Water Content of Plant Tissues: So Simple That Almost Forgotten?

Enhancing drought resistance in Dracocephalum moldavica L. through mycorrhizal fungal inoculation and melatonin foliar application

This research focused on improving the drought tolerance of Dracocephalum moldavica, a plant vulnerable to water stress, by exploring the combined effects of melatonin spray and mycorrhizal fungus Glomus intraradices inoculation. The experiment was designed as a factorial randomized study to evaluate the plant's morphological, physiological, and phytochemical responses under different drought conditions (100%, 75%, and 50% field capacity). The findings revealed that the combination of melatonin and mycorrhizal inoculation significantly improved the morphological traits of Moldavian balm under drought conditions. Under severe drought (50% field capacity), chlorophyll a and b levels increased by 26.3% and 35.5%, respectively, when both treatments were applied. Stress indicators, including electrolyte leakage and malondialdehyde content, were substantially reduced with the simultaneous application of melatonin and mycorrhizal symbiosis, indicating decreased cellular damage. Moreover, the combined treatment resulted in the highest activities of the antioxidant enzymes catalase and peroxidase, suggesting that these treatments bolster the plant's oxidative stress defense mechanisms. Additionally, drought stress alone led to an increase in secondary metabolites like phenolic and flavonoid compounds, which were further amplified by the treatments. The study also observed significant alterations in the essential oil composition of the plant. Drought stress increased the levels of α-pinene, 1,8-cineole, and borneol, and these increases were even more pronounced with the combined treatments. Conversely, the levels of geraniol and geranial decreased under drought stress and further with treatment. Overall, this research demonstrates that melatonin and Glomus intraradices inoculation can effectively enhance drought tolerance in Dracocephalum moldavica by improving its physiological characteristics and biochemical composition.

Enhancing nickel stress tolerance in Micro-Tom tomatoes through biopriming with Paraburkholderia phytofirmans PsJN: insights into growth and physiological responses

Introduction

The strategic utilization of plant growth-promoting (PGP) rhizospheric bacteria is a sustainable approach to mitigating the negative effects of anthropogenic activities and excessive nickel (Ni) accumulation in plants. Given that the specific effects of symbiotic interactions depend on the direct relationship between the plant species, bacterial strain, and heavy metals (HMs), this study aimed to investigate the effects of Paraburkholderia phytofirmans PsJN seed priming on Ni tolerance in adult Micro-Tom tomato plants (Solanum lycopersicum L.).

Methods

Sterilized Micro-Tom seeds were bioprimed with P. phytofirmans PsJN for 24 hours and then sown into the soil. Non-primed, imbibed seeds were used as a control. After 10 days, the seedlings were transferred to a Hoagland nutrient solution. Chronic (10 μM Ni) and acute (50 μM Ni) stress conditions were induced by supplementing the Hoagland solution with Ni salt. The experiment lasted approximately 75 days, covering the complete life cycle of the plants. Various physiological and biochemical parameters were analyzed.

Results

Significant differences (p < 0.05) were observed between non-primed and bioprimed tomato plants in terms of fruit yield. Bioprimed tomatoes exhibited higher resilience to Ni stress, particularly under acute stress conditions. Non-primed tomatoes treated with 50 μM Ni showed statistically lower concentrations of chlorophyll a and total chlorophylls compared to bioprimed tomatoes. Moreover, proline content was generally lower and more stable in bioprimed plants, indicating reduced oxidative stress.The activity of antioxidant enzymes exhibited distinct patterns between nonprimed and bioprimed tomatoes.

Conclusion

The findings suggest that biopriming with P. phytofirmans PsJN enhances Micro-Tom tomato resilience and growth under Ni stress. This technique appears to mitigate Ni-induced stress effects, particularly at higher Ni concentrations, making it a promising strategy for improving tomato performance in Ni-contaminated environments. Future studies should explore the underlying molecular mechanisms and field applications of this biopriming approach.

Inoculation with plant growth-promoting bacteria mitigates the negative impacts of 2 °C warming on the photosynthesis, growth, and nutritional value of a tropical C4 grassland under field conditions

Human-induced climate change is causing Earth's temperature to rise, and models indicate a persistent increase in the next years. Temperature is one of the most important factors regulating the carbon flux of natural and managed ecosystems. In the last decades, the use of plant growth-promoting bacteria in C4 grasses has emerged as an important alternative to alleviate the negative impacts of abiotic factors on plant metabolism, growth, and forage nutritional quality. In this study, we investigated the effects of warming (+2 °C) on the photosynthesis, plant water status, growth, and nutritional quality of a managed pasture of Brachiaria (syn. Urochloa) Mavuno inoculated or not with Azospirillum brasilense and Pseudomonas fluorescens. We evaluated two levels of temperature (ambient and elevated) under two levels of inoculation (inoculated and non-inoculated) in a multifactorial design. Our results showed that inoculation stimulated root growth and increased photosynthetic rates through higher stomatal conductance and improved photosystem II performance, presumably resulting in higher productivity, crude protein content, and forage digestibility with reduced lignin and fiber fraction. Warming increased non-photochemical quenching and electron transport rate in the wet season, but decreased midday maximum quantum efficiency of PSII photochemistry during dry season, relative water content, productivity, and forage quality and digestibility. When inoculated plants developed under a warmer atmosphere, the positive effects of inoculation completely counteract the negative impacts of warming on photosynthesis, growth, nutritional quality, and digestibility, resulting in a pasture with reduced lignin content and improved heating dissipating capacity and digestibility. Our results demonstrated that A. brasilense and P. fluorescens co-inoculation is a sustainable option to fully mitigate the negative impacts of elevated temperature on Mavuno grass pastures. These findings highlight the potential of microbial inoculants in enhancing forage resilience and productivity under climate stress.

Integrating Microalgal Chlorella Biomass and Biorefinery Residues into Sustainable Agriculture and Food Production: Insights from Lettuce Cultivation

Microalgal biomass offers a promising biofertilizer option due to its nutrient-rich composition, adaptability, and environmental benefits. This study evaluated the potential of microalgal-based biofertilizers-microalgal Chlorella biomass, de-oiled microalgal biomass (DMB), and de-oiled and de-aqueous extract microalgal biomass (DAEMB)-in enhancing lettuce growth, soil nutrient dynamics, and microbial community composition. Lettuce seedlings were cultivated with these biofertilizers, and plant growth parameters, photosynthetic pigments, and nitrogen uptake were assessed. Soil incubation experiments further examined nutrient mineralization rates, while DNA sequencing analyzed shifts in rhizosphere microbial communities. Lettuce grown with these biofertilizers exhibited improved growth parameters compared to controls, with Chlorella biomass achieving a 31.89% increase in shoot length, 27.98% in root length, and a 47.33% increase in fresh weight. Chlorophyll a and total chlorophyll levels increased significantly in all treatments, with the highest concentrations observed in the Chlorella biomass treatment. Soil mineralization studies revealed that DMB and DAEMB provided a gradual nitrogen release, while Chlorella biomass exhibited a rapid nutrient supply. Microbial community analyses revealed shifts in bacterial and fungal diversity, with increased abundance of nitrogen-fixing and nutrient-cycling taxa. Notably, fungal diversity was enriched in biomass and DAEMB treatments, enhancing soil health and reducing pathogenic fungi. These findings highlight microalgal biofertilizers' potential to enhance soil fertility, plant health, and sustainable resource use in agriculture.

Decoding the physicochemical basis of resurrection: the journey of lichen Flavoparmelia caperata through prolonged water scarcity to full rehydration

Desiccation tolerance is a complex phenomenon observed in the lichen Flavoparmelia ceparata. To understand the reactivation process of desiccated thalli, completely dried samples were rehydrated. The rehydration process of this lichen occurs in two phases. The first phase, characterized by rapid rehydration, involves the conversion of non-functional reaction centers (RCs) into functional PSII RCs, and the accumulation of ROS along with the increment in SOD antioxidant enzyme. These coordinated mechanisms initiate the light reaction of photosynthesis by forming active light-harvesting complexes (LHCs). This adaptation ensures efficient recovery, as evidenced by specific energy fluxes (ABS/RC, TR/RC, ET/RC, and DI/RC), phenomenological fluxes (ABS/CS, TR/CS, ET/CS, and DI/CS), quantum efficiencies (ФP0, ФE0, and ФD0), primary and secondary photochemistry, photochemical and non-photochemical quenching, and performance index, highlighting the essential role of rapid water uptake in restoring turgor pressure for cell structure and function maintenance. The interconnected network of antioxidant defenses, including catalase (CAT) and peroxidase (POD), underscores the plant's ability to cope with oxidative stress during resilience. The acid phosphomonoesterase (PME) enzymatic activity corresponds to its role in releasing phosphate for essential cellular functions and post-rehydration thallus growth. The activity of CAT, GPOD, and PME signifies the gradual reactivation of lichen F. caperata. Moreover, the investigation into chlorophyll a fluorescence emphasizes the efficient reactivation of the photosynthetic process in F. caperata. In conclusion, lichen F. caperata demonstrates significant potential for desiccation tolerance through the rapid transformation of chloroplasts, chlorophylls, and PSII RCs from their inactive to active states upon rehydration. This research not only enhances our understanding of desiccation tolerance in resurrection plants but also highlights the importance of lichens, particularly F. caperata, as valuable models for studying plant resilience in challenging environments.

Do Endangered Glacial Relicts Have a Chance for Effective Conservation in the Age of Global Warming? A Case Study: Salix lapponum in Eastern Poland

The abiotic stresses to which plants are exposed, especially in times of climate change, can result in the disruption of natural plant physiological processes. Sudden atmospheric phenomena may increase the risk of failure in protecting rare and extinction-threatened plant species by translocation. This study aimed to determine the effect of extreme ambient temperatures on the condition and physiological response of Salix lapponum plantlets used for their reintroduction into the natural habitat. Salix lapponum plants obtained by micropropagation methods at different stages of growth under laboratory conditions were subjected to a biological experiment. Plants were exposed for 12 h to temperature extremes (0 °C and 30 °C), after which the values of selected markers of the biochemical response were determined, such as photosynthetic pigments and anthocyanin content, guaiacol peroxidase and catalase activity, the presence of ROS and the RWC value. The study showed that plants at early growth stages were sensitive to low-temperature stress. In contrast, older ones showed a stronger response to high temperature, marked by an increased anthocyanin content and guaiacol peroxidase activity. It was also found that a short exposure to temperature extremes did not change the photosynthetic pigment content or catalase activity. The results of the study may be an important indication for the optimization of plant acclimatization methods in the process of their active protection by species translocation.

Cytotoxic activity of callus extract from Vachellia farnesiana (L) Wight & Arn

The in vitro cultures of Vachellia farnesiana (L) Wight & Arn. have demonstrated cytotoxic activity through callus extract on the HeLa cell line. Explants excised from in vitro-grown seedlings from seeds of two different locations were inoculated on Murashige and Skoog (MS) culture media containing various concentrations of N-6 benzyladenine (BA) or kinetin with 2,4-dichlorophenoxyacetic acid (2,4-D). Optimal efficiency in friable callus induction (100%) was achieved in leaf explants cultured on MS media containing 2.32 µM BA + 13.57 µM 2,4-D. Plant tissues (callus and leaf) were extracted and subjected to quantitative phytochemical analysis, revealing the highest total alkaloid and phenolic content in leaf extracts from Queretaro adult specimens (339.5 ± 20.9 mg atropine equivalents (AE) per g dry extract (DE) and 158.4 ± 12.5 mg gallic acid equivalents (GAE) per g DE, respectively). In contrast, callus cultures exhibited significantly higher total triterpene content (356-381 mg ursolic acid equivalents (UAE) per g DE) compared to leaf extracts (208-243 mg UAE/g DE). Both leaf and callus extracts displayed cytotoxic activity against the HeLa cell line, with a significantly lower half-maximal inhibitory concentration (IC50) for leaf extracts (28-32 µg/mL) compared to callus cultures (43-66 µg/mL), suggesting that alkaloids were primarily responsible for the cytotoxic activity. Furthermore, this study provides valuable insights into the controlled production of bioactive compounds with cytotoxic activity, with callus serving as a rich source.

High-throughput phenotyping reveals multiple drought responses of wild and cultivated Phaseolinae beans

Introduction

Although drought resistance of a plant may be achieved through morphological, structural, physiological, cellular, and molecular adaptations, most studies remain limited to quantifying the effect of drought on biomass.

Methods

Using a highthroughput phenotypic imaging system, we evaluated the drought resistance of 151 bean accessions (Phaseolinae; Fabaceae) in an explorative approach, by quantifying five different traits simultaneously: biomass, water use efficiency (WUE), relative water content (RWC), chlorophyll content (NDVI), and root/shoot ratio. Since crop wild relatives are important resources for breeding programs, we analyzed both wild and cultivated accessions, most of which have never been evaluated for drought resistance before.

Results

We demonstrate that the five traits are affected very differently by drought in the studied accessions, with significant correlations existing only between the biomass and WUE indicators (r=0.39), and between the RWC and NDVI indicators (r=0.40). When grouping accessions by subgenus or by species, large intraspecific and withinsubgenus variation was found. For this reason, we performed a cluster analysis, which grouped the accessions into five distinct clusters with similar response profiles. We also correlated the drought resistance for each accession to local climate variables at their original collection sites. The biomass, WUE, and RWC indicators were significantly correlated to annual precipitation (r=0.40, r=0.20, r=0.22, respectively), confirming that accessions from arid environments are generally more drought resistant.

Discussion

Our results demonstrate that the drought resistance of Phaseolinae beans is a multifaceted characteristic and cannot be simply quantified through biomass. Furthermore, the broader knowledge of the drought resistance of the accessions studied here may prove an invaluable resource for future crop production.

A frozen suspension external calibration strategy for elemental quantitative imaging of fresh plant soft tissues by LA-ICP-MS with cryogenic ablation cell

A simple and reliable external calibration strategy of LA-ICP-MS for fresh plant soft tissues was developed. The prepared plant suspension was frozen by the designed cryogenic ablation cell and used as external standard for quantitative elemental imaging analysis of fresh plant tissues. The controllable water content of the prepared external standards provides a similar matrix with fresh soft tissues, and a homogeneous elemental distribution could be ensured due to the fine grinding particle sizes. More interestingly, the presence of water increased the signal intensity produced by the suspension by a factor of 1.6 (Pb) to 66.6 (La) compared to that of the pressed cake. The excellent dispersing property and advantage of long-term use were achieved owing to the employment of 0.1% PAANa as suspending agent. A series of plant reference materials were analyzed, and the relative errors of most elements were less than 10 %, indicating that there is a reliable accuracy of the proposed method. The limits of detection (LODs) ranged from 0.1 ng·g-1 (La) to 1279 ng·g-1 (S). This method was used for elemental imaging analysis in rice leaves under arsenic stress, and the results were consistent with previous studies, which mean that the proposed method could provide technical support for researchers in the fields of agriculture and environment.

Frost Damage Mitigation in Flowers and Fruitlets of Peach and Almond from the Application of a Multi-Attribute Approach Biostimulant

To prevent frost damage in fruit trees, growers employ passive and active methods, and one of these second methods is the use of biostimulant compounds against abiotic stress. In this study, two trials were conducted to evaluate the effectiveness of a multi-attribute approach biostimulant-containing α-tocopherol, boron, and glycols, in peach ('UFO-4' cultivar) and almond ('Vairo' cultivar) trees. In a first trial, one-year-old shoots with flowers were collected after 24 h, 48 h, and 96 h of the biostimulant applications. Two different application rates of the product (1000 and 2000 cc ha-1) were tested and compared to an untreated control. In a second trial, one-year-old shoots with fruitlets were collected after 24 h of the biostimulant applications. In this case, only an application rate (2000 cc ha-1) was tested. In the two trials, the collected one-year-old shoots were subjected to different frost temperatures using a controlled environment chamber. The damage level was assessed by a morphological analysis of the flowers and fruitlets 96 h after each frost cycle simulation. The lethal temperatures (LT10, LT50, and LT90) of each treatment were calculated by probit analysis. The product applied 24 h and 48 h before the frost simulations significantly decreased the LT10 and LT50 in 1.5 °C in peach flowers, and 2.5 °C in almond flowers (a temperature reduction of 50% and 75%, respectively). These results were more consistent when the application volume was 2000 cc ha-1, instead of 1000 cc ha-1. Significant differences between treated and non-treated fruitlets were observed only in almond fruitlets, with LT10 and LT50 being 0.5 °C lower in treated fruitlets (20% reduction). In conclusion, the multi-attribute approach biostimulant applied 24 or 48 h before the frost reduced the mortality of peach and almond flowers, but its effectiveness to protect fruitlets after bloom was inconsistent.

Incorporation of Three Different Optical Trains into the IR-MALDESI Mass Spectrometry Imaging Platform to Characterize Artemisia annua

Artemisinin is the leading medication for the treatment of malaria and is only produced naturally in Artemisia annua. The localization of artemisinin in both the glandular and non-glandular trichomes of the plant makes it an ideal candidate for mass spectrometry imaging (MSI) as a model system for method development. Infrared matrix-assisted laser desorption electrospray ionization MSI (IR-MALDESI-MSI) has the capability to detect hundreds to thousands of analytes simultaneously, providing abundance information in conjunction with species localization throughout a sample. The development of several new optical trains and their application to the IR-MALDESI-MSI platform has improved data quality in previous proof-of-concept experiments but has not yet been applied to analysis of native biological samples, especially the MSI analysis of plants. This study aimed to develop a workflow and optimize MSI parameters, specifically the laser optical train, for the analysis of Artemisia annua with the NextGen IR-MALDESI platform coupled to an Orbitrap Exploris 240 mass spectrometer. Two laser optics were compared to the conventional set up, of which include a Schwarzschild-like reflective objective and a diffractive optical element (DOE). These optics, respectively, enhance the spatial resolution of imaging experiments or create a square spot shape for top-hat imaging. Ultimately, we incorporated and characterized three different optical trains into our analysis of Artemisia annua to study metabolites in the artemisinin pathway. These improvements in our workflow, resulted in high spatial resolution and improved ion abundance from previous work, which will allow us to address many different questions in plant biology beyond this model system.

Assessing the nutritional quality of Pleurotus ostreatus (oyster mushroom)

There is a huge gap between food production and the exploding population demands in various parts of the world, especially developing countries. This increases the chances of malnutrition, leading to increased disease incidence and the need for functional foods to reduce mortality. Pleurotus ostreatus are edible mushrooms that are cheaply sourced and rich in nutrient with the potential to be harnessed toward addressing the present and future food crisis while serving as functional foods for disease prevention and treatment. This study evaluated the nutritional, proximate, vitamins and amino acids contents of Pleurotus ostreatus. The proximate composition of Pleurotus ostreatus in this study revealed that it contains 43.42% carbohydrate, 23.63% crude fiber, 17.06% crude protein, 8.22% ash, 1.21% lipid and a moisture content of 91.01 and 6.46% for fresh and dry samples of Pleurotus ostreatus, respectively. The monosaccharide and disaccharide profile of Pleurotus ostreatus revealed the presence of glucose (55.08 g/100 g), xylose (7.19 g/100 g), fructose (19.70 g/100 g), galactose (17.47 g/100 g), trehalose (7.37 g/100 g), chitobiose (11.79 g/100 g), maltose (29.21 g/100 g), sucrose (51.60 g/100 g) and lower amounts of cellobiose (0.01 g/100 g), erythrose (0.48 g/100 g) and other unidentified sugars. Potassium, Iron and Magnesium were the highest minerals present with 12.25 mg, 9.66 mg and 7.00 mg amounts, respectively. The vitamin profile revealed the presence of vitamin A (2.93 IU/100 g), C (16.46 mg/100 g), E (21.50 mg/100 g) and B vitamins with vitamin B2 having the highest concentration of 92.97 mg/kg. The amino acid scores showed that Pleurotus ostreatus had more non-essential amino acids (564.17 mg/100 g) than essential amino acids (67.83 mg/100 g) with a ratio of 0.11. Lysine (23.18 mg/100 g) was the highest essential amino acid while aspartic acid (492.12 mg/kg) was the highest non-essential amino acid present in Pleurotus ostreatus. It had a higher concentration of acidic amino acids, 492.12 mg/100 g (77.87%), followed by neutral amino acids, 106.66 mg/100 g (16.88%) and least were the basic amino acids, 23.18 mg/100 g (3.67%). Based on the nutritional assessment of the Pleurotus ostreatus analyzed in this study, it can be concluded that it can serve as an important functional food source that can be exploited to meet the increasing food demands and reduce micronutrient deficiencies in many parts of the world, especially developing countries.

Drought Resistance and Ginsenosides Biosynthesis in Response to Abscisic Acid in Panax ginseng C. A. Meyer

Drought stress adversely affects the production of the perennial medicinal herb Panax ginseng C.A. Meyer. Phytohormone abscisic acid (ABA) regulates many processes in plant growth, development, and response to environments. However, whether drought resistance is regulated by ABA in Panax ginseng remains unknown. In this study, we characterized the response of drought resistance to ABA in Panax ginseng. The results showed that the growth retardation and root shrinking under drought conditions in Panax ginseng were attenuated by exogenous ABA application. Spraying ABA was shown to protect the photosynthesis system, enhance the root activity, improve the performance of the antioxidant protection system, and alleviate the excessive accumulation of soluble sugar in Panax ginseng under drought stress. In addition, ABA treatment leads to the enhanced accumulation of ginsenosides, the pharmaceutically active components, and causes the up-regulation of 3-hydroxy-3-methylglutaryl CoA reductase (PgHMGR) in Panax ginseng. Therefore, this study supports that drought resistance and ginsenosides biosynthesis in Panax ginseng were positively regulated by ABA, providing a new direction for mitigating drought stress and improving ginsenosides production in the precious medicinal herb.