Photochemical efficiency in bean plants (Phaseolus vulgaris L. and Vigna unguiculata L. Walp) during recovery from high temperature stress

Comparative study of the toxicity mechanisms of quinolone antibiotics on soybean seedlings: Insights from molecular docking and transcriptomic analysis

The ecological effects of quinolone antibiotics (QNs) on non-target organisms have received widespread attention. The toxicological mechanisms of three common QNs, that is, enrofloxacin, levofloxacin, and ciprofloxacin, on soybean seedlings were investigated in this study. Enrofloxacin and levofloxacin caused significant growth inhibition, ultrastructural alterations, photosynthetic suppression, and stimulation of the antioxidant system, with levofloxacin exhibiting the strongest toxic effects. Ciprofloxacin (<1 mg·L-1) did not have a significant effect on the soybean seedlings. As the concentrations of enrofloxacin and levofloxacin increased, antioxidant enzyme activities, malondialdehyde content, and hydrogen peroxide levels also increased. Meanwhile, the chlorophyll content and chlorophyll fluorescence parameters decreased, indicating that the plants underwent oxidative stress and photosynthesis was suppressed. The cellular ultrastructure was also disrupted, which was manifested by swollen chloroplasts, increased starch granules, disintegration of plastoglobules, and mitochondrial degradation. The molecular docking results suggested that the QNs have an affinity for soybean target protein receptors (4TOP, 2IUJ, and 1FHF), with levofloxacin having the highest binding energy (-4.97, -3.08, -3.8, respectively). Transcriptomic analysis has shown that genes were upregulated under the enrofloxacin and levofloxacin treatments were mainly involved in ribosome metabolism and processes to synthesize oxidative stress-related proteins. Downregulated genes in the levofloxacin treatment were primarily enriched in photosynthesis-related pathways, indicating that levofloxacin significantly inhibited gene expression for photosynthesis. Genes expression level by quantitative real-time PCR analysis was consistent with the transcriptomic results. This study confirmed the toxic effect of QNs on soybean seedlings, and provided new insights into the environmental risks of antibiotics.

Response of Amaranthus tricolor to cesium stress in hydroponic system: Growth, photosynthesis and cesium accumulation

Remediation of the cesium-contaminated environment is of paramount importance, and phytoremediation is a cost-effective and green technique. In this paper, the response of Amaranthus tricolor to cesium ions in hydroponic solution was investigated at various cesium concentration (0, 0.05, 0.2, 0.4 and 0.6 mM), in terms of the growth weight, height and photosynthesis. The maximal Cs content in stems and leaves of A. tricolor was 13.05 mg/g dry wt under spiked Cs level of 0.4 mM in solution. The maximal transfer factor (TF) and bioconcentration factor (BCF) were 1.87 and 181.25 respectively, when the corresponding Cs content in roots and shoots was 7.04 mg/g and 13.05 mg/g dry wt respectively. TFs are higher than 1 in the conditions of normal plant growth. The growth of A. tricolor was enhanced after the treatment of Cs at low concentrations (0.05 and 0.2 mM), while it was inhibited at 0.4 and 0.6 mM. The leaf number and dry weight of stem, leaf parts and root parts were maximum at the spiked cesium level of 0.2 mM, which significantly increased by 19.19%, 47.56% and 94.56% respectively, compared with the control samples. Under 0.6 mM cesium stress, curl and withering of the leaves occurred, and the plant growth and cesium accumulation dropped to the minimum. Cs at the spiked level of 0.6 mM in solution inhibited the performance of PSII, especially in terms of blockage in electron transfer process beyond Q_A and restraint of P700 reduction. On contrast, the performance of PSII was enhanced by the spiked Cs at level of 0.2 mM, leading to the growing density of reaction centers per excited cross-section and increasing electron transfer process beyond Q_A. In summary, A. tricolor has potential for remediating the Cs-contaminated environment.

Cowpea: a low-cost quality protein source for food safety in marginal areas for agriculture

Cowpea is a low-cost protein source for human nutrition for the world's impoverished regions. Therefore, the yield and total grain protein content (TGPC) of two modern commercials genotypes, Novaera and Gurguéia, and two traditional local genotypes, Paulistinha and EPACE-10, were studied. Also, leaf area and dry weight, leaf soluble protein content, and chlorophyll a fluorescence, parameters related to photosynthetic capacity, were used to evaluate genotypes. Under optimal conditions, the yield of EPACE-10 and Paulistinha, with higher TGPC, was lower than for Gurguéia and Novaera, which showed lower TGPC. The four cowpea genotypes showed high lysine content and low methionine and cysteine. The results revealed a negative correlation between yield and TGPC. The modern commercial genotype Novaera showed a high yield with low TGPC but a higher globulin and albumin content than Gurguéia. Thus, it can be used in high-input agriculture. In contrast, the traditional local genotype EPACE-10, with high TGPC and higher amino acid content than Paulistinha, is indicated for low-input agriculture in marginal areas for food safety under climate changes.

Systematic biology analysis on photosynthetic carbon metabolism of maize leaf following sudden heat shock under elevated CO2

Plants would experience more complex environments, such as sudden heat shock (SHS) stress combined with elevated CO₂ in the future, and might adapt to this stressful condition by optimizing photosynthetic carbon metabolism (PCM). It is interesting to understand whether this acclimation process would be altered in different genotypes of maize under elevated CO₂, and which metabolites represent key indicators reflecting the photosynthetic rates (P_N) following SHS. Although B76 had greater reduction in P_N during SHS treatment, our results indicated that P_N in genotype B76, displayed faster recovery after SHS treatment under elevated CO₂ than in genotype B106. Furthermore, we employed a stepwise feature extraction approach by partial linear regression model. Our findings demonstrated that 9 key metabolites over the total (35 metabolites) can largely explain the variance of P_N during recovery from SHS across two maize genotypes and two CO₂ grown conditions. Of these key metabolites, malate, valine, isoleucine, glucose and starch are positively correlated with recovery pattern of P_N. Malate metabolites responses to SHS were further discussed by incorporating with the activities and gene expression of three C₄ photosynthesis-related key enzymes. We highlighted the importance of malate metabolism during photosynthesis recovery from short-term SHS, and data integration analysis to better comprehend the regulatory framework of PCM in response to abiotic stress.

Change in Photosystem II Photochemistry During Algal Growth Phases of Chlorella vulgaris and Scenedesmus obliquus

Sensitivity of photosynthetic processes towards environmental stress is used as a bioanalytical tool to evaluate the responses of aquatic plants to a changing environment. In this paper, change of biomass density, chlorophyll a fluorescence and photosynthetic parameters during growth phases of two microalgae Chlorella vulgaris and Scenedesmus obliquus were studied. The photosynthetic growth behaviour changed significantly with cell age and algae species. During the exponential phase of growth, the photosynthesis capacity reached its maximum and decreased in ageing algal culture during stationary phase. In conclusion, the chlorophyll a fluorescence OJIP method and the derived fluorescence parameters would be an accurate method for obtaining information on maximum photosynthetic capacities and monitoring algal cell growth. This will contribute to more understanding, for example, of toxic actions of pollutants in microalgae test.

Alterations in photochemical efficiency of photosystem II in wheat plant on hot summer day

In this study the effect of increasing temperature on photochemical efficiency of PS II in wheat plants has been studied on a hot summer day (9:00 AM (Control)-7:00 PM) by measuring Chl a fluorescence. Increasing temperature for a short period of time (2-4 h), in nature affects the efficiency of PS II complex reversibly and does not cause permanent damage to any of the components of photosystem II. A scheme has been provided to demonstrate the sequence and severity of events which get affected maximum by temperature stress.

Analysis of elevated temperature-induced inhibition of photosystem II using chlorophyll a fluorescence induction kinetics in wheat leaves (Triticum aestivum)

Wheat is the major crop plant in many parts of the world. Elevated temperature-induced changes in photosynthetic efficiency were studied in wheat (T. aestivum) leaves by measuring Chl a fluorescence induction kinetics. Detached leaves were subjected to elevated temperature stress of 35 °C, 40 °C or 45 °C. Parameters such as Fv/Fm, performance index (PI), and reaction centre to absorbance ratio (RC/ABS) were deduced using radial plots from fluorescence induction curves obtained with a plant efficiency analyser (PEA). To derive precise information on fluorescence induction kinetics, energy pipeline leaf models were plotted using biolyzer hp3 software. At 35 °C, there was no effect on photosynthetic efficiency, including the oxygen-evolving complex, and the donor side of PSII remained active. At 40 °C, activity was reduced by 14%, while at 45 °C, a K intermediate step was observed, indicating irreversible damage to the oxygen-evolving complex. This analysis can be used to rapidly screen for vitality and stress tolerance characteristics of wheat growing in the field under high temperature stress.