No abstract

The objective of this study was to evaluate the effect of silicon (Si) on iron (Fe) deficiency in sorghum plants grown in a nutrient solution, seeing that sorghum crops are sensitive to iron deficiency and Si may alleviate this deficiency. Nonetheless, the nutritional mechanisms underlying this process have not been fully elucidated in this plant species. Treatments were arranged in a 2 × 2 factorial scheme and completely randomized block design, in the absence or presence of Si (2 mmol L −1) and under Fe deficiency or sufficiency, with five repetitions. The sources of Si and Fe were stabilized sorbitol sodium and potassium silicate (Si = 113.4 g L −1) and Fe-EDDHA chelate (Fe = 6%), respectively. The plants were cultured in pots filled with washed sand, and Si was supplied via nutrient solution at a concentration of 2 mmol L −1. The concentrations of Fe used in this study were 368 μmol L −1 for sufficiency conditions and 55.2 μmol L −1 for deficiency conditions. Our results showed that Si has a beneficial effect on sorghum plants under Fe deficiency by increasing the chlorophyll content and decreasing concentration of malondialdehyde (MDA). In addition, the application of Si increased the efficiency of translocation and utilization of Fe in plants under this micronutrient deficiency. In conclusion, Si reduced Fe deficiency in sorghum plants by increasing the concentration of photosynthetic pigments, reducing lipid peroxidation, improving the efficiency of Fe translocation and utilization, and resulting in a greater dry weight accumulation.

Leaf spraying of manganese (Mn) is widely used in annual crops due to its deficiency in the soil. Silicon (Si) addition in the spray solution with Mn could favor physiological and nutritional aspects and the production of corn and sorghum plants. This study aimed to evaluate the effects of Mn and Si supplied by leaf spraying on leaf nutrition of corn and sorghum under Mn deficiency. Two experiments were carried out: one with corn and other with sorghum grown in pots filled with sand and using nutrient solution. Corn experiment consisted of a 4 × 2 factorial scheme, with Mn concentrations of 0.0, 0.29, 0.58, and 0.87 g L −1 in the absence and presence of Si (0.476 g L −1) applied on leaves at the V4 and V6 stages. The experiment with sorghum was carried out in a 4 × 2 factorial arrangement, with Mn concentrations of 0.0, 0.17, 0.34, and 0.51 g L −1 in the absence and presence of Si (0.476 g L −1) applied on leaves at the V4 and V6 stages. Physiological and dry mass production variables were evaluated in both experiments to verify the effect of Si and Mn on plant nutrition. Leaf spraying of Mn associated with Si increased micronutrient accumulation, relative chlorophyll index, quantum efficiency of PSII, and reflected on dry mass production of corn and sorghum plants. Leaf spraying of Mn associated with Si in the spray solution is agronomically viable for corn and sorghum plants.

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.

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.