Effects of lanthanum on the growth and essential oil components of lavender under osmotic stress

Rare earth metallic elements in plants: assessing benefits, risks and mitigating strategies

Rare earth elements (REEs) comprises of a uniform group of lanthanides and scandium (Sc) and yttrium (Y) finding their key importance in agriculture sectors, electronic and defense industries, and renewable energy production. The immense application of REEs as plant growth promoters has led to their undesirable accumulation in the soil system raising concerns for REE pollution as upcoming stresses. This review mainly addresses the chemistry of REEs, uptake and distribution and their biphasic responses in plant systems and possible plausible techniques that could mitigate/alleviate REE contamination. It extends beyond the present understanding of the biphasic impacts of rare earth elements (REEs) on physio-biochemical attributes. It not only provides landmarks for further exploration of the interrelated phytohormonal and molecular biphasic nature but also introduces novel approaches aimed at mitigating their toxicities. By delving into innovative strategies such as recycling, substitution, and phytohormone-assisted mitigation, the review expands upon existing knowledge of REEs whilst also offering pathways to tackle the challenges associated with REE utilization.

A critical review on the development of lanthanum-engineered biochar for environmental applications

Biochar and lanthanum (La) have been widely used in environment. However, there is a lack of knowledge and perspective on the development of La-engineered biochar (LEB) for environmental applications. This review shows that LEBs with a variety of La species via pre-/post-doping routes are developed for environmental applications. Specifically, precipitation, gelation, and calcination are the common sub-processes involved in the pre-/post-doping of La on the resultant LEB. The dominant La species for LEBs is La(OH)₃, which is formed through precipitation of La ions with various bases. Various La carbonates, e.g., LaOHCO₃, La₂(CO₃)₃, La₂CO₅, and NaLa(CO₃)₂, are also involved in the preparation of LEBs. The LEBs are high-efficient in the adsorption of phosphate, arsenic, antimonate and fluoride ions, attributed to the strong affinity of La to oxyanions and Lewis hard base. Lanthanum is also favorable for co-doping with transition metal species to further enhance the performances in adsorption or catalysis. This review also analyzes the prospects and future challenges for the preparation and application of LEBs in environment. Finally, this review is beneficial to inspire new breakthroughs on the preparation and environmental application of LEBs.

Distribution of rare earth elements (REEs) and their roles in plant growth: A review

The increasing use of rare earth elements (REEs) in various industries has led to a rise in discharge points, thus increasing discharge rates, circulation, and human exposure. Therefore, REEs have received widespread attention as important emerging pollutants. This article thus summarizes and discusses the distribution and occurrence of REEs in the world's soil and water, and briefly introduces current REEs content analysis technology for the examination of different types of samples. Specifically, this review focuses on the impact of REEs on plants, including the distribution and fractionation of REEs in plants and their bioavailability, the effect of REEs on seed germination and growth, the role of REEs in plant resistance, the physiological and biochemical responses of plants in the presence of REEs, including mineral absorption and photosynthesis, as well as a description of the substitution mechanism of REEs competing for Ca in plant cells. Additionally, this article summarizes the potential mechanisms of REEs to activate endocytosis in plants and provides some insights into the mechanisms by which REEs affect endocytosis from a cell and molecular biology perspective. Finally, this article discusses future research prospects and summarizes current scientific findings that could serve as a basis for the development of more sustainable rare earth resource utilization strategies and the assessment of REEs in the environment.

Inducing red pigment and inhibiting citrinin production by adding lanthanum(III) ion in Monascus purpureus fermentation

Monascus pigments (MPs) are widely used natural colorants in Asian countries. The problems of low extracellular red pigment (ERP) and high citrinin remain to be solved in Monascus pigment production. The effect of lanthanum(III) ion (LaCl₃) on Monascus purpureus fermentation was investigated in this study. The yields of ERP and biomass respectively reached maxima of 124.10 U/mL and 33.10 g/L by adding 0.4 g/L La³⁺ on the second day in the total 8-day fermentation; simultaneously, citrinin was decreased by 59.93% and 38.14% in the extracellular and intracellular fractions, respectively. Reactive oxygen species (ROS) levels were obviously improved by La³⁺ treatment, while the activities of catalase (CAT) and superoxide dismutase (SOD) were increased compared with the control. The ratio of unsaturated/saturated fatty acids in mycelia was increased from 2.94 to 3.49, indicating that the permeability and fluidity of the cell membrane were enhanced under La³⁺ treatment. Gene expression analysis showed that the relative expression levels of Monascus pigment synthesis genes (pksPT, mppB, mppD, MpFasB2, and MpPKS5) were significantly upregulated by La³⁺ treatment, and in contrast, the relative expression levels of citrinin synthesis genes (ctnA, pksCT and mppC) were markedly downregulated. This work confirmed that LaCl₃ possesses the potential to induce red pigment biosynthesis and inhibit citrinin production in M. purpureus fermentation. KEY POINTS: • La³⁺ induced red pigment and inhibited citrinin production in Monascus fermentation. • La³⁺ regulated genes expression up for Monascus pigment and down for citrinin. • La³⁺ increased the UFAs in cell membrane to enhance the permeability and fluidity.

Potential roles of melatonin and sulfur in alleviation of lanthanum toxicity in tomato seedlings

Owing to the active use of rare-earth elements in many areas, it is necessary to study their behavior in the environment and their biological impact on plants. Despite the role of melatonin and sulfur in plant growth, development and abiotic stress tolerance; it is still not clear how they have a strong regulatory influence and synergistic effect on growth, physiological and biochemical characteristics of plants under different environmental stresses. Therefore, this study highlights how melatonin and sulfur together potentially involved in a reversal of lanthanum-inhibited photosynthetic and growth responses in tomato seedlings. Here, we reported that seedlings grown in a medium containing 150 μM lanthanum exhibited increased overproduction of reactive oxygen species (ROS) and lipid peroxidation together with increased Chlorophyll degradation, and activity of chlorophyllase, proline dehydrogenase and glycolate oxidase (GOx), and decreased photosynthesis and growth. However, the application of melatonin and sulfur showed significant responses on tomato seedlings, although the response of their combined treatment was more effective by further increasing photosynthesis and growth under lanthanum toxicity. Melatonin supplied with sulfur suppressed ROS formation, lipid peroxidation and activity of GOx, and increased photosynthesis by upregulating activities of carbonic anhydrase and ribulose-1,5-bisphosphate carboxylase/oxygenase. Also, sulfur supplementation with melatonin to seedlings resulted in an elevation in the accumulation of Chl and proline by increasing δ-aminolevulinic acid and activity of δ-aminolevulinic acid dehydratase and Δ¹-pyrroline-5-carboxylate synthetase activity. The administration of melatonin with sulfur substantially induced upregulation of enzymes (superoxide dismutase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase) activities involved in the antioxidant system, thereby mitigating ROS-induced oxidative damage. Thus, this study provides strong evidence that melatonin and sulfur have strong regulatory influence and synergistic role in alleviating the adverse effect of lanthanum-toxicity by increasing photosynthesis and growth.

Microcapsules based on octenyl succinic anhydride (OSA)-modified starch and maltodextrins changing the composition and release property of rose essential oil

Octenyl succinic anhydride (OSA)-modified starch and maltodextrins (MDs) are important carbohydrate polymers as wall materials. However, few studies have shown whether these two wall materials affect the composition of core materials. In this work, we investigated the effects of OSA-modified starch and MD on the release property of essential oils. Results showed that among the seven characteristic aroma components (CACs) of rose essential oil (REO), the esters released the fastest, followed by the alcohols, while the release of the phenols was the slowest. Environmental factors such as temperature and relative humidities (RHs) had significant influences on the release kinetics of CACs in REO. This work provides new insights into the use of OSA-modified starch and MDs as wall materials for encapsulating complex and bioactive components.

The mechanism behind lack-of-effect of lanthanum on seed germination of switchgrass

Switchgrass (Panicum virgatum L.) is a perennial warm-season C₄ grass identified as a model species for bioenergy feedstock production. Lanthanum (La) as a rare earth element can stimulate the physiological processes of plant growth. The purpose of this study was to investigate the effect of lanthanum on seed germination of switchgrass. However, no significant differences in seed germination were found. The energy dispersive X-ray analysis showed that abundant lanthanum deposits resided on the pericarp and testa of the seed while few lanthanum deposits were present on the aleurone and endosperm. This phenomenon demonstrates that a semi-permeable layer, which could restrict or impede solute exchange, while allowing the permeability of internal and external water and gas, may be located between the testa and aleurone. Light microscopy and histochemical analysis revealed that the main chemical composition of the semi-permeable layer would be expected to be suberin because the layer was stained yellow with aniline blue. The quantum chemical calculations predict that the intervals between adjacent carbon chains in suberin molecule are so small that lanthanum ([La(H₂O)₈]³⁺) cannot pass through the suberin molecule. In conclusion, the seed germination of switchgrass is not affected by lanthanum because the semi-permeable layer restricts the penetration of lanthanum into the embryo.