Maria Pilarska

Cadmium (Cd) and lead (Pb) contamination may alter common buckwheat (Fagopyrum esculentum Moench cv. ‘Korona’) physiology and composition. The objective was to determine whether common buckwheat maintains physiological performance under controlled Cd and Pb exposure while assessing metal transfer to harvested achenes. A 12-day in vitro phytotoxicity assay based on seed germination and root elongation and a six-week pot experiment were conducted. Cd had a stronger impact on in vitro seed germination and root growth than Pb. Under the highest metal treatments, soil concentrations reached 14,733.98 µg g⁻¹ DW for Cd and 5621.60 µg g⁻¹ DW for Pb; concentrations in leaves and achenes were substantially lower, although Cd transfer to the achenes remained relevant to food safety. Adult plants showed no consistent treatment-related changes in leaf water content, photosynthetic pigments, or F_v/F_m. Biochemical analyses detected treatment effects in proline, H₂O₂, SOD, CAT, and total phenolics. The treatment with 1000 mg L⁻¹ of Cd showed the highest leaf SOD activity and mature-achene total phenolic content. The largest observed compositional difference was the high lysine content under 5000 mg L⁻¹ of Cd in leaves and mature achenes, but this coincided with substantial Cd contamination and therefore cannot be interpreted as biofortification or a nutritional benefit. Overall, responses were non-monotonic and organ-specific, indicating substantial physiological adjustment during short-term exposure while confirming Cd transfer to mature achenes as a food-safety concern.

Progressive soil salinisation is a major constraint to agriculture, and deciphering resistance strategies in plants adapted to such harsh environments has the potential for improving salinity tolerance in crops. Efficient regulation of the photosynthetic light reactions is a key element of acclimation to adverse environmental conditions, as it ensures optimal production of reducing power and ATP. The annual halophyte Mesembryanthemum crystallinum has long served as a model plant for studying stress response mechanisms. In this species, exposure to salt stress induces a transition from C ₃ photosynthesis to crassulacean acid metabolism (CAM). This review summarises the latest findings on the regulation of photosynthetic electron transport (PET) under salinity in M. crystallinum , focusing on their potential dependence on CAM. It also suggests a model in which the plastoquinone pool plays a major role in PET acclimation.

Proteins belonging into cryptochrome/photolyase family act as either blue light photoreceptors or as enzymes responsible for repair of pyrimidine dimers produced under UV. Surprisingly, the members of plant-specific photolyase/blue-light receptor 2 (PPL/PHR2) subclade of this family, are almost completely uncharacterized. Here, we focused on the physiological role of protein encoded by Arabidopsis At2g47590 gene. Our results demonstrate for the first time its crucial role in cotyledon greening and maintenance of plant fitness. Based on the phenotype of the mutant in At2g47590 gene i.e. albino cotyledons and pale green true leaves we named this gene GERALT ( GER MINATION AL BINO T RANSIENT). Using different approach including analysis of plant phenotypes, chloroplast sizes and architecture, transcriptomes, photosynthetic pigments, maximum PSII quantum yield (F _V /F _M ) we show that the proper plant functioning is the effect of co-operation of GERALT-dependent and -independent pathways with the role of the former diminishing with plant age. Lower levels of transcripts dependent on plastid encoded polymerase and higher levels of these dependent on nuclear encoded polymerase, smaller chloroplasts with large grana stacks and very weakly developed stromal thylakoids, lower levels of photosynthetic pigments with higher chlorophyll a/b ratio, are among characteristic features of geralt plants. We believe that these results encourage scientific community to study PPL/PHR2 proteins which seems to play a special role in plants.

We have analyzed the effect of salinity on photosystem II (PSII) photochemistry and plastoquinone (PQ) pool in halophytic Mesembryanthemum crystallinum plants. Under prolonged salinity conditions (7 or 10 days of 0.4 M NaCl treatment) we noted an enlarged pool of open PSII reaction centers and increased energy conservation efficiency, as envisaged by parameters of the fast and slow kinetics of chlorophyll a fluorescence. Measurements of oxygen evolution, using 2,6-dichloro-1,4-benzoquinone as an electron acceptor, showed stimulation of the PSII activity due to salinity. In salt-acclimated plants (10 days of NaCl treatment), the improved PSII performance was associated with an increase in the size of the photochemically active PQ pool and the extent of its reduction. This was accompanied by a rise in the NADP⁺/NADPH ratio. The presented data suggest that a redistribution of PQ molecules between photochemically active and non-active fractions and a change of the redox state of the photochemically active PQ pool indicate and regulate the acclimation of the photosynthetic apparatus to salinity.

Editorial: Chloroplast redox state: new insights into stress responses and acclimation

Reactive oxygen species (ROS) signalling is crucial in modulating stress responses in plants, and NADPH oxidases (NOXs) are an important component of signal transduction under salt stress. The goal of this research was to investigate whether the regulation of NOX-dependent signalling during mild and severe salinity differs between the halophyte Eutrema salsugineum and the glycophyte Arabidopsis thaliana. Gene expression analyses showed that salt-induced expression patterns of two NOX genes, RBOHD and RBOHF, varied between the halophyte and the glycophyte. Five days of salinity stimulated the expression of both genes in E. salsugineum leaves, while their expression in A. thaliana decreased. This was not accompanied by changes in the total NOX activity in E. salsugineum, while the activity in A. thaliana was reduced. The expression of the RBOHD and RBOHF genes in E. salsugineum leaves was induced by abscisic acid (ABA) and ethephon spraying. The in silico analyses of promoter sequences of RBOHD and RBOHF revealed multiple cis-acting elements related to hormone responses, and their distribution varied between E. salsugineum and A. thaliana. Our results indicate that, in the halophyte E. salsugineum, the maintenance of the basal activity of NOXs in leaves plays a role during acclimation responses to salt stress. The different expression patterns of the RBOHD and RBOHF genes under salinity in E. salsugineum and A. thaliana point to a modified regulation of these genes in the halophyte, possibly through ABA- and/or ethylene-dependent pathways.

The role of an endophytic Zygomycete Mucor sp. in growth promotion and adaptation of the photosynthetic apparatus to increased energy demands of its hosts Arabidopsis arenosa and Arabidopsis thaliana was evaluated. Inoculation with the fungus improved the water use efficiency of the plants and allowed for them to utilize incident light for photochemistry more effectively by upregulating the expression of several photosystem I‐ and II‐related genes and their respective proteins, proteins involved in light harvesting in PSII and PSI and carbon assimilation. This effect was independent of the ability of the plants to acquire nutrients from the soil. We hypothesize that the accelerated growth of the symbiotic plants resulted from an increase in their demand for carbohydrates and carbohydrate turnover (sink strength) that triggered a simultaneous upregulation of carbon assimilation. Arabidopsis plants inoculated with Mucor sp. exhibited upregulated expression in several genes encoding proteins involved in carbohydrate catabolism, sugar transport, and smaller starch grains that indicate a significant upregulation of carbohydrate metabolism.