Mona Soliman

AbstractIn a controlled environment experiment, we studied how physiological changes in leaves during the vegetative phase regulate final grain yield of wheat crops in salt-affected soils. We also hypothesized that amendments such as biochar (SB) and selenium-chitosan nanoparticles (Se-NPs) can protect wheat plants from salt injury. 20-day-old wheat plants were submitted to 4-week salt stress (3000 ppm NaCl). Soybean straw biochar was mixed with soil media at planting and Se-NPs (30 ppm) was sprayed 5 days after the first salt stress treatment. At the end of 4-week Se-NPs treatment, one set of plants was harvested for studying leaf level physiological changes. The salt-stressed plants accumulated significantly high leaf Na+ (~ 13-fold increase), which trigged oxidative and osmotic damage. This salt-induced cellular injury was evident from significantly high levels of lipid membrane peroxidation and inhibited photosynthesis. Our study suggested that leaf physiological impairment in wheat plants was translated into poor biomass production and grain yield loss at crop maturity. Compared with control, salt-stressed plants produced 43% lesser biomass during vegetative phase, and 62% lesser grain yield at maturity. Amendments such as SB and Se-NPs protected the plants from salt-induced cellular injury by restricting Na+ transport toward leaf tissues. Plants treated with NaCl + SB + Se-NPs accumulated 50% less Na+ concentrations in leaves compared with NaCl-treated plants. Our study also suggested that SB and Se-NPs can restore ionic homeostasis and carbon assimilation in salt-stressed wheat by upregulating key transporter genes in leaves.

Under the present era of changing climate, non-biotic pressures such as low or high temperature stress, constant heat waves, ultra-violet (UV) radiations, oxidizing agents, heavy metal and metalloids and salinity are continuously increasing and pose significant retardations in plants’ physiological processes to a great extent. Plants are equipped with adaptive mechanisms which enable them to withstand these induced effects. However, in today’s era, when the global temperature is increasing at an alarming rate, these mechanisms are not sufficient to protect plants from stress-induced growth and photosynthetic inhibitions. The application of plant growth regulators (PGRs) has gained an interesting insight in this regard. The melatonin (Mel) and hydrogen sulphide (H2S) are emerging plant elicitors which impart abiotic stress tolerance in diverse crop plants. The ameliorative role of these PGRs under various abiotic pressures in controlling diverse adaptive mechanisms in diverse crop plants is a topic that is still in infancy stage. Therefore, in the present chapter, the role played by Mel and H2S in regulating complex physiological and morphological adaptive mechanisms under myriads of abiotic pressures is apprehensively discussed.

Climate change has become the global concern due to its drastic effects on the environment. Agriculture sector is the backbone of food security which remains at the disposal of climate change. Heat stress is the is the most concerning effect of climate change which negatively affect the plant growth and potential yields. The present experiment was conducted to assess the effects of exogenously applied β-sitosterol (Bs at 100 mg/L) and eucalyptus biochar (Eb at 5%) on the antioxidants and nutritional status in Thymus vulgaris under heat stressed conditions. The pot experiment was conducted in completely randomize design in which thymus plants were exposed to heat stress (33 °C) and as a result, plants showed a substantial decline in morpho-physiological and biochemical parameters e.g., a reduction of 59.46, 75.51, 100.00, 34.61, 22.65, and 38.65% was found in plant height, shoot fresh weight, root fresh weight, dry shoot weight, dry root weight and leaf area while in Bs + Eb + heat stress showed 21.16, 56.81, 67.63, 23.09, 12.84, and 35.89% respectively as compared to control. In the same way photosynthetic pigments, transpiration rate, plant nutritional values and water potential increased in plants when treated with Bs and Eb in synergy. Application of Bs and Eb significantly decreased the electrolytic leakage of cells in heat stressed thymus plants. The production of reactive oxygen species was significantly decreased while the synthesis of antioxidants increased with the application of Bs and Eb. Moreover, the application Bs and Eb increased the concentration of minerals nutrients in the plant body under heat stress. Our results suggested that application of Bs along with Eb decreased the effect of heat stress by maintaining nutrient supply and enhanced tolerance by increasing the production of photosynthetic pigments and antioxidant activity.

Abstract Increasing ultraviolet (UV) radiation is causing oxidative stress that accounts for growth and yield losses in the present era of climate change. Plant hormones are useful tools for minimizing UV-induced oxidative stress in plants, but their putative roles in protecting tomato development under UVC remain unknown. Therefore, we investigated the underlying mechanism of pre-and post-kinetin (Kn) treatments on tomato plants under UVC stress. The best dose of Kn was screened in the preliminary experiments, and this dose was tested in further experiments. UVC significantly decreases growth traits, photosynthetic pigments, protein content, and primary metabolites (proteins, carbohydrates, amino acids) but increases oxidative stress biomarkers (lipid peroxidation, lipoxygenase activity, superoxide anion, hydroxyl radical, and hydrogen peroxide) and proline content. Treatment of pre-and post-kinetin spraying to tomato plants decreases UVC-induced oxidative stress by restoring the primary and secondary metabolites’ (phenolic compounds, flavonoids, and anthocyanins) status and upregulating the antioxidant defense systems (non-enzymatic antioxidants as ascorbate, reduced glutathione, α-tocopherol as well as enzymatic antioxidants as superoxide dismutase, catalase, ascorbate peroxidase, glutathione peroxidase, glutathione-S-transferase, and phenylalanine ammonia-lyase). Thus, the application of Kn in optimum doses and through different modes can be used to alleviate UVC-induced negative impacts in tomato plants.

Graphical abstract

The contamination of heavy metals is a cause of environmental concern across the globe, as their increasing levels can pose a significant risk to our natural ecosystems and public health. The present study was aimed to evaluate the ability of a copper (Cu)-resistant bacterium, characterized as Bacillus altitudinis
MT422188, to remove Cu from contaminated industrial wastewater. Optimum growth was observed at 37°C, pH 7, and 1 mm phosphate, respectively. Effective concentration 50 (EC
50
), minimum inhibitory concentration (MIC), and cross-heavy metal resistance pattern were observed at 5.56 mm, 20 mm, and Ni > Zn > Cr > Pb > Ag > Hg, respectively. Biosorption of Cu by live and dead bacterial cells in its presence and inhibitors 1 and 2 (DNP and DCCD) was suggestive of an ATP-independent efflux system.
B. altitudinis
MT422188 was also able to remove 73 mg/l and 82 mg/l of Cu at 4th and 8th day intervals from wastewater, respectively. The presence of Cu resulted in increased GR (0.004 ± 0.002 Ug
−1
FW), SOD (0.160 ± 0.005 Ug
−1
FW), and POX (0.061 ± 0.004 Ug
−1
FW) activity. Positive motility (swimming, swarming, twitching) and chemotactic behavior demonstrated Cu as a chemoattractant for the cells. Metallothionein (MT) expression in the presence of Cu was also observed by SDS-PAGE. Adsorption isotherm and pseudo-kinetic-order studies suggested Cu biosorption to follow Freundlich isotherm as well as second-order kinetic model, respectively. Thermodynamic parameters such as Gibbs free energy (∆G°), change in enthalpy (∆H° = 10.431 kJ/mol), and entropy (∆S° = 0.0006 kJ/mol/K) depicted the biosorption process to a feasible, endothermic reaction. Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Energy-Dispersive X-Ray Spectroscopy (EDX) analyses revealed the physiochemical and morphological changes in the bacterial cell after biosorption, indicating interaction of Cu ions with its functional groups. Therefore, these features suggest the potentially effective role of
B. altitudinis
MT422188 in Cu bioremediation.

Environmental stresses alter the growth and productivity of crop plants by affecting the key metabolic pathways. Among these pathways, photosynthesis 14holds a key position contributing immensely to overall development and productivity. The tolerance levels to different abiotic stresses vary considerably from species to species. Abiotic stresses significantly alter photosynthetic functioning by upsurging the production of toxic reactive oxygen production leading to disruption of the photosynthetic components like electron transport, photosystems I and II, adenosine triphosphate (ATP) generation, and carbon fixation by overall influence on the enzymes regulating the carbon fixation process. Both C3 and C4 systems display differential behavior in response to abiotic stresses. The alteration in the stomatal and nonstomatal attributes ultimately affects the photosynthesis considerably. Designing plants with improved photosynthetic functioning is imperative with focus on the antioxidant machinery of the chloroplast, PSII repair mechanisms, redox homeostasis, and the associated signaling components. The present review addresses the influence of abiotic stresses on photosynthetic functioning and the mechanisms contributing to amelioration of the damaging effects.

Biochar Magic against Abiotic Stresses - 1

The present study was conducted to examine the potential role of Plantago ovata Forsk leaf extract (POLE) which was applied at various concentration levels (control, hydropriming, 10, 20, 30, and 40% POLE) to the wheat ( Triticum aestivum L.) seedlings. Drought stressed was applied at 60% osmotic potential (OM) to the T. aestivum seedlings to study various parameters such as growth and biomass, photosynthetic pigments and gas exchange characteristics, oxidative stress and response of various antioxidants and nutritional status of the plants. Various growth parameters such as gaseous exchange attributes, antioxidants and nutritional status of T. aestivum were investigated in this study. It was evident that drought-stressed condition had induced a negative impact on plant growth, photosynthetic pigment, gaseous exchange attributes, stomatal properties, and ion uptake by different organs (roots and shoots) of T. aestivum . The decrease in plant growth resulted from oxidative stress and overcome by the antioxidant (enzymatic and non-enzymatic) compounds, since their concentration increased in response to dehydration. Seed priming with POLE positively increased plant growth and photosynthesis, by decreasing oxidative stress indicators and increasing activities of antioxidant (enzymatic and non-enzymatic) compounds, compared to the plants which were grown without the application of POLE. Our results also depicted that optimum concentration of POLE for T. aestivum seedlings under drought condition was 20%, while further increase in POLE (30 and 40%) induced a non-significant ( P < 0.05) effect on growth (shoot and root length) and biomass (fresh and dry weight) of T. aestivum seedling. Here we concluded that the understanding of the role of seed priming with POLE in the increment of growth profile, photosynthetic measurements and nutritional status introduces new possibilities for their effective use in drought-stressed condition and provides a promising strategy for T. aestivum tolerance against drought-stressed condition.

The influence of dry leachates of Acasia saligna was tested on the seedling growth, photosynthesis, biochemical attributes, and gene expression of the economically important crops, including wheat ( Triticum aestivum L.), radish ( Raphanus sativus L.), barley ( Hordeum vulgare L.) and arugula ( Eruca sativa L.). Different concentrations (5%, 10%, 15%, 20%, and 25%) of stem extract (SE) and leaf extract (LE) of A. saligna were prepared, and seedlings were allowed to grow in Petri plates for 8 days. The results showed that all plant species exhibited reduced germination rate, plant height, and fresh and dry weight due to leachates extracts of A. saligna . Moreover, the activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX), exhibited differential regulation due to the extract treatment. The SOD was increased with increasing the concentration of extracts, while CAT and APX activities were decreased with increasing the extract concentrations. In addition, leachate extract treatment decrease chlorophyll content, photosynthesis, PSII activity, and water use efficiency, with evident effects at their higher concentrations. Furthermore, the content of proline, sugars, protein, total phenols, and flavonoids were reduced considerably due to leachates extract treatments. Furthermore, seedlings treated with high concentrations of LE increased the expression of genes. The present results lead to the conclusion that A. saligna contains significant allelochemicals that interfere with the growth and development of the tested crop species and reduced the crops biomass and negatively affected other related parameters. However, further studies are suggested to determine the isolation and purification of the active compounds present in A. saligna extracts.

The present study aimed to study the effect of dry leaf and stem leachates of Acacia saligna on wheat’s growth and enzyme functioning (Triticum aestivum) and barley (Hordeum vulgare). Leaf leachates (LL) and stem leachates (SL) of A. saligna were applied through root and nutrient solution in different concentrations i.e., 5, 10, and 15%. Treatment of LL and SL declined the growth in terms of height and dry weight in both tested plants in concentration-dependent manner with the maximal decline due to 15% LL. In addition, content of relative water, total chlorophylls, and carotenoids decreased in both wheat as well as barley. The activity of ascorbate peroxidase, monodehydro ascorbate reductase, dehydroascorbate reductase, and glutathione reductase increased considerably due to the treatment of LL and SL. The indigenous tolerance mechanisms in wheat and barley seedlings were further strengthened in wheat and barley by increased accumulation of glycine betaine, glutathione, and ascorbate in response to LL and SL treatment. Additionally, the activity of lipoxygenase and protease were increased significantly due to LL and SL treatment with a maximal increase at higher concentrations. From the present study it can be concluded that extracts of leaf and stem of A. saligna inhibit the growth of wheat and barley significantly with a concomitant increase in the functioning of the ascorbate-glutathione (AsA-GSH) cycle. Further, both crop species showed comparable responses to A. saligna leachates.

Minerals are the fundamental source of nutrients for plant functions such as photosynthesis, ATP currency, cellular respiration, metabolic activities, defense mechanisms, and tolerance to biotic and abiotic stressors. Minerals are the most significant component of plant nutrition and applying these minerals supplements can increase fruit output. The study’s main aim was to make agricultural farming easier by foliar applying newly created nutrients like Lebosol-calcium and Magnesium. The four treatments: To (Control), T1 (Lebosol-Mg-Plus, 3 ml/L), T2 (Lebosol-Ca-Forte, 3 ml/L), and T3 (Lebosol-Mg-Plus and Lebosol-Ca-Forte, 3 ml/L) was applied as foliar spray to the seedlings of tomato. It was found that T3 substantially enhanced tomato’s morphological features and yield. The treatment T3 significantly increased total soluble protein, chlorophyll content, and antioxidant enzyme activity. Furthermore, the foliar application of T3 considerably improved phenolic and ascorbic acid contents. The general anatomical features of the leaf, stem, and roots of tomato were qualitatively affected by the treatments. Application of Lebosol-Ca provided the highest total thickness of lamina, number of vessel elements, total phloem area, chlorenchyma layer, total area of vessel elements, xylem ratio, and increased palisade layer thickness, vessel diameter. Furthermore, T3 treatment showed a diverse impact on the internal structure of tomato organs, with palisade and spongy parenchyma growing to maximum values and vessel diameters expanding. T3 had also posed remarkable alterations in morpho-physiological, biochemical, and anatomical aspects in tested plants.

Pathogenic infestations are significant threats to vegetable yield, and have become an urgent problem to be solved. Rhizoctonia solani is one of the worst fungi affecting tomato crops, reducing yield in some regions. It is a known fact that plants have their own defense against such infestations; however, it is unclear whether any exogenous material can help plants against infestation. Therefore, we performed greenhouse experiments to evaluate the impacts of R. solani on 15- and 30-day old tomato plants after fungal infestation, and estimated the antifungal activity of nanoparticles (NPs) against the pathogen. We observed severe pathogenic impacts on the above-ground tissues of tomato plants which would affect plant physiology and crop production. Pathogenic infection reduced total chlorophyll and anthocyanin contents, which subsequently disturbed plant physiology. Further, total phenolic contents (TPC), total flavonoid contents (TFC), and malondialdehyde (MDA) contents were significantly increased in pathogen treatments. Constitutively, enhanced activities were estimated for catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX) in response to reactive oxygen species (ROS)in pathogen-treated plants. Moreover, pathogenesis-related genes, namely, chitinase, plant glutathione S-transferase (GST), phenylalanine ammonia-lyase (PAL1), pathogenesis-related protein (PR12), and pathogenesis-related protein (PR1) were evaluated, with significant differences between treated and control plants. In vitro and greenhouse antifungal activity of silver nanoparticles (Ag NPs), chitosan nanoparticles, and Ag NPs/CHI NPs composites and plant health was studied using transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectrophotometry. We found astonishing results, namely, that Ag and CHI have antifungal activities against R. solani. Overall, plant health was much improved following treatment with Ag NPs/CHI NPs composites. In order to manage R. solani pathogenicity and improve tomato health, Ag/CHI NPs composites could be used infield as well as on commercial levels based on recommendations. However, there is an urgent need to first evaluate whether these NP composites have any secondary impacts on human health or the environment.

Copper (Cu)-induced stress caused adverse effects to plant growth and productivity thus considered as a severe threat for sustainable crop production. This article presents an overview of copper stress in plants. Copper participates in many physiological processes as a co-factor for catalysis of many metalloproteins; however, problem occurs when excess amount of copper is present in cells. The high concentration of copper suppresses biomass accumulation and linear plant growth. Copper affected root growth stronger than shoot growth. The reduced mobility of Cu in soil is due to its strong binding to organic and inorganic colloids, where it acts as a barrier to Cu toxicity in terrestrial plants. Excess of Cu inhibits a large number of enzymes and interferes with several aspects of plant biochemistry, including photosynthesis, pigment synthesis, and membrane integrity. So, the most important effect of copper toxicity is associated with the blocking of photosynthetic electron transport, leading to the production of radicals which start peroxidative chain reactions. Copper induces oxidative stress that involves induction of lipid peroxidation in the plant which further cause a severe damage to the cell membrane. High copper concentration can disturb the chloroplast ultrastructure by disturbing the photosynthetic process. Like chromium and iron, copper is also a redox metal that can have direct involvement in inducing oxidative stress in plants. In addition, Cu stress induced -production of reactive oxygen species is well recognized and controlled at both the production and consumption levels, through increased antioxidative systems.

Ethylene is a simple gaseous phytohormone, a hydrocarbon C2H4, with various roles in the regulation of plant development, growth and stress responses, and whole biological processes. Ethylene modifies efficiency and all functions by sharing information with other signalling pathways in regular and stressful ecosystems. It can achieve a variety of different metabolic mechanisms with significant results based on the accumulation rate and plant sensitivity. The results indicate that ethylene generates dual properties in acceptable tolerances through the cellular and molecular regulation of plant mechanisms. This book helps to better understand the potential mechanisms in natural and stressful situations as a signal molecule in plant production and development. In addition, a study explores how ethylene signalling has been used as signals for some alternating pathways in agriculture. This chapter studies the adaptation and responses of plants under various stress factors as well as the response of various kinds of ethylene.