Boron (B) deficiency and copper (Cu) excess are common problems in citrus orchard soils. Citrus sinensis seedlings were exposed to 25 (B25) or 2.5 (B2.5) mu M H3BO3 and 0.5 (Cu0.5) or 350 (Cu350) mu M CuCl3 for 24 weeks. Cu350 upregulated 2210 (1012) genes and 482 (341) metabolites and downregulated 3201 (695) genes and 175 (43) metabolites in roots at B2.5 (B25). Further analysis showed that the B-mediated mitigation of Cu toxicity in roots involved the coordination of the following aspects: (a) enhancing the ability to maintain cell wall and plasma membrane stability and function; (b) lowering the impairment of Cu350 to primary and secondary metabolisms and enhancing their adaptability to Cu350; and (c) alleviating Cu350-induced oxidative stress via the coordination of reactive oxygen species (ROS) and methylglyoxal detoxification systems. Cu350 upregulated the abundances of some saccharides, amino acids and derivatives, phospholipids, secondary metabolites, and vitamins, and the expression of several ROS detoxification-related genes in roots of B2.5-treated seedlings (RB2.5), but these adaptive responses did not prevent RB2.5 from Cu-toxicity (oxidative damage). The study identified some genes, metabolites, and metabolic processes/pathways possibly involved in root Cu tolerance. Additionally, the responses of gene expression and metabolite profiling to Cu-B treatments differed between leaves and roots. Therefore, this study provided novel information for B to reduce Cu toxicity in roots and might contribute to the development of soil amendments targeting Cu excess in citrus and other crops.

Imazethapyr, a widely used herbicide, exhibits a long persistence in soils and can cause injury to rotational crops. Here, we discovered that imazethapyr inhibits primary root elongation in Arabidopsis by inhibiting cell division and expansion rather than damaging the organization of root meristem. Integration of transcriptomic and metabolomic analysis revealed that imazethapyr downregulated multiple genes related to cell wall loosening and modification, leading to increased cell wall thickness and inhibited cellular expansion in Arabidopsis roots. Furthermore, imazethapyr upregulated auxin biosynthesis and transport, resulting in enhanced auxin accumulation at root tips. Elevated auxin concentrations triggered apoplast alkalization and the inactivation of wall-loosening enzymes, further suppressing root growth. This research provides new insights into the molecular mechanism underlying imazethapyr phytotoxicity and offers potential strategies for developing crops that are better adapted to soils contaminated with imidazolinone herbicides.

The development of biodegradable slow-release fertilizers derived from lignocellulosic materials is essential for mitigating environmental pollution and ecological damage associated with petroleum-based components in conventional fertilizers, as well as for enhancing agricultural productivity. In this study, a Camellia oleifera Abel. shell based slow-release fertilizer (COSU) was prepared by molten urea impregnation method. FTIR NMR, SEM, EDX, BET and molecular dynamic simulation were used to reveal the urea storage and slow-release mechanisms of COSU at the cell wall and molecular level. These results indicated the role of the cellular tissue structure with its pore structure in the storage and slow release of urea and demonstrate the molecular behavior of urea adsorption and release on lignocellulosic chemical component. The maximum nitrogen loading rate of COSU was 36.58 % and the cumulative release rate over 28 days was 75.08 %, which met the GBT23348-2009 standard. The multiple coupling regulatory mechanism of the cell wall - lignocellulosic molecules of urea store and releasing were discussed and proposed. Pot experiments confirmed that the prepared slow-release fertilizer not only stimulated the growth of corn seedlings but also contributed to an increase in soil humus. The findings of this research provide a new insight and a solid theoretical foundation for the development of lignocellulose-based slow-release fertilizers, offering a sustainable alternative to traditional fertilizers and contributing to a greener agricultural future.

Mutation breeding is a promising technique used for improving crop plants' performance, including tolerance to aluminum in rice (Oryza sativa L.) cultivars. The presented research pursued developing aluminum-tolerant rice lines through mutation in two local rice cultivars, 'Mayas' and 'Adan'. Mutation induction using six doses of gamma irradiation included 50, 100, 150, 200, 250, and 300 Gy. The evaluation of root tolerance index proceeded for early selection of aluminum tolerant lines. In addition, root swelling, aluminum absorption, cross-sectional histology, and root lipid peroxidation incurred scrutiny. The results showed gamma irradiation (100 Gy) could produce aluminum stress tolerant lines from the cultivar Mayas. Aluminum-tolerant lines obtained totaled 91 through gamma irradiation in the local rice genotypes. The morphological traits of these aluminum-tolerant mutant lines underwent accumulation only at the root tip, cross-sectional histology with sclerenchyma thickening due to organic acids, and minimal cell wall damage. These lines need further evaluation to confirm their tolerance to aluminum stress, for rice cultivation on acid soils.

Hemp (Cannabis sativa L.) is a versatile crop that produces cellulosic bast fibres used in textiles and biocomposites. Is also finds use in phytoremediation, being a good candidate for the cultivation on marginal lands, such as those contaminated by heavy metals (HMs). HMs like cadmium (Cd) and zinc (Zn) are known to affect plant growth and impair the biosynthesis of cellulose and lignin at the cell wall level. Since cellulose is the major component in the gelatinous layer of bast fibres, HMs can impact the structure of hemp fibres and, consequently, their mechanical properties. This study investigates how varying concentrations of Cd and Zn in the soil affect the bast fibres of hemp plantlets. The chosen model is the hypocotyl, as it is ideal for studying bast fibre development: it exhibits a temporal separation between the elongation and thickening phases within a short period of approximately three weeks. C. sativa plantlets were grown for 20 days, and the hypocotyls sampled to perform histochemical observations, gene expression analysis, as well as to quantify biomass yield and Cd/Zn accumulation. Hemp plantlets grown in soils with the three highest Zn concentrations were smaller than the control group, whereas no decrease in size was observed under elevated Cd concentrations. However, at the highest Cd concentration, the root system exhibited enhanced development, accompanied by a significant increase in dry weight across all the concentrations tested. The quantification of Cd and Zn showed that the roots were the main organs accumulating HMs. Cd at the two highest concentrations decreased significantly the lumen area of bast fibres and increased their cell wall thickness. Zn decreased significantly the lumen area, but it did not impact the thickness of the cell wall at the highest concentration. Cd also increased the number of secondary fibres. Immunohistochemistry highlighted a different pattern of crystalline cellulose distribution with a signal that was less homogeneous in the presence of Cd and Zn. Gene expression analysis revealed changes in transcripts encoding cellulose synthases, fasciclin-like arabinogalactan proteins, class III peroxidases. The results obtained shed light on the molecular response and bast fibre histological changes occurring in young hemp plants exposed to Cd and Zn.

Key messageBoron is essential for plants, but excess can induce toxicity.AbstractBoron (B) is a vital micronutrient for plants, but excess B can induce toxicity symptoms and reduce crop yields. B bioavailability depends on soil properties, including clay type, pH, and organic matter content. Symptoms of B toxicity include reduced shoot and root growth, leaf chlorosis and necrosis, impaired photosynthesis, and disrupted pollen development. This review paper examines the current knowledge on B toxicity mechanisms, tolerance strategies, and management approaches in plants. This review covers (1) factors affecting B bioavailability; (2) toxicity symptoms in plants; (3) uptake, transport, and detoxification mechanisms; and (4) strategies. To mitigate toxicity, plants reduce B uptake, activate efflux transporters, compartmentalize B, and enhance antioxidant systems. On the basis of this review, future research should focus on identifying novel tolerance mechanisms, exploring genetic strategies for improved B management, and developing innovative agronomic interventions. These insights will facilitate the breeding and management of crops for enhanced productivity under B toxicity stress.

Both copper (Cu) excess and boron (B) deficiency are often observed in some citrus orchard soils. The molecular mechanisms by which B alleviates excessive Cu in citrus are poorly understood. Seedlings of sweet orange (Citrus sinensis (L.) Osbeck cv. Xuegan) were treated with 0.5 (Cu0.5) or 350 (Cu350 or Cu excess) mu M CuCl2 and 2.5 (B2.5) or 25 (B25) mu M HBO3 for 24 wk. Thereafter, this study examined the effects of Cu and B treatments on gene expression levels revealed by RNA-Seq, metabolite profiles revealed by a widely targeted metabolome, and related physiological parameters in leaves. Cu350 upregulated 564 genes and 170 metabolites, and downregulated 598 genes and 58 metabolites in leaves of 2.5 mu M B-treated seedlings (LB2.5), but it only upregulated 281 genes and 100 metabolites, and downregulated 136 genes and 40 metabolites in leaves of 25 mu M B-treated seedlings (LB25). Cu350 decreased the concentrations of sucrose and total soluble sugars and increased the concentrations of starch, glucose, fructose and total nonstructural carbohydrates in LB2.5, but it only increased the glucose concentration in LB25. Further analysis demonstrated that B addition reduced the oxidative damage and alterations in primary and secondary metabolisms caused by Cu350, and alleviated the impairment of Cu350 to photosynthesis and cell wall metabolism, thus improving leaf growth. LB2.5 exhibited some adaptive responses to Cu350 to meet the increasing need for the dissipation of excessive excitation energy (EEE) and the detoxification of reactive oxygen species (reactive aldehydes) and Cu. Cu350 increased photorespiration, xanthophyll cycle-dependent thermal dissipation, nonstructural carbohydrate accumulation, and secondary metabolite biosynthesis and abundances; and upregulated tryptophan metabolism and related metabolite abundances, some antioxidant-related gene expression, and some antioxidant abundances. Additionally, this study identified some metabolic pathways, metabolites and genes that might lead to Cu tolerance in leaves.

Background and Aims Soil salinization adversely threatens plant survival and food production globally. The mobilization of storage reserves in cotyledons and establishment of the hypocotyl/root axis (HRA) structure and function are crucial to the growth of dicotyledonous plants during the post-germination growth period. Here we report the adaptive mechanisms of wild and cultivated soybeans in response to alkali stress in soil during the post-germination growth period.Methods Differences in physiological parameters, microstructure, and the types, amounts and metabolic pathways of small-molecule metabolites and gene expression were compared and multi-omics integration analysis was performed between wild and cultivated soybean under sufficient and artificially simulated alkali stress during the post-germination growth period in this study.Key Results Structural analysis showed that the cell wall thickness of wild soybean under alkali stress increased, whereas cultivated soybeans were severely damaged. A comprehensive analysis of small-molecule metabolites and gene expression revealed that protein breakdown in wild soybean cotyledons under alkali stress was enhanced, and transport of amino acids and sucrose increased. Additionally, lignin and cellulose syntheses in wild soybean HRA under alkali stress were enhanced.Conclusions Overall, protein decomposition and transport of amino acids and sucrose increased in wild soybean cotyledons under alkali stress, which in turn promoted HRA growth. Similarly, alkali stress enhanced lignin and cellulose synthesis in the wild soybean HRA, which subsequently enhanced cell wall synthesis, thereby maintaining the stability and functionality of the HRA under alkali stress. This study presents important practical implications for the utilization of wild plant resources and sustainable development of agriculture.

The gap between serious soil heavy metals pollution and inefficient soil remediation threatens human health. This study proposed a method to improve the phytoremediation efficiency using bamboo vinegar (BV) solution and the potential mechanism was discussed. The results demonstrated that the application of BV increases the content of cadmium (Cd) in vacuole and cell wall hemicellulose 2 in leaves of Perilla frutescens. Simultaneously, it enhanced enzyme activities of superoxide dismutase and catalase in leaves. Therefore, this process alleviated the damage of Cd to functional tissues of Perilla frutescens, thus improving the tolerance of plants to Cd. Moreover, the BV application reduced the Cd content bound by root cell wall pectin fractions and insoluble phosphate, subsequently improving the ability of oxalic acids to carry Cd to the aerial parts. Consequently, the aerial parts obtained a larger amount of Cd enrichment. Overall, the Transfer Factor of Cd from roots to stems and enrichment of Cd in Perilla frutescens were maximally increased by 57.70 % and 54.03 % with the application of 50-fold and 300-fold diluted BV under 2 mg & sdot;L- 1 Cd stress, respectively. The results can provide a theoretical basis for the promotion of phytoremediation of Cd-contaminated soil treatment technology.

Cadmium (Cd), a widely distributed and highly toxic heavy metal, poses a severe threat to soil fertility and plant growth. Citric acid (CA), a small organic acid molecule, plays a crucial role in alleviating heavy metal toxicity in plants. However, the specific mechanism underlying how CA organizes and mitigates the damage caused by heavy metals to plant cells remains unclear. Therefore, we studied the impact of exogenous CA on Cd-induced stress in Iris tectorum. . The results showed that the addition of exogenous CA significantly increased the activity of antioxidant enzymes and altered the content of mineral elements including Fe, Zn, Ca, and Mn. Notably, compared to the Cd-only treatment, the proportion of Cd in the root cell walls increased by 14% in the presence of CA, and this increase was due to the ability of CA to regulate the amount of polysaccharide components in the root cell walls. CA affected the activity of pectinesterase (PME), changed the degree of pectinesterification (PMD), and enhanced the root cell walls' ability to bind Cd, thereby reducing the Cd content in the above-ground tissues and alleviating heavy metal toxicity in plants. In summary, this study provides robust evidence that supports the use of CA to improve the efficiency of urban soil remediation.