Search

Potassium (K) plays a crucial role in plant homeostasis, and its deficiency significantly impacts photosynthesis, triggering a decrease in growth and crop production. K starvation induced a significant reduction in the net photosynthetic rate, and the drop is associated with resistance of CO diffusion through stomatal conductance, mesophyll conductance, and lowered carboxylase activity of Rubisco, electron transport rate of PSII, and with many biochemical limitations. The complex interaction of all the above factors contributed to limiting photosynthesis under K starved conditions. Low chlorophyll content and poor chloroplast structure may also define photosynthetic processes and causes a decrease in crop growth and productivity under K starvation. Under abiotic stresses such as drought, waterlogging, temperature, salinity, and heavy metal, the application of exogenous K promotes plant tolerance by activating the antioxidant system, which limits the overproduction of reactive oxygen species (ROS), avoiding the associated oxidative damages where other signaling molecules such as nitric oxide (NO) and hydrogen sulfide (HS) may involve. The review highlights the decisive role of exogenous and endogenous K in modulating diverse physiological and biochemical processes in a healthy and stressful environment. Furthermore, this review appraises the involvement of K with another signaling molecule in enhancing abiotic stress tolerance in plants. Therefore, this review provides a comprehensive update on the relevance of K in higher plants. Its exogenous application should be a potential tool, especially in crops under adverse environmental conditions., Havza Imtiaz gratefully acknowledges the fnancial assistance rendered by the University Grant Commission, New Delhi, India, in the form of Non-net fellowship. FJC research is supported by a European Regional Development Fund-cofnanced grant from the Ministry of Economy and Competitiveness (PID2019-103924GB-I00) and the Plan Andaluz de Investigación, Desarrollo e Innovación (PAIDI 2020) (P18-FR-1359), Spain.

The involvement of auxin (IAA) in growth and development of plants is well known, but its role in the mitigation of metal stress, especially copper (Cu), is not fully understood; therefore, it is time to explore its involvement in minimizing the stress. A pot experiment was conducted to assess the protective function of IAA, applied to the foliage, on photosynthetic machinery, carbohydrate metabolism, and growth of Brassica juncea, grown with Cu (30 or 60 mg kg

Nanotechnology permits advance research in several areas and opens a large scope in the field of biotechnology and agriculture industry due to unique physiochemical properties. To fulfill the increasing demand of world population higher agricultural productivity is needed to boost the yield. This review presents the current literature and key role of nanoparticles on plant growth, development and yield. The synthesis of nanoparticles by green method with the use of plant extract which is nontoxic, cost effective, ecofriendly over physical and chemical methods. Phytochemical constituents in the plant extract such as phenols, proteins, flavonoids, carbohydrates, alkaloids and amino acids is responsible for the reduction of size of nanoparticles.

Copper (Cu) is an essential micronutrient prerequisite for various metabolic processes in plants. At optimum concentration, it performs a vital role in plant growth and development, while as at supra-optimal levels, it disturbs the normal growth in plants. Due to its dual behavior (vital and harmful), the present experiment was designed to assess the potential role of different Cu concentrations (30, 60, and 90) on Brassica juncea cv. Varuna plants. The experiment was set up in a randomized block design, and various physiological, biochemical, microscopic, and histochemical parameters were assessed at 30, 45, and 60 days after sowing. According to our findings, Cu inhibits growth at all concentrations over the control. The maximum reduction was reported in plants cultivated on Cu 90 mg kg−1 of soil. Cu inhibits the chlorophyll content, RUBISCO activity, photosynthetic parameters, PSII activity, electron transport, and maximum quantum yield, at all concentrations. Cu stress decreases nitrate reductase and carbonic anhydrase activity as well as reduction in relative water content and carbohydrate levels in treated plants. Cu levels induced oxidative stress molecules like reactive oxygen species and malondialdehyde content in test plants, due to which the enzymatic antioxidants (catalase, superoxide-dismutase, and peroxidase) as well as non-enzymatic antioxidants (glutathione, proline), were unregulated. Excess Cu level disturbs the essential nutrient and decreases the levels of nitrogen, phosphorus, and potassium while elevated levels of Cu were observed in test plants. From the above findings, we conclude that Cu displayed a toxic effect at all the concentrations and reduced growth, photosynthetic parameters, and biochemical parameters in Brassica juncea.

Abiotic stresses arising from atmosphere change belie plant growth and yield, leading to food reduction. The cultivation of a large number of crops in the contaminated environment is the main concern of environmentalists at present. To achieve food safety, a highly developed nanotechnology is a useful tool for promoting food production and assuring sustainability. Nanotechnology helps in better production in agriculture by promoting the efficiency of inputs and reducing relevant losses. This review examines the research performed in the past to show how zinc oxide nanoparticles (ZnO-NPs) influence the negative effects of abiotic stresses. The application of ZnO-NPs is one of the most effectual options for considerable enhancement of agricultural yield globally under stressful conditions. ZnO-NPs can transform the agricultural and food industry with the help of several innovative tools in reversing oxidative stress symptoms induced by abiotic stresses. In addition, the effect of ZnO-NPs on physiological, biochemical, and antioxidative activities in various plants has also been examined properly. This review summarizes the current understanding and the future possibilities of plant-ZnO-NPs research.

Nitric oxide (NO) plays a vital role in plant defense against various environmental stresses. However, the study on the defensive effect of NO on the phytotoxicity induced by zinc oxide nanoparticles (ZnO-NPs) remains scarce. In the present study, sodium nitroprusside (SNP, a NO donor) was used to investigate the mechanism of NO in ameliorating the ZnO-NPs toxicity in mustard (Brassica juncea (L.) Czern.) plants. The plants were treated with the different concentrations of SNP (100 µM) and ZnO-NPs (1000 and 2000 µM) either alone or in combination at 25 days after sowing (DAS) for five days consecutively. The results of our study shows that 100 µM of SNP proved highly effective in mitigating the toxicity induced by ZnO-NP. SNP significantly improve chlorophyll content that partially improve photosynthesis in ZnO-NPs stressed plants. Moreover, the defensive role of SNP in relieving the oxidative damage induced by ZnO-NPs is intimately linked to NO-induced antioxidative defense system. The spray of SNP increased the growth biomarkers as well as proline content in control as well as in ZnO-NPs-treated plants. Additionally, microscopic studies further reveal an increase in the size of stomatal aperture on SNP exposure in ZnO-NPs treated plants. Overall, this study provides the first evidence indicating the functions of SNP in alleviating the ZnO-NPs toxicity in mustard plants.

Copper (Cu) is an essential mineral nutrient for the proper growth and development of plants; it is involved in myriad morphological, physiological, and biochemical processes. Copper acts as a cofactor in various enzymes and performs essential roles in photosynthesis, respiration and the electron transport chain, and is a structural component of defense genes. Excess Cu, however, imparts negative effects on plant growth and productivity. Many studies have summarized the adverse effects of excess Cu on germination, growth, photosynthesis, and antioxidant response in agricultural crops. Its inhibitory influence on mineral nutrition, chlorophyll biosynthesis, and antioxidant enzyme activity has been verified. The current review focuses on the availability and uptake of Cu by plants. The toxic effects of excess Cu on seed germination, plant growth and development, photosynthesis, and antioxidant response in plants are discussed. Plant tolerance mechanisms against Cu stress, and management of Cu-contaminated soils are presented.

Glucose (Glc), a monosaccharide, accumulates in plants as a minor product of photosynthesis as well as a breakdown product of sucrose. Glucose regulates various physiological processes in plants; therefore, the present experiment was carried out to assess its role in mustard plants. Seeds of Brassica juncea were sown into pots filled with soil and farmyard manure. Glc treatments were provided as a foliar spray at the 25-day stage of growth for 5 days consecutively. Plants were sampled at the 30, 45 and 60-day stage of growth to assess various biological and biochemical parameters. Glc promoted the growth of plants in the following order of concentration: 30 mM > 20 mM > 40 mM > 10 mM > 50 mM > 0 mM. Glc treatment augmented photosynthetic efficiency by elevating primary photochemistry, stomatal movement and conductance, internal CO2 concentration, transpiration rate, and net photosynthetic rate leading to enhanced synthesis of carbohydrate. A decline in photosynthesis at higher sugar accumulation was prevented by its utilization during respiration. Moreover, the activity of photosynthetic (rubisco and carbonic anhydrase) and respiratory enzymes (hexokinase, succinate dehydrogenase, and fumarase) also increased, which suggests that Glc-mediated growth promotion depends on the dynamics between anabolic and catabolic pathways. Generation of reactive oxygen species, antioxidant enzyme activity, and elemental status, which affect the rate of photosynthesis, were also regulated in Glc-treated plants.

The salt stress limits the production of mustard throughout the world and it is one of the major abiotic stresses. Crop productivity is declining due to the limited area of fertile land. In order to investigate the effects NO donor on salt tolerance and the recovery of Brassica juncea. (L) cv. RGN-48, sodium nitroprusside (SNP) was applied at 1, 10 or 100 µM concentrations as foliar spray for five days consecutively. SNP triggered a significant increase in the main antioxidative enzymes including catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD) along with the increase in the enzymes involved in nitrogen metabolism (nitrate reductase), photosynthesis and respiration (carbonic anhydrase, rubisco, fumarase, hexokinase and succinate dehydrogenase). On the other hand, decrease in programmed cell death (PCD) and the contents of hydrogen peroxide (H2O2), superoxide anion (O2.−) and malondialdehyde (MDA) was observed in NaCl-stressed plants subjected to the different concentrations of SNP. Consequently, the spray of SNP restored several photosynthetic attributes i.e. SPAD chlorophyll, chlorophyll fluorescence and gas exchange parameters in NaCl-stressed plants. These results suggested that exogenous application of SNP is useful in ameliorating the toxicity generated by NaCl in mustard plants.

Auxins (Aux) are primary growth regulators that regulate almost every aspect of growth and development in plants. It plays a vital role in various plant processes besides controlling the key aspects of cell division, cell expansion, and cell differentiation. Considering the significance of Aux, and its potential applications, a study was conducted to observe the impact of indole acetic acid (IAA), a most active and abundant form of Aux on Brassica juncea plants growing under natural environmental conditions. Different concentrations (0, 10−10, 10−8, 10−6 M) of IAA were applied once in a day at 25-day stage of growth for 5 days, consecutively. Various parameters (growth, photosynthetic, biochemical, oxidative biomarkers and nutrient composition) were assessed at different days after sowing (DAS). Scanning electron microscopy (SEM) of leaf stomata, reactive oxygen species (ROS) localization in leaf and roots, and confocal microscopy were also conducted. The results revealed that all the IAA concentrations were effective in growth promotion and ROS reduction, however, the 10−8 M of IAA exhibited the maximum improvement in all the above mentioned parameters as compared to the control.

It is known that auxin and nitric oxide have the ability to ameliorate various abiotic stresses in plants individually. However, their interactive effects on the stress generated by salt in plants are not reported yet. Therefore, the present study was conducted to explore the effectiveness of sodium nitroprusside (SNP), a donor of nitric oxide and IAA (Indole acetic acid) individually and in combination on the photosynthetic efficiency, antioxidative enzyme activities, and plant biomass under salt stress. Twenty-five-day-old plants were exposed to SNP and IAA individually and in combination for 5 days continuously, and it was found that both SNP and IAA showed almost similar response at 30 and 45 days of old plants and increased studied parameters over their respective controls. However, the interactive effect of both SNP and IAA excelled over the individual response of SNP and IAA. On the other hand, the presence of salt in soil significantly decreased the parameters studied. Furthermore, stress generated by NaCl was overcome by the exogenous application of SNP, IAA alone as well as in combination at both the stages of samplings. However, the combination of IAA and SNP was more effective at 45 DAS where the value of plant biomass and photosynthetic efficiency was more in comparison to control plants. The level of antioxidant enzymes and proline was further enhanced by SNP and IAA and maximum values were reported in the plants received both SNP and IAA under NaCl stress. This enhanced antioxidant system and proline accumulation could ameliorate the stress induced by NaCl in plants that was reflected by the improved plant biomass, and photosynthetic efficiency in comparison to control plants.

Flavonoids are a special category of hydroxylated phenolic compounds having an aromatic ring structure. Among several subclasses of flavonoids, the flavonol subclass contains a special compound – quercetin. Quercetin is a bioactive natural compound built upon the flavon structure, i.e., C6(ring A)-C3(ring C)-C6(ring B). It facilitates several plant physiological processes such as seed germination, pollen growth, antioxidant machinery, and photosynthesis, as well as induces proper plant growth and development. Quercetin is a powerful antioxidant, so it potently provides plant tolerance against several biotic and abiotic stresses. This review highlights the role of quercetin in increasing several physiological and biochemical processes in under stress and non-stress environments. Additionally, this review briefly assesses the role of quercetin in mitigating biotic and abiotic stresses, e.g., salt, heavy metal, and UV stress. Furthermore, the biosynthesis of flavonoids along with fresh advances and regulation in its signaling pathway, as well as the role of quercetin in plant signaling is also discussed.

Melatonin (MEL) is an antioxidant molecule, present throughout plant kingdom, animals, and microbes. It is a well-known free radical scavenger and modulates growth and development in plants against various abiotic and biotic stresses. The present study was done to investigate the role of MEL as a foliar spray on the morphological, physiological, and biochemical parameters in Brassica juncea cv. Varuna. Five different doses (10, 20, 30, 40, or 50 μM) of MEL were applied as foliar spray to the leaf of plant at 25 days after sowing (DAS) and continued up to 30 DAS once in a day. The plants were sampled at 30, 45, and 60 DAS to assess various parameters. The present results indicate that most of the parameters, i.e., growth, photosynthetic, nutrients, and enzyme activities increased in a concentration dependent manner. MEL application reduced the accumulation of reactive oxygen species (ROS) by enhancing the antioxidant enzyme activities. Microscopic examinations further revealed a significant increase in the size of the stomatal aperture in the presence of MEL. Out of the various concentrations tested, 40 μM of MEL proved best and can be used for further studies.

Nitric oxide (NO) acts as a gaseous diffusible plant growth regulator. It plays an important role in growth and development of plants. Therefore, in present study mustard plants were sprayed with different concentrations of sodium nitroprusside (0, 10–4 M, 10–5 M and 10–6 M), a donor of NO, at 25 days after sowing to assess different physiological parameters. The results indicate that foliar spray of SNP upregulate chlorophyll content, chlorophyll fluorescence along with gaseous exchange parameters which further boost overall photosynthetic efficiency. A gradual increase in carbon metabolism (total reducing sugars, total carbohydrate content, glucose, fructose, sucrose and starch content) was also observed in SNP-treated plants as compared to control. Nutrient status (carbon, nitrogen, phosphorus, sulfur, potassium and magnesium) of leaves also shows a significant increase. The activity of various enzymes associated with nitrogen metabolism, CO2/HCO3− homeostasis, glycolysis, Calvin cycle and Krebs cycle (nitrate reductase, carbonic anhydrase, hexokinase, rubisco, fumarase and succinate dehydrogenase) were also increased in the presence of SNP. It was also reported that O2−, H2O2 and MDA were decreased in SNP-treated samples. SNP application also upregulate antioxidative defense system by increasing the activity of antioxidant enzymes, i.e., CAT, POX and SOD. Thus, it can be concluded from the present observation that SNP proved beneficial and alter most of the parameters which ultimately improve photosynthetic efficiency in mustard plants.

Plant hormones play important roles in controlling how plants grow and develop. While metabolism provides the energy needed for plant survival, hormones regulate the pace of plant growth. Strigolactones (SLs) were recently defined as new phytohormones that regulate plant metabolism and, in turn, plant growth and development. This group of phytohormones is derived from carotenoids and has been implicated in a wide range of physiological functions including regulation of plant architecture (inhibition of bud outgrowth and shoot branching), photomorphogenesis, seed germination, nodulation, and physiological reactions to abiotic factors. SLs also induce hyphal branching in germinating spores of arbuscular mycorrhizal fungi (AMF), a process that is important for initiating the connection between host plant roots and AMF. This review outlines the physiological roles of SLs and discusses the significance of interactions between SLs and other phytohormones to plant metabolic responses.

Nanotechnology now plays a revolutionary role in many applications; nanomaterials have experienced significant importance in both basic and applied sciences as well as in bio-nanotechnology. Zinc oxide nanoparticles (ZnO-NPs) have become one of the most important metal oxide NPs in biological applications due to their beneficial impacts. The purpose of this study was to explore the effects of ZnO-NPs in reducing Cd toxicity by studying the growth, photosynthesis reactions, antioxidant system, oxidative stress, and protein content in Lycopersicon esculentum (tomato). ZnO-NPs induced an upregulation of antioxidative enzymes which protect the photosynthetic apparatus in plants. Seeds of tomato were sown to create nursery. At 20 days after sowing (DAS), seedlings were transferred to soil pots. Varied concentrations (0.4, 0.6 or 0.8 mM) of Cd were applied to the soil after 24 and 25 DAS. Zinc (Zn; 50 mg/L) and ZnO-NPs (50 mg/L) treatments were given continuously for 5 days from 31 to 35 DAS and sampling took place at 45 DAS. The results indicate that a Cd-generated oxidative burst in the form of elevated hydrogen peroxide (H2O2) levels resulted in a decline in cell viability through enhanced activity of the antioxidant system and proline content; the data increased on follow-up treatment with ZnO-NPs. Foliar application of ZnO-NPs significantly enhanced plant height, fresh, and dry weight of plant, leaf area, SPAD chlorophyll, photosynthetic attributes, i.e., net photosynthetic rate (PN), transpiration rate (E), internal CO2 concentration (Ci), and stomatal conductance (gs). Application of ZnO-NPs reduced the adverse effects generated by Cd and increased protein content, activities of nitrate reductase and carbonic anhydrase over the control in both stressed and non-stressed plants. Additionally, microscopic studies showed a marked increase in stomatal aperture after ZnO-NPs treatment in the presence or absence of Cd. This was associated with decrease in malondialdehyde and superoxide radical (O2−) levels. The present study suggests that ZnO-NPs can be effectively used to reduce the toxicity of Cd in tomato plants and may also be suitable for testing on other crop species.