Effect of nano NPK fertilizer, cytokinin, and gibberellic acid on vegetative growth and chemical constituents of Paulownia (Paulownia tomentosa L) plants

Abstract: The investigation sought to examine the effects of nano NPK, cytokinin, and GA3 on the growth and chemical composition of Paulownia tree seedlings. The experiment comprised three treatments: Nano NPK at concentrations of 0 and 6 g L^-1, applied monthly from April to September; cytokinin at concentrations of 0, 100, and 200 mg L^-1, applied thrice in March, July, and September; and GA3 at concentrations of 0, 200, and 400 mg L^-1, applied biannually in May and August. Plant sprayed with 6 g L^-1 Nano NPK increased all vegetative and chemical parameters compared with control. Furthermore, plants sprayed with 200 mg L^-1 cytokinin increase plant height to 96.67 cm, leaves number 31.22 leaf plant^-1, stem diameter 5.56 cm, leaves area 277.83 cm², nitrogen content in leaves 1.65 %, and total carbohydrate in leaves 8.94 % compared with control. In contrast, the plants sprayed with 400 mg L^-1 GA3 plant height increased to 92.11 cm, leaves number 29.50 leaf plant^-1, leaves area 257.90 cm², nitrogen and phosphorus content in leaves 1.77- 2.80 %, and total carbohydrate in leaves 8.30 %. Nonetheless, plants treated with 200 mg L^-1 GA3 exhibited an increase in total chlorophyll content in leaves to 24.40 mg g^-1 fresh weight in comparison to the control group. Further investigation is necessary to ascertain whether higher concentrations than those employed in this study may produce better outcomes.