Calcium silicate ameliorates zinc deficiency and toxicity symptoms in barley plants through improvements in nitrogen metabolism and photosynthesis

Zinc (Zn) deficiency causes serious issues to plant growth and development, negatively affecting crops in many world regions. On the other hand, Zn toxicity impairs plant growth, producing physiological alterations, and even cell death. In plants, two of the processes that most determine growth are nitrogen (N) metabolism and photosynthesis. In the last decades, several authors proved that silicon (Si) and calcium (Ca) mitigate the effects of various abiotic and biotic stresses in plants. The objective of this research is to study the effect of Si application to barley (Hordeum vulgare cv. Nure) plants grown under Zn deficiency and Zn toxicity. Hence, barley plants were grown in hydroponics and supplied with a low Zn dose (0.01 µM ZnSO4) and a high Zn dose (100 µM ZnSO4) and were supplied with CaSiO3. Parameters related to Zn accumulation, N metabolism, and photosynthesis were measured. Zn stress affected leaf Zn concentration and reduced biomass in barley plants. Both Zn toxicity and deficiency inhibited N metabolism and enhanced photorespiration, increasing stress symptoms. CaSiO3 mitigated Zn stress effects, probably regulating Zn levels in plant cells and enhancing N metabolism and photosynthesis. We conclude that CaSiO3 could be beneficial to grow barley plants in soils with high or low availability of Zn.