Sodium (Na) and potassium (K) have comparable crustal abundances and similar physicochemical properties. However, due to the predominance of NaCl over KCl in natural salinity, most studies on plant salt responses have focused on NaCl, leaving responses to KCl salinity largely unexplored. To compare plant responses to Na and K salts, the euhalophyte Salicornia europaea was grown under equimolar (100 mM) NaCl and KCl treatments. NaCl salinity enhanced plant dry biomass, succulence, water relations, and the accumulation of organic osmolytes, whereas KCl salinity induced defence responses, lignin deposition, and caused complete plant mortality within 7 weeks. The levels of signalling molecules (H2O2, NO, and H2S) showed distinct patterns between NaCl and KCl treatments. Genes involved in ion compartmentation (HKT1, NHX1, SOS1, and VHA-A) were upregulated only under NaCl salinity. Moreover, NaCl reduced cellular ammonium levels, whereas KCl led to its accumulation, accompanied by declines in amino acid and protein contents, suggesting a disruption of ammonium assimilation under KCl stress. Comparative studies involving two glycophytes and four halophytes revealed that whereas glycophytes exhibited similar or less growth inhibition under KCl than NaCl, halophyte growth was severely inhibited by KCl but stimulated by NaCl. Notably, ammonium accumulation patterns differed between the two plant types; being higher under NaCl in glycophytes, but higher under KCl in halophytes. Overall, despite the chemical similarity between Na+ and K+ ions, our findings demonstrate that K fails to activate adaptive signalling pathways to salt stress, highlighting ion-specific mechanisms underlying halophyte tolerance to NaCl salinity.
Mitogen-activated protein kinases (MPKs) are involved in the cold response of plants; however, in tomatoes, their regulation has been studied only at the mRNA level. In this study, a comparative analysis of the transcriptional and translational regulation of the MAPK cascade in tomato (Solanum lycopersicum) under cold stress and hardening was conducted using polysomic profiling with parallel sequencing of total and polysomic RNA fractions. For representatives of all four groups (A–D), as well as the upstream kinases SlMAPKKK, we calculated mRNA differential expression and translational efficiency. Most cascade components were regulated predominantly at the translational level and mRNA levels remained stable. Groups C and D were profiled for the first time under cold conditions, and candidate translational cold regulators were identified.
Drought stress is a major environmental constraint limiting growth, water relations, and metabolic stability in pepper (Capsicum annuum). This study evaluated the individual and combined effects of melatonin (MEL) and salicylic acid (SA) on drought tolerance by assessing growth, water status, photosynthetic pigments, oxidative stress markers, osmotic adjustment, and antioxidant defence systems. Plants were grown under non-stressed and drought-stressed conditions and treated with MEL, SA, or their combination. Drought stress significantly reduced fresh weight, relative water content, and photosynthetic pigments, while increasing accumulation of hydrogen peroxide and malondialdehyde, indicating severe oxidative damage. Exogenous application of MEL and SA alleviated these effects, with the combined treatment providing the greatest protection. Under drought, the combined application improved biomass accumulation and tissue hydration, preserved chlorophyll and carotenoid contents, reduced oxidative damage, and increased proline accumulation. It also markedly increased superoxide dismutase, catalase, and peroxidase activities, showing enhanced detoxification of reactive oxygen species. These findings demonstrate that the greater drought tolerance conferred by the combined treatment is associated with coordinated regulation of water balance, redox homeostasis, osmotic adjustment, and photosynthetic stability. The combined application of MEL and SA is a promising strategy for improving drought tolerance in pepper cultivation.
This study investigated the anatomical and physiological effects of exogenous meta-topolin (mT) at different concentrations (0, 0.25, 0.50 mM) on the leaves of cold-susceptible cultivar Kahramanmaraş-1 (KM-1) and cold-tolerant cultivar Çoban F1 (ÇF1) of pepper (Capsicum annuum) before cold stress (4°C). Leaf thickness of ÇF1 was higher than KM-1 at optimum (25°C) and low temperatures. Long-term cold stress reduced stomatal density while increasing leaf thickness in KM-1. At 48 and 60 h of stress, both cultivars showed increased malondialdehyde (MDA) and ion leakage, while FW, actual water content (AWC), and relative water content (RWC) decreased. Under cold stress, 0.25 mM mT increased RWC, AWC, and FW in KM-1 at 48 and 60 h, and at 60 h in ÇF1, without changing DW. It decreased the upper stomatal density of ÇF1 and index ratio at 60 h. At 24 h of stress, all mT concentrations increased ferric-reducing antioxidant power (FRAP), peroxidase (POD) activity, protein, phenolic compounds, H2O2, MDA, and leaf thickness. At 48 h, ÇF1 showed higher flavonoid, FRAP, and POD activity when compared with KM-1. All mT applications increased total protein content and decreased MDA levels at 48 and 60 hcompared with stress alone. mT positively supported tolerance to cold stress in pepper through anatomical and physiological mechanisms.
This study examined short-term responses of barley to polyethylene and polyvinyl chloride microplastics in a controlled 60-day greenhouse rhizobox experiment with three replicates per treatment. Microplastics were applied at 0, 2, and 4% of dry soil mass, corresponding to high experimental loadings of 20,000 and 40,000 mg kg−1, respectively. Bulk and rhizosphere soils were evaluated separately using enzyme zymography, nutrient analysis, amplicon sequencing, microbial network analysis, Mantel tests, and structural equation modeling. Higher polyethylene exposure and both polyvinyl chloride treatments reduced superoxide dismutase activity by 16.27–39.12%, increased peroxidase activity by 33.09–67.07%, and reduced net photosynthetic rate by 18.02–24.79%. Microplastic treatments also altered the availability of ammonium, nitrate, and Olsen phosphorus and reorganized the spatial distribution of extracellular enzyme activity. Selected β-1,4-glucosidase, β-1,4-xylosidase, and 4-N-acetyl-glucosaminidase hotspots increased, whereas phosphatase hotspots declined across all microplastic treatments. Changes were also detected in bacterial and fungal diversity and microbial network organization, with lower bacterial network complexity and greater fungal network complexity in the rhizosphere. Structural equation modeling explained approximately 60% of the variation in net photosynthetic rate, with barley antioxidant enzyme responses and soil hydrolytic activity showing the strongest negative associations. These results provide short-term evidence that high microplastic loadings can modify interconnected plant and rhizosphere processes under controlled greenhouse conditions. Given the limited replication, short experimental duration, and high exposure levels, these responses should not be interpreted as evidence of field-level causality. Field experiments using environmentally realistic concentrations and longer exposure periods are required to determine their agricultural relevance.
