Silicon is a chemical element that has many positive effects on some qualitative and quantitative characteristics of many plant species such as ornamental plants. The aim of this research was to investigate the impact of silicon spray on growth and photosynthetic characteristics of chrysanthemum. This study was performed as a factorial completely randomized design with 2 factors: silicon source in 2 forms (sodium and calcium silicate) and the concentration of silicate in five levels (0, 50, 100, 150 and 200 mM) in perlite: coco-peat medium with 3 replications and 2 observations. Traits such as leaf area, leaf number, leaf temperature, fresh and dry weight of leaves, chlorophyll index, chlorophyll a and b, net photosynthesis, transpiration and stomata conductivity were measured. The results showed that sodium and calcium silicate reduced leaf temperature but, increased other measured indices compared to control. The effect of silicon on these indices may be because of its effect on plant metabolism and photosynthetic system such as the concentration of Rubisco enzyme, increasing the transmission of photoassimilates from source to sink, increasing photosynthesis efficiency, changing the distribution of photosynthetic products, reducing oxidative substances, increasing carbohydrates and changing the concentrations of internal hormones.
