treatment improved PSI and PSII photochemical efficiency, increased regulated energy dissipation, and reduced unregulated energy loss under water deficit. Overall, seed priming with Si and SWE represents an effective, economical, and sustainable strategy for improving sesame tolerance to water deficit.

Halophytes are recognized for their adaptive capacity and potential applications in phytomanagement and ecosystem restoration. This study investigates the comparative physiology and antioxidant responses of two native halophytes, Caroxylon vermiculatum (L.) and Mesembryanthemum nodiflorum L., growing naturally in saline and metal-affected coastal environments. A comprehensive set of physiological and biochemical parameters was assessed, including macro- and microelements (Na, K, Ca, Fe, Zn, Cd), photosynthetic pigments (chlorophyll a, chlorophyll b, and carotenoids), soluble sugars, and proteins. In addition, oxidative stress markers (hydrogen peroxide, H₂O₂, and malondialdehyde, MDA), enzymatic antioxidants (superoxide dismutase, SOD, catalase, CAT, and guaiacol peroxidase, GPX), and non-enzymatic antioxidants (total phenolics, flavonoids, and proanthocyanidins) were evaluated. Antioxidant activities, including DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging and reducing power, were also measured. The results revealed clear species-specific adaptive strategies. Mesembryanthemum nodiflorum exhibited higher accumulation of Na and K, together with elevated levels of carotenoids and oxidative stress markers. This species showed translocation factors (TF > 1) for Na (~1.60) and K (~1.90), indicating efficient ion transport to aerial parts, while displaying low bioconcentration (BCF < 0.5 for most trace elements) and biological accumulation factors (BAF < 1), suggesting limited capacity for heavy metal accumulation. In contrast, Caroxylon vermiculatum showed higher concentrations of chlorophylls, carotenoids, phenolic compounds, flavonoids, and proteins, along with stronger superoxide dismutase activity. It also exhibited lower translocation of trace elements (TF < 1) and higher root retention of metals (BCF up to ~0.5), indicating a more effective exclusion and detoxification strategy. Overall, these findings demonstrate that M. nodiflorum relies on ion accumulation and translocation, whereas C. vermiculatum exhibits stronger ion regulation and antioxidant protection. Given the moderate BAF and BCF values observed, both species are more likely to contribute to phytomanagement through ion regulation and phytostabilization rather than efficient phytoextraction.

Water deficit is a major abiotic constraint limiting maize growth and productivity worldwide. Although silicon (Si) is not classified as an essential element, its beneficial effects on numerous crop species are well documented. Silicon has been shown to promote plant growth and enhance tolerance to abiotic stresses, particularly drought stress. Seed priming, a pre-sowing technique known to stimulate early germination processes, has emerged as a promising approach to enhance seedling establishment and stress tolerance in crops. In the present study, silicon-based seed priming was investigated as a strategy to alleviate the adverse effects of water deficit in maize (Zea mays) using two sodium silicate priming-solution concentrations (10 and 20 mM). Maize plants were subjected to six experimental treatments based on seed priming: three under well-watered conditions (no silicon seed priming and seed priming with 10 and 20 mM sodium silicate solutions) and three corresponding treatments combined with irrigation withdrawal for 15 days to induce drought stress. Morphological traits, biomass accumulation, photosynthetic pigment content, plant water status, and PSI- and PSII-related photochemical parameters were evaluated. Drought stress markedly reduced plant growth, biomass production, relative water content, chlorophyll pigment levels, and photosystem photochemical performance, reflecting a strong negative impact of water deficit on most measured parameters. In particular, root and shoot fresh weights decreased by 75% and 71%, respectively, compared with those of well-watered unprimed control plants, indicating a substantial reduction in biomass accumulation under drought conditions. Furthermore, drought conditions impaired photochemical performance and increased non-regulated energy dissipation, indicative of impaired photosynthetic performance. Silicon seed priming mitigated several drought-induced effects in a trait-dependent manner. Under water-deficit conditions, 20 mM Si produced the strongest improvement in root and shoot fresh weights, whereas 10 mM Si showed stronger responses for selected shoot-growth and PSI-related parameters. Both Si treatments improved leaf water status and photosynthetic stability to varying extents. Collectively, these results indicate that sodium silicate seed priming partially improves drought-related responses in maize seedlings under the conditions of this study by sustaining growth performance, preserving plant water status, and maintaining photosynthetic stability under water-deficit conditions.

Drought limits sustainable forage production in arid and semi-arid regions, where poor crop establishment is common, especially under inadequate irrigation. To address this challenge, research has turned to simple, rapid solutions that improve crop performance under variable conditions. Among green technologies, seed priming has gained attention as an eco-friendly and cost-effective approach. This study evaluates the effectiveness of seed hydropriming in alleviating the effects of water-deficit stress (40% of field capacity) on tall fescue (Festuca arundinacea Schreb.) at the seedling stage. Without priming, drought stress reduced root and shoot growth, tissue hydration, and nutrient uptake. By contrast, hydropriming improved drought tolerance by improving relative water content and ion supply and sustaining photosynthetic activity. These effects were accompanied by greater accumulation of proline and soluble sugars. Hence, (i) a regulated supply with essential mineral nutrients, (ii) an osmotic adjustment using the absorbed ions (such as K⁺, Ca²⁺, and Mg²⁺) in the vacuole and the accumulated osmotica (such as proline and soluble sugars) in the cytoplasm, and (iii) a maintained photosynthetic machinery together with improved root development are associated with enhanced drought tolerance in F. arundinacea plants issued from hydroprimed seeds. It seems that seed priming emerges more and more as a practical, low-cost technique to enhance drought resilience and support sustainable forage production under limited water conditions.

Soil salinity inhibits biological nitrogen fixation (BNF) in legumes, compromising nitrogen nutrition and crop productivity. This study evaluated whether two halotolerant Mesorhizobium ciceri strains (S1, S2) can sustain BNF and alleviate moderate salt stress (100 mM NaCl) in three Tunisian chickpea (Cicer arietinum L.) cultivars (Amdoun, Béja 1, and Nour). Inoculated and non-inoculated plants were grown under controlled conditions. Salinity reduced shoot dry weight by 37.5–42% and severely impaired nodulation (≈60% reduction) in non-inoculated plants. Bacterial inoculation significantly increased germination rate, shoot and root biomass, and nodule number compared to non-inoculated salt-stressed controls. Improved nodulation corresponded to better nitrogen nutrition, reflected by higher leaf chlorophyll content (a proxy for nitrogen status). However, direct measurements of nitrogenase activity (e.g., acetylene reduction assay) are needed to confirm enhanced BNF. Inoculated seedlings also exhibited lower oxidative stress markers (hydrogen peroxide and malondialdehyde) and enhanced antioxidant enzyme activities (superoxide dismutase and glutathione peroxidase), indicating reduced reactive oxygen species damage. Cultivar-specific responses were observed: Amdoun responded best to S1, Béja 1 to S2 for biomass recovery, while Nour showed strong antioxidant induction but limited growth gain. We conclude that halotolerant M. ciceri strains improve chickpea performance under salt stress primarily by sustaining BNF and nodulation, thereby maintaining nitrogen nutrition. Strain–cultivar compatibility is critical for optimizing this bio-inoculant strategy in saline agroecosystems. Our findings identify the combination of cultivar Béja 1 with strain S2 as the most promising for biomass recovery under moderate salinity, providing a practical, strain–cultivar matching framework that can guide the development of effective bio-inoculants for chickpea production in salt-affected areas of Tunisia and similar Mediterranean regions.

The use of phosphate-solubilizing bacteria (PSB) is a promising strategy to offset the harmful effect of combined salinity and low phosphorus availability

Using natural biostimulants such as plant extracts is a novel agronomic biofortification strategy to mitigate abiotic stresses such as salinity on crops. This study assessed seed priming effects on physiological and biochemical attributes of basil (Ocimum basilicum L.) under salinity (0 and 100 mM NaCl). Seeds were primed for 12h with distilled water (hydro-priming, H2O), moringa leaf (ME) and ginger rhizome extracts (GE). Salt stress reduced plant fresh weight and hydration, but priming with all agents alleviated salinity impact on basil. ME priming notably boosted fresh weight (+81%) and water content (+50%) compared to unprimed salt-exposed plants. ME-primed plants exhibited the highest proline (2-fold) and sugar (1.5-fold) contents contributing to the osmotic adjustment. Seed priming with ME also reduced malondialdehyde level (MDA) by about 50% enhancing membrane stability. ME also significantly modulated secondary metabolism through the stimulation of polyphenols (+88%), flavonoids (+98%) and total antioxidant activity (+1.4-fold). It upregulated key enzymes: Phenylalanine ammonia-lyase (PAL, +77%), Shikimate dehydrogenase (SKDH, +119%) and Polyphenoloxidase (PPO, +133%). Correlation analysis indicated that priming generally shifted correlation values from negative under salt stress to positive, with most r coefficients ranging between 0.8 and 1.00. Principal Component Analysis (PCA) clearly separated the primed and unprimed conditions, with the first two components explaining over 90% of the variability. Hence, these multivariate approaches confirm the beneficial effect of seed priming on basil growth and metabolism under salinity. Taken together, our findings provide new insights into the potential of using moringa leaf extract as a biostimulant to alleviate environmental stresses.