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.

Enhancement of salt tolerance in corn using Azospirillum brasilense: an approach on antioxidant systems.

Salinity has become one of the major factors limiting agricultural production. In this regard, different cost-effective management strategies such as the use of plant growth-promoting bacteria (PGPB) as inoculants to alleviate salt-stress conditions and minimize plant productivity losses have been used in agricultural systems. The aim of this study was to characterize induced antioxidant responses in corn through inoculation with Azospirillum brasilense and examine the relationship between these responses and the acquired salt-stress tolerance. Treatments were performed by combining sodium chloride (0 and 100 mM NaCl) through irrigation water with absence and presence of A. brasilense inoculation. The experiment was performed in a completely randomized design with four replications. Lipid peroxidation (malondialdehyde [MDA]), and nitrogen (N), sodium (Na+) and potassium (K+) contents, as well as dry biomass, glycine betaine, and antioxidant enzymes activities such as of superoxide dismutase (SOD, EC 1. 15. 1. 1), glutathione reductase (GR, EC 1. 6. 4. 2), guaiacol peroxidase (GPOX, EC 1. 11. 1. 7), and glutathione peroxidase (GSH-PX, EC 1. 11. 1. 9) were determined. Overall results indicated that plants treated with 100 mM NaCl showed the most pronounced salt-stress damages with consequent increase in MDA content. However, inoculated plants showed an enhanced capacity to withstand or avoid salt-stress damages. These results could be attributed, at least in part, to the increased activity of antioxidant enzymes. Our results suggest that A. brasilense may confer tolerance to salt stress in corn plants enhancing antioxidant responses, primarily by the enzymes GSH-PX and GPOX, and the osmolyte glycine betaine.

Exogenous silicon and salicylic acid applications improve tolerance to boron toxicity in field pea cultivars by intensifying antioxidant defence systems.

Field peas (Pisum sativum L.) are widely cultivated throughout the world as a cool season grain and forage crop. Boron (B) toxicity is caused by high B concentration in the soil or irrigation water, and is particularly problematic in medium or heavier textured soil types with moderate alkalinity and low annual rainfall. Previous studies have indicated that B-toxicity increases oxidative stress in plants, and B-tolerance has been considered an important target in field pea plant breeding programmes. Inducers of tolerance may be a promising alternative for plant breeding. Little research has been conducted on the combined use of silicon (Si) and salicylic acid (SA) to remediate B-toxicity in field peas. The present study revealed the physiological and biochemical plant responses of applying Si + SA under B-toxicity (15 mg B L-1) on two Brazilian field pea cultivars (Iapar 83 and BRS Forrageira). A semi-hydroponic experiment was conducted using a completely randomized factorial design (2 × 5): with two field pea cultivars and five treatments which were formed by individual and combined applications of Si and SA under B-toxicity plus a control (control, B, B + Si, B + SA, and B + Si + SA). Si (2 mmol L-1) was applied to plants in two forms (root and leaf), while for SA (36 µmol L-1) only foliar applications were applied. Our results demonstrated that the combined use of exogenous Si + SA in field peas increased tolerance to B-toxicity through an intensified antioxidant plant defence system, resulting in a better regulation of reactive oxygen species (ROS) production and degradation. It significantly increased total chlorophyll and carotenoids contents, the activities of major antioxidant enzymes, and reduced MDA and H2O2 contents, resulting in increased fresh shoot and total plant dry biomass. The application of Si + SA alleviated the inhibitory effects of boron toxicity in field peas, resulting in greater plant growth by preventing oxidative membrane damage through an increased tolerance to B-excess within the plant tissue. Therefore, the use of Si + SA is an important and sustainable strategy to alleviate B-toxicity in field pea cultivation.