Silicon Supplementation Modulates Physiochemical Characteristics to Balance and Ameliorate Salinity Stress in Mung Bean

Abstract

Mung bean is a low-cost high-protein legume that is sensitive to salinity. Salt stress has been demonstrated to be mitigated by silicon (Si). In legumes, the potential for silicon (Si)-mediated abiotic stress reduction has mainly been ignored. Moreover, there is little information on the specific role of comparable Si (sodium silicate) concentrations in salinity stress reduction. As a result, the current study investigated the impact of two distinct Si concentrations (1 and 5 mM) on the physiochemical features of the “mung bean,” one of the most extensively cultivated legumes, when exposed to salinity (10, 20, and 50 mM NaCl). Salinity stress reduced growth variables such as biomass, nodule formation, plant length, height, and photosynthetic measures, which were mitigated by silicon supplementation at 5 mM sodium silicate. The inclusion of silicon increased the expression of photosynthetic proteins such as PSI, PSII, and LHCs under salt stress. Salinity stress also caused oxidative damage in the mung bean in the form of hydrogen peroxide (H2O2) and superoxide radical (O2−), leading in increased lipid peroxidation (MDA) and electrolyte leakage. In contrast, 5 mM sodium silicate tends to scavenge free radicals, reducing lipid peroxidation (MDA) and electrolyte loss. This was linked to significant silica deposition in the leaf epidermis, which eventually functioned as a mechanical barrier in mitigating the deleterious effects of salt stress. Si supplementation also decreased Na+ uptake while increasing K+ uptake. Silicon, specifically 5 mM sodium silicate, was found to minimize salinity stress in mung bean by altering physio-chemical parameters such as photosynthetic machinery, Na+/K+ homeostasis, mechanical barriers, osmolyte production, and oxidative stress.

Physiological and Molecular Analysis Revealed the Role of Silicon in Modulating Salinity Stress in Mung Bean

“…However, salinity stress deleteriously disturbs plant germination, growth, the reproductive stage, and the capacity to biologically fix nitrogen in legumes. In mung bean, salinity has been observed to affect seedling germination and development [6], photosynthesis, nodulation [7], the accumulation of ROS, water status, membrane stability, and the content of pigments [7,8]. Of the various salinity management strategies, we intended to take advantage of the application of exogenous Si to combat salinity stress in mung bean because Si research so far has largely neglected legumes.…”

“…The position of silicon (Si) in terms of its "essentiality" for plant growth and development has been a reasonably debated topic among researchers. However, the plethora of research findings that have established Si as a proficient player in the alleviation of various abiotic stresses, such as salinity stress, drought stress, and metal toxicity, cannot be undermined either [7,[9][10][11]. The protective role of Si is usually seen in plants due to the polymerization of silicates in the endodermis and exodermis.…”

Silicon supplementation and jasmonate activation synergistically increase phenolic defences against a legume herbivore

“…Legumes possess root nodules that house nitrogen (N)-fixing rhizobial bacteria, which increase nitrogen availability for legumes and subsequent or adjacent non-N-fixing plants (Chmelíková et al 2015;Ryalls et al 2016) Murad & Muneer 2022). This could potentially undermine the effectiveness of Si in increasing legume resistance to herbivory because N is usually the limiting nutrient in insect herbivore diets (Mattson 1980); increased N availability via Si supplementation could therefore increase susceptibility to herbivory, assuming that this increase in N is not outweighed by the Siinduced reduction in digestibility of that N.…”

“…and other legumes (Nelwamondo & Dakora 1999;Izaguirre-Mayoral et al 2017;Putra et al 2022), especially when plants are under stress (e.g. Al Murad & Muneer 2022). This could potentially undermine the effectiveness of Si in increasing legume resistance to herbivory because N is usually the limiting nutrient in insect herbivore diets (Mattson 1980); increased N availability via Si supplementation could therefore increase susceptibility to herbivory, assuming that this increase in N is not outweighed by the Siinduced reduction in digestibility of that N.…”

Silicon supplementation and jasmonate activation synergistically increase phenolic defences against a legume herbivore

“…and other legumes (Izaguirre‐Mayoral et al, 2017; Nelwamondo & Dakora, 1999; Putra et al, 2022), especially when plants are under stress (e.g. Al Murad & Muneer, 2022). The mechanisms of these responses remain unknown but may be associated with an increased provision of carbon‐derived compounds from the legume to the rhizobial bacteria due to the substitution of structural carbon with Si and/or an increased transport of solute and gases from soil due to increased nodule permeability (Putra et al, 2020).…”