Agronomic biofortification of crops with selenium (Se) is an important strategy to minimize hidden hunger and increase nutrient intake in poor populations. Selenium is an element that has several ...physiological and biochemical characteristics, such as the mitigation of different types of abiotic stress. Selenoproteins act as powerful antioxidants in plant metabolism through the glutathione peroxidase (GSH) pathway, and provide an increased activity for enzymatic (SOD, CAT, and APX) and non-enzymatic (ascorbic acid, flavonoids, and tocopherols) compounds that act in reactive oxygen species (ROS) scavenging system and cell detoxification. Selenium helps to inhibit the damage caused by climate changes such as drought, salinity, heavy metals, and extreme temperature. Also, Se regulates antenna complex of photosynthesis, protecting chlorophylls by raising photosynthetic pigments. However, Se concentrations in soils vary widely in the earth's crust. Soil Se availability regulates the uptake, transport, accumulation, and speciation in plants. Foliar Se application at the concentration 50 g ha−1 applied as sodium selenate increases the antioxidant, photosynthetic metabolism, and yield of several crops. Foliar Se application is a strategy to minimize soil adsorption and root accumulation. However, the limit between the beneficial and toxic effects of Se requires research to establish an optimal dose for each plant species under different edaphoclimatic conditions. In this review, we present the compilation of several studies on agronomic biofortification of plants with Se to ensure food production and food security to mitigate hidden hunger and improve the health of the population.
•Se application at low concentration enhance chlorophyll and photosynthesis in plants.•Se activate the antioxidant metabolism in plants to combat ROS production.•Non-enzymatic compounds such ascorbic acid, flavonoids, and tocopherols are increased by Se application.•Se decrease damage caused by abiotic stresses such as drought, salinity, and extreme temperature.
Hormesis is a favorable response to low level exposures to substance or to adverse conditions. This phenomenon has become a target to achieve greater crop productivity. This review aimed to address ...the physiological mechanisms for the induction of hormesis in plants. Some herbicides present a hormetic dose response. Among them, those with active ingredients glyphosate, 2,4-D and paraquat. The application of glyphosate as a hormesis promoter is therefore showing promess . Glyphosate has prominent role in shikimic acid pathway, decreasing lignin synthesis resulting in improved growth and productivity of several crops. Further studies are still needed to estimate optimal doses for other herbicides of crops or agricultural interest. Biostimulants are also important, since they promote effects on secondary metabolic pathways and production of reactive oxygen species (ROS). When ROS are produced, hydrogen peroxide act as a signaling molecule that promote cell walls malleability allowing inward water transport causing cell expansion. . Plants'ability to overcome several abiotic stress conditions is desirable to avoid losses in crop productivity and economic losses. This review compiles information on how hormesis in plants can be used to achieve new production levels.
•Hormesis provides the first quantification of biological plasticity.•Application of some herbicides at low concentrations present a hormetic response.•Glyphosate, 2,4-D and Paraquat present a hormetic dose response.•Glyphosate has prominent role in shikimic acid pathway resulting in improved growth and productivity of several crops.
The production of cucumber under combined salinity and heat stress is a crucial challenge facing many countries particularly in arid environments. This challenge could be controlled through exogenous ...foliar application of some bio-stimulants or anti-stressors. This study was carried out to investigate the management and improving cucumber production under combined salinity and heat stress. Nano-selenium (nano-Se, 25 mg L-1), silicon (Si, 200 mg L−1) and hydrogen peroxide (H2O2, 20 mmol L−1) were foliar applied on cucumber plants as anti-stress compounds. The results revealed that studied anti-stressors improved growth and productivity of cucumber grown in saline soil regardless the kind of anti-stressor under heat stress. The foliar application of nano-Se (25 mg L−1) clearly improved cucumber growth parameters (plant height and leaf area) compared to other anti-stressor and control. Foliar Si application showed the greatest impact on enzymatic antioxidant capacities among the other anti-stressor treatments. This applied rate of Si also showed the greatest increase in marketable fruit yield and yield quality (fruit firmness and total soluble solids) compared to untreated plants. These increases could be due to increasing nutrient uptake particularly N, P, K, and Mg, as well as Se (by 40.2% and 43%) in leaves and Si (by 11.2% and 22.1% in fruits) in both seasons, respectively. The potential role of Si in mitigating soil salinity under heat stress could be referred to high Si content found in leaf which regulates water losses via transpiration as well as high nutrient uptake of other nutrients (N, P, K, Mg and Se). The distinguished high K+ content found in cucumber leaves might help stressed plants to tolerate studied stresses by regulating the osmotic balance and controlling stomatal opening, which support cultivated plants to adapt to soil salinity under heat stress. Further studies are needed to be carried out concerning the different response of cultivated plants to combined stresses.
•Foliar Si and Se application alleviate stress and increase cucumber yield.•Si increases photosynthetic parameters and chlorophyll content in cucumber plants.•Foliar Se application promotes biostimulant effect increasing cucumber plant biomass.•Both Se and Si foliar application boost plant growth and yield of cucumber under salinity and heat stress.
Phytate or phytic acid (PA), is a phosphorus (P) containing compound generated by the stepwise phosphorylation of myo-inositol. It forms complexes with some nutrient cations, such as Ca, Fe and Zn, ...compromising their absorption and thus acting as an anti-nutrient in the digestive tract of humans and monogastric animals. Conversely, PAs are an important form of P storage in seeds, making up to 90% of total seed P. Phytates also play a role in germination and are related to the synthesis of abscisic acid and gibberellins, the hormones involved in seed germination. Decreasing PA content in plants is desirable for human dietary. Therefore, low phytic acid (lpa) mutants might present some negative pleiotropic effects, which could impair germination and seed viability. In the present study, we review current knowledge of the genes encoding enzymes that function in different stages of PA synthesis, from the first phosphorylation of myo-inositol to PA transport into seed reserve tissues, and the application of this knowledge to reduce PA concentrations in edible crops to enhance human diet. Finally, phylogenetic data for PA concentrations in different plant families and distributed across several countries under different environmental conditions are compiled. The results of the present study help explain the importance of PA accumulation in different plant families and the distribution of PA accumulation in different foods.
•Phytic acid is a compound generated by the stepwise phosphorylation of myo-inositol.•Phytic acid is an anti-nutrient in the digestive tract of humans and monogastric animals.•Phytates also play a role in seed germination regulating abscisic acid and gibberellins.•This study shows the importance of phytates in different foods and relation to human and animal health.
Manganese (Mn) is an essential element for plants; however, high concentrations in certain soil conditions can cause toxicity symptoms in the plant tissue. Here, we describe Mn toxicity symptoms and ...Mn toxicity responses in soybean plants. Soybean plants exposed to excess Mn showed reductions in the CO2 assimilation rate and stomatal conductance, which in turn resulted in decreased shoot biomass. Furthermore, peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activity were higher in plants grown with the highest Mn concentration. The Mn doses increased the activity of antioxidant enzymes such as CAT, POD, and SOD. The toxicity symptoms presented by the leaves included hypertrophying of the adaxial epidermis and the formation of necrotic areas with purple-colored veins. Dramatic movement of calcium from the healthy region to the purple-colored necrotic region was observed, as was the exit of potassium from the necrotic area to the healthy region of the tissue. The high activities of POD and SOD in the presence of high Mn compartmented in the roots was the main physiological responses at high Mn uptake by soybean plants.
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•We demonstrated Mn toxicity responses and symptoms in soybean.•Excess of Mn reduced the CO2 assimilation rate and stomatal conductance.•Antioxidant enzymes increased in roots under excess of Mn.•We described the distribution of nutrients in soybean leaf under Mn toxicity.•Calcium move dramatically from the healthy to necrotic tissue region under high Mn.
In the agricultural industry, advances in optical imaging technologies based on rapid and non-destructive approaches have contributed to increase food production for the growing population. The ...present study employed autofluorescence-spectral imaging and machine learning algorithms to develop distinct models for classification of soybean seeds differing in physiological quality after artificial aging. Autofluorescence signals from the 365/400 nm excitation-emission combination (that exhibited a perfect correlation with the total phenols in the embryo) were efficiently able to segregate treatments. Furthermore, it was also possible to demonstrate a strong correlation between autofluorescence-spectral data and several quality indicators, such as early germination and seed tolerance to stressful conditions. The machine learning models developed based on artificial neural network, support vector machine or linear discriminant analysis showed high performance (0.99 accuracy) for classifying seeds with different quality levels. Taken together, our study shows that the physiological potential of soybean seeds is reduced accompanied by changes in the concentration and, probably in the structure of autofluorescent compounds. In addition, altering the autofluorescent properties in seeds impact the photosynthesis apparatus in seedlings. From the practical point of view, autofluorescence-based imaging can be used to check modifications in the optical properties of soybean seed tissues and to consistently discriminate high-and low-vigor seeds.
Selenium (Se) is a beneficial element to higher plants. Application of Se at low concentrations enhances the antioxidant metabolism reducing the reactive oxygen species (ROS) generated by plant ...membrane cells. This study aimed to evaluate how the application of Se in the forms sodium selenate and sodium selenite regulates ROS scavenging in field-grown cowpea plants. Seven Se application rates (0; 2.5; 5; 10; 20; 40 and 60 g ha−1) of each of the two Se forms were applied to plants via the soil. Photosynthetic pigments concentration, gas exchange parameters, lipid peroxidation by malondialdehyde (MDA) concentration, hydrogen peroxide concentration, activity of catalase (CAT, EC:1.11.1.6), glutathione reductase (GR, EC:1.6.4.2), ascorbate peroxidase (APX, EC:1.11.1.11) and Se concentration in leaves and grains were evaluated. In general, Se application led to a decrease in chlorophyll a concentration whilst leading to an increase in chlorophyll b, indicating conservation of total chlorophyll concentration. Application of 2.5 g ha−1 of Se as selenate provided a notable increase in total chlorophyll and total carotenoids compared to the other application rates. Selenate and selenite application decreased lipid peroxidation. However, each Se source acted in a different pathway to combat ROS. While selenate showed more potential to increase activity of APX and GR, selenite showed a higher potential to increase CAT activity. The negative correlation between CAT and GR is indicative that both pathways might be activated under distinct circumstances. The more prominent activity of CAT under high rates of selenite resulted in a negative correlation of this enzyme with chlorophyll a and carotenoids. Both selenate and selenite application increased sucrose and total sugars concentration in leaves of cowpea plants. Overall, these results indicate that application of Se in cowpea under field conditions stimulates distinct pathways to scavenge ROS. This could prove beneficial to mitigate oxidative stress during plant development.
•Selenate and selenite scavenge ROS by distinct antioxidant pathways.•Selenate shows higher potential to increase activity of APX and GR.•Selenite shows higher potential to increase CAT activity.•Selenium rates increase sucrose and total sugars in leaf tissues.•Antioxidant metabolism associated with total sugar prove beneficial to mitigate ROS.
Reactive oxygen species (ROS) such as hydrogen peroxide at low concentrations act as signaling of several abiotic stresses. Overproduction of hydrogen peroxide causes the oxidation of plant cell ...lipid phosphate layer promoting senescence and cell death. To mitigate the effect of ROS, plants develop antioxidant defense mechanisms (superoxide dismutase, catalase, guaiacol peroxidase), ascorbate-glutathione cycle enzymes (ASA-GSH) (ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase), which have the function of removing and transforming ROS into non-toxic substances to maintain cellular homeostasis. Foliar or soil application of fertilizers containing B, Cu, Fe, Mn, Mo, Ni, Se and Zn at low concentrations has the ability to elicit and activate antioxidative enzymes, non-oxidizing metabolism, as well as sugar metabolism to mitigate damage by oxidative stress. Plants treated with micronutrients show higher tolerance to abiotic stress and better nutritional status. In this review, we summarized results indicating micronutrient actions in order to reduce ROS resulting the increase of photosynthetic capacity of plants for greater crop yield. This meta-analysis provides information on the mechanism of action of micronutrients in combating ROS, which can make plants more tolerant to several types of abiotic stress such as extreme temperatures, salinity, heavy metals and excess light.
Micronutrient applied at low concentration increase the enzymatic antioxidant defense system making plants more tolerant to abiotic stresses. Display omitted
•Micronutrients fertilizer application increase antioxidant metabolism in plants.•ROS scavenge system is enhanced by foliar application of micronutrients.•Micronutrients supply increase photosynthesis and yield of several crop species.•Adequate supplementation with Cu, B, Fe, Mn, Mo, Ni, Se and Zn should be investigated on doses-response in plant species.
There are conclusive evidences of selenium (Se) deficiency in Brazilian soils and foods. Brazil is the largest producer and consumer of coffee worldwide, which favors agronomic biofortification of ...its coffee. This study aimed to evaluate effects of foliar application of three formulations and six rates of Se on antioxidant metabolism, agronomic biofortification and yield of coffee beans. Seven Se concentrations (0, 10, 20, 40, 80, 100 and 160 mg L−1) were applied from three formulations of Se (sodium selenate, nano-Se 1500, and nano-Se 5000). Selenium application up to 40 mg L−1 increased the concentration of photosynthetic pigments such as chlorophylls, pheophytins and carotenoids in coffee leaves. Foliar application of Se ranging from 20 to 80 mg L−1 decreased lipid peroxidation and concentration of hydrogen peroxide, but increased superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase activities in coffee leaves. These results indicated that foliar Se application stimulates antioxidative metabolism to mitigate reactive oxygen species. Foliar application of 20 mg Se L−1 of sodium selenate increased coffee yield by 38%, and 160 mg Se L−1 of nano-Se 5000 increased dramatically coffee yield by 42%. Selenium concentration in grains ranged from 0.116 to 4.47 mg kg−1 (sodium selenate), 4.84 mg kg−1 (nano-Se 1500) and 5.82 mg kg−1 (nano-Se 5000). The results suggest the beneficial effect of Se on the increment of photosynthetic pigments, antioxidative metabolism, increased coffee yield and nutritional quality of grains. The recommended foliar Se application in this study can mitigate abiotic stressors such as high temperatures resulting in higher yield of coffee plants.
•Se application increase antioxidant metabolism in coffee plants.•Lipid peroxidation dramatically decrease in response to Se concentrations and sources.•Selenium application enhance photosynthetic pigments formation in coffee leaves.•Increased antioxidant system and chlorophyll resulted in higher coffee yield in response to selenium supply.
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