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 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.

Nutritional deficiency in scarlet eggplant limits its growth by modifying the absorption and use efficiency of macronutrients.

The intensity damages caused by nutritional deficiency in growing plants can vary with nutrients. The effects caused by nutrient omission in the plant nutritional efficiency in relation to the absorption and use of the missing nutrient, and the reasons why these damages reflect in other nutrients have not yet been reported in the culture of scarlet eggplant. A better understanding of the nutritional mechanisms involved may clarify why certain nutrients cause greater limitations than other during plants growth. Thus, this study was designed with the aim of evaluating the damages caused by macronutrients deficiency in the culture of scarlet eggplant in the accumulation of these nutrients, nutritional deficiency, plants growth and in visual symptoms. The experiment was carried out in a controlled environment where plants were cultivated in a hydroponic system. Treatments consisted of supplying a complete Hoagland and Arnon solution (CS), and other nutrient solutions with individual omissions of nitrogen (-N), phosphorus (-P), potassium (-K), calcium (-Ca), magnesium (-Mg) and sulphur (-S). When a nutrient deficiency arose, nutritional analyses, growth and visual symptoms were analyzed. The omissions of N, S and K in the nutrient solution resulted in lower accumulation of all macronutrients in both the above and below ground biomass. Individual omissions resulted in nutritional imbalances with reflexes in the absorption efficiencies and use of the missing nutrient, as well as of other nutrients, revealing that the metabolism involves multiple nutritional interactions. Losses of nutritional efficiencies of macronutrients caused detrimental effects on plants growth, with reduced height, stem diameter, number of leaves, leaf area, and biomass production in above ground and below ground. From the losses in production in above ground biomass, the order of macronutrients limitation was N, S, K, Ca, Mg, and P, with reductions of 99, 96, 94, 76, 51 and 46%, respectively, in comparison to plants cultivated in CS. The most limiting nutrients were N, S, and K, seen that its deficiencies affected the metabolism of all other nutrients. This study demonstrates the importance of an adequate nutritional management of N, S, and K in the cultivation of scarlet eggplant.