Titanium Increases the Antioxidant Activity and Macronutrient Concentration in Tomato Seedlings Exposed to Salinity in Hydroponics

Investigating foliar application of bulk and nanoparticles titanium dioxide on fennel productivity to mitigate the negative effects of saline irrigation water

BACKGROUND

Fennel essential oils are fragrance compounds used in food and pharmaceutical sectors. One of the major impediments to expansion of fennel farming in Egypt's reclamation areas is saline water. Titanium dioxide (TiO2) or TiO2 nano particles (TiO2NP) can be utilized to boost the yield of aromatic plants cultivated under saline irrigation water. Saline water, particularly which contains sodium chloride can harm fennel plant; consequently, it was predicted that fennel production would fail in Egypt's reclaimed area, where the primary source of irrigation is groundwater consisting sodium chloride. This study sought to help fennel respond to sodium chloride by applying Ti forms to their leaves in order to reduce the detrimental effects of sodium chloride on them for expanding their production in the newly reclamation areas as a natural source of essential oil. Ti forms were applied as foliar application at 0, 0.1, 0.2 TiO2, 0.1 TiO2NP, and 0.2 TiO2NP, mM under irrigation with fresh water (0.4 dS m-1), or saline water (51.3 mM or 4.7 dS m-1).

RESULTS

Plants exposed to 0.1 mM TiO2NP under fresh water resulted in the maximum values of morphological characters, estragole, oxygenated monoterpenes and photosynthetic pigments; while those subjected to 0.1 mM TiO2NP under saline water gave the greatest values of essential oil, proline, antioxidant enzymes and phenols. The greatest amounts of soluble sugars were recorded with 0.2 mM TiO2NP irrigated with saline water. Plants subjected to 0 mM TiO2 under saline water produced the greatest values of flavonoids, hydrogen peroxide and malondialdehyde.

CONCLUSION

To mitigate the negative effects of salty irrigation water on fennel plant production, TiO2NP application is suggested as a potential strategy.

Salinity Stress Tolerance in Plants

Soil salinization negatively impacts plant development and induces land degradation, thus affecting biodiversity, water quality, crop production, farmers' well-being, and the economic situation in the affected region. Plant germination, growth, and productivity are vital processes impaired by salinity stress; thus, it is considered a serious threat to agriculture. The extent to which a plant is affected by salinity depends mainly on the species, but other factors, including soil attributes, water, and climatic conditions, also affect a plant's ability to tolerate salinity stress. Unfortunately, this phenomenon is expected to be exacerbated further by climate change. Consequently, studies on salt stress tolerance in plants represent an important theme for the present Special Issue of Plants. The present Special Issue contains 14 original contributions that have documented novel discoveries regarding induced or natural variations in plant genotypes to cope with salt stress, including molecular biology, biochemistry, physiology, genetics, cell biology, modern omics, and bioinformatic approaches. This Special Issue also includes the impact of biostimulants on the biochemical, physiological, and molecular mechanisms of plants to deal with salt stress and on the effects of salinity on plant nutrient status. We expect that readers and academia will benefit from all the articles included in this Special Issue.

Titanium dioxide nanoparticles improve element uptake, antioxidant properties, and essential oil productivity of Melissa officinalis L. seedlings under in vitro drought stress

In vitro drought stress has a considerable impact on the mass production of active compounds in medicinal plants. Nevertheless, photosynthesis, nutrient uptake, and protein synthesis may be negatively affected by drought, which results in poor growth. Titanium dioxide nanoparticles (TiO2 NPs) have recently been shown to play an important role in increasing nutrient uptake, resistance to various environmental stresses, and better plant growth. Regarding the importance of pharmaceutical metabolites of Melissa officinalis L., this experiment aimed to assess the role of TiO2 NPs in improving physiological responses and phytochemical properties in M. officinalis under in vitro drought stress. For this, two-week-old seedlings were cultured on Murashige and Skoog (MS) medium supplemented with 0, 50, and 100 mg L-1 TiO2 NPs and 0, 3, and 6% (w/v) polyethylene glycol (PEG). Two weeks after treatments, a reduction of chlorophyll, protein content, essential elements, and enhancement of H2O2 and malondialdehyde (MDA) levels were seen as a result of drought stress. It was observed that M. officinalis partially responded to the drought by increasing non-enzymatic antioxidants, including phenolics, flavonoids, and anthocyanin and ascorbate peroxidase activity. Moreover, PEG-induced drought stress increased some important essential oil content such as limonene, alpha-pinene, myrcene, γ-3-carene, citral, and carvacrol; however, the results showed that TiO2 NPs not only increased the quantity of essential oils but also led to tolerance to the drought stress by increasing photosynthetic pigments, antioxidant systems, absorption of essential nutrients, and decreasing H2O2 and MDA levels.

Titanium nanoparticles activate a transcriptional response in Arabidopsis that enhances tolerance to low phosphate, osmotic stress and pathogen infection

Titanium is a ubiquitous element with a wide variety of beneficial effects in plants, including enhanced nutrient uptake and resistance to pathogens and abiotic stresses. While there is numerous evidence supporting the beneficial effects that Ti fertilization give to plants, there is little information on which genetic signaling pathways the Ti application activate in plant tissues. In this study, we utilize RNA-seq and ionomics technologies to unravel the molecular signals that Arabidopsis plants unleash when treated with Ti. RNA-seq analysis showed that Ti activates abscisic acid and salicylic acid signaling pathways and the expression of NUCLEOTIDE BINDING SITE-LEUCINE RICH REPEAT receptors likely by acting as a chemical priming molecule. This activation results in enhanced resistance to drought, high salinity, and infection with Botrytis cinerea in Arabidopsis. Ti also grants an enhanced nutritional state, even at suboptimal phosphate concentrations by upregulating the expression of multiple nutrient and membrane transporters and by modifying or increasing the production root exudates. Our results suggest that Ti might act similarly to the beneficial element Silicon in other plant species.