Silicon (Si) is a very beneficial element for plants, as it improves their growth under various stresses, including more frequent water shortage and increased UV radiation. Ambient UV radiation is crucial for normal plant development and may also increase plants' resistance to drought. We studied the effect of water availability on leaf contents of Si and other elements in C3 and C4 cereals (barley and proso millet), and the effect of ambient UV radiation on element uptake and leaf functional traits under water shortage. We were also interested in the impact of soil structure on leaf Si content (tufted hairgrass) and the effect of varying leaf Si content on leaf functional traits. In addition, we compared leaf Si content between species and developmental stages (barley and spelt). Different leaf morphological, biochemical, optical, and physiological properties were analysed, some environmental factors were monitored along, soil structure was studied, and contents of selected elements in leaves and soil were measured. Barley (C3) was more vulnerable to water shortage than proso millet (C4), which was significantly reflected in reduced leaf contents for most of the studied elements. Water shortage affected leaf Si content the most. Ambient UV radiation positively affected some of the leaf functional traits, but did not significantly mitigate the negative impact of water shortage on Si uptake. Soil structure was less important for leaf contents of Si and other elements than water availability. Leaf Si content significantly affected leaf optical properties and leaf contents of other elements, and differed between species as well as between different developmental stages.
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