Alleviation of Ammonium Toxicity in Salvia splendens 'Vista Red' with Silicon Supplementation.

Ammonium (NH 4 + ) toxicity seriously hampers the yield and quality of salvia plants because most varieties or sub-species are highly sensitive to NH 4 + . Silicon (Si) is an alternative that is used to minimize these disturbances and maintain better growth under NH 4 + toxicity. Nevertheless, the mitigatory effects of Si on NH 4 + -stressed salvia are unknown. Therefore, this study was carried out to determine how Si assists to alleviate the NH 4 + toxicity degree in salvia. To this end, salvia plants were cultivated in a controlled environment supplied with a constant N (nitrogen) level (13 meq·L -1 ) in the form of three NH 4 + :NO 3 - ratios (0:100, 50:50, 100:0), each with (1.0 meq·L -1 ) or without Si. Physiological disorders and typical NH 4 + toxicity symptoms, as well as interrupted photosynthesis, were observed in the 100% NH 4 + -treated plants. Furthermore, cation uptake inhibition and oxidative damage were also imposed by the 100% NH 4 + supply. In contrast, in the presence of Si, the NH 4 + toxicity degree was attenuated and plant growth was ensured. Accordingly, the NH 4 + toxicity appearance ratio decreased significantly. Furthermore, Si-treated plants showed an ameliorated photosynthetic ability, elevated internal K and Ca levels, and enhanced antioxidative capacity, as reflected by improved major antioxidant enzyme activities, as well as diminished accumulation of ROS (reactive oxygen species) and MDA (malondialdehyde). Our findings enlightened the agronomic importance of additional Si to nutrient solutions, especially pertaining to bedding plants at risk of NH 4 + toxicity.