Silicon mitigates the negative impacts of salt stress in soybean plants.

BACKGROUND: Soybean is widely cultivated around the world, including regions with salinity conditions. Salt stress impairs plant physiology and growth, but recent evidence suggests that silicon (Si) is able to mitigate this stressful condition. Therefore, the purpose of this study was to evaluate how different strategies of Si application impact on salt stress tolerance of an intermediate Si accumulator species (soybean). Therefore, we applied four treatments: Si-untreated plants (Si 0); foliar spraying at 20 mmol L-1 (Si F); nutritive solution addition at 2.0 mol L-1 (Si R), and combined foliar spraying at 20 mmol L-1 plus nutritive solution at 2.0 mmol L-1 (Si F + R). We investigated how Si application modified growth, leaf gas exchange, photosynthetic pigments, chlorophyll fluorescence, relative water content (RWC), nutrient accumulation, and ion homeostasis of soybean plants submitted to different levels of salt stress (50 and 100 mmol L-1 NaCl). RESULTS: Salinity induced an expressive reduction in ion accumulation, plant water status, and growth of soybean, while Si application promoted contrary effects and increased potassium (K+ ) accumulation, water status, photosynthetic pigment content, chlorophyll fluorescence parameters, and gas exchange attributes. Additionally, Si application enhanced Si accumulation associated with decreased Na+ uptake and improved morpho-physiological growth. CONCLUSION: The use of exogenous Si can be an efficient strategy to attenuate the harmful effects of salt stress in soybean plants. The best application strategy was observed with combined foliar spraying with Si included in the nutritive solution (Si F + R). © 2023 Society of Chemical Industry.

Prescient diagnostic analysis for boron nutritional status in soy crops.

Boron is the most limiting micronutrient for soybean yield; therefore, accurate identification of its nutritional status is important for adequate fertilization management and maximize soybean yield potential. Currently, tools for nutritional status interpretation of B, such as the CND and DRIS are used; however, their efficacy is not considered to identify the true nutritional status of B. In this research, we investigated the efficacy of these methods to identify the nutritional status of B in 140 commercial soybean crops to obtain nutritional standards for the DRIS and CND methods. In addition, an experiment of B dose calibration (0, 300, 600, 1200 and 1800 g ha-1) was installed to assess the quality of nutritional diagnoses using the PDA. The experimental approach tested the limits of 0.25, 0.50, and 1.00 for the NRr and values of 1%, 5%, or 10% for YR. The DRIS method was more effective, and, on average, its variations increased yield by 27% compared to CND, with the best performance of DRIS when NRr = 1.00 was adopted with 10% for YR. This study highlights the need for reliable and accurate diagnostic methods with global implications for crop sustainability by improving the efficacy of B fertilization programs and crop yield.

Applicability of DRIS in bananas based on the accuracy of nutritional diagnoses for nitrogen and potassium.

DRIS (Diagnosis Recommendation Integrated System) is a tool used in the interpretation of leaf analyses that values the balance of nutrients, an important fact for a better assessment of the nutritional status of banana plants. Its usefulness depends on the ability to identify the nutrients that limit productivity in order to correct possible nutritional imbalances, but there is a lack of research in all crops, including bananas, to assess the accuracy of these diagnoses, which have a worrying global implication. To this end, this study evaluates DRIS norms for banana cultivation in Ecuador and the use of accuracy measurements for nutritional diagnosis, verifying the capacity of DRIS to detect true nutritional status based on plant response. The database created here contains 233 results referring to productivity and leaf contents of N, P, K, Ca, Mg, S, Cl, Fe, Mn, Cu, B, and Zn for banana trees in 2018, 2019, and 2020. Then, a field experiment evaluated doses of nitrogen and potassium and the accuracy of DRIS norms for N and K. The results show that the DRIS of banana produced in Ecuador depends on the nutrient being variable according to the crop nutritional status. The DRIS norms for diagnosis of N and K result in an acceptable accuracy to identify only deficiencies and toxicities, respectively, indicating the need for adjustments in these standards for later use in the field. Thus, there is a need for more research aiming to adopt calibrated DRIS diagnostic norms to assess the nutritional status of bananas in Ecuador.

Silicon and boron on cauliflower induce attractiveness and mortality in Plutella xylostella.

BACKGROUND: Boron (B) and silicon (Si) are fundamental for brassica nutrition, and in some cases, they have potential as an insecticide. Plutella xylostella (L.) (Lepidoptera: Plutellidae), one of the most economically important agricultural pests, is difficult to control due to the resistance to insecticides and the absence of alternative control methods. RESULTS: Cauliflower leaves sprayed with Si and B showed a higher concentration of the beneficial element and micronutrient, respectively. When evaluating the firmness of the cauliflower leaves, it was found that the plants with leaf sprayings of Si and B did not differ statistically from each other. However, they showed an increase in firmness, in relation to the plants of the control treatment. Leaf spraying of Si and B on cauliflower did not influence the number of eggs/female. The attractiveness index showed that both Si and B applications stimulated the presence of second instar larvae, being more stimulating in relation to the control treatment. However, the use of Si and B in isolation showed a positive result, since it caused high mortality in diamondback moth larvae compared to the control treatment. CONCLUSION: The application of both foliar fertilizers positively affects the attractiveness index of the larvae, being attractive; however, both Si and B caused high mortality (~80%). The results showed that Si and B have the potential to control P. xylostella and serve as a basis for alternative pest management in brassica crops. © 2022 Society of Chemical Industry.

Silicon modifies C:N:P stoichiometry and improves the physiological efficiency and dry matter mass production of sorghum grown under nutritional sufficiency.

Silicon (Si) may be involved in the modification of C:N:P stoichiometry and in physiological processes, increasing sorghum growth and grain production. The objective was to evaluate the effect of Si supply on C:N:P:Si stoichiometry, physiological response, growth, and grain production of sorghum. The experiment was carried out in pots with four concentrations of Si: 0; 1.2; 2.4; and 3.6 mmol L-1 in a completely randomized design, with six replicates. Physiological attributes and dark green color index were measured and grain and biomass production were determined. Posteriorly, the plant material was ground to determine silicon (Si), carbon (C), nitrogen (N), and phosphorus (P) contents in order to analyze C:N:P:Si stoichiometry. C:Si and C:N ratios decreased at all Si concentrations applied (1.2, 2.4, and 3.6 mmol L-1) and in all plant parts studied, being lower at 3.6 mmol L-1. The lowest C:P ratios of leaves and roots were observed at 3.6 mmol L-1 Si and the lowest C:P ratio of stems was observed at 1.2 mmol L-1 Si. Si concentrations were not significant for the N:P ratio of leaves. The highest N:P ratio of stems was observed at 3.6 mmol L-1, while the lowest N:P ratio of roots was observed at 2.4 and 3.6 mmol L-1. Regardless of photosynthetic parameters, the application of 1.2 mmol L-1 Si enhanced photosynthetic rate. The application of 2.4 and 3.6 mmol L-1 enhanced stomatal conductance and dark green color index. The mass of 1000 grains was not influenced by Si applications, while Si applications at all concentrations studied (1.2, 2.4, and 3.6 mmol L-1) enhanced shoot and total dry matter, not affecting root dry matter and grain production. In conclusion, Si supply modifies C:N:P:Si stoichiometry and increases physiologic parameters, growth, development, and grain production in sorghum.

Impact of Si on C, N, and P stoichiometric homeostasis favors nutrition and stem dry mass accumulation in sugarcane cultivated in tropical soils with different water regimes.

Studies with silicon (Si) in sugarcane indicate a greater response in productivity in plants under stress, and the underlying mechanisms of Si in the crop are poorly reported. In this context, the benefits of Si in the crop's stem production are expected to occur at the C:N:P stoichiometry level in plant tissues, benefiting plants with and without stress. However, the extension of this response may vary in different soils. Thus, this research aimed to evaluate if fertigation with Si modifies the C:N:P stoichiometry and if it can increase sugarcane's nutritional efficiency and vegetative and productive parameters. Therefore, three experiments were installed using pre-sprouted seedlings to cultivate sugarcane in tropical soils belonging to the Quartzarenic Neosol, Eutrophic Red Latosol, and Dystrophic Red Latosol classes. The treatments comprised a 2 × 2 factorial scheme in each soil. The first factor was composed without water restriction (water retention = 70%; AWD) and with water restriction (water retention = 35%; PWD). The second factor presented Si concentrations (0 mM and 1.8 mM) arranged in randomized blocks with five replications. Fertigation with Si increases the Si and P concentration, the C and N efficiency, the C:N ratio, and the dry mass production. However, it decreases the C and N concentration and the C:P, C:Si, and N:P ratios in sugarcane leaves and stems regardless of the water regime adopted in the three tropical soils. Cluster and principal components analysis indicated that the intensity of the beneficial effects of Si fertigation on sugarcane plants varies depending on the cultivation soil and water conditions. We found that Si can be used in sugarcane with and without water stress. It changes the C:N:P homeostasis enough to improve the nutritional efficiency of C, P, N, and, consequently, the dry mass accumulation on the stems, with variation in the different cultivated soils.

Forms of application of silicon in quinoa and benefits involved in the association between productivity with grain biofortification.

Multiple aspects of the physiological and nutritional mechanisms involved with silicon (Si) absorption by quinoa plants remain poorly investigated, as well as the best way of supplying this element to crops. Thus, this study aimed at evaluating whether the application of Si increases its uptake by quinoa plants and consequently the use efficiency of N and P, as well as the levels of phenolic compounds in the leaves, crop productivity and the biofortification of grains. For this purpose, the concentration of 3 mmol L-1 of Si was tested, according to the following procedures: foliar application (F), root application in the nutrient solution (R), combined Si application via nutrient solution and foliar spraying (F + R), and no Si application (0). The provision of Si through the leaves and roots promoted the highest uptake of the element by the plant, which resulted in an increased use efficiency of N and P. Consequently, such a higher uptake favored the productivity of grains. The optimal adoption of the application of Si through leaves and roots promoted the highest Si concentration and ascorbic acid content in quinoa grains.

Interaction of silicon and manganese in nutritional and physiological aspects of energy cane with high fiber content.

BACKGROUND: Silicon (Si) is a multiple stress attenuator element in plants, however more research is needed to elucidate the actions in the plants defense system with low nutrition of manganese (Mn) for a prolonged period, and the attenuation mechanisms involved in the effects of Mn deficiency on energy cane with high fiber content. Thus, the objective of this study was to evaluate whether Si reduces the oxidative stress of the energy cane grown in low Mn in nutrient solution, to mitigate the effects of Mn deficiency, improving enzymatic and non-enzymatic defense, uptake of Mn the plant growth. METHODS: An experiment was carried out with pre-sprouted seedlings of Saccharum spontaneum L. in a 2 × 2 factorial scheme in five replications in which the plants were grown under sufficiency (20.5 µmol L-1) and deficiency (0.1 µmol L-1) of Mn combined with the absence and presence of Si (2.0 mmol L-1) for 160 days from the application of the treatments. The following parameters were evaluated: accumulation of Mn and Si, H2O2, MDA, activity of SOD and GPOX, total phenol content, pigments, and quantum efficiency of PSII. RESULTS: Mn deficiency induced the oxidative stress for increase the H2O2 and MDA content in leaves of plants and reduce the activity of antioxidant enzymes and total phenols causing damage to quantum efficiency of photosystem II and pigment content. Si attenuated the effects of Mn deficiency even for a longer period of stress by reducing H2O2 (18%) and MDA (32%) content, and increased the Mn uptake efficiency (53%), SOD activity (23%), GPOX (76%), phenol contents, thus improving growth. CONCLUSIONS: The supply of Si promoted great nutritional and physiological improvements in energy cane with high fiber content in Mn deficiency. The results of this study propose the supply of Si via fertirrigation as a new sustainable strategy for energy cane cultivation in low Mn environments.

Silicon as a Sustainable Option to Increase Biomass With Less Water by Inducing Carbon:Nitrogen:Phosphorus Stoichiometric Homeostasis in Sugarcane and Energy Cane.

Climate change has prolonged periods of water deficit in sugarcane and energy cane crops. This condition induces an imbalance of the carbon (C): nitrogen (N): phosphorus (P) stoichiometric homeostasis, impairing accumulated nutrients from being converted into biomass. Silicon (Si) supplementation can mitigate the damage caused by water deficit in plants by improving the C:N:P balance, increasing C, N, and P use efficiencies and the biomass conversion, and reducing climate change effects on crops. This study assesses the beneficial effects of Si applied through fertigation associated with foliar spraying on the alleviation of damage caused by severe water deficit in sugarcane and energy cane for intermediate and long periods. In addition, the effects in maintenance of nutritional homeostasis we assessed and C, N, and P use efficiencies on sugarcane and energy cane under those conditions were increased. Four experiments were conducted during the first growth cycle of each species. The effect of fertigation associated with Si foliar spraying was evaluated by applying Si only during the seedling formation phase in sugarcane and energy cane grown under severe water deficit for 60 days after transplanting (intermediate period). Then, the effect of Si applied during seedling formation and supplemented after transplanting was evaluated in sugarcane and energy cane grown under severe water deficit for 160 days after transplanting (long period). The Si supply decreased C contents, modified the C:N:P ratio, and increased C, N, and P use efficiencies in plants of both species under water deficit at the intermediate and long periods after transplanting. The effects of applying Si through fertigation associated with foliar spraying during seedling formation mitigated the damage caused by severe water deficit in the intermediate period, which was mainly observed in sugarcane. When supplemented with Si after transplanting, the mitigating effects occurred in both species under severe long period water deficit. Therefore, the Si supply through fertigation associated with foliar spraying is a viable alternative to provide Si to the plant. It also comes with beneficial effects that partially reverse the damage to nutritional homeostasis and increase nutritional efficiency in plants under severe water deficit.

Silicon mitigates nutritional stress of nitrogen, phosphorus, and calcium deficiency in two forages plants.

Forages are one of the most cultivated crops in the world. However, nutritional deficiency is common, specifically in N, P, and Ca in many forage-growing regions. Silicon (Si) can attenuate the stress caused by nutritional deficiency, but studies on Si supply's effects on forage plants are still scarce. This research was carried out to evaluate whether the Si supply can mitigate the effects of N, P, and Ca deficiencies of two forages and the physiological and nutritional mechanisms involved. Two experiments were carried out with two forage species (Urochloa brizantha cv. Marandu and Megathyrsus maximum cv. Massai). We used nutrient solution under balanced nutrition conditions and nutritional stress due to the lack of N, P, and Ca combined with the -Si and +Si. The deficiencies of N, P, and Ca in both forages' cultivation caused damage to physiological and nutritional variables, decreasing the plant dry matter. However, in both forage species, the Si addition to the nutrient solution decreased the extravasation of cellular electrolytes and increased the content of phenolic compounds, the green colour index, the quantum efficiency of photosystem II, the efficiencies of use of N, P and Ca and the production of shoot dry matter. The beneficial effects of Si were evidenced in stressed and non-stressed plants. The research emphasised the advantage of using Si to grow U. brizantha and M. maximum under N, P, and Ca deficiency, contributing to their sustainable cultivation.

New outcomes on how silicon enables the cultivation of Panicum maximum in soil with water restriction.

Climate change increases the occurrence of droughts, decreasing the production of tropical forages through the induction of physiological stress. Si is expected to broaden the limit from physiological stress of forages grown under water restriction, which may come from an improvement in the stoichiometric homeostasis of Si with N and C, favoring physiological aspects. This study assessed whether Si supply via fertigation improves physiological aspects and the water content in the plant by means of an antioxidant defense system and changes in the C:N:Si stoichiometry during the regrowth of two cultivars of Panicum maximum grown under two soil water regimes (70 and 40% of the soil's water retention capacity). The forages studied are sensitive to water deficit without silicon supply. The application of Si via fertigation attenuated the water deficit, favoring plant growth by stabilizing the stoichiometric homeostasis C:N and C:Si, which are responsible for increasing the plant capacity of converting accumulated C in dry mass, favoring the water content of the plant tissue and the photosynthetic efficiency. This study highlights the importance of the physiological function of Si, and effects on the stoichiometry of C and N, which are neglected in most research on forages grown under water restriction.

Warming and soil water availability affect plant-flower visitor interactions for Stylosanthes capitata, a tropical forage legume.

The reproductive success of a zoophilous plant species depends on biological interaction with pollinators, which involves both the provision and exploitation of flower resources. Currently, there is little information about how future climate change scenarios will impact interactions between plants and their flower visitors in the tropics. This study analyzes the effects of warming and two soil water conditions on interactions between the tropical forage legume species Stylosanthes capitata and its floral visitors during the flowering period. We used a temperature-free air-controlled enhancement (T-FACE) facility to simulate future warming scenarios by increasing canopy temperature. The tested treatments were: irrigated and ambient canopy temperature (Control); non-irrigated and ambient canopy temperature (wS); irrigated and elevated canopy temperature (eT, +2 °C above ambient canopy temperature); and non-irrigated and elevated canopy temperature (wSeT). The effects of treatments on the time of flower opening and closing, sugar concentration in the nectar, and plant-flower visitor interactions were assessed. In the warmed treatments, S. capitata flower opening occurred ~45 min earlier compared to non-warmed treatments, and flowers remained opened for only ~3 h. Further, the sugar concentration in the nectar from eT was 39% higher than in the Control. The effects of warming on floral biology and flower resource production in S. capitata had an impact on the plant-floral visitor relationships with the bees Apis mellifera and Paratrigona lineata, the most abundant potential pollinating floral visitors, and the butterfly visitor Hemiargus hanno. Additionally, around noon, the interactive and additive effects of the combined wS and eT treatments decreased insect visiting frequency. These results suggest that warming and soil water deficiency could affect flower-visitor interactions and thus the reproductive success of S. capitata in tropical belts.

Water deficit modifies C:N:P stoichiometry affecting sugarcane and energy cane yield and its relationships with silicon supply.

Climate change has increased the occurrence of water deficit in regions where sugarcane and energy cane are cultivated, jeopardizing dry matter production of stems. It was hypothesized that the reasons behind this fact relate to C:N:P stoichiometric modifications in these species that impair the conversion rates of accumulated nutrients in the stems, which could be attenuated by supplying silicon (Si) to the crops. Thus, the aims of this study were to evaluate the effects of water deficit in sugarcane and energy cane ratoons in the presence and absence of Si, in the C:N:P stoichiometry of stems, in the use efficiency of these nutrients and in the accumulation of dry matter in stems. Two experiments were carried out, using sugarcane (Saccharum officinarum) and energy cane (S. spontaneum), cultivated in pots filled with a Typic Quartzipisamment. The treatments for both experiments were arranged in a factorial scheme 2 × 2, without (70% of the soil's water retention capacity) and with (30% of the capacity) water deficit, without and with the application of Si via fertirrigation, associated with foliar pulverization, both at a concentration of 2.5 mmol L-1, arranged in randomized blocks. The reduction in dry matter production of stems in both species caused by water deficit was due to modifications of the C, N and P stoichiometric homeostasis, but the benefit of Si in these plants when increasing dry matter production was not a reflection of the change in homeostasis, thus it may be involved in other mechanisms that remain unknown and should be further studied.

Are the interaction effects of warming and drought on nutritional status and biomass production in a tropical forage legume greater than their individual effects?

MAIN CONCLUSION: Drought alone and drought plus warming will change the nutrient requirements and biomass distributions of Stylosanthes capitata, while warming will be advantageous only under well-watered condition for the next decades. Climate change effects on natural and managed ecosystems are difficult to predict due to its multi-factor nature. However, most studies that investigate the impacts of climate change factors on plants, such as warming or drought, were conducted under one single stress and controlled environments. In this study, we evaluated the effects of elevated temperature (+ 2 °C) (T) under different conditions of soil water availability (W) to understand the interactive effects of both factors on leaf, stem, and inflorescence macro and micronutrients concentration and biomass allocation of a tropical forage species, Stylosanthes capitata Vogel under field conditions. Temperature control was performed by a temperature free-air controlled enhancement (T-FACE) system. We observed that warming changed nutrient concentrations and plant growth depending on soil moisture levels, but the responses were specific for each plant organ. In general, we found that warming under well-watered conditions greatly improved nutrient concentration and biomass production, whilst the opposite effect was observed under non-irrigated and non-warmed conditions. However, under warmed and non-irrigated conditions, leaf biomass and leaf nutrient concentration were greatly reduced when compared to non-warmed and irrigated plants. Our findings suggest that warming (2 °C above ambient temperature) and drought, as well as both combined stresses, will change the nutrient requirements and biomass distributions between plant aerial organs of S. capitata in tropical ecosystems, which may impact animal feeding in the future.

Silicon via nutrient solution modulates deficient and sufficient manganese sugar and energy cane antioxidant systems.

Manganese (Mn) is highly demanded by Poaceae, and its deficiency induces physiological and biochemical responses in plants. Silicon (Si), which is beneficial to plants under various stress conditions, may also play an important role in plants without stress. However, the physiological and nutritional mechanisms of Si to improve Mn nutrition in sugarcane and energy cane, in addition to mitigating deficiency stress, are still unclear. The objective of this study is to evaluate whether the mechanisms of action of Si are related to the nutrition of Mn by modulating the antioxidant defense system of sugarcane plants and energy cane plants cultivated in nutrient solution, favoring the physiological and growth factors of plants cultivated under Mn deficiency or sufficiency. Two experiments were carried out with pre-sprouted seedlings of Saccharum officinarum L. and Saccharum spontaneum L. grown in the nutrient solution. Treatments were arranged in a 2 × 2 factorial design. Plants were grown under Mn sufficiency (20.5 µmol L-1) and the deficiency (0.1 µmol L-1) associated with the absence and presence of Si (2.0 mmol L-1). Mn deficiency caused oxidative stress by increasing lipid peroxidation and decreasing GPOX activity, contents of phenols, pigments, and photosynthetic efficiency, and led to the growth of both studied species. Si improved the response of both species to Mn supply. The attenuation of the effects of Mn deficiency by Si depends on species, with a higher benefit for Saccharum spontaneum. Its performance is involved in reducing the degradation of cells by reactive oxygen species (21%), increasing the contents of phenols (18%), carotenoids (64%), proteins, modulating SOD activity, and improving photosynthetic and growth responses.

Silicon mitigates nutritional stress in quinoa (Chenopodium quinoa Willd.).

Nutritional deficiency is common in several regions of quinoa cultivation. Silicon (Si) can attenuate the stress caused by nutritional deficiency, but studies on the effects of Si supply on quinoa plants are still scarce. Given this scenario, our objective was to evaluate the symptoms in terms of tissue, physiological and nutritional effects of quinoa plants submitted to nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) deficiencies under Si presence. The experiment consisted of a factorial scheme 6 × 2, using a complete solution (CS), -N, -P, -K, -Ca, -Mg combined with absence and presence of Si (1.5 mmol L-1). Symptomatic, physiological, nutritional and evaluation vegetative were performed in quinoa crop. The deficiencies of N, P, K, Ca and Mg in quinoa cultivation caused visual symptoms characteristic of the deficiency caused by respective nutrients, hence decreasing the plant dry mass. However, Si supply attenuated the deficiency effects by preserving the photosynthetic apparatus, increasing the chlorophyll production, increasing the membrane integrity, and decreasing the electrolyte leakage. Thus, the Si supply attenuated the visual effects provided by deficiency of all nutrients, but stood out for N and Ca, because it reflected in a higher dry mass production. This occurred because, the Si promoted higher synthesis and protection of chlorophylls, and lower electrolyte leakage under Ca restriction, as well as decreased electrolyte leakage under N restriction.

Silicon modifies C:N:P stoichiometry, and increases nutrient use efficiency and productivity of quinoa.

Recognizably, silicon has a beneficial effect on plant growth and productivity. In this respect, it is also known that the C, N and, P stoichiometric ratios and nutrient conversion efficiency allow identifying the interactions between elements while helping to understand the role Si plays in plant growth. This study aims to investigate whether increasing Si concentrations (0, 1, 2, and 3 mmol L-1) supplied in the nutrient solution is uptaken by quinoa, modifies the C:N:P stoichiometry while increasing nutritional efficiency and crop productivity as well. Our results revealed that the Si supply by promoting a decline in the C levels, associated with greater uptake of N and P, especially decreased the C:N and C:P ratios, favoring the C metabolism efficiency, and modulated the N and P use efficiency for biomass accumulation. This improved nutritional performance and greater use efficiency of C directly favored quinoa productivity. The future perspective is to encourage new field studies with this species to adjust silicon fertilization management to different soils aiming at enhancing quinoa productivity on a sustainable basis.

Silicon attenuates calcium deficiency by increasing ascorbic acid content, growth and quality of cabbage leaves.

Calcium (Ca) deficiency in cabbage plants induces oxidative damage, hampering growth and decreasing quality, however, it is hypothesized that silicon (Si) added to the nutrient solution may alleviate crop losses. Therefore, this study aims at evaluating whether silicon supplied in the nutrient solution reduces, in fact, the calcium deficiency effects on cabbage plants. In a greenhouse, cabbage plants were grown using nutrient solutions with Ca sufficiency and Ca deficiency (5 mM) without and with added silicon (2.5 mM), arranged as a 2 × 2 factorial in randomized blocks, with five replications. At 91 days after transplanting, the plants were harvested for biological evaluations. In the treatment without added Si, Ca deficiency promoted oxidative stress, low antioxidant content, decreased dry matter, and lower quality leaf. On the other hand, added Si attenuated Ca deficiency in cabbage by decreasing cell extravasation while increasing both ascorbic acid content and fresh and dry matter, providing firmer leaves due to diminished leaf water loss after harvesting. We highlighted the agronomic importance of Si added to the nutrient solution, especially in crops at risk of Ca deficiency.

Tomato phytochromes B1 and B2 are part of the responses to the nutritional stress induced by NPK deficiency.

Phytochromes are red-light photoreceptors that play an important role in regulating many responses of plants, including its nutritional control. Nutrient deficiency in plants has become a constraint for agricultural production; thus, we investigated the role of phytochromes B1 and B2 in the nutritional, physiological, and growth changes of the control genotype (WT) and both phyB1 and phyB2 tomato mutants (deficient in phyB1 and phyB2) under nutritional sufficiency and individual deficiency of N, P, and K. Under complete solution, the plants of phyB1 and phyB2 had a decreased N, P, and K accumulation compared with WT and consequently a reduced content of chlorophyll and carotenoids, and dry weight production. In the condition of N deficiency, phyB1 had decreased N absorption, pigments concentration, and plant dry weight, while increased oxidative stress of membranes (MDA content). Similarly, phyB2 also had reduced N absorption. The deficiency of phyB1 mitigated the effects of P deficiency as phyB1 mutant had improved nutritional and physiological responses, increasing plant dry weight production. In contrast, phyB2 reduced N accumulation, quantum efficiency of photosystem II (Fv/Fm), and the concentration of pigments, while it increased MDA. Under K deficiency, phyB1 displayed a reduced P accumulation, as well as the total concentration of chlorophylls and carotenoids and K use efficiency. An increased concentration of MDA was found in phyB2 plants, as well as a reduction in chlorophylls concentration and in the use efficiency of K. Together, these results indicate a new perspective on the control of phytochromes in the nutrition of tomato plants under nutritional stress.

Silicon supplied via foliar application and root to attenuate potassium deficiency in common bean plants.

Potassium (K) deficiency affects physiological performance and decreases vegetative growth in common bean plants. Although silicon (Si) supplied via nutrient solution or foliar application may alleviate nutritional stress, research on the bean crop is incipient. Thus, two experiments were carried out: initially, a test was performed to determine the best source and foliar concentration of silicon. Subsequently, the chosen Si source was supplied in nutrient solution via roots or foliar application to verify whether Si supply forms are efficient in alleviating the effects of K deficiency. For these purposes, a completely randomized 2 × 3 factorial design was used, with two levels of K: deficient (0.2 mmol L-1 of K) and sufficient (6 mmol L-1 of K); and Si: in nutrient solution via roots (2 mmol L-1 of Si) or foliar application (5.4 mmol L-1 of Si) and control (0 mmol L-1 of Si). Our findings revealed that Si supplied via foliar spraying using the source of sodium silicate and stabilized potassium at a concentration of 5.4 mmol L-1 was agronomically viable for the cultivation of bean plant. K deficiency, when not supplied with silicon, compromised plant growth. Moreover, root-and-foliar-applied Si attenuated the effects of K deficiency as it increased chlorophylls and carotenoids content, photosynthetic activity, water use efficiency and vegetative growth. For the first time, the role of Si to mitigate K deficiency in the bean crop was evidenced, with a view to further research on plants that do not accumulate this beneficial element.