This study aimed at characterizing some adaptive changes in Plantago lanceolata L. exposed to harsh conditions of a desert-like environment generating physiological stress of limited water availability and exposure to strong light. It was clearly shown that the plants were capable of adapting their root system and vascular tissues to enable efficient vegetative performance. Soil analyses, as well as nitrogen isotope discrimination data show that P. lanceolata leaves in a desert-like environment had better access to nitrogen (nitrite/nitrate) and were able to fix it efficiently, as compared to the plants growing in the surrounding forest. The arbuscular mycorrhiza was also shown to be well-developed, and this was accompanied by higher bacterial frequency in the root zone, which might further stimulate plant growth. A closer look at the nitrogen content and leaf veins with a higher number of vessels and a greater vessel diameter made it possible to define the changes developed by the plants populating sandy habitats as compared with the vegetation sites located in the nearby forest. A determination of the photosynthesis parameters indicates that the photochemical apparatus in P. lanceolata inhabiting the desert areas adapted slightly to the desert-like environment and the time of day, with some changes of the reaction center (RC) size (photosystem II, PSII), while the plants’ photochemical activity was at a similar level. No differences between the two groups of plants were observed in the dissipation of light energy. The exposure of plants to harsh conditions of a desert-like environment increased the water use efficiency (WUE) value in parallel with possible stimulation of the β-carboxylation pathway.

Somatic hybridisation in the carrot, as in other plant species, enables the development of novel plants with unique characteristics. This process can be induced by the application of electric current to isolated protoplasts, but such electrofusion requires an effective hybrid cell identification method. This paper describes the non-toxic fluorescent protein (FP) tagging of protoplasts which allows discrimination of fusion components and identification of hybrids in real-time during electrofusion. One of four FPs: cyan (eCFP), green (sGFP), yellow (eYFP) or the mCherry variant of red FP (RFP), with a fused mitochondrial targeting sequence, was introduced to carrot cell lines of three varieties usingAgrobacterium-mediated transformation. After selection, a set of carrot callus lines with either GFP, YFP or RFP-labelled mitochondria that showed stable fluorescence served as protoplast sources. Various combinations of direct current (DC) parameters on protoplast integrity and their ability to form hybrid cells were assessed during electrofusion. The protoplast response and hybrid cell formation depended on DC voltage and pulse time, and varied among protoplast sources. Heterofusants (GFP + RFP or YFP + RFP) were identified by detection of a dual-colour fluorescence. This approach enabled, for the first time, a comprehensive assessment of the carrot protoplast response to the applied electric field conditions as well as identification of the DC parameters suitable for hybrid formation, and an estimation of the electrofusion success rate by performing real-time observations of protoplast fluorescence.

The mechanism of ethylene (ET)–regulated salinity stress response remains largely unexplained, especially for semi-halophytes and halophytes. Here, we present the results of the multifaceted analysis of the model semi-halophyte Mesembryanthemum crystallinum L. (common ice plant) ET biosynthesis pathway key components’ response to prolonged (14 days) salinity stress. Transcriptomic analysis revealed that the expression of 3280 ice plant genes was altered during 14-day long salinity (0.4 M NaCl) stress. A thorough analysis of differentially expressed genes (DEGs) showed that the expression of genes involved in ET biosynthesis and perception (ET receptors), the abscisic acid (ABA) catabolic process, and photosynthetic apparatus was significantly modified with prolonged stressor presence. To some point this result was supported with the expression analysis of the transcript amount (qPCR) of key ET biosynthesis pathway genes, namely ACS6 (1-aminocyclopropane-1-carboxylate synthase) and ACO1 (1-aminocyclopropane-1-carboxylate oxidase) orthologs. However, the pronounced circadian rhythm observed in the expression of both genes in unaffected (control) plants was distorted and an evident downregulation of both orthologs’ was induced with prolonged salinity stress. The UPLC-MS analysis of the ET biosynthesis pathway rate-limiting semi-product, namely of 1-aminocyclopropane-1-carboxylic acid (ACC) content, confirmed the results assessed with molecular tools. The circadian rhythm of the ACC production of NaCl-treated semi-halophytes remained largely unaffected by the prolonged salinity stress episode. We speculate that the obtained results represent an image of the steady state established over the past 14 days, while during the first hours of the salinity stress response, the view could be completely different.

Drought is a major stressor affecting tree physiology and is expected to intensify under climate extremes. Stems, partly due to their photosynthetic capacity, tend to be more drought-resilient than leaves. This study aimed to assess stem photosynthetic and its impact on carbon balance in leafless stems under drought conditions. Severe drought caused a marked decline in stem and root water potential (Ψ) and reduced stem water vapor conductance (g_tw) by about 40%. Despite this, stems retained the capacity for active gas exchange: though with reduced stem CO₂ efflux (ECO₂) and enhanced CO₂ refixation, which increased from about 40% under control conditions to ~55%–60% after drought, accompanied by a twofold increase in intrinsic water use efficiency (iWUE). Chlorophyll a fluorescence and pigment analyses indicated that the integrity of photosystem II (PSII) was preserved under drought, supporting sustained corticular photosynthesis. Concentrations of chloride, malate, and citrate in the xylem sap did not change significantly under drought, indicating a high capacity of stems to maintain homeostasis. Stable isotope analyses revealed drought-induced shifts in δ¹³C, consistent with altered carbon allocation following leaf abscission. These results confirm that stem photosynthesis and CO₂ reassimilation contribute significantly to stem metabolic resilience, mitigating drought-induced carbon losses and helping to preserve plant survival.

Background: Photosynthetic activity in plant stems, particularly in woody plants and shrubs, is well known and documented. Nevertheless, our knowledge about the role of photochemical processes occurring in the stems of cultivated plants and their contribution to plant growth and development, including the root system, still remains unclear. Therefore, this study aims to determine the role of cells equipped with chloroplasts and located in the stems of tomato ( Solanum lycopersicum L.) plants and whether changes in the activity of the photochemical processes affect the development of the plant’s root system and aboveground organs. Results: The described study was conducted on tomato plants with stems covered with a doubled agrotextile (DP) that absorb 99% of incident light and on plants growing without coverage (NDP). Stem darkening led to the changes in the intensity of photochemical processes in these organs - a decrease in both the maximum and actual photochemical efficiency [F _v /F _m and Y(II)], as well as an increase in energy dissipation, both controlled (NPQ – non-photochemical quenching) and uncontrolled [(Y(NO) - non-regulated energy dissipation in photosystem II] way. These changes correlate with alterations in the anatomy of the stem cross-section. Darkening led to an increase in stem surface conductance to water vapour but a decrease in stem CO ₂ efflux. The root length and dry mass of DP plants were significantly reduced compared to the roots of NDP plants. No significant differences were observed for the shoots (leaves + stems). The substantial changes in the structure of chloroplasts located in the stem cells of DP were also observed, with visible signs of ageing and disintegration of these organelles. In addition, the composition of the nitrogen forms in the soil where the plants were grown was different between DP and NDP. The soil from DP plants showed a higher total nitrogen content; however, unlike the ammonium and nitrate forms (NH ₄ ⁺ and NO ₃ ⁻), the nitrite form (NO ₂ ⁻) was present at a lower concentration in this substrate compared to that of the NDP plants. Darkening did not have a direct effect on the δ¹³C and δ¹⁵N composition between NDP and DP plants, nor on the carbon-to-nitrogen ratio in the leaves, roots, and stems. Nevertheless, based on the obtained results for δ¹³C, δ¹⁵N, and the nitrogen-to-carbon ratio, some general trends can be observed. Conclusions: The obtained results suggest that photochemical processes occurring in tomato stems have an important influence on the development of the tomato plant, especially on the root system. Limited light access to the stems restricts root system growth and development, but shows no visible negative effects on the above-ground parts of the tomato plants in this study. However, indirect effects on shoot growth and development cannot be excluded. Restricting light exposure to the stems likely reduces energy production in the form of energy carriers, such as ATP and NADPH, resulting in decreased efficiency of assimilate transport to the root. This disrupts the plant’s nitrogen uptake and balance, and in turn limits root system development. Moreover, it can be assumed that the chloroplasts present in tomato stems differ structurally and, as a consequence, functionally from those in leaves, which are specialised for efficient photosynthesis. Because a well-developed root system is an important factor affecting plant growth and yield, the obtained results may suggest the possibility of agronomic practices aimed at increasing the efficiency of photochemical processes and photosynthesis in the stems, and consequently improving yields.

The mechanisms and factors regulating ethylene (ET) biosynthesis and its action remain largely unexplored, particularly in CAM-facultative and (semi)halophytic plants. The use of Mesembryanthemum crystallinum L. (ice plant) provides a unique opportunity to examine plastoquinone (PQ) - ET interactions in semi-halophytes and CAM-facultative plants simultaneously. Here, we present the results of an analysis of the common ice plant's response to prolonged (14-day) salinity stress and DCMU, which maintains the PQ pool in a more oxidised state, thereby mimicking darkness conditions. Differentially expressed gene (DEG) analysis showed that the expression of genes involved in ET regulation was not significantly altered after DCMU application. However, in C₃ plants not affected by salinity stress, the expression of genes related to both photosystems, photosynthesis, and the photosynthetic electron transport chain was significantly affected by DCMU. We propose that sustained salinity stress and the occurrence of CAM photosynthesis render physiological processes insensitive to disruptions caused by a modified PQ pool redox state. The UPLC-MS analysis of the ET biosynthesis pathway central intermediate - 1-aminocyclopropane-1-carboxylic acid (ACC) - confirmed the molecular analysis results, as ACC content was similarly affected in salinity untreated and treated plants. Moreover, the analysis of key antioxidative system components, namely catalase and superoxide dismutases, suggests that PQ pool redox state does not directly regulate them. Instead, an alternative regulation mechanism involving reactive oxygen species (ROS) accumulation and a ROS-induced signalling cascade has been proposed.