Silicon Supplement Improves Growth and Yield Under Salt Stress by Modulating Ionic Homeostasis and Some Physiological Indices in Hordeum vulgare L

The application of silicon through external means has been proved to accelerate stress tolerance in different plant species. In this regard, we conducted an experiment to evaluate the role of silicon applied through rooting media on growth and yield of barley ( Hordeum vulgare L.) under salinity stress. Silicon (200 ppm) was applied through rooting media to barley ( Hordeum vulgare L.) genotypes [salt tolerant-B10008 and salt sensitive-B14011] subjected to 200 mM NaCl stress. A remarkable decline in growth (shoot and root lengths and biomass accumulation), leaf relative water contents (LRWC), chlorophyll constituents, and ionic concentrations (K + , Ca 2+ , P, and Si), with a substantial increase in total soluble proteins (TSP) and concentrations of Na + and Cl − , was observed under salt stressed compared to control plants. Salinity stress lowered the efficiency of Photosystem II (PSII) by hindering absorption/transport of electrons through thylakoid membranes; decrease in size of reaction centers (Fv/Fo) and delayed electron transport from PSII to ETC (Fm/F O ) further confirmed by the appearance of K- and L-bands. Alternatively, the fertigation of silicon (Si) through rooting media significantly ( P < 0.001) enhanced the uptake of essential nutrients i.e., Ca 2+ , P, K + , and Si, while lowered the uptake and/or accumulation of Na + and Cl − concentration in salt-stressed barley plants. Similarly, the PSII efficiency was enhanced by maintaining photosynthetic apparatus intact under salt-stressed plants. The yield response was also lowered in salt-stressed barley plants, whereas Si application improved yield-related attributes (grains weight, number of tillers, and number of grains). Salinity (200 mM NaCl) stress reduced growth (26–58%) and biomass accumulation (25–34%) while application of silicon through rooting media enhanced growth (29–36%) and biomass (16–19%) in barley (B-10008, B-14011) genotypes as compared to salt-stressed plants. This boost in growth after silicon supplement showed improved chlorophyll contents, photosynthetic efficiency, ionic balance, and ultimately better yield (26–55%). Although the tolerant genotype (B-10008) showed better salt tolerance, still the response of sensitive genotype (B-14011) was outstanding after silicon application in saline environment.