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Aims The aim of this study was to compare the efficiency of three defense mechanisms (ionic balance, osmotic adjustment and counteracting oxidative stress) under low, moderate and high soil salinity in two related species of contrasting tolerance to salinity: the halophyte Aster tripolium and the glycophyte Aster alpinus , and to elucidate their phytohormone-mediated regulation. Methods The phytohormonal profiling was performed to asses correlations between the pool of plant growth regulators and parameters depicting ionic homeostasis, osmotic adjustment and antioxidant system. Results Defense mechanisms in both species were based on accumulation/activity of distinct compounds (Na + and K + ions, antioxidants), but differences among species concerned particularly soluble carbohydrates and betaines. The halophyte accumulated mannitol, uronic acids and sucrose, while the glycophyte mostly glucose and proline-betaine. The halophyte responses also correlated with changes in the content of plant growth promoting PGRs, as well as jasmonates and benzoic acid. The glycophyte responses corresponded with changes in content of abscisic acid and ethylene precursor, as well as salicylic acid. Conclusions We provided evidence that benzoic acid rather than salicylic acid is involved in salt tolerance in the halophyte and elevated SA content may enhance vulnerability to salt excess. An important element of tolerance trait is also JA-GA network that influences the intensity of defense responses. This study uncovers new aspects of internal phytohormonal regulation of plant reaction to soil salinity and enables further insight into extremophyte biology.

Avoidance and reduction of soil contamination with heavy metals is one of the most serious global challenges. Nowadays, science offers us new opportunities of utilizing plants to extract toxic elements from the soil by means of phytoremediation. Plant abilities to uptake, translocate, and transform heavy metals, as well as to limit their toxicity, may be significantly enhanced via genetic engineering. This paper provides a comprehensive review of recent strategies aimed at the improvement of plant phytoremediation potential using plant transformation and employing current achievements in nuclear and cytoplasmic genome transformation. Strategies for obtaining plants suitable for effective soil clean-up and tolerant to excessive concentrations of heavy metals are critically assessed. Promising directions in genetic manipulations, such as gene silencing and cis- and intragenesis, are also discussed. Moreover, the ways of overcoming disadvantages of phytoremediation using genetic transformation approachare proposed. The knowledge gathered here could be useful for designing new research aimed at biotechnological improvement of phytoremediation efficiency.

Halophytes are salt-tolerant plants with ethnomedicinal value and growing potential in food and cosmetics; their adaptability to extreme conditions makes them promising candidates for sustainable agriculture and crop development in salt-affected areas. In vitro plant tissue culture further supports this by enabling resilient plant production in the face of climate and food security challenges. In this study, in vitro cultures of two medicinal halophytes from the genus Plantago (P. coronopus and P. crassifolia) were established to optimize their micropropagation protocol. Seed germination percentages, growth parameters, micropropagation rates, rooting efficiency, and physiological condition were evaluated. Growth media (modified MS medium) differed in the type of cytokinin. The seed germination efficiency was monitored at weekly intervals for 8 weeks, and other growth parameters were evaluated in 6- and 12-week cultures. Differences in both the rate and efficiency of in vitro germination between the two species were observed, with approximately 73% germination reached by P. coronopus and 47% by P. crassifolia after 4 weeks, and 80% and 53% after 8 weeks, respectively. The addition of 0.5 mg dm−3 kinetin plus 0.5 mg dm−3 IAA (indole acetic acid) proved to be effective in promoting growth in P. coronopus, resulting in longer plantlets and higher multiplication rates, while the addition of meta-topolin (mT) was a better stimulator of shoot and root growth in P. crassifolia. The highest multiplication coefficient, 6.22 for P. coronopus and 4.90 for P. crassifolia, was obtained on the P1 medium for both species. Importantly, medium with mT also had a stimulating effect on rooting in both species over the long term (12-week culture). The developed PTC enables efficient propagation and trait selection in halophytes, supporting sustainable large-scale production of the studied Plantago species, and facilitating future research on salt stress tolerance.

The aim of this study was to investigate how introducing halophilic sulfur-oxidizing bacteria (SOB) Halothiobacillus halophilus to the growth substrate affects the physiological and biochemical responses of the halophyte Tripolium pannonicum (also known as sea aster or seashore aster) under salt and cadmium stress conditions. This study assessed the plant’s response to these stressors and bacterial inoculation by analyzing various factors including the accumulation of elements such as sodium (Na), chloride (Cl), cadmium (Cd) and sulfur (S); growth parameters; levels of photosynthetic pigments, proline and phenolic compounds; the formation of malondialdehyde (MDA); and the plant’s potential to scavenge 2,2-Diphenyl-1-picrylhydrazyl (DPPH). The results revealed that bacterial inoculation was effective in mitigating the deleterious effect of cadmium stress on some growth criteria. For instance, stem length was 2-hold higher, the growth tolerance index was 3-fold higher and there was a 20% increase in the content of photosynthetic pigments compared to non-inoculated plants. Furthermore, the SOB contributed to enhancing cadmium tolerance in Tripolium pannonicum by increasing the availability of sulfur in the plant’s leaves, which led to the maintenance of an appropriate, about 2-fold-higher level of phenolic compounds (phenylpropanoids and flavonols), as well as chloride ions. The level of MDA decreased after bacterial application in all experimental variants except when both salt and cadmium stress were present. These findings provide novel insights into how halophytes respond to abiotic stress following inoculation of the growth medium with sulfur-oxidizing bacteria. The data suggest that inoculating the substrate with SOB has a beneficial effect on T. pannonicum’s tolerance to cadmium stress.

Pulsatilla turczaninovii is an important medicinal plant, valued for high ornamental value of melliferous flowers. We assessed the efficiency of reproduction under in vitro conditions and the ex situ growth capacity of this important representative of the world flora. The seed germination percentage was assessed, followed by determination of micropropagation rate and rooting efficiency. Then, the possibility of plant development in three consecutive growing seasons was assessed. The in vitro germination percentage was approximately 55%. The highest multiplication coefficient, amounting to 5.17, was obtained on modified MS medium supplemented with 2.5 mg L−1 2iP and 1.0 mg L−1 IAA. Our study provided unique insight on biochemical background of root regeneration in P. turczaninovii. In comparison with standard auxin-supplemented rooting medium, the treatment with 1.0 mg L−1 level of ethylene precursor ACC elevated rooting by about 20%. The total content of soluble sugars was proved to be biomarker of rhizogenesis in the studied species. Their concentration was positively correlated with rooting efficiency, while a level of phenolic was positively correlated with the length of regenerated roots, and their number per rosette. The cultivation of the acclimatized material was successfully carried out and was evaluated over three subsequent years. In the third year of cultivation, the plants entered the stage of generative development and most of them bloomed profusely.Key messageThe protocol of Pulsatilla turczninowi propagation, rooting, hardening and ex situ cultivation was developed. Biochemical background of adventitious rooting process in a representative of Pulsatilla genus is reported for the first time.

In vitro techniques may provide a suitable tool for effective propagation and conservation of plant species representing various ecological niches. The elaboration of such protocols is also prerequisite for selection of heavy-metal-tolerant plant material that could be afterwards used for restoration or remediation of polluted sites. In this study, culture protocol for Gypsophila fastigiata propagation was developed. The highest multiplication coefficient, which reached 6.5, and the best growth parameters were obtained on modified MS medium supplemented with 1.0 mg L−1 2iP and 0.2 mg L−1 IAA. The obtained cultures were treated with different concentrations of lead nitrate (0.1, 0.5, and 1.0 mM Pb(NO3)2) or cadmium chloride (0.5, 2.5, and 5.0 μM CdCl2). The growth parameters, photosynthetic pigments, and phenolic compound content were examined in order to evaluate whether tested metal salts can have an adverse impact on studied culture. It was ascertained that Pb ions induced growth disturbances and contributed to shoot wither. On the contrary, the proliferative shoot cultures were established on media containing Cd ions and the multiplication coefficients and shoot length increased on all media enriched with CdCl2. Chlorophylls and carotenoid contents were negatively affected by application of 5.0 μM of cadmium; nevertheless, in shoots treated with 2.5 μM CdCl2, increased accumulation of photosynthetic pigments occurred and their amount was similar to untreated culture. Adaptation to Cd was associated with stimulation of phenolic compound synthesis. Hence, we have reported on unambiguous positive result of in vitro selection procedure to obtain vigorous shoot culture tolerant to cadmium.

Land degradation due to salinity and prolonged drought poses significant global challenges by reducing crop yields, depleting resources, and disrupting ecosystems. Halophytes, equipped with adaptive traits for drought and soil salinity, and their associations with halotolerant microbes, offer promising solutions for restoring degraded areas sustainably. This study evaluated the effects of halophilic sulfur-oxidizing bacteria (SOB), specifically Halothiobacillus halophilus, on the physiological and biochemical responses of the halophyte Plantago coronopus L. under drought and salt stress. We analyzed the accumulation of ions (Na, Cl, K) and sulfur (S), along with growth parameters, glutathione levels, photosynthetic pigments, proline, and phenolic compounds. Drought significantly reduced water content (nearly 10-fold in plants without SOB and 4-fold in those with SOB). The leaf growth tolerance index improved by 70% in control plants and 30% in moderately salt-stressed plants (300 mM NaCl) after SOB application. SOB increased sulfur content in all treatments except at high salinity (600 mM NaCl), reduced toxic sodium and chloride ion accumulation, and enhanced potassium levels under drought and moderate salinity. Proline, total phenolic, and malondialdehyde (MDA) levels were highest in drought-stressed plants, regardless of SOB inoculation. SOB inoculation increased GSH levels in both control and 300 mM NaCl-treated plants, while GSSG levels remained constant. These findings highlight the potential of SOB as beneficial microorganisms to enhance sulfur availability and improve P. coronopus tolerance to moderate salt stress.

This study examined the use of an artificial soil substrate in a mine waste reclamation area and its effect on plant metabolic functions. Research was conducted by determining the relationship between the plants’ biochemical features and the properties of plant growth medium derived from post-flotation coal waste, sewage sludge, crushed stone and fly ash on the surface of the mine waste disposal area. Trees and shrubs were established on the material and allowed to grow for eight years. The study determined that the applied plants and the naturally occurring Taraxacum officinale were suitable for physio-biochemical assessment, identification of derelict areas and reclamation purposes. An evaluation of a soil substrate applied to post-mining areas indicated that it was beneficial for plant growth since it activated the metabolic functions of herbaceous plants, shrubs, and trees. The study showed that soil substrate can be targeted to improve plant stress tolerance to potentially toxic elements (PTEs). These data suggest the potential for growth and slower susceptible response to Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. It is possible that the constructed soil-substitute substrate (biosolid material) would be an effective reclamation treatment in areas where natural soil materials are polluted by PTEs. This observation may reflect a more efficient use of soil substrate released from the cycling of organic biogene pools, in accordance with the circular economy approach. In further studies related to land reclamation using sewage sludge amendments, it would be necessary to extend the research to other stress factors, such as salinity or water deficiency.

This study attempted to determine short-term responses to drought and salt stress in different Silene vulgaris genotypes and to identify potential abiotic stress biochemical indicators in this species. Four populations from contrasting habitats were subjected to drought and three levels of salinity under controlled greenhouse conditions. The determination of several growth parameters after the stress treatments allowed for ranking the tolerance to stress of the four analyzed populations on the basis of their relative degree of stress-induced growth inhibition. This was then correlated with changes in the leaf levels of monovalent ions (Na+, Cl−, and K+), photosynthetic pigments (chlorophylls a and b, carotenoids), osmolytes (total soluble sugars, proline), and non-enzymatic antioxidants (total phenolic compounds and flavonoids). Despite the observed differences, all four populations appeared to be relatively tolerant to both stress conditions, which in general did not cause a significant degradation of photosynthetic pigments and did not generate oxidative stress in the plants. Drought and salinity tolerance in S. vulgaris was mostly dependent on the use of Na+ and K+ for osmotic adjustment under stress, a mechanism that appeared to be constitutive, and not stress-induced, since relatively high concentrations of these cations (without reaching toxic levels) were also present in the leaves of control plants. The inhibition of additional transportation of toxic ions to the leaves, in response to increasing external salinity, seemed to be a relevant mechanism of tolerance, specifically to salt stress, whereas accumulation of soluble sugars under drought conditions may have contributed to tolerance to drought.

The growing demand for Thymus serpyllum biomass to produce drugs, cosmetics and spices necessitates the search for innovative methods mitigating the negative effects of environmental stressors in order to improve its yield under unfavorable conditions. Due to the exposure of plants to salinity stress (SS), we investigated the effect of sugar beet molasses (SBM) on the growth and biochemical parameters related to plants’ response to SS. Wild thyme plants were treated for 5 weeks to sodium chloride and 3% molasses solution using two modes of application (soil irrigation or foliar sprays). Plants irrigated by SBM showed slighter stem growth inhibition than control plants, high stress tolerance index and maintained a constant root water content under salt stress. Moreover plants treated with 100 mM NaCl and soil-applied SBM had lower lipid peroxidation level, showed lower POD activity, higher total soluble protein content and maintained a more even free amino acids level, compared to the control treatments. The concentration of potassium ions was higher in the case of plant roots irrigation with sugar beet molasses compared to control plants. In this experiment, most of the growth and biochemical parameters from foliar molasses-sprayed plants did not differ significantly from the control. We provided evidence that soil-applied SBM beneficially changed the plant’s biochemical response to salt stress. On the basis of the obtained results, we conclude that this soil amendment contributes to the strengthening of plant protection against this harmful environmental factor.