The effect of Zn NPs on some growth, biochemical and anatomical factors of chickpea plant stem under UVB irradiation

This study explored the role of zinc oxide nanoparticles (ZnO NPs) in mitigating UV-B radiation effects on chickpea ( Cicer arietinum L.) plants. Chickpea plants were grown hydroponically for 45 days and exposed to UV-B radiation for 30 minutes daily over 15 days after reaching the six-leaf stage. ZnO NPs were applied at 50 mg/L and 100 mg/L before UV-B exposure. UV-B reduced root length (40 %), shoot fresh weight (17 %), shoot dry weight (15 %), stem thickness (39 %), and pith parenchyma thickness (5 %), while increasing root fresh weight (59 %), root dry weight (12 %), total phenolic content (TPC, 185.77 %), total flavonoid content (TFC, 94.44 %), and DPPH free radical scavenging activity (31.94 %). ZnO NPs (50 mg/L and 100 mg/L) increased root length (15 % and 25 %), shoot length (21 % and 12 %), shoot fresh weight (56 % and 63 %), and shoot dry weight (40 % and 79 %), respectively. TPC increased by 8 % with 50 mg/L ZnO NPs, while TFC rose by 30 % with 100 mg/L ZnO NPs. DPPH activity improved by 15.78 % and 3.59 % at 50 mg/L and 100 mg/L ZnO NPs, respectively. Stem thickness increased by 12 % and 31 %, and pith thickness by 18 % with 50 mg/L ZnO NPs. UV-B reduced sclerenchyma, xylem, and epidermal cell thickness but increased xylem cell length and pith parenchyma, xylem, and epidermal cell width. Application of 100 mg/L ZnO NPs enhanced xylem thickness, phloem vessel thickness, vascular tissue thickness, and collenchyma tissue thickness. Overall, ZnO NPs demonstrated significant potential in alleviating UV-B-induced damage and improving chickpea plant growth and anatomical integrity. • UVB led to decrease in chickpea shoot and root length, shoot fresh and dry weight. • UVB decreased the thickness of sclerenchyma, xylem, and length of epidermal cells. • UVB increased length of xylem cells and the width of pith parenchyma. • ZnO NPs led to the improvement of shoot growth factors in chickpea plants.