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Main conclusion: Secondary metabolites play important roles in osmotic adjustment, ion homeostasis, and redox signaling in wheat under salinity stress. Together, these functions support plant acclimation to saline conditions. Integrative omics approaches can clarify the regulation of their biosynthetic pathways. Applying this knowledge in targeted breeding may accelerate the development of saltresilient wheat cultivars. Salt stress is a major environmental challenge that adversely affects wheat growth, developmental cascades, and grain yield and quality. As a major staple crop, it is imperative to improve wheat's salt tolerance for ensuring food security in increasingly saline agricultural environments. Secondary metabolites, a diverse group of organic compounds not directly involved in primary metabolic processes, play significant roles in plant stress responses and adaptation. These compounds include phenolics, terpenoids, and alkaloids, each contributing to plant defense mechanisms through antioxidant activities, osmoprotection, and stress signaling. This review focuses on the pivotal role of secondary metabolites in enhancing wheat's resilience to salt stress. It explores how these metabolites contribute to various aspects of salt tolerance, including ion regulation, osmotic adjustment, and oxidative stress management. By examining recent research findings, this review aims to highlight the specific secondary metabolites involved in wheat's response to saline conditions and their potential mechanisms of action. Ultimately, the review seeks to provide insights into how leveraging secondary-metabolite pathways can lead to the development of wheat varieties with improved salt tolerance, contributing to sustainable agriculture and food security.

Main conclusion: In the Negev, substantial vapor stems from the wet soil following rain events and therefore cannot be considered as dew but rather as distillation. Distillation provided ~ 35% and ~ 60% of the vapor-driven liquid for the cobbles and rock slabs, respectively, implying that lithobionts may benefit from vapor condensation also in non-dewy deserts. Lithic chlorolichens (lichens with green algae as photobionts) and cyanobacteria cover almost all rock surfaces in the Negev Highlands, where chlorolichens are believed to mainly benefit from non-rainfall water (NRW), i.e., dew and vapor at high relative humidity. Since chlorolichens may also inhabit non-dewy deserts and vapor may also stem from the wet soil (which once condenses is termed distillation), we hypothesized that vapor that stems from the wet soil may also benefit lithic chlorolichens. To evaluate the potential amount accumulated on these rocky surfaces, whether by NRW or soil vapor plus distillation (jointly termed as indirect rain water, IRW), 3-year-long measurements were conducted in the Negev using cloths attached to a pair of rock slabs and a pair of cobbles. Taking 0.05 (reflecting vapor adsorption) and 0.1 mm (reflecting vapor condensation), which allows for net photosynthesis by chlorolichens and cyanobacteria, respectively, we found that: (1) the average number of days with NRW and IRW ≥ 0.05 mm was respectively 128.7 days and 28.0 days (for cobbles) and 37.3 days and 19.3 days (for rock slabs), with dew (which occurs along the year) and distillation (limited to days after rain events) occurring respectively for 36.7 days and 20.0 days (cobbles) and 28.0 days and 6.0 days (rock slabs), (2) average annual amounts of NRW and IRW ≥ 0.05 mm were respectively 11.5 mm and 3.9 mm (for cobbles) and 2.7 mm and 1.8 mm (for rock slabs), with dew and distillation being respectively 4.7 mm and 3.1 mm (for cobbles) and 0.5 mm and 0.9 mm (for rock slabs), (3) average annual daytime duration of > 0.05 mm for NRW and IRW were respectively 307.8 h and 83.9 h (for cobbles) and 81.0 h and 46.7 h (for rock slabs) with dew and distillation lasting respectively 103.8 h and 60.2 h (for cobbles) and 10.3 h and 17.6 h (for rock slabs). Given that daylight duration primarily dictates growth, we may conclude that: (1) cobbles receive substantially higher amounts of NRW and IRW than rock slabs, (2) the amount of distillation received on cobbles (3.1 mm) was not substantially lower than that of dew (4.7 mm). As far as the annual daylight wetness duration for cobble-dwelling lichens is concerned, distillation provided 36.7% of the total duration provided by vapor. Since IRW may occur also in dewless deserts, such as the Mojave Desert, it may partially explain lithic lichen inhabitation in the Mojave and other non-dewy deserts.

Main conclusion: The recalcitrant seeds of Brosimum alicastrum, a widespread tropical tree, have an exceptional ability to resist desiccation, which we propose has contributed to the dominance of the species across a broad precipitation gradient in forests of Latin America. Seed desiccation sensitivity is relatively common in tree species of tropical rain forests. For such species, pre-germination survival may be as important as seedling establishment in determining reproductive success, yet the adaptive traits important for survival are poorly understood. We studied seeds of Brosimum alicastrum Sw., a dominant tree species across a very broad precipitation gradient in Central America. This ecological success seems counterintuitive to the putative presence of seed desiccation sensitivity, that potentially severely limits propagule survival. We evaluated the anatomical, chemical and physiological traits for pre-germination survival in Brosimum alicastrum. Seeds were subjected to a series of desiccation experiments to determine the role of the seed coat and cuticular layers in controlling the rate of water loss. The structural properties were characterised using light and electron microscopy and complemented by biochemical and biophysical characterization of the seed cuticle. We confirm that Brosimum alicastrum seeds are highly desiccation sensitive but exhibit an exceptional resistance to desiccation. We show that the mechanisms for this trait of exceptional control of water loss are multifaceted and relate to the structural, biochemical and biophysical properties of the cuticle surrounding the embryo. When the cuticle is punctured, seed resistance to drying is lost and the seeds die rapidly. We propose that, combined with dispersal by winged fauna, this unique feature of seed desiccation resistance enables this species to colonise and occupy a broad range of edaphic and precipitation niches and so contribute to its prevalence in the forests of Latin America.

Main conclusion: Exogenous substances can enhance plant tolerance to low-temperature stress through five primary mechanisms. The rational application of these substances during early spring cold snaps and other unexpected low-temperature events at various growth stages can effectively mitigate crop damage and ensure stable yields. Low-temperature stress (LTS) is one of the main abiotic stress factors limiting plant growth and development and crop yield. It severely affects plant yield and even causes death by interfering with cell membrane stability, inhibiting photosynthesis, and causing metabolic imbalance. In recent years, exogenous substances (ESs) regulation technology has become an important research direction for improving plants' resistance to LTS due to its high efficiency and operability. Multiple ESs have been shown to effectively alleviate LTS in plants. This paper systematically reviews the research findings on 82 ESs from 121 literature sources and summarizes the molecular physiological mechanisms by which these substances alleviate LTS. The mechanisms of action mainly include the following five aspects: (1) enhancing the antioxidant defense system; (2) optimizing plant hormone balance; (3) maintaining and enhancing photosynthetic efficiency; (4) accumulating osmoprotective substances; (5) improving plant nutritional status. In addition, we explored in depth how to effectively utilize exogenous substances with potential and efficiency to address the challenges posed by LTS in agricultural production. This paper summarizes the research progress on the mechanisms of exogenous substances in resisting LTS, providing theoretical basis and technical support for crop cultivation and stable production in response to LTS.

Main conclusion: Insights from paclitaxel research inspire elucidation of hypericin biosynthesis, highlighting gene identification, multi-omics integration, and biotechnological strategies enabling scalable and sustainable production of valuable Hypericum secondary metabolites. Paclitaxel (Taxol^®), a major plant-derived anticancer drug, exemplifies how research on complex natural products can lead to both breakthrough therapies and innovative strategies for scalable production. Building on this model, this review examines how advances in paclitaxel research have inspired new approaches to studying and producing other pharmaceutically important metabolites, particularly hypericins in Hypericum species. Complementary strategies, ranging from in vitro cultures and elicitor treatments to metabolomic and transcriptomic profiling, have shown promise in enhancing hypericin production, paralleling advances achieved with paclitaxel. Despite their known antiviral and anticancer properties, the biosynthetic pathway of hypericins remains only partially resolved. Current evidence supports a polyketide origin involving emodin and related intermediates, yet key enzymatic steps, particularly those leading to dimeric structures, are still unknown. Although candidate enzymes such as the polyketide synthase HpPKS2 have been identified in Hypericum species, much of the pathway remains unresolved. Given the biosynthetic parallels, fungal systems synthesizing related polyketide metabolites represent promising comparative models for elucidating the hypericin pathway and advancing metabolic engineering efforts. Insights derived from paclitaxel research may thus guide future strategies for elucidating, optimizing, and sustainably producing hypericins and other specialized metabolites across the genus Hypericum.

Main conclusion: Enhanced Apiaceae germination performance by seed priming involves promoting pre-germination growth of the underdeveloped (small) embryos, reduction in hormone contents, and priming with abscisic acid (ABA) improved ageing resilience. Different seed priming technologies are used to improve germination performance and seedling vigour of vegetable crops. Daucus carota (carrot), Pastinaca sativa (parsnip), and other Apiaceae produce morphologically dormant single-seeded fruit halves (mericarps) as dispersal units. In mature mericarps, the underdeveloped (small) embryo is embedded in abundant endosperm tissue, and pre-germination embryo growth to a critical embryo:seed (E:S) length ratio is a requirement for the completion of germination by radicle emergence. We investigated how hydropriming and additive priming with gibberellins (GA), abscisic acid (ABA), and gas plasma-activated water (GPAW) affected carrot and parsnip mericarp germination and ageing sensitivity accessed using a wet ageing assay (80% RH, 42 °C). Carrot and parsnip mericarp priming enhanced germination speed (germination rate GR_50%), maximal germination percentage (G_max), and germination vigour. This was associated with enhanced pre-emergence embryo growth inside hydroprimed, hormone-primed, and GPAW-primed mericarps. Hydropriming affected the hormone contents and ABA sensitivity of parsnip mericarps. It reduced the contents of bioactive GAs and indole-3-acetic acid ~ 2.1 and ~ 7.7-fold, and of the germination inhibitors ABA and cis-(+)-12-oxo-phytodienoic acid ~ 9.2 and ~ 6.0-fold, respectively. Hydroprimed carrot and parsnip mericarps were more sensitive in the wet ageing assay. GPAW-priming increased carrot salinity tolerance but did not increase its wet ageing resilience to a controlled deterioration treatment (CDT). In contrast, GPAW-priming increased the wet ageing resilience of many other vegetable seeds and cereal grains. ABA-priming not only enhanced embryo growth and germination performance, it also increased the wet ageing resilience of carrot and parsnip mericarps. We conclude that ABA-priming and GPAW-priming are promising technologies to improve vigour and wet ageing resilience of primed seeds.

Main conclusion: Polyploidization enhances drought tolerance in A11 of Malus toringo. In polyploid A11 leaves, drought stress elevates soluble sugars and induces moderate ABA synthesis while sustaining photosynthesis to enhance drought tolerance. Malus toringo (Siebold) Siebold ex de Vriese, an apple rootstock, is known for its salt-alkali resistance and post-grafting vigor but has poor drought tolerance. Despite increased interest in polyploid rootstocks due to their improved drought tolerance, research on the drought resilience of polyploid M. toringo is lacking. In this study, we explored the mechanisms underlying drought stress responses in polyploid M. toringo strains by grafting diploid A12, triploid D13, and tetraploids A11 and A13 seedlings onto two-year-old Malus hupehensis rootstocks. The experimental findings revealed that the A11 and D13 plants are more drought resistant than the A12 plants, while the A13 plants exhibited lower drought tolerance. Under drought stress conditions, they displayed higher net photosynthetic rates and antioxidant enzyme activity than the A12 plants and had a higher leaf wax content. Transcriptomics analysis revealed that many differentially expressed genes between the significantly more drought-tolerant tetraploid A11 and its diploid control A12 were related to stress-related metabolic pathways. Notably, in the starch and sucrose metabolic pathways, the starch and sucrose levels in the A11 plants were significantly lower, while the glucose, fructose, and sorbitol content was higher, indicating enhanced osmoregulation. Concurrently, the downregulation in the sucrose phosphate synthase gene (MdSPS1) was accompanied by the upregulation in that of the sucrose invertase gene (MdNINV1). In conclusion, the polyploid A11 and D13 plants were more drought resistant than the diploid A12 plants, providing new insights for exploring apple rootstock germplasms with superior drought tolerance.

Main conclusion: Natural variation in SlAMT1.1 among wild tomatoes may influence post-translational regulation, allowing sustained ammonium uptake under high N supply and providing alleles that can be employed to improve N uptake efficiency in crops. Cultivated plants, particularly tomato (Solanum lycopersicum), require substantial nitrogen (N) inputs to achieve high commercial yields. This demand often leads to the excessive application of costly N-based fertilizers during cultivation. Wild tomato species represent valuable genetic resources for enhancing N uptake efficiency. In many plants, ammonium is the preferred N source, transported by proteins of the AMMONIUM TRANSPORTERS (AMT) family. Here, we characterized the extensive genetic diversity of an AMT1.1 ortholog across both cultivated and distantly related wild tomato species. Phylogenetic and diversity analyses revealed marked divergence in the SlAMT1.1 sequence between cultivated tomato accessions and wild Solanum (section Lycopersicon) species. Comparative analyses of SlAMT1.1 alleles from the Arcanum and Neolycopersicon groups showed enhanced uptake of ¹⁵N-labeled ammonium in roots under repressive ammonium resupply conditions. Notably, we found that the feedback inhibition of ammonium uptake, typical in domesticated tomato roots, was lost in these wild accessions, indicating the presence of a novel regulatory mechanism that adjusts uptake capacity across a wide range of ammonium availability. Our findings indicate that variation in the SlAMT1.1 gene largely explains the observed differences in ammonium uptake between domesticated tomatoes and their wild relatives. Therefore, the natural genetic variation present in the wild tomato SlAMT1.1 alleles offers valuable potential for genomic-based breeding strategies to sustainably improve ammonium uptake in crops.

To elucidate the phytobiochemical mechanisms underlying differentiation among wild populations of Tithonia diversifolia (Helms) A. Gray and establish how soil parameters regulate metabolic pathways.

Methods: 90 individuals from three populations (Ixtaczoquitlán, Orizaba, Rafael Delgado; Veracruz, Mexico) were analyzed. A multi-analytical approach included lipid profiling by gas chromatography-mass spectrometry (GC-MS), identification of secondary metabolites via HPTLC, quantitative bromatological analyses, photosynthetic pigment quantification, and comprehensive edaphoclimatic characterization. Statistical modeling integrated soil chemistry, climatic dynamics, and phytobiochemical responses.

Results: Populations exhibited distinct metabolic phenotypes shaped by edaphic stress. Plants from Rafael Delgado expressed a classical hormetic response under moderate stress (neutral pH, high EC and CEC, low organic matter, clayey soil), with upregulation of biosynthetic pathways resulting in higher protein content (27.25 ± 1.12% DW) and a diverse fatty acid profile (seven compounds). In contrast, Ixtaczoquitlán and Orizaba populations, under more favorable soils, maintained homeostatic regulation prioritizing primary metabolism, with higher chlorophyll accumulation (1.96 ± 0.10 mg g^-1) but reduced synthesis of defensive compounds. Foliar pH remained stable (6.7 ± 0.3) across sites, suggesting a robust self-regulation capacity despite edaphoclimatic variability.

Conclusions: Stress-induced metabolic switching emerges as a key adaptive mechanism in this non-model species, highlighting how environmental gradients reprogram biosynthetic pathways. Hormesis-driven enhancement of bioactive compounds positions T. diversifolia as a promising system for biotechnology aimed at stress-induced biocompound production. These findings advance the state of the art in plant metabolic plasticity and support the sustainable exploitation of renewable ethnobotanical resources.