Differential tissue differentiation in lemon balm following the application of selenium nanoparticles

The aim of this study was to investigate the effect of application of selenium nanoparticles on anatomy and pattern of tissue differentiation in lemon balm. Plants were treated with nano-selenium (nSe; 0, 10 and 50 mg/l) and bulk selenium (BSe). The results of this study indicated that nanoselenium had a positive and beneficial effect at a concentration of 10, but a concentration of 50 induced toxicity. The microscopic assessment of stem cross sections showed that the diameter of the central cylinder was increased compared to the control. The highest increase was related to the seedlings exposed to the 50 and 10 mg/l. Stem thickness and diameter in the nSe-treated seedlings at 50 mg/l and bulk 10 mg/l were increased compared to the control. Xylem diameter decreased in response to the supplements, the lowest belongs to the nSe50. Monitoring the leaf cross sections showed that nSe10 increased thickness of xylem diameter, palisade and sponge parenchyma compared to the control. Comparison of petiole cross-sections indicated that the thickness of the epidermis and the diameter of the central the central and lateral xylem were changed. While, 50 mg/l nSe declined these traits. Therefore, the results of this study indicate that the application of applied concentration-dependent selenium, in addition to inducing physiological and molecular changes, causes anatomical changes and tissue differentiation. Further research is needed in the future to determine the mechanism of these responses.